bowtienut

iTrader: (1)

Ideally, shoot for .035". I know guys like Ed have a measurement on EVERY hole and can squeeze tighter than that, but it's a risk not worth taking for us mere hobbyists
Your options of .015 deck clearance/.026 gasket, or zero deck with a .038 or .040 gasket are fine.

Ed Wright

iTrader: (1)

.026" & .015" is OK. I won't run one closer than .038" total. A lower RPM engine might get by a tad closer. I have hit pistons against the head at .036" total. That loads the rod bearing, and upsets ring seal.
I do measure every hole, and sand piston tops to equalize deck clearance.

bowtienut

iTrader: (1)

I defer to Ed. I wasn't thinking of the rpms that he turns!

kris72079

iTrader: (7)

Okay, on to the next issue...I just spoke to Callies on the phone regarding the availability of a Compstar Crank in a 3.875" stroke for a 1pc RMS. They do not sell one. This explains my inability to find one for sale. Can anyone recommend a suitable quality crank near the compstar price range? Or am I going to have to go the Eagle route?

nitrous2fast

iTrader: (2)

They are all talking about quench distance. The distance from the piston to the head surface when at TDC.

nitrous2fast

iTrader: (2)

What are you using to sand the piston tops with Ed?

Ed Wright

iTrader: (1)

I have a forged Scat crank in my old 383", one piece main seal. Very nice crank.

I have a piece of 3/8" steel plate a friend of mine parallel flat ground both sides.
I lay it on the shelf in my parts washer with the solvent pump running solvent over the black "wet or dry" automotive sand paper on it. Figure 8 motion, usually 100 to 120 grit if I need a couple thou off. Then slick it up with 320 or 400. Only works on flat tops of course. LOL

Glass is pretty flat, probably plexiglass glass too. Something like 1/2" or 3/4" plexiglass would probably be flat enough. Ace Hardware has plexiglass or clear plastic. Not sure how thick they carry.

purpleflamzz

that is the way it was when I bought it. I beleive it was dine to keep the CR low nd be able to spray a 200 shot. it was all newly assembled and started once before I got it, had antifreeze squirt out the drivers side head and block,
I tore it down only to find the head gasket upside down, freshened up all new gaskets, checked crank and bearings and all were fine, put it back together and it really runs but yes want tons of timing it scared me the first time I went past 36 total but it wants more I just don't know what it truly wants for total timing set at 36 total right now as a few people told me not to go further I have been at 42 total and it still runs without and detonation issues. havent had the chance yet this year to get it out of the garage, but will soon and get some more drive time on it.
where would you set timing?

Ed Wright

iTrader: (1)

AFR chambers are lazy, 40 degrees with those things is not unusual. I would be surprised if you actually have 11.2-1.

PA94Z

iTrader: (1)

You can use that 2 piece RMS crank from Compstar. You just need a adapter. Here's the one I use. Works great, setup with a alignment tool I bought from CV Products and no leaks.
http://www.summitracing.com/parts/mor-38315/overview/

purpleflamzz

I have wondered the same thing but don't exactly know what pistons are in it?
they are Ross Domed for nitrous but when I look at there chart they don't have a 4.030 piston on a 3.875 stroke so I can't plug in the numbers in a calculator without knowing the true dome measurement.
heads are 76cc though that was confirmed by AFR.
these are the early cnc competition ready castings not the newer race ready pretty machined ones.
Ed what would you think is the compression if you had give a educated guess?