Carburetor Issue

[tajoe]

Well, I got the carb back today and throttle shaft is a lot more solid.

Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.

Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.

:shock:You,ve gutta be kidding? You're telling us, when the eng. is warmed, you can completely shut your choke blade, and it won't load up and stall?

[rkellerjr]

Well, I got the carb back today and throttle shaft is a lot more solid.

Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.

Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.

Don't mean to sound coy on this but, are all the vaccuum connections on the carb plugged or have a hose attached? I know one of my front vacuum inlets on the carb had a "cover" or plug over it so it didn't leak until I properly attached it. I'm just trying to think outside the box.

[Zach]

Well, I got the carb back today and throttle shaft is a lot more solid.

Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.

Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.

:shock:You,ve gutta be kidding? You're telling us, when the eng. is warmed, you can completely shut your choke blade, and it won't load up and stall?

Well, I might’ve been doing the hand test a bit wrong. Choke completely shut, engine runs and doesn’t stumble, and hand over same thing. Although if I smash my hand and completely suffocate it it will die, I’ve been laying my hand over the primaries, it only dies if I force my hand a bit and feel the vacuum pull on my hand. Wondering if I’ve been doing this wrong the entire time.

Well, I got the carb back today and throttle shaft is a lot more solid.

Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Curb idle screw completely out, idle mixture screws set to best I can get at the moment 3ish turns out. Making around 16ish vacuum at 1000 rpm. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do. Could the APT screw cause a higher idle? It was bottomed out so I am unsure where it is supposed to be, did 2.5ish turns and it fixed my original acceleration issue but I am wondering if it needs tuning for idle or if its only for cruising air/fuel.

Just a bit annoyed, going on vacation to the Dominican in a few days so I wont be able to test anything. I appreciate all the help so far.

Don't mean to sound coy on this but, are all the vaccuum connections on the carb plugged or have a hose attached? I know one of my front vacuum inlets on the carb had a "cover" or plug over it so it didn't leak until I properly attached it. I'm just trying to think outside the box.

Hey I’ll take any advice, I believe everything is plugged and connected sufficiently I replace a lot of hoses and plugs. One thing I still need to try is unplug all vacuum lines and plug them to see if it’s a random vacuum device leaking.

[Zach]

This thread was locked for some reason, I wonder if I tapped it by accident. Anyways I did some more playing around, high idle cam was hitting a small bit but I fixed that, but it didn't solve any issues. I think I'm past vacuum leaks, hand over carb does in fact kill it. Now I am wondering if it is a timing issue, still set to 18 BTDC at 1k rpm using the factory vacuum line routes, manifold vacuum from carb through the emissions check valve. Or something is wrong with my idle circuit and it is dumping too much fuel or air. It was a stock rebuild and clean, I didn't add any hop ups, like jets, or idle bypass, etc. Just to restate it, curb idle screw can be completely unscrewed (transfer slot can only be seen a little bit), and the car will still run at 1k rpm 18 vacuum pretty steady.

[Bluebandit]

DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.

You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.

[Zach]

DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.

You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.

Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.

Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.

[nUcLeArEnVoY]

DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.

You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.

Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.

Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.

Wouldn't be the hot air choke passage since that's a calibrated vacuum leak thats meant to be there. In fact, that's how the later carbs get their air bypass, rather than drilled into the baseplate like the earlier carbs.

Just spit-ballin' here, but does that 1000 RPM actually sound and feel like 1000 RPM, or are you just looking at the factory tach? I had a "high idle" issue for a long time that only happened after I cruised for a bit in 4th gear... it would return to a higher idle than what I set it at, but lo and behold, I hooked up a Unova timing light with an RPM display and verified that I was actually idling where I should be, and that the factory tach was off. These days I just look at my oil pressure gauge to verify I'm at idle when I'm warmed up. 750 RPM reads dead center ar 40 PSI at operating temp.

[Zach]

DO you have a bit of slack in the throttle cable and trans kickdown cables. Could they be holding it slightly open. Still sounds like a vacuum leak somewhere. Try unhooking all the lines and capping off all ports. Make sure PCV valve is clean. They are designed to let a metered amount of air thru them at idle. If the valve is hanging slightly open it can let an excessive amount of air through. It wouldn't take much to effect the idle.

You mentioned earlier the distributor weights were sluggish. I had to remove my distributor and clean the inner shaft to loosen it up. Years of crud had made it almost inoperative. The weights could work their way out but the springs didnt have enough force to pull them back in fully. Once the shafts had been cleaned and lubed everything worked as it should. You could pull the weights apart and they would snap back in place when released. Now thinking about it, seems like I was having problems with a high idle when I found this.

Just have a throttle cable and no, taking the carb off the car I can physically see where the throttle blades are relative to the curb idle screw so I know for the fact they are completely shut or near completely shut (slightly open for a square transfer slot). PCV valve is brand new and the ball rattles around, I need to replace the valley pan gasket but I need the intake off to make that not a huge pain, it is in good enough shape to not cause a leak. Unhooking the PCV valve and plugging it causes no change besides pushing smoke through the air valve covers to the air cleaner. I can take a closer look at the weights and springs again, did a quick check and rubbed them down and cleaned them a tiny bit, didn't feel sticky just really strong but smooth.

Something that is now in my mind is that, I know for a fact the throttle blades are completely closed and were check by Cliff, IF I have a vacuum leak it has to come from below that, which only leaves, carb base gasket, carb flange gasket, intake manifold, and the little hole that transfers hot air below the carb. I sprayed a lot of carb cleaner around the base so I believe I can eliminate any fitment or gasket issues. Not sure the best way to check for intake manifold leaks, I sprayed carb cleaner around the right and left side and noticed no rpm change. One thing that I am not sure about is the emissions air passage that pushes air below carb through the manifold, this could be not working correctly, I don't have much information on it so this is a unknown area for me and I am not sure how to test it. Or the metal flange gasket I have for the carb is wrong, it was on the car when I took the carb off but I learned the carb was touched with before our ownership so I can't guarantee it is correct.

Wouldn't be the hot air choke passage since that's a calibrated vacuum leak thats meant to be there. In fact, that's how the later carbs get their air bypass, rather than drilled into the baseplate like the earlier carbs.

Just spit-ballin' here, but does that 1000 RPM actually sound and feel like 1000 RPM, or are you just looking at the factory tach? I had a "high idle" issue for a long time that only happened after I cruised for a bit in 4th gear... it would return to a higher idle than what I set it at, but lo and behold, I hooked up a Unova timing light with an RPM display and verified that I was actually idling where I should be, and that the factory tach was off. These days I just look at my oil pressure gauge to verify I'm at idle when I'm warmed up. 750 RPM reads dead center ar 40 PSI at operating temp.

Actually thought about hooking up another tac cause I’m not sure what 1000 rpm feels like compared to lower rpm’s on the car since it’s never idled low.  But shouldn’t the car still want to die if the curb idle screw is all the way out, makes me think there is still an issue somewhere. I can only test idle in neutral since Minnesota is currently covered in snow. Oil pressure jitters around 40.

[tajoe]

Does the car creep in gear, if you take your foot off the gas? Is your converter stock?

[Zach]

Does the car creep in gear, if you take your foot off the gas? Is your converter stock?

I should clarify it is a manual 4 speed transmission everything is stock, but the car will move without the gas pedal into 1st and cruise relatively quickly, another reason why I believe the current tac to be accurately showing 1k rpm.

[Bluebandit]

You mentioned the carb had been worked on before you got the car. Could it be possible its not the original carb. Reason im asking is I have 2 different carbs that came off my brother in laws 82 corvette w/a 350. I tried them both on my 305 and couldn't get either one to idle down. The idle screws were backed off to not touch on either one. I don't know for sure but I suspect the factory had them calibrated the idle flow air for the later smog engine they were designed for. I've also got older carbs that will idle down but not these.

[Zach]

You mentioned the carb had been worked on before you got the car. Could it be possible its not the original carb. Reason im asking is I have 2 different carbs that came off my brother in laws 82 corvette w/a 350. I tried them both on my 305 and couldn't get either one to idle down. The idle screws were backed off to not touch on either one. I don't know for sure but I suspect the factory had them calibrated the idle flow air for the later smog engine they were designed for. I've also got older carbs that will idle down but not these.

Pretty confident it is the original or at least a stock replacement, carb number matches the car, year, Pontiac, manual, etc and is the performance 800 cfm with the vent that was specifically made for performance Pontiac engines. In terms of what they messed with I am unsure but Cliff said he’s never seen a bottomed APT screw from factory, everything else inside the carb is stock I didn’t notice any other signs.

[Zach]

Well spent a week scouring the web for anything relating to high idle and can’t find anything that has helped so far, if it is a vacuum leak I cannot find where it coming from, carb runs the same with vacuum lines plugged, brake booster, pcv, etc. vacuum advance has no change at idle from what I can tell. However there is an oddity that it will run around 800 rpm just fine but has a slight hesitation, cannot reproduce it, happened after reconnecting all vacuum lines but it eventually builds rpm and stays at 1k, I’m wondering if the vac advance is sticking or it’s something distributer wise. Throttle linkage cannot be physically more closed.

Currently fighting below freezing temps so I might post pone this issue until summer, car will still run great it just has a slight idle issue.

[tajoe]

If your vac. adv. is stock, then it will be ported at the carb., (no vacuum). And the idle won't change when disconnected. But if you've hooked it up to manifold vac., then the idle should go down, when disconnected. Engs. run so much better when vacuum is hooked to the canister at idle. They run smoother, cooler, better mileage, and snappier throttle response.
As you probably know, when you set your initial timing, you plug the canister, and adj., then hook the vacuum back up. RPMs should increase if you're hooked to manifold vac. If this doesn't happen, either the canister is leaking internally, or maybe your mech. weights are stuck. (Just some more food for thought(. Keep at it. Depending on your cam, you should be able to idle at 700. Not sure if you mentioned the car creeping when idling.

[Zach]

If your vac. adv. is stock, then it will be ported at the carb., (no vacuum). And the idle won't change when disconnected. But if you've hooked it up to manifold vac., then the idle should go down, when disconnected. Engs. run so much better when vacuum is hooked to the canister at idle. They run smoother, cooler, better mileage, and snappier throttle response.
As you probably know, when you set your initial timing, you plug the canister, and adj., then hook the vacuum back up. RPMs should increase if you're hooked to manifold vac. If this doesn't happen, either the canister is leaking internally, or maybe your mech. weights are stuck. (Just some more food for thought(. Keep at it. Depending on your cam, you should be able to idle at 700. Not sure if you mentioned the car creeping when idling.

I can hook up manifold vacuum just to test for leaks, last time I opened distributer mech seemed to move fine and required a bit of force, tested vac adv with a vacuum gun and it seemed to operate fine. yeah stock spec is 775 rpm and I can't even get down to there. The times the car has idled at 800 it was stable but I can't reproduce it, so it isn't like it is dying just can't figure out what is causing the high rpms. Also not sure the definition of creep in terms of a manual car.

[tajoe]

Oops, sorry Zach, I keep forgetting your a stick. Won't be creeping with that. I think someone mentioned the accuracy of your tach. I'm sure you've already double checked that.
You've said the car runs fine, just idles higher than you think it should. You've also said your mech. idle screw is cranked all the way out. With a Cliff R carb. rebuilt, the initial timing set correctly, the curb idle screw taken out, and no vacuum leaks, it sure seems strange it won't go down. Is there a way you could post a quick video of it iding, with an underhood shot for about 30 sec, (with a couple quick revs,), and then a shot of it from the rear, to hear the exhaust? Sure would help here.

[Zach]

Oops, sorry Zach, I keep forgetting your a stick. Won't be creeping with that. I think someone mentioned the accuracy of your tach. I'm sure you've already double checked that.
You've said the car runs fine, just idles higher than you think it should. You've also said your mech. idle screw is cranked all the way out. With a Cliff R carb. rebuilt, the initial timing set correctly, the curb idle screw taken out, and no vacuum leaks, it sure seems strange it won't go down. Is there a way you could post a quick video of it iding, with an underhood shot for about 30 sec, (with a couple quick revs,), and then a shot of it from the rear, to hear the exhaust? Sure would help here.

Yeah for sure I can do a video, just set the APT screw to be more lean to test it out and got rewarded with a volcano of gas and a no start issues so once I sort that sorted out I can get a video in a day or so. Got a new timing light with rpm so I will verify that issue before too.

[Zach]

Going to post a long status update, to sum it up 99% chance that it is fixed.

Opened up the carb and set the APT screw to around 3 turns instead of 2, shouldn't affect idle but I was willing to try everything. Reset my float height cause I was dealing with flooding every time I took the carb on and off the manifold, issue fixed. Ordered 2 new thick air horn gaskets cause I broke the two that I had since I have opened my carb 50 times, one I have is good enough but should be replaced. Found the vacuum hose going from the charcoal canister to the fuel tank to be pretty rotted seemed to still be a solid connection but I wasn't taking chances. Started up the car everything was running great however my tach was still reading 1000 ish once the choke opened and was warm. I wanted to check if my tach was right so I went and bought a fancy timing light from hobo freight that shows rpm and all that, hooked it up and lo and behold it is starting my tach is ready around 300 rpm high and doesn't want to drop below 1000 rpm. Did a bunch of timing work and got to around 18 degrees at 750 rpm, which is really close to factory settings. I seem to have a bit of vacuum/ rpm fluctation, 0-50rpm / 0-0.5 vacuum, might need to adjust mixture screws but I am gonna wait till spring for that. Car seems to be running great, I am unsure what the car is supposed to sound like at 750 rpm since my tach never read right, but I am willing to believe my timing light. As nuclear said 40 psi of oil pressure around 800 is accurate and that is what I am getting. A new issue arose with starting after being hot, but that is for another thread. After all of this my issues ranged from vacuum leaks, throttle blades, wrong settings within carb, and a heck of a lot of other stuff. It is strange my tach reads wrong though? Anyone have any idea for that?

Appreciate everyone in here for the help, I think I am finally finished for carb work besides a small amount of tuning. Wouldn't of got solved this issues without this forum, there is only so much information out there and it is pretty hard to find. Thanks again!

[Zach]

Can't say I am thrilled, first day I was able to take the trans am out and it didn't run great at all. Car starts up cold or hot just fine and revs fine around 40 degrees out, no issues in the garage. Once I take it out on the road I notice a lot of hesitation as if I am running out of gas, when ever I try accelerating it likes to fall flat and not build RPMs and stutter. I notice it starts running slightly better as I am driving around and heat up the engine but this is after 20+ mins of running and getting gas a mile away, I believe the choke is working as it should and I don't see why it would cause the car to act this way. Once everything gets hot, choke is way past being off by now, the car starts to build idle RPMs to around 1100, if i accelerate it builds rpms fine but takes a significant amount of time to drop back down. Any ideas on what to check? Gonna post over at Cliffs as well.

I suspect it is running lean but unsure what to change.

[FormTA]

I no carb expert but that sounds rich to me. May be worth it to get a oxygen sensor/meter to see what is really going on there.

[Zach]

I no carb expert but that sounds rich to me. May be worth it to get a oxygen sensor/meter to see what is really going on there.

No carb expert here either I can just google things fast, from my research I thought it was a lean surge, I would expect black smoke if it was running this rich. Although not sure symptoms of a rich quadrajet. I am going to mess with the APT screw and richen it a bit to see, never tuned it.

I am thinking the TVS valve that adds timing when engine is hot is my suspect for increased RPM although I don't remember running hot, I have a large aluminum rad that keeps the temp steady at what ever the quarter mark is on the gauge, 190?

[Zach]

Going to summarize my main issue a bit fr after fiddling around with it, idle is great and revving in neutral is great, under load coming off idle, part throttle, and WOT, causes a bog/bucking acceleration, it will accelerate and open the secondaries but it is slow and bucks lightly. Adjusted the APT screw from 3.5 turns out - 4, small change I think, 4 - 4.5, no noticeable change.

[70_71_78]

It sure sounds like there may be other problems with this engine beyond carb. issues. Checking for a mechanically sound long block might be a good idea. A leak down test of each cylinder is a good place to start. Every cylinder needs a good valve and ring seal. A broken top ring can act real weird, seeming OK on a compression test, but fail a leak down. It can make low load driving symptoms similar to what you are describing while seeming normal at WOT. Compression entering the intake or exhaust while testing can reveal valve lash issues or burnt valve and seats or even carbon build up that is keeping them from sealing. The tools are not expensive and the time is worth it, if it keeps you from going in circles with an issue. How is the timing chain? Again, a simple test by rotating the crank one direction by hand and watching the rotor and reversing the direction to be sure the rotor moves as soon as the crank moves will reveal any wear. If it lags, it is worn. Too much wear and it may have jumped a tooth. Again, simple test that can help prevent wasted time. Once it is certain that the long block is sound, then distributor and carburetor operation and tuning should be addressed, and with both the devil is in the details.

[Zach]

It sure sounds like there may be other problems with this engine beyond carb. issues. Checking for a mechanically sound long block might be a good idea. A leak down test of each cylinder is a good place to start. Every cylinder needs a good valve and ring seal. A broken top ring can act real weird, seeming OK on a compression test, but fail a leak down. It can make low load driving symptoms similar to what you are describing while seeming normal at WOT. Compression entering the intake or exhaust while testing can reveal valve lash issues or burnt valve and seats or even carbon build up that is keeping them from sealing. The tools are not expensive and the time is worth it, if it keeps you from going in circles with an issue. How is the timing chain? Again, a simple test by rotating the crank one direction by hand and watching the rotor and reversing the direction to be sure the rotor moves as soon as the crank moves will reveal any wear. If it lags, it is worn. Too much wear and it may have jumped a tooth. Again, simple test that can help prevent wasted time. Once it is certain that the long block is sound, then distributor and carburetor operation and tuning should be addressed, and with both the devil is in the details.

Will definitely do at some point however it has 70k miles and was running strong pre carb besides some bad carb issues. The extra timing I am going to blame on the TVS emission plug, I don’t remember what the temp was at but it hasn’t happened since I corrected my timing and idle. Need to test for 0 degrees I don’t think my timing makes are correct. Secondary air valves were also too loose and dramatically helped although wasn’t able to finish yesterday. Changed oil yesterday as well and it was looking pretty good.

[Zach]

I am gonna say it is a timing issue, not sure if my timing marks are correct on the harmonic though. It runs significantly better when there is more timing 14-18 initial (factory) however my starter does not like it. 8 degrees initial is the absolute highest I can go in order for a smoothish crank on the starter. Currently in a decent spot but I know there is more power. I would run a high timing but I don't want to starter to constantly fail on me. The start issue only occurs when the engine is hot however. Maybe I can wrap it and see, don't have materials on hand for that at the moment though. Any ideas?

[FormTA]

Again, I'm not a good carb guy but maybe try removing the vacuum line to the brake booster and plugging it. Just to make sure it isn't sucking air there. Also double check with some brake cleaner or something that there isn't some crazy vacuum leak where the carb attaches.

[phil400]

8* initial is not enough timing for these engines14* degrees should not be so much timing that the starter hard starts. I could see and have experience 18*.  I've wrapped my starter solenoid with heat reflective tape and a put a heat shield, didn't make a dam difference, heat and old wires don't get along either check your main battery cable, and red wire going to the solenoid some guys also install Ford type solenoids. Or high torque mini starters. Problem with installing high torque mini starter is there several measurements and things to check before slapping it on but with 4 speeds bellhousing you can't gain enough access to measure properly without removing it.

Hot start issues is not uncommon for Pontiac's unfortunately.

[Zach]

8* initial is not enough timing for these engines14* degrees should not be so much timing that the starter hard starts. I could see and have experience 18*.  I've wrapped my starter solenoid with heat reflective tape and a put a heat shield, didn't make a dam difference, heat and old wires don't get along either check your main battery cable, and red wire going to the solenoid some guys also install Ford type solenoids. Or high torque mini starters. Problem with installing high torque mini starter is there several measurements and things to check before slapping it on but with 4 speeds bellhousing you can't gain enough access to measure properly without removing it.

Hot start issues is not uncommon for Pontiac's unfortunately.

Yeah it’s definitely heat soak, starts up fine with 18 but not reliable once hot. My band aid method was starting at 18 and retarding the timing until it started up while hot. Going to try heat wrapping the exhaust and starter with a shield and see how that gets me before I crank up the timing. Was interested in a mini starter but they can be pricey, also not what I wanted to hear in terms of install, sounds like a pain. In terms of cables, the positive coming from the battery is significantly higher gauge than the  red wires. There is definitely room for improvement there. Contacts should be clean. Thanks.

[firebirdparts]

Well, for sure, the starter is honest.  If you r e t ard the timing just far enough to start it, then that's perfectly a fine place to be, no matter what the timing marks say.  That's good info to have.  If the starter is dragging rather than "kicking back" then it may be accurate.

I enjoy trying to troubleshooot carburetors, but not so much via internet.  I don't have much to add here. 

[Zach]

Well, for sure, the starter is honest.  If you r e t ard the timing just far enough to start it, then that's perfectly a fine place to be, no matter what the timing marks say.  That's good info to have.  If the starter is dragging rather than "kicking back" then it may be accurate.

I enjoy trying to troubleshooot carburetors, but not so much via internet.  I don't have much to add here.

Appreciate the input, internet isn’t a great medium unless it’s videos in terms of carb troubleshooting but any info is good info. Not sure the definition of kick back vs dragging, starter sounds like any heat soak starter does or a dead battery, it will keep spinning the engine but not fast enough for anything to boom, normally getting pushed back by compression when I let off.

[b_hill_86]

Have you verified your timing marks on your balancer to make sure it hasn’t spun or you haven’t jumped a tooth?

Small side note, when I had header relate hot start issues I found that wrapping the header and leaving the starter unwrapped gave me the best result. Wrapping the starter itself allowed it to heat and seemed to prevent cooling. I’ve always meant to wrap my header but my “temporary” wrap consisting of a starter wrap around the header has provided me with 8-10 years of trouble free starting with the factory starter.

[Zach]

Have you verified your timing marks on your balancer to make sure it hasn’t spun or you haven’t jumped a tooth?

Small side note, when I had header relate hot start issues I found that wrapping the header and leaving the starter unwrapped gave me the best result. Wrapping the starter itself allowed it to heat and seemed to prevent cooling. I’ve always meant to wrap my header but my “temporary” wrap consisting of a starter wrap around the header has provided me with 8-10 years of trouble free starting with the factory starter.

Yeah verified timing within a degree and my harmonic seems accurate. Installed a mini starter and it is going great so far, was likely heat soak. Took it for a 30 min 80 degree drive and it started within a second after parking for a minute. Appreciate the help.

[b_hill_86]

What do you mean by “seems accurate”?

[Zach]

What do you mean by “seems accurate”?

Brought piston close to tdc didn’t account for dwell or anything and the grove on the harmonic was lined up to 0ish on the timing marker. Figured it would be way off more than a degree if it were to have slipped.

[b_hill_86]

Yea I would say so too. Just wanted to double check how you verified it but sounds like you have it covered. I may have asked before but where are you located again?

[Zach]

Yea I would say so too. Just wanted to double check how you verified it but sounds like you have it covered. I may have asked before but where are you located again?

Up in Minnesota, weather is finally nice enough to take the cars out. Got almost a foot of snow a few days ago now it’s in the 70s, pretty early spring for us.

[firebirdparts]

I'll say this much about troubleshooting the basic problem.  I am not someone who would realistically believe the engine would run fast with the choke open due to a vacuum leak.   There are two ways the throttle can stick open, the idle screw and the fast idle cam.  It seems like in your case the carb simply doesn't close correctly.  I haven't run into that in a rochester carb myself.