cvbadass Posted March 17, 2008 Report Posted March 17, 2008 I just put on a vitos hemi headII, it said that i would probably have to change my jetting. I went from 120 to 170 psi in both cylinders. I lost 2 mph on top, but seems to be alot quicker on getting there. Would i need to go bigger on my main jet or smaller? I am in florida near sea level with 270 mains. Quote
dajogejr Posted March 17, 2008 Report Posted March 17, 2008 I just put on a vitos hemi headII, it said that i would probably have to change my jetting. I went from 120 to 170 psi in both cylinders. I lost 2 mph on top, but seems to be alot quicker on getting there. Would i need to go bigger on my main jet or smaller? I am in florida near sea level with 270 mains. Nature of the beast.... With that much more compression, the pistons are fighting each other at max RPMs. You could back off the timing a hair...but, you have to ask yourself, is it worth losing the better acceleration for 2MPH? Or...take two teeth off the rear sprocket. It will pull taller gearing now. Your choice. Normally, with timing or compression changes you don't have to change jetting. But...as a disclaimer, just about any bolt on mod will tell you to check jetting. Get a good WOT run with new plugs and check for a nice brown smoke ring at the base of the porcelin. If you've got the smoke ring, you're ok.... Quote
sheerider1026 Posted March 17, 2008 Report Posted March 17, 2008 i would suggest lowering the compression down to about 160.. seems to be a good spot,, at 170 you are starting to lose top end power due to the pistons fighting to reach tdc like dajogejr said.. i am running about 160 and its hard to beat the performance i am getting with it.. so there is such a thing as tooo much.. Quote
cvbadass Posted March 18, 2008 Author Report Posted March 18, 2008 i would suggest lowering the compression down to about 160.. seems to be a good spot,, at 170 you are starting to lose top end power due to the pistons fighting to reach tdc like dajogejr said.. i am running about 160 and its hard to beat the performance i am getting with it.. so there is such a thing as tooo much.. would my set up be better with 19cc domes? I like the more power down low, it just feeels like i need another gear now! I am probably going up to 280 main and mix race/ premium gas, that should help right? Quote
cvbadass Posted March 19, 2008 Author Report Posted March 19, 2008 any one with any input? :shrug: Quote
tnr Posted March 20, 2008 Report Posted March 20, 2008 At 170lbs compression, I would run only race gas. Just my $0.02 Quote
dajogejr Posted March 20, 2008 Report Posted March 20, 2008 First things first, is your stock crank welded? Quote
cvbadass Posted March 22, 2008 Author Report Posted March 22, 2008 First things first, is your stock crank welded? no, everything internal is stock Quote
cvbadass Posted March 22, 2008 Author Report Posted March 22, 2008 no, everything internal is stock would i better off getting 19cc domes and lowering my compression a little? Quote
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