Cam question

William Jones · Posted: Mon Feb 02, 2009 10:12 am Post subject: Cam question

I was installing a new custom cam in my friends 351C and ended up having to install it 4 degree's adv to get enough PTV clearance since his cheap ass don't want to take the shortblock apart, this is 1 degree more than what was required by the cam sheet. What will this do to the cranking compression and rpm range. It was going to have 227 psi of cranking compresion and the expected shift point was 7800rpm.

Bam

af2 · Posted: Mon Feb 02, 2009 11:25 am Post subject:

You'll be fine. I don't understand going by cranking compression though. I don't see how that could be a tool.
Go by DCR if you are running pump gas and you will know if you are in the ball park.

William Jones · Posted: Mon Feb 02, 2009 1:06 pm Post subject:

It should lower the theorectical rpm band also correct? I knew it would raise the cyl pressure and that was why I was wondering about how much. He only runs race gas but we do spray Nitrous on top of it.

Bam

af2 · Posted: Mon Feb 02, 2009 3:40 pm Post subject:

William, 1*Lowering the RPM band? I run mine at 4* advanced and can't say that is true. There is more to it after many hours deciphering the Internet B.S. and what people I know are doing with good results.
That engine might like more cam timing. Haven't seen one that didn't to a point.

The V.P. clearance is more what I need to know when changing the cam timing around.
Adam

bowty1111 · Posted: Mon Feb 02, 2009 10:47 pm Post subject:

If you are only 1 degree off like af2 said it won't hurt a thing rpm range shouldn't change ,but around 100 to 200 rpm if that I think 4 degree's shift's rpm range 200 rpm or right around in there

bowty1111 · Posted: Mon Feb 02, 2009 10:51 pm Post subject:

remember when you change cam degree to pick up VP clearence on EX you lose clearence on INT and vise versa

William Jones · Posted: Tue Feb 03, 2009 8:39 am Post subject:

Yeah I have .098 on the exh now and 140 on the intake. The cam was designed with 4 degrees of adv into it so I am sitting at 5 degrees adv.

Bam

wagon train · Posted: Tue Feb 03, 2009 11:10 am Post subject:

As soon as you load the front cam bearing and put some wear in it, it will be farther off than that.

William Jones · Posted: Tue Feb 03, 2009 1:01 pm Post subject:

Thanks guys

Bam