Mr Maine

If you had a cam that was properly matched to the engine and it had 5 degrees of advance ground in, what would be the real life effect of retarding it 2 degrees, so essentially you have 3 degrees of advance now?

Say intake closing goes from 42 to 44 abdc...

Thoughts?
Thanks

cmattj

Usually engine builders with piston clearance issues on big dome pistons for valve to piston clearance issues.. Im not sure on reversion for marine . This link from comp cams may help you

http://www.compcams.com/Pages/413/ca...ion-angle.aspx

Mr Maine

Thanks for the link. I do know the theory, I guess I was thinking more real world in the boat. Would I be able to feel a little less low end, more top end or is 2 degrees negligible assuming the engine doesn't desparetly need more advance/retard to begin with.

GPM

I'm guessing about the same effect as the timing chain breaking in, slightly less bottom end slightly higher power band. I would think you would have to go 4 degrees to even notice it.

ICDEDPPL

iTrader: (1)

Apparently my cam likes 4* retard to the tune of almost 47 hp on top . Does not like advance one bit. Same for Mild thunderer . (per desk top dyno, thanx Mild Thunderer)
Will know for sure at dyno time.
Retarding makes the cam 'bigger'

GPM

Retarding makes the cam 'bigger' How ?

Mr Maine

My cam has 5 degrees of adance ground in. I have it retarded 2 degrees. Timing chain is already been used so no initial stretch. I think I will leave it. Intake closing went from 42 to 44.

SB

iTrader: (1)

IVC and EVO are the two most important events. IMHO.

Retarding makes these (and all events) later. Advancing, thus obviously makes these earlier.

Most 'typical' cams are installed (many are even ground this way) 4° advanced.

Most of the Merc/Crane Marine HR's are 5° advanced.

Mr Maine

SB, yeah, so going from 5 to 3. I always seem to run out of cam on the top end.

mike tkach

iTrader: (3)

it has been my experiance that it moves the peak power either higher or lower a little in the rpm band but no hp difference to speak of.i always install them straight up for marine use,espically in a supercharged deal.i am looking forward to moving it around on the dyno dan.we need to keep in mind that when we change cam timing it also changes piston to valve clearance.