Quote:
Originally Posted by Jay S
A better answer would probably have been the reasoning for the ICL’s we use. I start by using a event calculator, and adjust the ICL on the calculator until the EVC and IVO events are square. On a timing chain engine I always assume the cam timing events are running 2* behind, so what ever that ICL turns out to be, I subtract 2* for the installed ICL.
When we install a cam we start with the ICL found with it degreed in from the .050 down from each side of max lift. Then further check the duration on the opening side of the cam from .006 to .050. Then the closing side from .050 to .006. That gives me the cams span or asymmetric’s for most of the overlap triangle. If the cam is a modern performance cam, has no asymetric’s (Crower 60919, SPC-8, ect) and I want to bleed compression I find I can move the ICL timing and retard it, I.E. the exhaust events are running behind the intake events without sending a ton on heat into the intake charge, seems like the max is about 4 degrees. Which if I recall correct is on a SPC-8 or a Crower can almost be installed straight up. What ever the span is (closing side of the cam is longer duration than opening) I subtract that from that 4 degrees. That is the max retard I will use it it is assymtrical, which is easy on a Voodoo, because the EVC and IVO events end up being square.
If you end up using a 704 on a 110 with a stock head, keep in mind the stock Pontiac heads have a huge push on the low lift flows. Personally on a Pontiac I think it makes that 110 act like a 108 LSA . It does a ton of scavenging, then tries to move a bunch of air again when the piston is coming up and the intake is shutting. Which make good power and mid range tq. But add much compression with those things can be to much of a good thing, you will be running race gas. Paul Carter runs a lot of compression with the 704, but I am pretty sure he ports the heads. That cam and ported head combo is pulling the air in differently than a stock head. Harolds cams are very effective cams for cylinder fill, IMO, no need to get carried away on compression on the 110 LSA.
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Thanks Jay, I appreciate it. I've got to cc the chambers still, but honestly, I'm hoping that it ends up only around 9.5-1, instead of up at 9.7 to 9.8-1. If the 6X4 heads would come in around 94cc chamber after the valve job and new Ferrea valves installed, it would have right at 9.5-1, zero decked, .039" gasket, and 8cc valve relief. I think I would be really happy with that, along with the 704 and 110 seperation.