[79TA455]

Ok, so I sold the '81 Trans Am a few years ago and picked up the '76 and I have been trying to take it to the track but have not had the time until a couple of weeks ago.

Seat of my pants, I thought this car was faster but times prove me wrong. The '81 had a stock '78 400 with 3.08's and it ran 14.5 (best I recall) and the '76 ran a best of 14.9@93 mp/h with a stock (except intake) 400 and 2.73 gears. All night it was pulling around 15.2's and this is all with an outside temperature of around 86F.

The '76 is slower but it bogged something awful coming off the line; did not matter if I brought it up to the stall, did a burn out, did not do a burn out etc. Only thing I can think is carb. Any thoughts?

Also, was not sure where to post this so started here.

[gtofreek]

If you have a Q-jet carb, check the secondary air valve. It should have some spring tension to it, and snap back shut if you tap it with your fingers. If it is loose[ flap pops open easy, but has very little tension closing it], it will make it bog bad. There is a small 3/32" Allen head set screw to lock the adjustment screw in place. The 3/32" Allen head screw faces down, toward the intake. On the side of the carb, where the air valve shaft comes through the side, you will see the slot of a screw. Hold that screw, and loosen the 3/32" set screw under it, and turn the adjustment screw clockwise, until you get some tension. Maybe half turn once the air valve closes. Cliff can probably tell you better on the adjustment. But I set them so the valve snaps shut good with spring tension, but not too much as the valve will have a hard time opening, which will delay opening.

[79TA455]

Thanks gtofreek. It is the stock Quadrajet so I will check that.

[prostreet64]

You probably gave up a little bit with the 2.73 vs. 3.08 gears, but I imagine the difference in e.t. is likely due to the 'tune' on the '76, and the carb in particular. The bog may well be in the secondary air flap not opening at the right time. It is an easy adjustment but you may have to play around with it a little bit to dial it in. I would start with a setting of 1 to 1&1/2 second opening and see what that does. Also, have you checked the timing? And you mention a non-stock intake; what one do you have?

[79TA455]

Originally Posted by prostreet64

You probably gave up a little bit with the 2.73 vs. 3.08 gears, but I imagine the difference in e.t. is likely due to the 'tune' on the '76, and the carb in particular. The bog may well be in the secondary air flap not opening at the right time. It is an easy adjustment but you may have to play around with it a little bit to dial it in. I would start with a setting of 1 to 1&1/2 second opening and see what that does. Also, have you checked the timing? And you mention a non-stock intake; what one do you have?

I have not checked the timing on the car since I purchased it. I will have to have a look at the intake when I can get to the car (tonight), unless I remember before then. Might be an RPM Performer with the water cross-over separated.

The other thing I forgot to mention is that it falls on its face a bit once it hits second.

[steve25]

If the motor has more than 30k original miles on it and you have not replaced the timing chain your just kidding yourself and wasting money by taking it to track and looking for good numbers!!!!

The rpm manifold with stock heads will only serve to slow your 60 ft times with stock heads and those under 3.42 rear gears!

[Blued and Painted]

14.90's sounds about right for a low compression smog engine with a highway gear set. I dont believe a new chain set would net more than a 1/10th.
An increase of power without changing hard parts will be found in the mechanical advance curve and a correct air/fuel ratio.
Also look for exhaust down pipes being smashed flat where they turn back.

[Doug Hopkins]

Gearing could be worse than you think. 76 Trans Am gearing with the 400, auto. and AC was 2:41. 3:23 gears would wake it up along with good advance curve, good fuel pressure and little carb tuning. Make sure you have an extended tip plug in it. The chambers on the 76 head are huge and I had issues with non extended tip plugs with these heads.

[79TA455]

Originally Posted by Doug Hopkins

Gearing could be worse than you think. 76 Trans Am gearing with the 400, auto. and AC was 2:41. 3:23 gears would wake it up along with good advance curve, good fuel pressure and little carb tuning. Make sure you have an extended tip plug in it. The chambers on the 76 head are huge and I had issues with non extended tip plugs with these heads.

Yes, the car came with 2.41's but a previous owner put in the 2.73's; they are still a dog but they are great on the highway.

What plug would you recommend?

[Doug Hopkins]

Originally Posted by 79TA455

Yes, the car came with 2.41's but a previous owner put in the 2.73's; they are still a dog but they are great on the highway.

What plug would you recommend?

An AC R45TSX or any plug in that equivalent.

[NeighborsComplaint]

In addition to the secondary flap causing the bog, you may have a fuel delivery issue with the car falling flat on its face at the top of first gear as it upshifts to second. The gas tank pickup sock could be clogged, same with the filter at the carb.

[ta man]

Originally Posted by Doug Hopkins

An AC R45TSX or any plug in that equivalent.

Use a R45TS gap to. 045 not the recommended. 060 R45TSX...

[77 TRASHCAN]

Originally Posted by ta man

Use a R45TS gap to. 045 not the recommended. 060 R45TSX...

X2 TSX plug is an emissions crutch.

If the carb has the O.E. tune in it, it's needs some massaging that will help a bunch.
Send Cliff your carb number, tell him what you are doing. He will send you all the parts you need, to rebuild and tune it correctly the first time. Get his book also.

[Squidward]

Originally Posted by steve25

If the motor has more than 30k original miles on it and you have not replaced the timing chain your just kidding yourself and wasting money by taking it to track and looking for good numbers!!!!

The rpm manifold with stock heads will only serve to slow your 60 ft times with stock heads and those under 3.42 rear gears!

There is no such thing as a wasted day at the track looking for ANY numbers!

Either get out the money cannon and start blasting hot sticky gobs of cash, or play with what you have and chase 1 or 2 variables at a time.

[pontibeast]

Originally Posted by ta man

Use a R45TS gap to. 045 not the recommended. 060 R45TSX...

With a MSD 6AL and a high power coil do you think it still is better to leave it at .045?

[Cliff R]

"The '76 is slower but it bogged something awful coming off the line"

Good news that you are using the factory q-jet. The bog is EASY to correct, and those are excellent carburetors. Here's a clip of the same type of carb on my engine at the track.

https://www.youtube.com/watch?v=6zVdoLR-VzM

It's a stock 1977 Pontiac carb, with a few high performance parts and custom calibrated exactly for the application........Cliff

[Blued and Painted]

the delco x plugs with there .065 gap was the main cause for holes burnt in factory hei rotor buttons. And if you adjust the gap to .045 the ground strap electrode will be to long.
This brings up side gapping the plug and why i wont use two or three ground strap plugs. IMO Snake oil.

-- http://www.eatonbalancing.com/blog/2...-side-gapping/ --

[ta man]

Originally Posted by Squidward

There is no such thing as a wasted day at the track looking for ANY numbers!

Either get out the money cannon and start blasting hot sticky gobs of cash, or play with what you have and chase 1 or 2 variables at a time.

I agree ..you have a baseline to start with and tune from there..check the total timing those low compression motors love a lot of timing in the 38 to 40 range,learn to fine tune the secondary air flap door,fresh set of plugs.What intake is on it?What rpm were you shifting at?

[HydroBob]

make sure the accelerator pump is working properly.

[andrewb70]

This reminds me of the time when I took my 1970 GTO to the track for the first time. It felt super fast on the street with the 400 Pontiac, M22 muncie and a 3.31 rear gear...

I ran 15s @ less than 90 mph and that was when I decided to do something else.....

Andrew