VB242
I.M. Weasel
- Joined
- Sep 21, 2011
- Location
- Driving the No Malarkey Bus
I ordered a .140" cometic, it should knock the c/r down to around 8.6-1, depending on how much comes off the head. Now my concern is getting the timing belt on.
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I ordered a .140" cometic, it should knock the c/r down to around 8.6-1, depending on how much comes off the head. Now my concern is getting the timing belt on.
Or do what Volvo did.
<Oh noes that would be too easy.>
You will be giving up squish, which is actually worse...
What did they do?
I cc'd the head and it appears to be 49.7cc's. my thinnest feeler gauge .008" was a little tight, so I'm assuming John V is correct at the pistons being in .007" , this gives 10.94-1 on the summit calculator. I'm going to get the head skimmed and check it again. I'll probably order up a cometic thick enough to reduce the CR below 9-1. The pistons appear to be forged, but I'm no expert, I'll have the machinist look at one when I drop off the head.
7.5:1 CR and mechanical fuel injection.
Did you include the stock head gasket thickness in the calculation?
I used .040"
b230 gaskets are 1.2mm/.047" compressed. Would guess b21 is probably the same.
I thought it was .047 new and .040 compressed? The extra .007" gives 10.72-1
that?s what we are trying to do, numb-nuts. The more you pressurise it, the longer it gives a good push on the down stroke. And we have a big open chamber with hardly a quench pad in sight.Eh, no point in today?s era. Better fuel, tuning, etc. 7.5:1 is kinda useless unless you just wanna throw boost at it
New rings showed up today, ITM from Rock Auto, not chromed like machinist said I would get. He said hit the bores with 320 grit and assemble the pistons/cylinders with ATF . Should I do something different with the rings not being chromed? I will try to assemble the bottom end tomorrow with new big end rod bearings and turbo drain welded in oil pan. Machinist recommended .024"-.025" ring gap, this is ok per Haynes manual specs as well.
Dang, I guess I better pack up that thing and get a mailing address and get it sent, huh?
Math is important if you don’t want to keep trying to make it work. Math lets you do it once.
I asked about the gasket because the CR return on the calculator surprised me. It ran good, but we never got it tuned.
that’s what we are trying to do, numb-nuts. The more you pressurise it, the longer it gives a good push on the down stroke. And we have a big open chamber with hardly a quench pad in sight.
You can get away with a lot if you keep the octane up and the tune conservative (and fat). But that’s not how you make big power.