[gtofreek]

Originally Posted by chiphead

Wow, wow wow. You have my attention. Brace yourself, questions are coming. I have yet to read the original thread, so forgive me if some of this stuff is there.

Were the chambers opened up on the 670s? Do you have flow sheets? How much vacuum at idle? Why a 110 LSA? What plugs? Why low tension oil rings on a street motor?

This sort of shows what I found with my 670s, they wanted more timing than you would think. My motor ran best at 36-38* NA at 9:1. You would think that a compact chamber would require less timing, but the stock shape must really hurt flame travel.

How would this cam behave in a 9.2:1 400 with 6.8 rods?

Dave at SD Performance did the heads. The chambers were opened some. There are flow sheets posted in the thread about his engine. You can find it here.

http://forums.maxperformanceinc.com/...d.php?t=785341

Didn't think to get a vacuum reading.
Why not a 110 LSA? This is a short stroke engine. These Voodoo cams have such broad power bands, they don't need to be put on a 112°. They make more power on a 110. I think the stock, un-ported intake was the limiting factor here. I feel that is why it peaked at only 5400. Every pull peaked at 5400, no matter what we did. I think a ported intake will help this a bunch.

We used NGK plugs, heat range 8.

The ring pack is a modern metric ring pack[1.5mmx1.5mmx3mm]. It is what came standard with these CP pistons we got for it. It utilizes a Napier second ring which is a great oil control ring, so you don't need a high tension oil ring for them to control oil. Different story with a regular, taper face ring. Total rotating force needed to rotate completely assembled shortblock with rope seal = 17 ft. lbs. to break free, and 13-14 ft. lbs. to keep rotating. Compare that to about 35 Ft. Lbs. for a factory stock ring pack shortblock assembly.

9.2:1 is a little on the low end for this cam. Really need 9.5:1 or better if using it in a 400. In a 428 or 455, it would be fine at 9.2:1.