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1976 T/A ROUGH ENGINE- VERY ROUGH

 
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Larry
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PostPosted: Tue Apr 23, 2013 2:35 pm    Post subject: 1976 T/A ROUGH ENGINE- VERY ROUGH Reply with quote

My niece bought a one-owner '76 T/A that is pretty nice, but after sitting for many years needs work.

First order was to get it running and then all new brakes. She got it to my house so I could rebuild the #@!@#^*! Q-jet. I did and it hardly ran, and when it did, was very rough. Couldn't hardly get fuel into the bowl either.

Took the carb back off and opened up again (did I mention#@!@#^*! Q-jet?). Float and all was perfect, so we put on a new fuel pump. That helped. At least we got fuel, but still rough as a cob.

Then I smelled that sick smell of old, stale gas. I asked if she had put in new gas, and she said it was the gas that was in it... 15 years old! So we disconnected the fuel line from the tank and ran a hose from a gas can.

That helped a bit too, but it still is rougher than any engine I think I have ever worked on, spitting through the carb, backfiring, shaking like crazy.

Next step is to check the timing, but you can hardly see it on the 400 T/A with A/C. I think we will remove the alternator belt and tensioner idler pulley to see it. Oddly, if I move the distributor counterclockwise, I can stall the engine. But no matter how far I move it clockwise, it just doesn't make any difference... runs, but no rpm increase at all.

Have checked all the new wires and they are on properly. Also has new rotor, cap, and plugs.

My question is, do you think it has jumped a tooth but is just barely able to run (like it does)? Pontiacs are famous for timing chains/gears crapping out after 125k miles or so.

That is my next angle of attack, then compression test. But the engine is so severely shaking and barking, I am leaning more towards the timing. I can't imagine all the valves being so bad as to cause this, and there is not too much spitting through the carb, so intake springs aren't broken. Also, there is no lifter noise at all either.

Ideas??? Distributor gear? Cam lobes worn off?

I forgot to mention, after all of the above, we slapped on a big Holley that we know is good-- same lousy running...???

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Larry
Site Admin


Joined: 01 Jun 2006
Posts: 4768




PostPosted: Mon Apr 29, 2013 9:02 am    Post subject: Progress Report Reply with quote

Checked the timing, and it was right on the money.

Swapped out the Q-Jet with a Holley we knew worked, and it ran just as rough. Put the Q-Jet back on.

Bought a new distributor and stuck it in. Guess what? Fired right up and actually sounded smoother. Was able to finally run a bit and set carb air/idle.

It actually was able to take gas and rev. Much smoother. And, the longer it ran, the smoother it got. So, it appears the lifters were finally pumping up well and after 15 years of sitting, things were beginning to loosen up and work again.

By the time we quit, it was actually pretty darn smooth and restarting on command. We drained out the last of the old gas and will put in new stuff. Then feel safe in actually sending my niece down the road in an operational car.

One more '76 Trans Am back on the road!

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