I cant figure out my compretion ratio,

81.4 mm stroke b17 gsr crank
86 mm bore CP 13:1 pistons
42.7 cc combustion chamber b16 head
7.7 cc piston dome displacement
151.562 mm eagle 5.967 rods
211.84 mm b20 deck height
0.029" oem thicknesss head gasket with a 86mm bore

any help?

I would like to be around 12:1 max.

 

b17 itr crank?

 

yeppers

 

How can you run an OEM HG with an 86mm bore?

 

oem thickness i think i have to to keep the compresion down

 

b17 itr crank?

what motor did that come out of????

 

Ok, so are you saying the gasket bore is 86mm, but the thickness is .029"?

 

yes thickness is 0.29", that is the thickness of a oem gasket correct me if im wrong.
Yes the b17 crank out of a gen 2 gsr integra.

 

Also, are you using custom compression height pistons since your rods are 151.56mm?

 

Yes, thats the ~ compressed thickness but you havent confirmed the gasket bore diameter.

Ok, I see your edit now.

 

gasket bore diameter would be the same as the bore 86mm.

 

Are the pistons custom made? Because your average aftermarket B-series piston (30mm comp height) will sit ~ 10.42-10.5mm above the deck with those rods & stroke.

 

no, this is part of what im trying to figure out
stock stroke is 95mm half of which is max heigh from center line on the crank which is 42.5mm
stock rods are 141.7mm for a total of 184.2mm
81.4mm/2= 40.9mm+151.967mm=192.867mm
deck height is 211.84mm-192.867mm=18.973mm

im no pro but this is how i figured it

 

the no was for these are not custom pistons.

 

Why did you call it a Type-R?


Those are two different crankshafts.

 

Because Im a little slow

 

Your math is right.

Your rod is too long

81.4mm (stroke)/2 + 151.56mm (rod) + 30mm (avg B-series piston comp height) = 222.26mm

 

So there will be enough room they will not hit the head? It will actually be 15.2mm below where the stock center line of the wrist pin would fall.

 

You stated the deckheight of your B20 is 211.84mm which seems right because I've measure my LS block before and it came out to damn near the same specs.

Im saying that your piston will be popping out the cylinder, and will very likely make contact with the head. I'd sell those and buy the proper size rod for that stroke (with that block), although there isnt much aftermarket support for that crank so if you want to use it you might have to have custom rods made.

You'd probably be better off just getting a B18 A/B crank with the appropriate rods, IMO.

 

Im trying to keep it close to a 1.75 rod/stroke ratio.
The B18 and B20 have the same deck height I thought the B20 was higher?
My head is going to explode.

 

The B18A/B & B20B/Z Im 99.9% sure have the same deckheights + utilize an 89mm crank w/137mm rod

 

Really? Wow if I would have know that it would have saved me a ton of time.

 

I did the math again with a shorter eagle rod it will be a little taller longer than the stock setup
https://honda-tech.com/forums/showthread.php?t=2504346

Stock B20
95mm stroke
42.5mm from crank center line
+142.75mm rods
___________________________
185.25mm total height
-211.4mm deck height
___________________________
-26.15mm from top of the deck


My setup
81.4mm stroke
40.9mm from crank center line
+148.895mm eagle rods
___________________________
189.795mm total height
-211.4mm deck height
___________________________
-21.605mm from top of the deck

 

The B20A & B21 block might have a higher deckheight, but I honest dont much about that block so I couldnt say for any certainty.

 

Right, but as you know you still have to account for the piston compression height.