Am I Missing Something Here? Help

[josh]

OK having a brain fart. I'm trying to do the calculations for a set of 1.25:1 rockers and it's not adding up. First off I bumped the compression by flycutting the heads, now have 50cc chambers, .090\" deck hight, 78.4x90.5 should be 8.8:1.
I'm running a engle 125 and the spec I have for it is .460\" lift and 301 duration so I multiplied that by 1.25 and got .575\" that's my total lift right? This is where i'm confused- got the head sitting here, with a dial indicator on the tip of the valve stem and open it to .575\" and the leading edge of the valve is going to mash the piston (tried to measure by how much and it's .280\"-.090\" deck=.190\") thats with no .100\" saftey margin.
So am I screwing up somewhere? What I don't get is with the stock lifters I had no issues and the way I'm trying to figure it out .460\" would of hit too. The only thing that changed was flycutting about .070\"( I think) off the heads.
Do I have to get the pistons notched? I hope not cause that would lower the comp ratio and then I would have to take more off the heads.............going around in circles. ]
Someone please set me straight all this thinkin' is not good on a Sunday morning hangover :!:  

[josh]

A light bulb just came on inside duuuuh...........when the piston is at TDC both valves are closed so my little problem isn't really a problem.....right? Man I should sober up before trying to think :wacko: . I think i'll put some plasterseen on the piston top of the piston and rotate it before buttoning it up though, just to be safe.

[Billyisgr8]

An engle 125 lifts with 1.25 rockers   .475 not  .575  (   It has .418 lift with a 1:1 rocker...380 at the cam)  What size valves are you running?  Somebody else would probably know if they had to notch the pistons.  I don't think a piston needs to be notched with a 125 if your valves are 40 x 35.  Modeling clay will tell you forsure.  Definitly do a mock up of the whole engine without sealant on it with all torque values.  I just got bit by not torquing all the head studs  but did do a dry assembly and on final assembly a headstud pulled out, not fun with all the sealants on everything.

Kevin

[Hansk]

A little off topic but I think .090\" is a lot of deck hight.  Some where around .040\" would be the ultimate I think .

[Chris]

sounds like your case needs facing, need to reduce your deck height....  

[josh]

I know .090\" is a bit much but when I had the case punched for the 90.5's he didn't face it. And then when I mocked it up I ended up having 8.2:1 comp so I left it alone. What do everyone here run for hight? I've read mixed things on what's best, from .0000\" for all the burn in the chamber to reduce shock load on the cylinder to .035-.050\" for \"squish.  Will my .090\" hurt anything?

Oh ya thanks kevin for the proper spec on my cam, guess I got a little carried away with the calculator. The valve are 40 by 35.5.

[josh]

I just found this article ondeck hight wonder how much heat he's talking?

[Hansk]

Not sure how much heat he's talking but lots of motors
have run a long time with that(.090 +) much deck(my own included)
but it seems a waist to me. I now have about .047\" deck .

 

[josh]

I hear ya, next time I build one will be setting up for .000\"...................I've recently been dreaming of a 2276 turbo with charge cooler on megasquirt ......drool!