mcollinstn

All 502's that GM offered in "crate format" were externally balanced - just like your cracked motor.
Rotating assemblies on all GM crate 502's are forged and plenty good enough for mild supercharging.
Headgaskets need to be marine rated (unless you are strictly freshwater).

Squish height is more important than pushrod issues.
Running a squish of 0.035" to 0.045" will snuff detonation under boost much better than larger clearances. Running a 0.060" Cometic will likely give you a 0.075" or more squish depending on where your slugs deck is. My vote is zero-deck it and run .045 gaskets. THEN check where you are on your hydraulic lifter travel. If you still have more than .030" remaining lifter travel then you're good to go. If not, then put .030" shims under the rockers. Squish height trumps rocker adjustment.

Verify brass freeze plugs. If the motor comes with a water pump, you should swap it with the marine pump from the 454. The ZZ502 cam requires headers that introduce cooling water WAY FAR AWAY from the ports, or water ingestion can cause bent rods, destroyed motor, etc (which is likely what happened to the guy who had a bad experience). It's always better to match the cam to your application with a custom grind, but with the ZZ502, you HAVE to prevent water reversion or you'll lose the motor.

Your oil pressure bypass spring needs checked, and sizing will depend on whether you run the remote filter and which oil cooler you run. Chances are, the standard pressure relief spring is way too soft. The standard oil pump is a high volume, and most late model GMPP crate motors are already running welded pickups - check yours to make sure.

Always opt for the larger bore (502 over 454/496) due to the natural unshrouding of the valves. The smaller bore restricts flow out of the ports unless bore notching is used.

Aftermarket rods? Custom piston heights? Internally balanced cranks? Not unless your budget allows it and you want to push the envelope. Internal balancing is always preferred, but not necessary at rpms you'll be running.

Cast iron exhaust manifolds and a ZZ502 cam is ASKING FOR TROUBLE. It can work, but it's too close to the edge for my preferences.

Non-SC procharger oiling - not a problem. I assume your oilpan is already fitted with the return bung.. The volume of oil through the supercharger is very low, and is only enough to keep the bearings in fresh oil and to carry some of the excess heat away. The main deal here is to make certain that your idling oil pressure is above 25 psi and that you idle for at least a couple of minutes after a hard run before shutting it off. It's never going to be problematic like an air cooled turbocharger and the way those puppies can cook the oil - but the idling is still a good practice. Idle a couple of minutes after run, and on startup, idle a couple of minutes before you hammer it. If your procharger has some hours on it, go ahead and put bearings and seals in it now. Inspect the gears while you're at it, but they should be fine at your boost levels.

MC

low buck

KidNova;

A million thanks for your reply. I've had a post in the Eliminator fourm for a while and no replies. I guess anyone named "Low Buck" with a deck boat has cooties ...

The old 454mag /prchgr set up was great. Ability to cruise at low speeds with a load of passengers out on the deck. With just wifey and I behind the windshield I got a best of 76 mph gps bouncing it off the 5000 rev limiter (ran out of gas after that). Prop to go up after 502 is broke / dialed in.

I'm thinking about a new "OEM 454/502 mag efi" cam to keep the time at idle around the docks and slow passengers cruise tolerable. I'm hoping the bump up to a 502 combined with some bolt on mods. will get me an enlistment in the 80 mph club. Ok, it's a plastic pontoon

I'd prefer not to risk the reversion potential therefore some plug-n-play exh. manifold are of interest. Open for suggestions, please ...


"No one of us is as smart as all of us"

low buck

mcollinstn

You appear to be both a gentlemen and a scholar.

Kind thanks

mcollinstn

The 454/502 EFI Mag cam is WAY MILD and a NEW one is WAY EXPENSIVE.
For that same money, you can get a great custom grind and for less money you can get a plenty good catalog grind that will serve you better.

Procharged Multiport EFI motors can run a lot of cam before "behavior" of the motor becomes impolite. The ZZ502 cam we're discussing will not be "impolite" acting - it will just lurk there waiting to run your day.

HP500 or 500EFI cam is about where you need to shop. Something in that "level" of cam. If you're buying a new Merc cam, that's what I would point you towards. The Crane 731 grind is also a GREAT compromise cam.

But if you're dead set on a mild cam, then just use the one from your cracked motor. Save your $450 and send somebody a gift card that you haven't seen in a while.

MC

low buck

Well, I couldn't be more thankful for the knowledgable feedback from everyone, thanks!

It looks like the cracked block 454 Mag mpi, w/ 5# procharger is gravitating towards a "hybrid" 502 Mag mpi 5# build.

Same great 454 mag base motor except new ZZ502 short block. I had suggestions of using a 500efi cam, looked at the specs and read a little. It seems like a good application. My goal is to get into the 80mph club with this rebuild (75-76mph on gps was old best). It's an eliminator deckboat (just lost 1/2 of audience) which gets hammered for not much more than a minute here and there. I need to keep the lower rpm cruiseability for when folks are out in the wind on the deck.

If I was to use my cast iron rect. port heads w/ the 500 efi cam what upgrades to the valve train would you suggest?

-What springs? Isky 8005's? Comp Cam 929's?
-What retainers / locks etc?
-What rocker arms?
-Anything else? I don't know what i don't know .....

All input is truly appreciated.

Quote for the day: "If you learn what you need to know, and do things correctly, they will work as you wish every time"


Thanks

mcollinstn

500 EFI cam is good cam.
Both springs you mention are more than good enough - the preference usually points towards the Isky, but the Comp are fine, too. I have some springs I would price you as well.

That is enough cam that you'll want to plan on replacing (or at least removing and testing) the springs at 200 hours). Lifters as well. Speaking of lifters, that cam is a little too much lift for your stock lifters. You'll have to use (more expensive) long travel lifters, but you can still use the dogbones. They say .570 is the limit for the stock lifters, but it really depends on your particular block and cam. At any rate, you're pushing it past the "gray area" and will need the long travel lifters.

Rockers? Harland Sharp or Crane forged aluminum are plenty good enough. Stay away from Chinese rockers, and you do not need anything exotic. Standard ratio is fine.

You'll be going to new rocker studs with that change as well.

"Normal" retainers and locks are fine. If you are getting heads on your zz502, it comes with good springs and hardware. If you are reusing your 454 heads, then go with new locks and retainers from comp or crane or whoever you like. Super 7's are nice but it's not necessary.
I've got a bunch of titanium stuff if you're dead set on it.

Valves? If you want to run high boost, you'll need to upgrade your exhaust valves. If you keep the boost low and don't go nuts, your regular stainless valves will endure some decent abuse.
Examine your exhaust valves closely and look for signs of tuliping or excessive face heat. If you see any erosion or droop, then the material is not adequate for what you have been doing and should be upgraded.

mc

whoya

iTrader: (1)

Im running a 741 cam for at least 7 years now with the stock crate GM Gen 6 roller lifters and no issues.

dba900

Really interesting thread here and I thank everyone for their valuable insight/advice. Since reversion is an issue with stock ZZ502s, what headers would the wiser minds recommend? Or, is it better to just get any decent aftermarket header and get a marine-grind cam?

low buck

Dba900

Good question, I hope there are many replies. It seems as with everything there are plenty of gray areas ......

I'm leaning towards being conservative on the cam for my efi 502. The reversion thing is scary !!!! Still researching aftermarket exhaust manifolds, if nothing else, for weight reduction.

Any positive / negative recommendations for "plug-n-play" replacement exhaust manifolds for the 454 / 502 meag efi's?

thanks all ...

Nordicflame

iTrader: (4)

Low Buck,
Please see PM regarding a 500EFI short block pan to lifters I'm finishing up...
Thanks,
Dave