I have decided to hold off on getting heads so now I dont know how to get my DCR to 8.5 without taking the Chamber to 62cc's. with the F14 and a .040 head gasket i typed in my SCR/DCR and it it was 10.34 and 7.93 what are my other options to raise the DCR?

-Matt

 

i would say about the only way you can raise dcr without smaller cc heads will be to advance the cam.

 

so i tryed +2 and +4 for the advance on teh cam and it stayed 7.93? Is this an acceptable number to have or do i really need to have it at 8.5?

 

The DCR will change when you advance or retard the cam. If it doesn't change then something is being done wrong.

 

I assumed it is a 112 so i get ~10.64 SCR with the .040
DCR for 112+2 = ~ 8.02
DCR for 112+4 = ~ 8.22

Just be careful with PTV.

 

Then the question is "is it worth it for the gain in DCR" versus the changing of the valve events by advancing the cam 2 or 4 degrees? Or what is more important? The valve events or DCR? Inquiring minds need to know.

 

ive been reading about valve events but i dont understand anythign when it comes to what needs to happen and when.

Predator will i have PTV issues? im running the T=rex now and that cam has more duration higher lift and a 110 LSA and you assued correct thisone is on a 112

 

guys wat is dcr?

 

dynamic compression ratio

 

I assume you are running a Trex with stock gaskets which are .054
Now with a .040 you are loosing .014 PTV right off the bat.

112+4 will fit but how tight, I dunno, this is why I said just be carefull. It would be tight on the exhaust.

 

The issue with advancing or retarding the cam is that the overlap period is affected relative to TDC. Opening before TDC allows more exhaust scavanging, with the positive and negative effects of that. Idle, reversion etc. Opening after allows better exhaust expulsion, but reduced intake induction. Its a pretty complex balancing act.
This event is the most complex of the cams action. Ive been trying to get my head around all the events and figuring out why you would want it one way or the other etc.
Most of the articles and sites on the topic pretty much recommend installing straight up as designed.

 

Well advancing a cam too much will make it exhaust biased from TDC which in return will make it fall off the powerband quicker after peak.
If you want the cam to carry the peak power longer, you'll need to make it intake biased from TDC. In my practices I tend to like them equidistant to try and benefit from both sides without having the cam spin to the moon. It all depends on the application desired.

 

thanks what are the benefits of a high or low dcr?