replacement Cam

[Cudadrag]

Looking to replace Mopar Purple grind P4120663 cam. (312 dir .590 lift) in 451 B-block stroker motor. After replacing 452 steel heads (Open 81cc) with B1 (Closed 68cc) Guess what happened? Mopar cam and lifter damage. B1 springs (Comp 928) Seat load: 160@1.880", Open load: 383@1.250" are designed for .590 to .650 lift cam. My tired Mopar .590 lift cam ground a couple lifters.

I am looking for replacement. A roller option is not out of the question but a stronger Mech/solid Flat tap would due.

My primary concern is that I am using stock forged 383/400 rods and was told .590 lift is about as high as you should go due to clearance issues. (Though it appears a higher lift would work.)

All open thoughts are welcomed.

[toad490]

Your going to have to check your valve to piston clearance. The depth of your valve pockets is going to be what determines your max lift, rod length has nothing to do with it, your pistons will have a different pin location than stock or should.

[toad490]

http://cranecams.com/?id=2&show=faq

What is a Quick Way to Check Valve to Piston Clearance on an Assembled Engine?

Low tension checking springs, Part Number 99881-2, must be used (instead of your normal spring) to mock up your valve train and to check the piston to valve clearance on the engine. Assemble the valve train and verify correct lifter preload or valve lash. By mounting a dial indicator on the cylinder head with the plunger?s tip on the valve spring retainer, you can quickly check the clearance.

Hand rotate the engine through a complete cycle (two rotations of the crankshaft), stopping at several points before and after Top Dead Center (T.D.C.) to check the valve clearance. The least amount of clearance will usually occur between 15 degrees before T.D.C. and 15 degrees after T.D.C. This also provides a graphic illustration that gross valve lift does not determine piston to valve clearance, as the piston is fairly far down in the cylinder when maximum valve lift is reached.

By pushing the rocker arm down with your finger, the valve will contact the piston. The amount of movement shown on the dial indicator is the valve clearance at that point of engine rotation. Rotate the crankshaft a few degrees and re-check the clearance. As the piston moves through this area, the dial indicator reading will lessen, then become larger as you rotate the engine past the critical point. The shortest reading you get is the actual valve to piston clearance.

What is the Critical Point of Crankshaft Rotation for Checking Valve to Piston Clearance?

The critical point for both valves is the ?Overlap Period? as the exhaust cycle is ending and the intake cycle is beginning. You must start checking the clearance before and continue after T.D.C. on both the intake and exhaust to be sure you have the correct readings through the overlap period.

You can find all the tools required for checking valve to piston clearance (as well as degreeing a cam) in Crane Cams? Tune-A-Cam Kit, Part Number 99030-1.

[rampage_82]

Man I would definately suggest you go ahead and pull the bottom end apart and clean everything... That was how I destroyed my 440, was from a damn wiped cam. Also I would also say that the Roller will make more power for you, as well as act a lot nicer than the .590 cam. Heck even the street rollers will make more power, such as the Comp 308R or even the 292XR which is going to be my choice for my stroker in my shop...

[Cudadrag]

Originally Posted by toad490

Your going to have to check your valve to piston clearance. The depth of your valve pockets is going to be what determines your max lift, rod length has nothing to do with it, your pistons will have a different pin location than stock or should.

Thanks Toad.. Actually I am aware of valve clearance and the centerline of this clearance. What I was told (Have not seen myself) is that because of the stroke diff and that the stock rods are so thick they actually can come in contact with a cam lobe of a high lift cam. I guess it's why many use those thinner Chevy rods in this type of stroker setup. As I mentioned I cannot see this. I looks there is room. But now that Comp Cams has gotten back it will be a mood point. After reviewing my engine specs they recommend a custom grind cam that is actually alittle smaller then the .590 lift My Mopar cam was. Their numbers say .580. (I guess the Mopar cam was pretty close.) also they recommend a longer duration (Was 312 and they recommend 278.) I think I am going with their grind.

Also yes I am cleaning and freshening the motor (New rings and bearings.) The cam shavings went everwhere. The crank and rods look good but will have them re-balanced. No sense in half ass.



Thanks again!

[toad490]

I was told the same thing with mine, and it's a 4.25 stroke, stock journals and big aluminum rods with a .731 lift and they cleared. I don't know for sure but I think you'd have to get above a 4.5 stroke before it'd be a problem. .02

[JVMopar]

Cudadrag- I don't know where you get your machine work done, but seeing that your in Maple Grove I highly suggest Wheeler Racing Engines in Blaine, mn. He specializes in Mopar Hemi and RB and of course does other engines as well.

[rampage_82]

Originally Posted by toad490

I was told the same thing with mine, and it's a 4.25 stroke, stock journals and big aluminum rods with a .731 lift and they cleared. I don't know for sure but I think you'd have to get above a 4.5 stroke before it'd be a problem. .02

Or go to the 3.38 Stroke, then the duration becomes very tricky... because the pistons just don't get out of the way fast enough... LOL

[toad490]

Originally Posted by rampage_82

Or go to the 3.38 Stroke, then the duration becomes very tricky... because the pistons just don't get out of the way fast enough... LOL

We're talking about between cam lobes and the big end of the rods..... LOL

[rampage_82]

Originally Posted by toad490

Your going to have to check your valve to piston clearance. The depth of your valve pockets is going to be what determines your max lift, rod length has nothing to do with it, your pistons will have a different pin location than stock or should.

Sorry I guess I got confused by this part of the conversation... LOL I didn't read further down my bad....