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b20 head options

oemoilleaks said:
6 bolt. The pistons are, I believe, the ones out of the b23 engine. Whatever IPD sold in the kit back then.
Click to expand...

They're B21 flat tops.

With different wrist pins iirc.

B%2021%20F%20Pistons%201_zpsyp1ma8qa.jpg


B%2021%20F%20Pistons%202_zpseaetbitc.jpg


B%2021%20F%20Pistons%203_zpsatfvwtfs.jpg


B%2021%20F%20Pistons%205_zps0c3ng3cj.jpg


oemoilleaks said:
Just got back from the machine shop. We went over everything needed to get done... It all seems good.

But the question arose about how high to push the compression ratio.

Initially my plan was to deck the b20f head down to b20e height (3.34in) and try to achieve around 11:1 CR
my machinist advised against this saying he's more comfortable with an 8.5:1. dishing the piston to not reduce squish.

I think I was able to convince him to come up to about 9.5:1 but I think we have to draw the line there.

Is this too high? Is there any risk if I going higher?
Click to expand...

Cali ethanol swill gas?
 
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I forget exactly, but mine is slightly above 11:1. Higher than I would have normally gone, but my R-sport head was shaved *WAY* the hell down when I got it. I think about 12:1 on top of a 2..0L bottom end, even higher on top of 2.1L. I got as many CC's into the head chamber as I felt comfortable with, and then used dished B21 pistons to get the rest.

It's mostly fine on 93 octane. Maybe some mid-range pinging on hot days.

Block decked to zero the piston height at TDC (although that isn't really needed), .036 Cometic gasket.
 
The ipd 6 bolt big bore pistons were proprietary - same bore as factory (or Mahle) B21 flat tops, but with a 22mm wrist pin instead of the B21's 24mm. They were made in Japan, and only around 150 sets were manufactured.

Forged pistons in this configuration are available new, though I don't think anyone is making a cast version.

Redwood Chair said:
They're B21 flat tops.

With different wrist pins iirc.

Cali ethanol swill gas?
Click to expand...
 
volvorelix said:
The ipd 6 bolt big bore pistons were proprietary - same bore as factory (or Mahle) B21 flat tops, but with a 22mm wrist pin instead of the B21's 24mm. They were made in Japan, and only around 150 sets were manufactured.

Forged pistons in this configuration are available new, though I don't think anyone is making a cast version.
Click to expand...

Who is making them?

I don?t want to go down this whole path and then have the pistons fail on me. So I?m highly considering just biting the bullet on forged pistons for this setup.
 
Call John V. He can get whatever you want. Probably has them stocked on a shelf somewhere ready to go. I think he has 160mm rods for the engine too.
 
centason said:
Call John V. He can get whatever you want. Probably has them stocked on a shelf somewhere ready to go. I think he has 160mm rods for the engine too.
Click to expand...

I can get them made.
But if there is an on the shelf source I would like to know about it!
 
oemoilleaks said:
Just got back from the machine shop. We went over everything needed to get done... It all seems good.

But the question arose about how high to push the compression ratio.

Initially my plan was to deck the b20f head down to b20e height (3.34in) and try to achieve around 11:1 CR
my machinist advised against this saying he's more comfortable with an 8.5:1. dishing the piston to not reduce squish.

I think I was able to convince him to come up to about 9.5:1 but I think we have to draw the line there.

Is this too high? Is there any risk if I going higher?
Click to expand...


After all these years ..still have to repeat: talking compression ratio without reference the intake valve closing ATDC is just taling..Dynamic compression is what counts... a 11.2 comp engine with an intake valve close like just say 60+ degrees 9of crank rotation= AFTER BDC means you aren't making any compression at all until the crank has rotated 1/3 of the 180 degrees it is going to rotate before its at TDC...

Only starts making compression when that hole is closed by the intake valve..
Your machine shop should have been drilling this into your head..

If they weren't you need to know why they weren't..

And John Mc has his story of squish/quench a little reversed

The is more than 30 years of proven beneficent advantages of det reduction with distances at or about 1mm...or .040" and it has been standard practice for many with every motor build for 34-35 years..

There is pages and pages of unverified, 1st rebuild guys changing all kinds of conceivable dimensions in their build AMONG OTHERs distance block to head of 0,8 aka .032" or so being THE DECISIVE factor in why their motor is not detonating...
Their fervent reports is like that of the converted...

And only a meanie would point out that a great many have build zero engines at .040 or 1mm to compare that versus their 0,8 or 0,9mm gasket thickness engines....no compare/contrast, and no base line...no, zero "single item change"...making their professions of faith in the glory of less than 1mm engines seem mildly put, less than convincing. (that 0,1 or 0,2mm is "decisive")
 
175 for forged slugs is like a deal for all four? The last set of arias I bought for the chevy was 1500 for pistons, pins, rings
 
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John V said:
After all these years ..still have to repeat: talking compression ratio without reference the intake valve closing ATDC is just taling..Dynamic compression is what counts... a 11.2 comp engine with an intake valve close like just say 60+ degrees 9of crank rotation= AFTER BDC means you aren't making any compression at all until the crank has rotated 1/3 of the 180 degrees it is going to rotate before its at TDC...

Only starts making compression when that hole is closed by the intake valve..
Your machine shop should have been drilling this into your head..

If they weren't you need to know why they weren't..

And John Mc has his story of squish/quench a little reversed

The is more than 30 years of proven beneficent advantages of det reduction with distances at or about 1mm...or .040" and it has been standard practice for many with every motor build for 34-35 years..

There is pages and pages of unverified, 1st rebuild guys changing all kinds of conceivable dimensions in their build AMONG OTHERs distance block to head of 0,8 aka .032" or so being THE DECISIVE factor in why their motor is not detonating...
Their fervent reports is like that of the converted...

And only a meanie would point out that a great many have build zero engines at .040 or 1mm to compare that versus their 0,8 or 0,9mm gasket thickness engines....no compare/contrast, and no base line...no, zero "single item change"...making their professions of faith in the glory of less than 1mm engines seem mildly put, less than convincing. (that 0,1 or 0,2mm is "decisive")
Click to expand...

John, it's my understanding you need some pretty phenomenal computer software and calculus/graphing to actually calculate dynamic compression ratio.

I can tell you right now, much of what has been said here isn't from first rebuild guys. You don't have to only post when you feel the need to assert yourself as the self-proclaimed TB engine builder.
 
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