Where to install cam

[racinnut15xm]

Ive asked about heads and other questions along the way on this build.

Its a 383, 441 heads with 2.02/1.6 that have been bowl hogged and slightly cleaned up in the ports, stock rocker arms per rules, icon 4 valve relief pistons coming in at 9-1, 6in rods, 2701 intake with a gas 2barrel going on top.

I told the guy to order a howards cam and they were out of it so he got one close to it but it has more duration. 112791-12 is the part number its showing intake centerline of 108. Ive got it at 103 now. Leave it alone or retard it closer to 108?

One track we run has a vacuum rule and the other has a 175psi rule. Running more at the 175psi rule track than the other.

[DaleHays]

Me, I always speak with the actual cam grinder - tell them my application, etc.. Did it come with a timing card? It should tell you where to install it at. Typically the timing information at .050 is there for a reason - which is where I usually start. If the tag says the cam (the profile) should be at .050 lift at X degrees before TDC, then I take my degree wheel and setup the crank to be at that spot, then I install the cam so the profile is at .050 lift on obviously the correct lobe and opening ramp. This should get you very dang close - or the cam timing tag is wrong. Then I check all the timing numbers to see if the cam is ground correctly (to match the tag). I have definitely found cams that were off . . . and then we get to have a conversation with my cam grinder!

Some cams come with advance "built in" - some don't . . . all depends on the grinder. Also, depending on your track application and RPM power-band, the specific installation may change.

[swampbuggy]

Personally i would leave it advanced. Mark H.

[racinnut15xm]

Me, I always speak with the actual cam grinder - tell them my application, etc.. Did it come with a timing card? It should tell you where to install it at. Typically the timing information at .050 is there for a reason - which is where I usually start. If the tag says the cam (the profile) should be at .050 lift at X degrees before TDC, then I take my degree wheel and setup the crank to be at that spot, then I install the cam so the profile is at .050 lift on obviously the correct lobe and opening ramp. This should get you very dang close - or the cam timing tag is wrong. Then I check all the timing numbers to see if the cam is ground correctly (to match the tag). I have definitely found cams that were off . . . and then we get to have a conversation with my cam grinder!

Some cams come with advance "built in" - some don't . . . all depends on the grinder. Also, depending on your track application and RPM power-band, the specific installation may change.

That last part is the real reason for the question. Knowing it has more duration than i believe it really needs and a wider LSA will advancing it help those issues? I went and read the 2nd tracks rules again, it shows 16" at 1000rpm

[engineguyBill]

Best bet is to install the cam "straight up". Most high performance cams are ground at the factory with a few degrees (2 to 4 typically) of advance, therefore advancing or retarding the cam upon installation does not typically result in any measurable performance increases.

[sjre]

If im reading this right the cam is ground on a 112 w/4 deg advance(108 icl) there is no way id install it at 103 or 11 deg advanced!

[racinnut15xm]

If im reading this right the cam is ground on a 112 w/4 deg advance(108 icl) there is no way id install it at 103 or 11 deg advanced!

LSA is 112
ICL on card is 108

[geraldtson]

If it's limited circle track heavy car it may need a lot of advance (depending). You could try a cranking compression test where you've got it installed now and retard it a couple degrees at a time while rechecking compression. A lot of work but will give you more understanding.How is it performing at 103? Whats the application? You may want to go in 4 degree increments to speed your results?

[racinnut15xm]

If it's limited circle track heavy car it may need a lot of advance (depending). You could try a cranking compression test where you've got it installed now and retard it a couple degrees at a time while rechecking compression. A lot of work but will give you more understanding.How is it performing at 103? Whats the application?

Yes it a 3000 pd metric car, the track with the vacuum rule actually requires 3200. He has a powerglide with convertor right now. This is the first motor of this type I've built, i race modifieds.