95" Big bore piston-compression?
Outstanding HDF Member
Joined: May 2008
Posts: 2,166
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From: la
you need to figure out what your goal is before you start any build and go from there,cast pistons are fine for under 10.5-1,as far as 1.900 valves,if your cam dosnt have alot of TDC lift ,its not an issue(MUST BE CHECKED) figure out what you want to acomplish,and get back on the forum,you`ll get some good idea`s if we know what you want
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Joined: Sep 2009
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From: deland,florida
My TDC lift is .185/.157, 37's w/1.725 rockers, the HG was .047 I'm going with a .030, I decided to stay 96 for now and my heads are at Big Boyz for a street port and a shave. I have been told the 1.90 will fit with no problem by one porter "AMS" but others say no. I don't want to cut on my pistons because I can't do it accurate, it would kinda make cc'ing the heads a waste. I was going to stay stock valves for now and go bigger when the cubes got bigger. If I knew for sure I could do it without piston work I would go 1.90 now. I don't want to go with larger pistons until my crank is balanced for them.
Last edited by prodrag1320; Jan 14, 2010 at 03:18 PM.
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Joined: Jun 2006
Posts: 12,776
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From: san antonio
My TDC lift is .185/.157, 37's w/1.725 rockers, the HG was .047 I'm going with a .030, I decided to stay 96 for now and my heads are at Big Boyz for a street port and a shave. I have been told the 1.90 will fit with no problem by one porter "AMS" but others say no. I don't want to cut on my pistons because I can't do it accurate, it would kinda make cc'ing the heads a waste. I was going to stay stock valves for now and go bigger when the cubes got bigger. If I knew for sure I could do it without piston work I would go 1.90 now. I don't want to go with larger pistons until my crank is balanced for them.
Tourer
Joined: May 2008
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From:
youll be ok with 1.900,.185 & 157 isnt much.took a head i have here with 1.900/1.625 opened them up to your tdc lift and heads of valves didnt come near the gasket surface,so as long as you pistons aint comeing up out of the cylinders,you`ll be fine.not real crazy about useing clay either,we`ve seen valves bend(dosnt take much).the easiest & safest way to check for valve to piston contact is to remove the springs,but leave the seal on(or use old seals),mark your TDC lift + .060 off the top of the seal on the valve(use dykem),get the piston @ TDC,push the valve down to the mark,no contact your fine,if there is contact,dykem the valve pocket and spin the valve,it`ll show where it needs to be machined,or if you cant even get to the mark before contact,measure the amount left,and thats how much you will need to machine down into pocket.
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Joined: May 2008
Posts: 2,166
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From: la
Thanks Kirby, If I can do the 1.90 intake without piston work I'll go for it. Bean already told me I would need to check but if I find they don't fit that would put me where I don't want to be. 1, I don't want to cut my pistons. 2, I don't want to go with bigger pistons until my crank is balanced for them. DJL, I only have 6,000 miles and the cylinder walls look fine, if I pull the pistons it would make it hard for me to stay 96 for now and I'm not ready to do the bottom. Thanks
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