1972 350 cant go too fast

[zepelak]

my 72 is having trouble going faster than 60mph, weve replaced distributors, rebuilt carbs, and changed the timing chain.

we dont know what to do, anyone heard of this problem? i could use some help

[Big Dan58]

If you have an automatic transmission, you might have a plugged filter. Replace the trans fluid and filter. I had a `68 GTO with the same problem and replaced it and that solved the problem. Mine took a few extra seconds to shift into gear from neutral. The fluid wasn’t passing too well.

[AKWE-gt]

Originally Posted by zepelak

my 72 is having trouble going faster than 60mph, weve replaced distributors, rebuilt carbs, and changed the timing chain.

we dont know what to do, anyone heard of this problem? i could use some help

maybe the timing marks on the cam and crank aren't lined up. had someone rebuild one of our race engines, lined the up the wrong marks and the engine wouldn't rev higher than 4800rpm. what is the engine doing ie: stumbling or hesistating?

[mike_24_oh]

i had a 1979 chevy truck that done that it had a 454 it was the muffler it was cloged you might take a look at that

[zepelak]

no it isnt the mufflers, ive gone through two of them and the problem still persists, infact the problem was the reason why the mufflers had to be changed. I dont think the problem with the gto is the same problem because i dont have any trouble reving the engine past a point, if it's in neutral or first gear i can get all the way to 5000 (then i shift or let off).

No, the problem is that when i go out for a drive and i get to the speeds 60-80 the car starts sputtering, and the tachometer starts jumping arround everywhere. If i keep trying to accelerate the car wont go any faster and it eventually backfires (which is what took out the old mufflers). We've changed all the parts we thought could be causing this problem (distributor points, after that failed: changed the distributor to a hei, then we changed the plugs and wires, then we changed the fuel pump, then the timing chain, fuel filter, rebuilt the carburator, and looked at the valves). The only thing left we havent changed is the cam, but many people tell me that wont do anything to solve this problem (yet they cant tell me what will). So basically I cant think of anything if switching out the cam doesnt work. Anyone have any ideas before i have to do all the work that goes along with the cam?

[dolluper]

Make sure your vaccum advance is working right , if that was a used distributer make sure the shaft is not binding on the bushings common prob wont advance properly

[archery300]

I'm having a similar problem with a 66 cutlass I just bought with a 70=455 in it. They also changed to a later model HEI. I was told today that the advance, vacuum and mechanical probably aren't working right. the vacuum line is on the wrong carb outlet and the mechanical is working hardly at all. I'm going to change it out tomorrow, as I'm convinced that it has to be a timing problem to get backfires. Mine is worse cold when I first start it up, but won't rev under load. For yours to sputter and have the tach bounce around, you might have an intermittent short in your electrical to the tach or distributor. Check your wiring to both.

Originally Posted by zepelak

no it isnt the mufflers, ive gone through two of them and the problem still persists, infact the problem was the reason why the mufflers had to be changed. I dont think the problem with the gto is the same problem because i dont have any trouble reving the engine past a point, if it's in neutral or first gear i can get all the way to 5000 (then i shift or let off).

No, the problem is that when i go out for a drive and i get to the speeds 60-80 the car starts sputtering, and the tachometer starts jumping arround everywhere. If i keep trying to accelerate the car wont go any faster and it eventually backfires (which is what took out the old mufflers). We've changed all the parts we thought could be causing this problem (distributor points, after that failed: changed the distributor to a hei, then we changed the plugs and wires, then we changed the fuel pump, then the timing chain, fuel filter, rebuilt the carburator, and looked at the valves). The only thing left we havent changed is the cam, but many people tell me that wont do anything to solve this problem (yet they cant tell me what will). So basically I cant think of anything if switching out the cam doesnt work. Anyone have any ideas before i have to do all the work that goes along with the cam?