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Hi guys,

I've recently been offered to buy a zz502 with edelbrock aluminum heads. The seller claims it is a zz502, but before I go see it I would like to know how to differentiate it from the standard 502 H.O.


Are there any number stampings or differences that show it's a zz502 rather than a 502 H.O.? Can anyone help?

Thanks,
 

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Short blocks are the same but the ZZ has GMPP alum heads not edelbrock.

Also want to make sure your actually getting a HO/ZZ shortblock. There may be some truck short blocks with flat top pistons and small cams floating around out there.
 

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Think the only difference ho 502 vs zz502 shortblock is different cam.
 

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1969 Chevelle 2 Door Sport Coupe Malibu COPO clone
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Hi guys, I've recently been offered to buy a zz502 with edelbrock aluminum heads. The seller claims it is a zz502, but before I go see it I would like to know how to differentiate it from the standard 502 H.O. Are there any number stampings or differences that show it's a zz502 rather than a 502 H.O.? Can anyone help? Thanks,
:cool: It's a good idea to ask for help: a buddy of mine bought a 70 Monte with what he thought was a high performance "502." Unfortunately he didn't do his homework and he ended up with a HT 502 (or some such non-muscle 502 engine). There were at least 3 versions of the 502's: HT502 (a "truck" crate engine with peanut ports), 502 HO, and ZZ502.

There's some good info here: Big Block GM Engines | GM Performance Engines | 454 502 572 Chevy Crate Engines | GM Crate Motors

Do a search of "ZZ502 PDF" and you should find a PDF from Chevrolet Performance covering the ZZ502 engine and what to look for.

As pointed out above, the real ZZ502 would have GMPP/CPP Heads and they'll be stamped as such. Edelbrock made the heads for Chevrolet so the Edelbrock heads they should be as good as the heads that Edelbrock made for GMPP/CPPDEPENDING on which Edelbrock heads your seller put on the short block. You'll want to see the receipt to learn which heads they are (some have 110 CC combustion chambers and some have 119 CC combustion chambers...).

AND to beat what should be a dead horse: STAY AWAY FROM THE 454 HO and the ZZ454.
 

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I would stay away from the 502 also. The GM crate engines are junk.
I have a ZZ502 crate engine. I agree with you. Durability or oil usage is not a problem but the valvetrain is crap. I have put thousands more into an already pricey engine to get an 11.45 timeslip. Better off getting an engine built or buy a crate engine from a reputable builder. ZZ502 has stamped rocker arms, mild cam, vac carb, all needed replacing.
 

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I had the truck version of the 502. Same bottom end parts (cranks, rods, pistons, etc.). camshaft was the only difference. I would not hesitate to buy a truck version, use it as a leader advantage for negotiating.

A lot of negative comments on a GM 502 but after running mine on boost given the fact it had over 3000hrs on the engine without a hiccup, I would definitely recommend this motor As a purchase for anyone.
 

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I have a ZZ502 crate engine. I agree with you. Durability or oil usage is not a problem but the valvetrain is crap. I have put thousands more into an already pricey engine to get an 11.45 timeslip. Better off getting an engine built or buy a crate engine from a reputable builder. ZZ502 has stamped rocker arms, mild cam, vac carb, all needed replacing.
There have been a few guys on here that have run low 11's with the stock ZZ502.

Why would you need an exotic valvetrain with a cam with less than .550" lift ?

That cam is great for the street. Not everyone wants pathetic gas mileage and a rough idle. Just keeping things in perspective. :wink2:

I've heard a lot of criticism of the 850 vacuum carb, but you can order the engine without it.
 

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I would stay away from the 502 also. The GM crate engines are junk.
Most of the GM crate engines need to be blueprinted as they were built for streeting around town not drag racing. My old service manager is on his 2nd 502 in his Nova and at the track it's a pig. The 502 needs a better cam for sure and with getting the clearances right the engine will perform pretty good. Heck back in the mid 70's everyone I knew that bought an LS7 had to go through them as they were put together very badly back then.
 

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Most of the GM crate engines need to be blueprinted as they were built for streeting around town not drag racing. My old service manager is on his 2nd 502 in his Nova and at the track it's a pig. The 502 needs a better cam for sure and with getting the clearances right the engine will perform pretty good. Heck back in the mid 70's everyone I knew that bought an LS7 had to go through them as they were put together very badly back then.
Mine was kind of an impulse purchase as a local bodyshop ordered it and the customer could not pay so I got what I thought was deal. Friend who owns a speed shop told me not to. Should have listened. New Straub cam, morel lifters and stiffer springs in it now. Just have to put it back in my 69SS.
 
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