glroland

Hi everyone,

I have a 1972 LT1 that recently started jerking / hesitating on acceleration. Its mostly happening in lower gears getting up into higher RPM levels, although it will happen in 3 or 4 while approaching highway speeds as well. Just to check my bases, I replaced the fuel filter, tuned the fuel mixture at idle, ensured vacuum pressure is good/no leaks, etc. I haven't replaced the spark plugs yet (was dreading it based on some of your comments). Most articles are saying that fuel/air/ignition is the cause of this and sometimes mention fuel pump.

Any advice for a newbie? I'd love to focus on the most likely cause rather than guess (wasting time and money).

Thanks!

Dynra Rockets

Welcome.

Good luck with that as it could be several things given that info. I would start with a timing light to verify ignition is advancing though the rev range and then verify the carb accelerator pump is squirting as should. Report back if those two check out.

If you cant do that then try Roswell North Automotive at Crabapple/92. A couple of the guys there have vintage 'vettes.

MelWff

you said you have an LT-1 and you changed the fuel filter. An LT-1 has a Holley with two fuel filters one in the inlet of each fuel bowl. Did you change both filters?
Did you remove the cap and rotor and inspect them for cracks and wear?
did you check the resistance of the spark plug wires, 1K Ohm per foot of wire maximum?
did you check the resistance of the primary and secondary circuits of the ignition coil?

paul_nz

I would also check the points, condensor and dwell settings

glroland

Oops Let me get back to you.

Cap Yes, Rotor no.

Thank you for the ideas!!!! I'll get back to you soon.

63split63

How old are the plug wires ? You may want to change them .

theandies

Tell your brother-in-law not to be a jerk when riding in your Corvette.

7T1vette

Your fuel filter may be plugged up to the point that it won't pass enough fuel at WOT conditions (especially in lower gear ranges). It could well be other things, too...but that's a good place to start.

REELAV8R

I would check the timing.

glroland

Thanks for the feedback. As an update, I went through a lot of your recommendations and am currently working on the timing. For higher visibility, I posted the question to make sure I'm doing this correctly here:
https://www.corvetteforum.com/forums...post1596462579

Per the above, I replaced the second fuel filter. It was dirty but not that bad. Spark plug wires look good - I think they replaced them not long before I bought it a couple of years ago. Already said the distributor cap was good and not cracked, but I checked the rotor as well and it looks new. I'm planning to replace the ignition coil today, since they are relatively inexpensive and mine looks original (dinged up, etc).

Regarding "verify ignition is advancing though the rev range", is that a matter of watching timing while slowly reving the engine to ensure its a smooth curve with the timing values?

Regarding "verify the carb accelerator pump is squirting as should", fuel is squrting into 2 of the barrels of the carb when the accelerator cable is pulled. In my Holly, I only see 2 jets that would do this even though its a 4 barrel. Is that what you mean?

I tried Roswell North Automotive at Crabapple/92 and they didn't seem comfortable working on an older corvette. Mentioned I had heard some of their mechanics had experience with these and they weren't aware. I have been going to Peach State Classics in Alpharetta with good luck and they are going to look at this next week if I don't fix it first. I'm enjoying learning to do this on my own though.

Many thanks! I'm impressed with the community here.

HeadsU.P.

Here's two more absolutely free ideas. Remove dizzy cap. Take a "dry" paper towel without any cleansers and wipe the inside of the cap. Now look at the towel. That is called carbon tracking. Almost invisible substance that can raise havoc inside that cap, causing juice to go to the wrong plug or not at all.

Second. Follow the numbers 5 & 7 plug wires from the cap to their plugs. Don't let those two cuddle . . . . . . . (crossfire).