Author Topic: 1980 301T carb rebuild  (Read 15838 times)

jjr

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1980 301T carb rebuild
« on: April 21, 2012, 09:45:13 PM »

  Here is a 1980 301T carb rebuild.

  In my 1981 carb rebuild thread I introduced the Heated
 ultrasound cleaner, which does amazing work. But still,
 I wasn't perfectly happy with the presentation.

  On this carb and thread, I have added a blast cabinet (benchtop)
 and Cliff's recommended extra fine glass bead media.

  Shazam! That was the missing item. I am now happy with the
 end result. Teaming up the ultra sonic cleaner and glass bead
 blasting is the winning team.

  Here is the carb after the blast cabinet:







  Looks nearly new doesn't it... <grin>

  I am currently teaching myself the rebush job on a junk throttle
 plate. This carb actually had a damaged throttle plate, it was bent
 and cracked, so it got replaced with another.

  Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #1 on: April 21, 2012, 09:46:03 PM »
 
 APT stands for Adjustable Part Throttle... huh?

 The best way to explain APT without a semester of carb theory is
performance. A Qjet has to perfectly match fuel with engine condition,
and in a performance engine, a demanding task.

 The APT is actually part of the Power metering system.

 A Power metering system basically responds to the work an engine is
doing and adds more fuel in this condition. Engine vacuum is a great
way to detect this, but an imperfect way to control it.

 The power piston responds to engine vacuum and adds fuel as it can
but being only vacuum operated kinda stupid.

 Enter the APT, a manual trim to the power system.

 In todays cars -  the computer handles the fuel injection curve, back
then we had carb adjustment screws.

 Back then the thing was designed to be user adjustable, but GM put a big
fat plug over the screw. EPA regs of the day made GM set this adjustment
according to emmisions. Today only the best understand that it exists
and is adjustable. Cliff, often modifies the plug to an removable access
screw for user tuning.

 Let's go look at where this thing is and what it looks like...
 


 In that pic, I made a homemade tool based on Cliff Ruggles instructions
and for less than a dollar. The Hole behind the APT channel is the power
piston channel, we'll look at that later.

 Here's the creation engaging the APT screw head...



 Gently slide over the odd shaped screw head...



 Screw and spring removed (for a proper cleaning) this carb was set at
2.75 turns from bottom, close to the 3 turns out "default" if unknown.



 Next, let's pull those original idle tubes, Cliff gave us some new ones...

 How hard could that be?

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #2 on: April 21, 2012, 09:46:50 PM »

 Cliff Ruggles recommends that you either clean out the idle
tubes, or replace them, Since he sends perfect new ones with
his rebuild kit, why not change them.

 I have more often just verified them as clean with fine wire,
but let's replace these. 

 With the first few threads of a small screw you can engage the
tops of the tubes. Then by using a small inexpensive hand torch,
similar to a large lighter, heat the walls around the idle tubes.

 Once hot, it takes a small tug and they come right out.
 




 Cliff says that often debris can collect in the bottom of the idle tube
channels and the best thing to do is pull them and replace them.



 Easy enough, and we'll be happy we did it after hearing the idle quality.

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #3 on: April 21, 2012, 09:47:44 PM »
 Rebuilding your carb isn't just about tools and fancy machines.

 When this carb came in, the owner surmised it was running lean.

 As I took it apart I saw that his carb had been dropped, and probably
hard. He had mentioned a binding and I see why.

 In this first pic you will see a cracked throttle plate casting
and a noticeably bent shaft.

 This damage left a pretty good sized air leak as well.

 Close scrutiny is important when rebuilding your carb.
 


 a close up of the damaged casting:



 here's what it "should" look like:



 Both shafts from replacement throttle plate are good.



 As it says, while a good replacement throttle plate, it has shaft wear
as this too will leak air. Bushings will be installed.



 and work continues...

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #4 on: April 21, 2012, 09:48:37 PM »
 Ok, in this installment we are going to cover two things.

 1) Air Plate removal via grinding off staked screw heads

 2) Secondary upper Air Valve shaft removal and secondary cam
    inspection

 To remove the choke plate, Primary throttle plates, secondary throttle
plates and upper air valve plates we need to overcome the factory system
of staking these screws into position. They did this so the screws couldn't
possibly loosen and fall into the engine.

 I use Dremels, as this allows me to do small, fine work easily.
 


 Here's the cam, already out, but why we are taking these steps to
check or replace it.



 To get the secondary upper air valve shaft out, we need to unhook the
spring to let the shaft loose for removal.

 (Thanks Cliff!)



 Here's a shot that shows the cam in action. This cam is locked onto
the upper secondary air valve shaft and is responsible for lifting the
secondary metering rods and adding lots of extra fuel on demand.

 The sweet howl from when the secondaries open if you will...



 Here's the shaft out and a close up of the cam. Cliff Ruggles's shop
are the only carb kits sold on the market that give you a new cam (premium kit).



 And here I put the cam back in location (removed) so that you can get an
feel for where it is and kinda how it works.



 Ok, once this shaft is out, and like all the others on your carb... it's
time to clean them for good operation.

 Do you have $7-$8 and a Walmart nearby?. Go buy the universal Winchester
gun cleaning kit. This deal gives you some impressive tools to ensure that
your carb will work silky smooth.

 Here I run a brush into the support areas, 30 years of old sticky goo and
cooked on dry oil are removed.



 Rifle barrels can be somewhat long so they give you a couple of extensions,
what a bargain!. Here I run through the whole length of support areas.



 We are about ready to ship this main body and air horn off to Cliff for
the proper chromatic acid dip that I cannot do yet. This gives the carb
the proper color that it had on day one, it's also somewhat of a protective
coating. Necessary for a show car, optional for a nice resto or driver.

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

Re: 1980 301T carb rebuild
« Reply #4 on: April 21, 2012, 09:48:37 PM »

jjr

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Re: 1980 301T carb rebuild
« Reply #5 on: April 21, 2012, 09:49:32 PM »
 With this carb/thread I have also added Tin-Zinc plating to my arsenal
of rebuild abilities...

 Plating parts is good for three reasons.

 1) to keep rust at bay

 2) to add a soft metal layer to a worn part in order to reduce moving friction.

 3) to look good! <grin>

 Here's the inexpensive setup from Eastwood.
 


 In this close up, I have plated the choke blade and High speed idle cam.

 The choke blade "had" rust, was blasted and now plated. Now, it will look
good for a decade or two. <grin>

 The High speed idle cam had a little wear, got blasted and now plated. It's
action will be smooth once again.



 I will be doing other parts as needed so that it will look good and move
like it's in warm butter!

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #6 on: April 21, 2012, 09:50:15 PM »

 Throttle plate shafts back in and links reattached.
 


 Throttle plate reassembled, just about done.
 
 The action on this, with the bushings installed, is super smooth!



 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #7 on: April 21, 2012, 09:51:26 PM »
 While the main body is away being colored (chromatic acid dipped, factory style).

 I am preparing parts for reassembly.

 Here's the Power Piston assembly. Since the bottom is open to vacuum and the assembly
sits on a spring, the top of the cavity needs a nice new seal. This is not included
with auto parts chain store kits usually, But Cliff sends you one.
 


 The assembly gently taps apart as shown...



 Now we can replace this tired, cooked old seal with a new one.

 Some carb parts are prone to a little rust, those get blasted and then plated.

 Here's the carb hanger comparison after the TLC:



 Many parts on Qjet's have different specs, this effects how they work. Often,
instead of a part number on small things, just a letter is used. Here's
a "P" hanger.



 In cleaning up the secondary metering rods I discovered that they were not
correct for this carb model... These are too lean for 301T.



 Here's the correct rod for the 301T:



 This is the side by side comparison so you can understand the difference...

 A bigger rod blocks more fuel, a smaller rod is richer...

 Note the tapers are carefully designed and deliberate.





 Also note that they are cleaned and polished.

 In this next shot is the primary rods and jets. The secondary jets are set, but
the primaries are screwed in. The jets are marked (hard to see) 070. And the
rod is marked 50P which I will need to confirm.



 But really, it's all marked and quite tunable.

 work continues...

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #8 on: April 21, 2012, 09:52:11 PM »

 Well... I hit a bump in the road...

 After find the wrong secondary metering rods, I went to work
verifying that the primary jets/metering rods were right.

 The jets came back stock 070's but the 50P main metering
rods were wrong. The bump I hit was that I could find the
exact GM part number, but matching the stamping was beyond what
I had reference of. Hard to imagine, I know. <grin>

 So, what did I do? I called Cliff Ruggles. During that delightful
conversation, I learned that Cliff ran and raced a few turbo cars
in his time. AND... he has helped 301T folks before.

 As I ran through a rather dry litany of part numbers, Cliff kinda
refocused me and I agreed that why chase the originals when 1980
was emissions paranoid.

 Cliff also mentioned that today's gas has less energy in it, so
it needs to richer to get power.

 Cliff is an old time Pontiac guy and not a stranger to the 301T.

 I accepted his sage advice and got richer jets and richer main
metering rods, and a better power valve spring for this build.

 This owner is getting a masterpiece is going to help this community
with a superior carb recipe.

 Cliff advised that very often the original metering rods and jets
are worn and junk. Something I hadn't realized... for literally
a few dollars you can have new, precise stuff - or turn up the
volume if you like. <grin>

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #9 on: April 21, 2012, 09:53:08 PM »
 The main castings are back! For this build, I had Cliff dip this carb
in the manner that the factory did.
 


 Bottom of main body...



 Notice that the wells have been tapted for short threaded screws and
Marine Tex applied to seal.



 Top view, main body, dipping seals float bowl as well.



 I've started adding the cleaned up pipes. *Note in this pic,
main body wasn't quite in place yet.



 There's a big gasket that fits between the throttle plate and main
body, but at this point it's fitted on correctly.



 Front view, again, I missed it not being lined up, this too from earlier
in the sequence of shots.
 


 Work will continue while we are waiting for the new jets and primary
metering rods.

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #10 on: April 21, 2012, 09:53:58 PM »
 Tuned parts arrival, New power spring, 71 Jets and 44L main metering
rods.
 


 The 50P rods that were in this carb were incorrect, replaced with 44L main
metering rods on advice form Cliff. Note the big difference!



 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #11 on: April 21, 2012, 09:54:39 PM »
 
 Going back together now...

 Throttle plate attached to main body.
 
 Note: Owner agreed that an adjustable choke was worth a few minutes
and three self tapping screws. Generally, choke setting is pop riveted
into place... Now, this owner can trim the choke as they see fit.



 Choke assembly complete. Perfectly cleaned and many parts plated, linkage
action works like it's in warm butter.



 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #12 on: April 21, 2012, 09:55:21 PM »
 I had a short day today, but we got a few things done.

 Needle valve seat (windowed version), Primary jets, idle
tubes, APT (3.75 turns as per Cliff), and idle mixture screws.



 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #13 on: April 21, 2012, 09:56:20 PM »

  The needle valve AND it's seat have to make for a nice
fit and seal. If you don't, gasoline will always flow past the valve,
over fill the bowl and then leak out and over the sides only slightly
slowed down by the gaskets.

 If you don't have a MityVac or other inexpensive vacuum tool, it's
cost now will pay you back by avoiding tons of frustration and a
potential safety hazard.



 Here's a close up of the valve in the end of the vacuum test rig.



 Now, when you get a Cliff Ruggles rebuild kit (is there really a reason
to get any other?) you get a much nicer, better flowing needle valve seat
and viton tipped needle valve. The windowed version fills the bowl more
quickly, and the inlet is larger (the way it should be).



 I didn't get the angle quite right, but you can see the obvious difference.



 Even new, these parts won't be perfect, so we must gently grind or
lap the seat so the needle valve and seat form a perfect seal. Way back
in High School, my shop teacher taught us to use valve lapping compound
to make the seat right. It works pretty well, but I use a somewhat finer
approach. Buffing compounds... I always have them on hand for other parts
and for plastic polishing, very cheap to buy.
 Rather than possibly destroy a needle valve, I use the famous Cotton
tipped applicators that CSI folks use. The soft cotton head holds a little
compound and form fits the seat and allows for excellent control.



 The applicators are cheap, and the compound sticks too... A must have!



 You don't gotta memorize which does what, every package outlines it
for you.



 Folks, the secret to your classic car running well is in the details.

 From the factory, all these cars were tuned EPA paranoid. They ran like
they had head colds. You don't have to repeat that today.

 In this thread, and build in particular, I have been showing you what
makes a difference.

 We have corrected the secondary metering rods, gotten better primary
rods and jets, and a nice high flo seat that's windowed. It's been
cleaned and every circuit clean of debris.

 Professional service on a carb is one of the many secrets to performance.
<grin>

 Back to work, there's a Pace Car waiting for this carb!
 
 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #14 on: April 21, 2012, 09:57:29 PM »

 Well... got the bottom/main body basically done today!

 Check ball, Check ball retainer, Accel well window, float and setting
including needle valve (15/32") main metering rods to assembly, new power
circuit spring and assembly into position.



 Here's a close up of the APT screw and the bar that rides on top of
it. The screw position directly lifts the entire main metering assembly.



 Float arms have notch in insert, as do main metering rods.



 New nylon retainer (white) easily holds assembly in place.



 Here's a closer shot.



 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

Re: 1980 301T carb rebuild
« Reply #14 on: April 21, 2012, 09:57:29 PM »



jjr

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Re: 1980 301T carb rebuild
« Reply #15 on: April 21, 2012, 09:58:12 PM »
 Air horn details/parts going back together...



 Air valve tension spring replaced.



 Air valve cam replaced.



 This carb may be going home next week!

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

jjr

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Re: 1980 301T carb rebuild
« Reply #16 on: April 21, 2012, 09:59:01 PM »

 Air Horn gasket in place, Main Metering assembly must be slipped
in place via small die cut through lines. Take your time.



 Check that it still moves freely after gasket installation.



 Gently ease the air horn down, all the screws go in, add the externals...



 All done and going home!!!


 
 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

Maryland Bandit

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Re: 1980 301T carb rebuild
« Reply #17 on: May 10, 2012, 07:18:17 AM »
That is one EXCELLENT tutorial on how a Q jet goes back together. This needs to be a sticky! Beautifull work Joe!

JKbride

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Re: 1980 301T carb rebuild
« Reply #18 on: July 14, 2013, 07:53:22 AM »
Wow, outstanding!
Big John
1980 Indy TA
1992 TA Convertible (Jamaica Yellow)

fiream773

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Re: 1980 301T carb rebuild
« Reply #19 on: October 01, 2013, 07:18:28 AM »
Pure, unadulterated Q-Jet porn!  Well done & thanks for posting - this is of benefit to ANYBODY willing to tackle a DIY Q-Jet build.  8-)

Life is short - Drive sideways.

Re: 1980 301T carb rebuild
« Reply #19 on: October 01, 2013, 07:18:28 AM »
You can help support TAC!