Oh dear lord, what is that trend all about? That is new to me. Where was that? Around here some lifted trucks, sure. And a group of slammed ones with Mafia/Gangster somethingstupidoranother all over them, but they keep to themselves. Any cruise around here has tons of classics and customs, hot rods, street rods, antiques.

Similar experience I had with the ZZ4 on a 1961 Corvette restomod I have.
I was soo disappointed in the engine, and unwilling to go thru the head, cam changes it needs (especially on a new engine).
I drove the car to the muffler shop and back home ...and with a lot tuning had 86 miles in it when I parked the car ...never drove it again with that engine.

The short block is a good start...4 bolt, good crank and rods...after that it is a real disappointment. A cheap crate 383 will eat it alive...or it would on the one I have.
Of course like Patrick Swayze said in Road House..."opinions vary".

....."opinions vary".

Ain't it the truth though.

Last GG show I was a guy was all proud n stuff about modifying his new Vette. He successfully changed
out the floor mats. WOW. he did it in his own driveway all by himself. !!!!!!!!

This one was a first time car show at an audio/video company that installs sound systems, tint and aftermarket equipment for trucks and cars so I can understand that they would attract the peanuts. lol. Im told this trend is called the "Carolina Squat"...

I mean I love a good corvette every now and then but there a dime a dozen. If your entering a car show to win a trophy, why would you bring your stock corvette knowing there will be 15 others just like it.

As for the zz4 being a disappointment, it makes me nervous that once I get this figured out, it wont have what I want. We built a 340 for my dads 69 dodge dart awhile back (it now has a 440 with a 6 pack) and that thing ripped. It dynoed at 275hp and threw you back in the seat with 3.73 gears. As of right now my zz4 doesnt even come close.

IF I bothered with looking into my tame 700R4 2nd-3rd shift, and if I let it wind up more now that I can use the FiTech display as a tach, I would say it runs great. 1st gear really snaps back hard, and did with the 600cfm that was on it as well.

What did you find disappointing about it? Ive seen a few videos on youtube where cars/trucks with this engine are able to rip a little and others where it was a complete dog. Of course a lot of other variables like gearing for example go into this but I dont have much to compare it too other than my dads 340 dart that I drove years ago and back to my old circle track racing days as a kid. I guess I can compare it to my 2003 Avalanche 5.3L with just under 300hp...not. BTW, my avalanche would smoke my zz4 in its current state...wait. Theres an idea, i'll pull the Vortec LM7 from my avalanche, cam it and put it in the chevelle...

I have a ZZ4 that I installed back in 2006. The vacuum advance curve on the HEI distributor had too much advance (like 20 deg.) and would ping with light pedal and full throttle. It ran best with manifold vacuum. It would get too hot with ported vacuum at idle and ran rougher than with manifold vacuum. Then I installed Atomic TBI EFI years ago with an MSD box, coil and distributor, plus a Rick’s tank with internal pump and return line. I chose Atomic because it was the only self-programming EFI at the time that controlled timing. The Atomic EFI solved the pinging problem. I never could push the engine with the HEI because of the pinging, but it does seem to have more power with EFI. Still running with manifold vacuum advance internal to the throttle body (ported vacuum had the same effect as with HEI). I have full Doug’s headers with X crossover & Magniflow exhaust, serpentine accessories with AC, and dual electric fans. The rest of the drive train is a TCI 700R4 and a 3.55 12-bolt posi. The power from this setup is plenty for my street use, even with the AC on. I’ve got about 36k miles on the ZZ4.

I’ve had two problems. The timing cover gasket started leaking. Common problem. Good thing I decided to fix the leak because the oil pickup tube was about to fall off - discovered when removing the pan.

When I swapped in the ZZ4, the LS swaps weren’t popular. If I had to change again, I’d definitely go with a modern LS.

Sounds like a good setup. I like the old school setups to be honest, not into the newer fuel injection swaps.

As I said, decades ago, I worked out the distributor curves for the ZZ engines, and we did a bunch of them, as Limeworks Speed Shop used those engines exclusively for their built from scratch cars. It works, simple, low cost.

Leave initial timing and mechanical curve alone, speed up mechanical advance with softer springs, start curve 850/900 RPM's, limit 3,000 RPM's. Stock mechanical advance springs look soft, until you stretch them. Stock ZZ mechanical curve rate starts about 1,300 RPM's, limits way past 5,500 RPM's, to compensate for the ported vacuum advance curve added where it shouldn't have ever been in the first place.



Vacuum advance, set up a degrees stop to give 8 to 10 degrees, plug into full manifold vacuum source, idle timing will go to 20/22 degrees, just what that engine wants. FIXED.


Full instructions, with pics are still free, no strings, no ads, address for them is above in another response.


Don't do the mods, live with, and enjoy the over heating, poor performance and rotten fuel economy.

Now, GMPP did NO in car setup/testing/tuning with the ZZ engines, they were all done on a dyno, in which, not one has never been driven around a block, and dyno's love excessive timing and jetting, way past real world settings. The reason no vac adv was used, EMISSIONS reg's were in play, and if GM didn't do that, no engine sales in both Communist Kalifornia and Colorado. NOTHING says you can't modify after you buy it if it is installed in a pre-emissions vehicle.


I have more than 1,500 people that have done these mods to their ZZ large HEI distributors, not one has said to me that it did not wake their engine up, and make it run one heck of a lot better.

Unfortunately, the majority of this is greek to me but I sure will confer with the shop and this information...

Make a stop for the vacuum advance for the pull pin to limit travel to .110 inch. Install vac adv, plumb for full manifold vacuum, leave initial timing at 12 degrees.

Leave one stock spring on the mechanical advance, find a softer one, so the curve starts 850 RPM's, limits 3,000 RPM's, done with that.

Should run remarkably better.

Dave Ray, are you recommending 12* initial timing to get 34* (12 + 22) total at 3000 rpm?

Why not, that is how total is done.

Then, to the initial, add full manifold vacuum sourced vacuum advance of 10/12 degrees, for an IDLE of 22/24 degrees after the engine starts.

Mine seems to run better at 18 initial. I didnt try adjusting for total tho.

And what actual IDLE timing (18 is too low)? If no vacuum advance added, you have lost the war.