ZZZ Engine Red Line?

[toms71elko]

I have an early ZZZ 350 and wonder what redline was for that engine. Long Tube headers, aluminum heads, hi rise, etc. This was a transplant so the stock tach shows 5000.
Also, does anyone know the original hp rating for this engine?

Thanks!

[MagicRat]

They only made about 1200 of these, a nice pretty rare piece.

345 hp,

370 ft-lbs at around 3200-4400 RPM

IMO since the torque drops off past 4500 rpm, there probably is not much use revving it above 5k rpm, so use that as the redline.
At that point, you'll probably go faster by upshiftng anyways.

Besides, IMO a 5 k redline is pretty conservative, but safe.
There is not much point in risking scattering such a nice piece.

[toms71elko]

THANKS MAGIC RAT! I've thought about going through it as it has an annoying knock sound that reminds me of tappits. We've taken the lifters and rods out of it and checked for wear but they seem pretty solid. When I got it it had an old and very large Quadrajet on it. I've since gone to an easier to maintain Edelbrock 600 and it runs much better. (Sorry Quad guys!) Its still strong enough to burn the 275 60 15 tires off my 71 El Camino so I don't think the problem is in the lower end. It's not very loud, but I know the sound and it drives me crazy.

Its hooked up to a 350 trans with shift kit and 12 bolt posi. Since it runs at 2-1 ratio mph to rpm in third gear...90mph = 4500 rpm someone told me I probably had 3.73 gears?

[MagicRat]

I think the 3.73 estimate is correct.

Does the noise go away somewhat when the engine warms up? These engines had hypereutectic pistons (apparently, GM's first use of the type).
These pistons expand more than a typical cast piston when they warm up, so the piston-to-wall clearance (when cold) is greater than on a normal engine. This produces considerable piston slap when cool with a resulting tapping/rattling noise.
However, the pistons expand as they warm up and take up this excess clearance and should eliminate most of the noise.

If the sound is consistent, hot or cold, perhaps some investigation is in order - you may have a collapsed pistons skirt, etc.

[toms71elko]

No, its pretty consistent, although at time it seems a little quieter than others. It reminds me of a noisy lifter. One mechanic suggested it might be a bad cam bearing but since I'm not ready to tear it apart I just figured I'd live with it. It is noisier when idling or when you let off the accelerator. It just sounds kind of loose to me.

[MagicRat]

Originally Posted by toms71elko

It is noisier when idling or when you let off the accelerator.

Hmmmmm ......... that sounds like something in the reciprocating assembly. Sometimes piston slap or a loose wrist pin quiets down when under load.

[toms71elko]

They only way to know that is to pull the pistons? Thanks again for all the help!!!!