intake valves hitting piston on stroker motor need help

is there only a certain size cam you can use when building a stroker motor. my brothers 350 is bored 60 and the heads are shaved 40. the cam is a crane blue race with a 302/302 .50 lift so do i need to get a cam with smaller lift on intake? any help on this subject would be appreciated

Reply to
sooner_disciple73
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Reply to
Stan Weiss

Very unusual for the intakes to hit the pistons, make sure you have the cam phased properly. I assume this engine hasn't run, this was found in the build process? "sooner_disciple73" wrote in message news:sooner snipped-for-privacy@no-mx.nodomain.com...

Reply to
Shep

What ratio rockers are you using? Cut the pistons.

Reply to
DieInterim

As everybody has already suggested, this is not uncommon if you don't take precautions when building the engine.

Did you actually measure the piston top to deck when assembling it? You know what the lift is and you also know you lost 0.040 inches when you milled the heads.

You can preassemble the engine with a little molding clay on the top of the piston and gently turn the engine through a valve cycle and actually measure the valve clearance (if any).

Don't cut it too close, because a little valve float can deal you surprises.

And my answers are the same as everybody elses...you can relieve the piston top sometimes, or change the rocker ratio, or destroke, or use a cam with less lift, or even use a thick copper head gasket.

Reply to
<HLS

I know you are not the OP but, I wanted to add my thoughts to your observations.

He should also use one of those special low tension valve checking springs when checking valve-to-piston clearance. That way, the lifter won't be compressed by the valve spring as it opens. Also, cutting a head that much can really screw up valve train geometry for a leaned on engine. This has to be corrected somehow during the build. This engine probably should have been built with only one cylinder to start to find the worst possible case of piston contact. If that clears, bring 'er up to TDC and manually open the valve until it either bottoms the spring or hits the piston while watching a dial indicator to see if that distance is greater than the effective lift at the valve. If that doesn't pass, the piston valve releifs will need to be machined for clearance assuming there is enough meat in the piston crown to allow this. If not, either the pistons or the cam must be replaced with something compatible. Cutting the pistons may also affect engine balance which means they should be checked for equal mass after machining is completed.

All that said, it never ceases to amaze me how many folks decide they like some combination and proceed to assemble it without bothering the so much as find out whether the parts are reasonably compatible. I find it is fairly easy to gather information to educate myself from other peoples mistakes. Most rodders are glad to share their experience with various combinations. The tech support guys at most cam and psiton suppliers have a pretty good idea which parts will or will not work w/o mods and whether the mods will be extensive or minor.

Lugnut

Reply to
lugnut

Reply to
Shep

If this is truly a stroked motor, did you install shorter rods or pistons with the wrist pin higher in the piston? If not, you're probably pushing the pistons out the top of the bore.

Reply to
Andy Asberry

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