2020-B1-9

Author Topic: New Build 455 Timing  (Read 400 times)

D94

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New Build 455 Timing
« on: January 03, 2020, 12:15:10 PM »
Looking for some info on initial timing. 455 (.045) over which I think puts me at about 467.
 Engine specs are:

 Butler/ Edelbrock D-port Aluminum heads 72cc flow 310cfm
 Edelbrock Pontiac Performer manifold
 Comp Cams Custom grind- 256/264 @0.50  .597 lift  110 LSA
 Compression 10.25:1
 Aftermarket HEI Coil on Cap 65K volt coil
 NGK BKR6E plugs  gapped .40
 4spd.

Starts and idles fine ( happy ) at 850 rpm 24-26 initial timing ( no vacuum advance, all vacuum ports plugged). At about 3000rpm timing hits 40 jumps back down like it's maxxing out (around 16-18 built in to dizzy I guess ).

Does this sound right? I'm thinking it's a little too advanced at initial, but I can't find any info on built PONTIAC engines to compare it. I keep going back to my carb ( rebuilt Holley 750) which I'm using for startup, could be suspect. Seems to be running rich ( even after adjusting carb )

Any info would be great.. Thx
 

Bluebandit

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Re: New Build 455 Timing
« Reply #1 on: January 04, 2020, 12:23:43 AM »
Do you have the stock weights in your distributor or aftermarket? Timing around 12-18 initial and 32-36 total  is pretty common. Also the Performer isn't the best choice for your combo, the runners are smaller than stock intakes.

oldskool

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Re: New Build 455 Timing
« Reply #2 on: January 04, 2020, 12:44:25 AM »
Sounds like a BIG cam requiring big spring pressure. Do you drive this car on the street ?

If you're gonna run that much initial, you need to make some sort of advance stop, to reduce the amount of mechanical advance that is added as rpm increases. 

There a lots of ways to make a stop. Some weld up the slot a bit. I used a small screw thru one of the spare holes in the bar that the rotor bolts to. It's just a small allen head metric screw, which is just the right size to self tap thru the bar. Bought the screw at Fastenal. Told the guy what I wanted & he tried lots of screws til he got one that just barely wouldn't go thru the hole. It was snug, but tapped the threads without breaking. Now I'm talkin about a factory HEI.

If you use the screw method, you'll need to grind off a small amount of material from the rotor, so it will clear the screw head. If the screw head reduces the advance more than you want, you can grind off part of the head. Or, you can put the screw in from the bottom so that the head will not be the part that stops the advance.
« Last Edit: January 04, 2020, 12:52:22 AM by oldskool »

D94

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Re: New Build 455 Timing
« Reply #3 on: January 05, 2020, 06:52:45 AM »
Thx for the info guys.
Blue, yes I believe although it's an aftermarket HEI it was built to factory specs in that regard. I'm looking into that. Also, I know the Performer is not the best right now,I've been looking into a few different manifolds Perf. RPM, Torker II, or maybe a Northwind but not sold on that one just yet.
Oldskool, yes it will mostly be a street/weekend fun car. I was hoping that I wouldn't have to get involved with modifying the dizzy as you and others have described. I was just wondering if I was compensating for idle rpm with timing because of a bad carb or something else. I've been reading about idle transfer slot adjustments. Sounds like if there way off they'll just dump fuel and you're idle/air mixture screws are ineffective which is another issue I'm having. Like I said I'm way rich no matter what I do. I have a new tuned carb ordered, so I guess I'll know more after I try that. I was just curious if anyone else maybe had the same or similar symptoms. Once I figure it out I'll post a follow up. Thx again for the info, appreciate it.

Bluebandit

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Re: New Build 455 Timing
« Reply #4 on: January 05, 2020, 01:21:05 PM »
I suspect the distributor might be  giving you problems, check out this thread from PY http://forums.maxperformanceinc.com/forums/showthread.php?t=828286
If your front transfer slots are exposed too much it will render the idle adjustment screws ineffective as you are experiencing. Slots opened too far starts the main fuel circuit. What you can do is open the rear throttle plates a bit to allow the fronts to close and regain some adjustability of the idle screws.

D94

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Re: New Build 455 Timing
« Reply #5 on: January 13, 2020, 09:09:04 AM »
Quick update :
Received the new "tuned "Brawler 850 race carb and installed yesterday with new NGK platinum plugs .035 gap. Initial timing @idle 9 degrees at 600rpm vacuum 8-9 runs and starts great. Started at 12 ran great but was getting a little spit when turning engine off. Backed it down to 9 and seems that's where it wants to be. Was up around 30-32 at about 2600rpm so I think I'm close. This is with open headers may change when I put exhaust on. Thx everyone for help.

Re: New Build 455 Timing
« Reply #5 on: January 13, 2020, 09:09:04 AM »
You can help support TAC!

 



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