Replacing Cam on a 502?
Thread Starter
Drifting
Joined: Aug 2001
Posts: 1,606
Likes: 14
From: Vacaville, CA
Replacing Cam on a 502?
I have a steel head crate 502 HO roller motor with less than 400 miles on it. The motor peters out at a measly 4,000 RPM and has little top end HP. 
I believe it has the milder; 211*/230*@0.50 & .510/.540 lift cam.
The ZZ 502 has a 224*/234*@0.50 & .527/.544 lift cam.
I am planning on replacing the cam with the ZZ 502 cam to get more top end HP. It appears that the ZZ 502 short block is identical to mine. The heads are completly different as they are aluminum and give a 9.6:1 compression ratio as my steel heads are only 8.75:1.
A friend states that I should replace the roller lifters to "match" the cam. I want to keep this mod as low budget as possible. I can see replacing the lifters if changing to a Comp or Crane cam to match, but being both GM cams and the lifters having less than 400 miles on them is this really necessary?
Also, does anyone know if the ZZ 502 cam would work with the slightly lower compression heads?
Thanks!
I believe it has the milder; 211*/230*@0.50 & .510/.540 lift cam.
The ZZ 502 has a 224*/234*@0.50 & .527/.544 lift cam.
I am planning on replacing the cam with the ZZ 502 cam to get more top end HP. It appears that the ZZ 502 short block is identical to mine. The heads are completly different as they are aluminum and give a 9.6:1 compression ratio as my steel heads are only 8.75:1.
A friend states that I should replace the roller lifters to "match" the cam. I want to keep this mod as low budget as possible. I can see replacing the lifters if changing to a Comp or Crane cam to match, but being both GM cams and the lifters having less than 400 miles on them is this really necessary?
Also, does anyone know if the ZZ 502 cam would work with the slightly lower compression heads?
Thanks!
Pro
Joined: Nov 2007
Posts: 710
Likes: 0
From: Northern Florida
What youve confirmed is, your 211/230 cam is really all about low end torque ; with a 502 cid, youve got the inherent low end torque capability already to get you off the line quickly (especially if you have a higher numerical Rearend) ....so you need a cam selection based on strong mid to upper range coming in around 2500-2800 rpms or so. I would consider a roller cam with matching roller lifters in the vicinity of 240/250 duration if you arent too concerned with a noticable lope at idle . Ive got a built 468 cid / 540 h.p. / 600 tq 1970 Vette with stock 336:1 rear for street only, that provides super low end torque with mighty strong pull to redline using a Lunati Roller Cam 230/242 duration , .575.595" lift, 112 lsa with fairly decent street manners (AirGap dual plane Intake, EDL alum. heads , 800 cfm Mighty Demon Carb with annular boosters) --- the thing is a real rocket .
Pro
Joined: Nov 2009
Posts: 684
Likes: 0
From: Alberta
I'd look at putting in thinner head gaskets and/or milling the heads FIRST and then a choose a better cam than the ZZ502 once you figure out how much clearance you've got to do this, if any. Try and get some of that compression back to help you with the bigger cam specs........reason is I was looking at buying a ZZ454 and could have gotten it up to a still pump gas driveable 10.5 - 1 (that's a 30-40HP gain right there before my planned cam swap) doing exactly that (and it was easily doable as well according to some of the more knowledgable guys here) but finally decided to go a different route when the time comes.
I know you mentioned budget and I can certainly respect that since I am operating under one as well.......so if that's not in the budget, I'd still get new lifters and the correct valve springs (you'll need those) if it was me, just to be safe.......the cam will probably work fine IMHO.
So, since you gotta buy lifters and springs to go with the cam, might as well get a complete kit since you are almost there already, and just choose one with even better specs, as much as the lower compression will let you of course.
It's a slippery slope eh ?
I know you mentioned budget and I can certainly respect that since I am operating under one as well.......so if that's not in the budget, I'd still get new lifters and the correct valve springs (you'll need those) if it was me, just to be safe.......the cam will probably work fine IMHO.
So, since you gotta buy lifters and springs to go with the cam, might as well get a complete kit since you are almost there already, and just choose one with even better specs, as much as the lower compression will let you of course.
It's a slippery slope eh ?
Last edited by 10caipirinhas; Jan 5, 2010 at 04:46 PM.
Le Mans Master
Joined: May 2003
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Stock roller lifters....OK -IF you don't go over .555 lift. Then they have to be replaced or your 'Dogbones' will be rattling!!!
Richard
Richard
Intermediate
Joined: Jan 2010
Posts: 37
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since this is a roller cam set up, yes you can use the lifters you have now, roller cams are billit or harded steel. the lifters do not mate like a flat tappet cam does. but do check the springs for spring bind, or other parts in the valve train will brake, push rods, rocker arms ect..
