Gm oe steel cam regrind limits.

[Bill Chase]

I have an l31 vortec cam, some lobe pitting from sitting with a blown head gasket the oil was drained, but not flushed. 5 years later it has some definite pitting, maybe .005-.010 deep on about half of the lobes. Just curious what, if any, performance can be had regrinding this core. If it could be ground to the zz4 cam spec or close and be reliable it may be a good option for me.

[CamKing]

You can add about .020"-.030" lobe lift, add about 10 degrees of duration, and move the LSA about 2 degrees.

[skinny z]

You can add about .020"-.030" lobe lift, add about 10 degrees of duration, and move the LSA about 2 degrees.

Can the same said for an off the shelf aftermarket hydraulic roller?
Or is it spec specific?
As an example, COMP XFI:Int. 274/224, .358" lobe, Ex. 282/230, .355" lobe. 110 LSA.
Could the duration split be tightened up and possibly ground to a 108 LSA? Bring the intake side closer to 280-282? The lobe lift is suitable enough.
And if I may ask, what is the cost of a regrind?

[CamKing]

It's cam core specific. Each cam core part# is roughed in to a given lift, duration, and LSA, then heat treated a given depth. Some have a very deap heat treat, some do not.
I have no idea what comp uses for cores, so I have no idea how much they can be changed.
The GM O.E. cam cores, I'm very familiar with, so I know how much they can be changed.

[Bill Chase]

It's cam core specific. Each cam core part# is roughed in to a given lift, duration, and LSA, then heat treated a given depth. Some have a very deap heat treat, some do not.
The GM O.E. cam cores, I'm very familiar with, so I know how much they can be changed.

Curious Mike, can the same be said for some of the gmpp cams? like the old zz4, zz502, etc? i picked up a used zz4 at a swap meat back this spring for beer money basically. It's rough ground between the lobes and bearing journals, but definately a steel core. Maybe from when Crane ground them for gm? Only markings on the end "071" rough measured and its definately zz4 lobe lift and has the fuel pump lobe.

[ProPower engines]

It's cam core specific. Each cam core part# is roughed in to a given lift, duration, and LSA, then heat treated a given depth. Some have a very deap heat treat, some do not.
The GM O.E. cam cores, I'm very familiar with, so I know how much they can be changed.

Curious Mike, can the same be said for some of the gmpp cams? like the old zz4, zz502, etc? i picked up a used zz4 at a swap meat back this spring for beer money basically. It's rough ground between the lobes and bearing journals, but definately a steel core. Maybe from when Crane ground them for gm? Only markings on the end "071" rough measured and its definately zz4 lobe lift and has the fuel pump lobe.

I have a take out from a ZZ-502 and it has a cast rear journal and dist. gear section pressed and pined.
But its more gold color compared to the rough machining in the pic.

[Bill Chase]

It's cam core specific. Each cam core part# is roughed in to a given lift, duration, and LSA, then heat treated a given depth. Some have a very deap heat treat, some do not.
The GM O.E. cam cores, I'm very familiar with, so I know how much they can be changed.

Curious Mike, can the same be said for some of the gmpp cams? like the old zz4, zz502, etc? i picked up a used zz4 at a swap meat back this spring for beer money basically. It's rough ground between the lobes and bearing journals, but definately a steel core. Maybe from when Crane ground them for gm? Only markings on the end "071" rough measured and its definately zz4 lobe lift and has the fuel pump lobe.

I have a take out from a ZZ-502 and it has a cast rear journal and dist. gear section pressed and pined.
But its more gold color compared to the rough machining in the pic.

the vortec cam, and this zz4 cam definately dont have a cast distributor gear. makes me wonder how old it is.

[ProPower engines]

This engine was purchased in 2019 and ran briefly in a camaro.
It was pulled and the hyd. cam was pulled and a solid Isy roller and related valve train updates were done.
Don't know the production date but up here most stuff don't sit long at the local dealers show rooms before they are gone.
But I did credit my customer $400 for the cam and lifters and hold down hardware as solid tie-bar lifters went back in.
I figured it would be a nice update for a 454.

[CamKing]

It's cam core specific. Each cam core part# is roughed in to a given lift, duration, and LSA, then heat treated a given depth. Some have a very deap heat treat, some do not.
The GM O.E. cam cores, I'm very familiar with, so I know how much they can be changed.

Curious Mike, can the same be said for some of the gmpp cams? .

Yes.

[1980RS]

On my street car I laid down 231hp at the rear wheels with the L-31 cam which I though was pretty respectable. Later I replaced it with the LT4 Hot Cam, it was like I put a 125hp bottle on the 350 engine.

[CamKing]

On my street car I laid down 231hp at the rear wheels with the L-31 cam which I though was pretty respectable. Later I replaced it with the LT4 Hot Cam, it was like I put a 125hp bottle on the 350 engine.

Yea, and the hot cam is a POS, compared to anything designed this century.
We have a few circle track classes that have to run the GM Hot Cam, so I designed a cam with the same lift, and duration at seat, .050", and .200".
With all the same specs as the Hot Cam, mine picks up close to 20 ft/lbs.

[1980RS]

On my street car I laid down 231hp at the rear wheels with the L-31 cam which I though was pretty respectable. Later I replaced it with the LT4 Hot Cam, it was like I put a 125hp bottle on the 350 engine.

Yea, and the hot cam is a POS, compared to anything designed this century.
We have a few circle track classes that have to run the GM Hot Cam, so I designed a cam with the same lift, and duration at seat, .050", and .200".
With all the same specs as the Hot Cam, mine picks up close to 20 ft/lbs.

If the Hot Cam was on a 106 lca it would be a lot better of me.

[F-BIRD'88]

So if you want to pump up the torque a bit with the GM Hot Cam what happens if you simply advance it a bit more..? 20 ft/lbs in the low/ mid range?

[Walter R. Malik]

We had a deal with the local scrap yard that we would buy the cam from any LG4 305 engine from the 80's and and early 90's with a hydraulic roller.
That was the regular 305, not high performance, because that cam had a 109 separation and was really good for regrinding.

The Ford 302 "Crown Victoria" cam had a 107.5 separation and great for regrinding; however it had the regular 302 firing order, not the HO.

[CamKing]

On my street car I laid down 231hp at the rear wheels with the L-31 cam which I though was pretty respectable. Later I replaced it with the LT4 Hot Cam, it was like I put a 125hp bottle on the 350 engine.

Yea, and the hot cam is a POS, compared to anything designed this century.
We have a few circle track classes that have to run the GM Hot Cam, so I designed a cam with the same lift, and duration at seat, .050", and .200".
With all the same specs as the Hot Cam, mine picks up close to 20 ft/lbs.

If the Hot Cam was on a 106 lca it would be a lot better of me.

That would be better, but the racing classes that mandate the Hot cam, check the lift, duration, and lobe centerlines.
I had to design a cam that would pass tech, and still make more torque.