Camshaft sizing help

[496 polara]

The only way to be confident they won't hit is to measure. That being said I would be surprised if there was an issue on such a small cam. Lots here smarter than me,hopefully they will chime in. @PRHeads spec'd my cam and has forgotten more than I will ever know on camshafts.

 

[Krooser]

Measure the combustion chambers, how far in the hole the pistons are. If they are .100 down you would be wise to limit the cam size because a low compression engine won't like a big cam.

My go to cam guy is Mike Jones @ Jones Cam Tecnologies. I stay away from all the big name cam outfits that sell cams ground by big factories in Michigan then get put in their box.

You don't need a custom cam but you DO need professional advice. Get on the phone but don't call Memphis.

 

[PRHeads]

Once the new heads are on hand, pull one of the old heads off, and using a head gasket of the correct thickness ……..
Put a piston at 10*ATDC, remove one of the intake valve springs, place the new head on the block(snug it down with a bolt or two), and measure how far the valve can open before it contacts the piston.
This is the valve drop.

Once you have that number you can get an idea of how much duration you can run without having valve to piston clearance issues.

For example, a Comp XR280HR, in at 106 and using a 1.5RR will have about .170 valve lift at 10*atdc(closest point).
You’d like at least .060” clearance, so you’d need at least .230” valve drop at that point for that cam to work.
Dropping down to the XR274HR would add about .020” of clearance.

While not great for compression or power, pistons sitting farther down the hole provide more clearance for longer duration cams.
The typical deck clearances for BBM flat tops that don’t have valve pockets range from about .050”(rare) to .150”.

 

[33 IMP]

There ^^^^^^ is your answer.
I feel pretty confidant that the cam 496 Polara suggested will fit, and be a good choice. .
But you can't go wrong asking questions of reputable cam guys.
Jones, Bullet, PRH.
Just be prepared to answer as many questions about your car and usage as you can.

 

[PRHeads]

If one knew the piston deck clearance, the gasket thickness, and measured how far the edge of the intake valve was from the gasket surface of the head(straight edge and feeler gauges)…….. you could add those up and it would give you an idea if there’s any reason for concern.

If you don’t know the deck clearance of the piston…….. you’re just taking a WAG.

 

[Geoff 2]

As others have mentioned, cams for low compression engines require careful thought. They are already HP compromised due to the low CR. The 280 cam that PR mentioned would be as big as I would go.

 

[BrettL]

The only way to be confident they won't hit is to measure. That being said I would be surprised if there was an issue on such a small cam. Lots here smarter than me,hopefully they will chime in. @PRHeads spec'd my cam and has forgotten more than I will ever know on camshafts.

Ok im working

 

[BrettL]

Ok everyone you’ve given me plenty to think about and quite a few task to get done. I will get busy on this and get the heads coming probably just order without springs so I can get the one that match the cam when I cross that road. And as always thanks a ton for all of your wisdom I really appreciate it.

 

[PRHeads]

The dual spring option on Stealths would be adequate for pretty much any HR cam you’d be looking at for your combo.

 

[BrettL]

The dual spring option on Stealths would be adequate for pretty much any HR cam you’d be looking at for your combo.

Ok then I will definitely order with springs then thank you

 

[PRHeads]

The dual springs.