Hey all i have a question about a zz502. the max. rpm rating is 5800 rpm is this due to the fact the cam runs out at 5800 or is this due to the strength of the engine ( rod bolts, valve train,etc) i am likely getting one and if so i will be stepping on the cam, carb and giving it a slight port clean up and i need to know if it will handle some more rpm? Thanks guys if anyone knows will they fill me in or maybe the GM fellow that replies here often can let me know. Ralph

anybody?

I'm no expert, but from what i gathered its a couple of things. One is the cam size, its not very big and there isnt much point to go over 6000. Another is valve float with the hydraulic cam. "5800 max rpm" is a way GM can cover their ass since most valve float will happen above 6000 rpm. I know for certain the engine can handle 6000+ in terms of bottom end. If you get a bigger cam, i'd suggest making sure you have a set of springs that will definatly support the extra rpms. I recall Wes Colby telling me he put in some stiffer springs and ran his once near stock 502 to 6200 without problems. He also had 1.8 rockers. Another thing to consider if you want to runner higher rpms on a regular basis, is an oil pan with a wind screen and baffles. Keeps the oil in the sump, and off the crank. Safer to run high rpm's and gives more power.

What are your ET goals?

Ralph,

I have a zz502 and although it has a lot of cubes and torque, it falls flat on it's face at 5500.....that being with the stock hydraulic roller. The max compression of the motor(9.6:1 unless you mill the heads) limits your cam choice a lot IMHO. I think it's a good street motor and sounds great, but if you are building a strip motor, then just build one from the ground up and it'll be much cheaper.

Mike

You must be running iron heads?Alum heads would bring you up to 10.6.1.A cam change would help your rpm problem.I run a 502 pushing 6,700 rpms
with-out any problems.A cam from 2500-6500 would
work good.

To be more specific guys this will be a mostly street car some track duty am hoping for an 11 sec time slip,mostly stock 67 super t-10 4:11 gears would like a 6500 shift point and i will definitely be stepping up the cam and going to 900+ cfm carb with a lite port job, maybe even a small squirt if need be thats why the concern on the bottom end. Do you guys think a cam/spring change plus what i've mentioned will do the trick i'd hate to get ate up by a rice burner.

The bottom end is strong enough to spin more RPM's. The stock cam is 224/234@050 and 527/544 lift which is a very small cam for a 500" motor (GM has to warranty them). Most people that buy the 502's swap the cam out pretty quick. It is very easy to get 600+HP by running something like 250-260@050 with 625-650lift or so and a 950carb. Try another post with cam suggestions for ZZ502, harold should give U a couple to choose from. U could also do a search for 502 cam suggestions in the performance section have read many of them. The compression wont be a problem as there are many cams designed for lower compression especially in bigger motors due to the boat guys. I have a 94 502/440HP marine motor building for my 67 chevelle only real difference is mine has cast iron SQ ports & hyd. cam picked it up for $1500

The guy helping with my resto has done a bunch of 502 conversions. The cam upgrade datapoint is exactly right. He's done 10 or 11 502 crates, and 3 or 4 have put a bigger cam in - 2 before the engine was ever fired up. Guy bought a long block and had Kenny finish it up - including a blower - no change to the bottom end. Car makes 700hp easy. I'm not saying it's good for 700hp - I don't know what the limit is. All I know is I've seen the guy light 'em up several times - he drives the crap out of that car on the street and then races now and then at Sealy or somewhere like that. As far as I know it's still running strong. Going to Katy this week to pick up my car - I'll ask Kenny.

Best,

Mike

I think the limiting factor is definitely the cam and the heavy valve train. One of the upgrades I plan to do this s[ring is a set of Comp Cams beehive springs and titanium retainers. This really helps to reduce the weight and make the valve train more stable past 5500 RPM.

Andrew

All things being equal, the 502 Chev. crate is a good engine package as is or with a little more cam. Before I would consider trying to make a 502 "radical", I would have to consider going to a Dart or Merlin Block. You can get both of these as crates in a lot of engine combos. The only advantage to the Chevy 502 is it is still a Chevrolet manufactured engine, although the heads are Edelbrock. A basic Merlin comes in at 509CI and uses all the standard Mark IV hardware.

Originally posted by driver:
You must be running iron heads?Alum heads would bring you up to 10.6.1.A cam change would help your rpm problem.I run a 502 pushing 6,700 rpms
with-out any problems.A cam from 2500-6500 would
work good. I do stand corrected, no I am running the GM Signature Series aluminum oval ports with 110cc chambers which, at that time, was the smallest chamber aluminum head that was available. Recently, I know that Edelbrock has the 100cc "high comp" heads, so yes, you can get maybe a 10:5 to 10:6 compresssion. The fact remains, the cam is too mild.

Mike

I agree there are alot of "packages" out there but there are alot of ? marks to go with them. Keep the info coming guys i really appreciate it! Ralph

Yikes - did I write that? What I meant was...

FWIW, I have done some relatively extensive investigation re "crate" motors (not just bm and wp, but the whole lot now). IMO, "crate" applies only to the big 3 - GM, Ford, Mopar - they've been doing it for a long time, tons of R&D behind the effort. Other supposed crates are really "semi-custom" builds, where there is a target parameter for every component and a general target performance range. Aside from the most basic component - the block - the rest of the components in a "semi-custom" will likely be whatever is close to spec and the mfg can get the best deal on (best profit margin).

Sooooo, if you want something with more thump than the zz502, I'd strongly recommend going to a reputable local independent. You may pay a little more or a little less, but the peace of mind is invaluable.....

Best,

The cam and valvetrain have to be the limiting factor on the rpm.

I'm using a Chet Herbert solid roller #CB6H 258..270 int.-.050-exh. .685..683 int.-lift-exh.
and aluminum BowTie heads and shift at 7200rpm. This is with a stock, untouched bottom-end.

Emil Dusek
71 Chevelle SS-504

1/8 6.6856@102.09 NA

With a cam, spring and lifter change we run the 502 to 7400 RPM in IHRA Stock Eliminator, with no other changes to the base engine.

Gary just the guy i was hoping would respond, does this mean you guys are using the stock rod bolts etc. and no porting work... what intake carb configuration are you using? Any issues with rocker stud pull out? I like what i'm hearing and i believe a zz502 will be in my future. Gary did you guys re-check clearences and or re-balance the motor or is it run as shipped and is this motor internal or externallly balanced? Thanks for your time all! Ralph

Gary you still around!

I don't know if you anyone mentioned this, but the main reason for the redline is the fact that it is a big block with a hydraulic roller, The hydraulic roller lifters are very heavy and don't rev very high, for the most part the only way to get that big block to rev higher is to use a solid roller, or a solid flat tappet if the block will accept it. Some people have good luck though and the roller hydraulic helps it rev. also another good idea was the beehive springs and titanium retainers. that could also help