JE 95mm pistons in a 94mm cylinder.

flyboat

Is there enough metal to bore my 94mm cimas to receive a set of JE 95mm pistons. I believe that is .020" bore job. I discovered I need a set of pistons with valve reliefs .260 deep. I found a set of JE 95's in the classifieds. they have the relief and domes to compensate for volume loss. They are advertised as racing piston, Will that make a big difference in a daily driver. Anyone have any experience with this.

I thought about using squishees if the relief is deep enough

Thanks
Roger
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modok · Posted: Sat Jan 19, 2013 4:36 pm Post subject:

1mm is .0394", not 020

You'd have similar thickness as 92 cima

why do you need .250 reliefs on a "daily driver"?

flyboat · Posted: Sat Jan 19, 2013 4:59 pm Post subject:

I rounded off to .040" total new diameter which is a 020" cut. .020 per side = .040. It isn't exactly a daily driver, but we drive it alot. The heads have been cut .120" and I am putting it back together with a Web 86B cam with a lift of 5.75 with 1.5 rockers. I have a valve to piston interference of .285 if I run a 0 deck. I am running a .055" deck with a 51 cc chamber = 10.6:1 cr. So, I think I need valve reliefs of .260". This leaves me .030" clearance. Does that sound safe.
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flyboat · Posted: Sat Jan 19, 2013 7:30 pm Post subject:

Modok, Is that the cylinder/piston combo that those in the know warn about. Something about the wall being too thin or the engine running hot due to lack of cooling with the thin wall.
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modok · Posted: Sat Jan 19, 2013 7:38 pm Post subject:

So they say, the 92 kit only has about 3mm wall thickness at the top, that is the absolute minimum for an iron cylinder by my rule of thumb.
But you know, those 92's do ok if not overheated, taken over 6000 rpm, or used in very high compression engines..............aka, lame engines Laughing

what is the need for this very high valve lift and very high compression, if this is a "street engine"?

flyboat · Posted: Sat Jan 19, 2013 7:42 pm Post subject:

turbo2go · Posted: Sat Jan 19, 2013 7:43 pm Post subject:

Have you mock assembled this engine and used clay on the pistons to come up with these figures or are you just doing the math? That sounds like a VERY deep notch for only .575" lift even with the heads being cut.
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modok · Posted: Sat Jan 19, 2013 7:46 pm Post subject:

I thought the same thing, 86b isn't an overlap monster, but maybe he has 48mm valves or something crazy.

If the heads need that kind of lift then so be it.

Pauter makes ductile iron cylinders............

flyboat · Posted: Sat Jan 19, 2013 7:58 pm Post subject:

turbo2go · Posted: Sat Jan 19, 2013 8:08 pm Post subject:

Thats not how it works. You need to put it together to find out for sure. I really doubt you will need any notches.
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flyboat · Posted: Sat Jan 19, 2013 8:14 pm Post subject:

I put a straight edge across the sealing surface of the head and the valve only opened .250 before it hit the straight edge. I am pretty confident there is interference,
The question is, can I bore my 94 cylinders to accept the 95 pistin
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modok · Posted: Sat Jan 19, 2013 8:31 pm Post subject:

well, yes you can bore them to 95

should you? no

you should mack it up and check the actual valve to piston clearance

flyboat · Posted: Sat Jan 19, 2013 8:39 pm Post subject:

Will do tomorrow
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slalombuggy · Posted: Sat Jan 19, 2013 10:39 pm Post subject:

I flycut my 044s .100 and have 585 lift at the valve with 44x37.5 valves. My valves don't even come close to the pistons. Mocking up the valve train and running it through a cycle is the only way to check for interference, you can't do it's statically.

brad

flyboat · Posted: Sun Jan 20, 2013 7:31 am Post subject:

Udo.B. · Posted: Sun Jan 20, 2013 8:18 am Post subject:

I have "powersleeved " them on the top side to 105mm . so it works great .
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flyboat · Posted: Sun Jan 20, 2013 10:13 am Post subject:

flyboat · Posted: Sun Jan 20, 2013 1:01 pm Post subject:

Did a dry run on the engine assembly today. You guys are right. I did not have any piston clearance issues. It has over .150" clearance. So all is well.

Let's change the subject. Spring Pressure. I have the new CB 650 springs. My install height is 1.650 to the top of the keeper. The keeper is .111" thick. Making the top of the spring 1.540. So which one is the correct mesurement to use for installed height. I know CB has info on spring pressures for these springs, but what seat pressure and max lift pressure do you like to run
Thanks
Roger
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andy198712 · Posted: Sun Jan 20, 2013 2:00 pm Post subject:

1.540
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flyboat · Posted: Sun Jan 20, 2013 2:06 pm Post subject:

OK, that will give me a seat pressure of 160 lb. I'll probably add a .010 shim just to protect the heads. That will increase my seat pressure to 164 lb. I wonder what the pressure is at max lift of .575"
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