I was able to find the information needed for Ross to figure out the
compression ratio for the pistons built by them. They said "Job number
105995 has a compression of 10.5:1 with valve pocket diameters of 2.150
intake and 1.700 exhaust."
What do they mean by valve pockets? And how is that used to figure out
compression ratio? I did tell them that R/T heads with 2.02"/1.625" valves
will be used. Maybe they pulled up all the R/T head specs to figure it out?
Also, what are the pros/cons of a 10.5:1 ratio. Seems a bit high. Here's
one opinion on the build:
"First, dump the cam that you got from ***. The lift is horrible. The
duration numbers are weak, and that LSA is going to be bleeding off all your
compression. Then again, looking at your pistons I recognize one of ******
typical tactics. He likes to sell people high compression parts like those
10.3:1 pistons, and then put in a real narrow LSA like that 108 degree
spread to keep a lot of overlap to make up for it. With both valves open for
an extended period you lose cylinder pressure. You're trading high static
compression numbers for low dynamic compression. That stuff has to go
somewhere, so it results in unburned fuel going out the exhaust, and also
blowing back up the intake. I wouldn't go lower than a 110, and that's even
pushing it. Try a 112, or 114 if you plan on adding boost later"
BTW, here's the cam specs:
Gross Valve Lift .480, Duration @ .050 210/220, Lobe Sep. 108.0
I have the short block built with this cam and pistons and before I go on,
now is the time to swap out pistons and cam. Although expensive to replace
parts now, it's cheaper then doing it later if it runs like crap.
Thanks for any advise!
James
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