b21ft overbore to b23ft

[croovlov]

I could not find an answer to this in the FAQ's or any of the threads. I have bored out b21 to b23 for non turbo cars with excellent results. Can the b21ft be bored out to b23ft because the pistons are only $80 each from Volvo for the B23ft. This is for my Nasa racing HPDE 242T. Would the cylinder walls be too thin for a turbo? I will be running about 13psi boost eventually.

Also, is the ipd boost adjustment valve a good way to go for raising boost?

Carlo

[mAydAy]

Well, you can, but you have to sonic check the block to make sure it can handle it because its a huge overbore. People have done it, and 13psi isn't all that much really.

The iPd valve is a good way of adjusting boost, and there are lots of other similar choices out there.

-Andy

[Dfer10]

its a 4mm bore so yea listen to mayday

[Matt Dupuis]

The only two blocks I've personally heard of splitting were B21 overbored to B23+

I wouldn't do it...

p.s., is $80 each a good price nowadays? A while ago you could get 'em for $120/set.

[mAydAy]

Yeah on that note, I think you can get custom pistons from either Arias or Venolia for cheaper than that......May be only for the B230FT, but an L-block B230FT with Arias's would be pretty bulletproof.


-Andy

[towerymt]

I'll be running a B21F block with std. B23ET pistons. Unfortunately I won't be able to tell you what it will handle until at least next summer. Hope to see 10psi before next spring, though.

[PRVersion]

is a b23 block really that hard to come by? wouldn't it save you the trouble of having to get your block sonic checked? and what if you sonic check your block, and it's no good? :???: :-P

[mAydAy]

is a b23 block really that hard to come by? wouldn't it save you the trouble of having to get your block sonic checked? and what if you sonic check your block, and it's no good? :???: :-P
If its no good, then you get another until you find a good one.

If you get a B23F block you have to bore it out, not sure if 1st/2nd overbore B23F pistons cost more or not.....

[Captain Bondo]

The B2x motors are famous for core shift and should be sonic checked before being bored larger than 1st OS. You're looking for numbers north of 0.100" on thrust.

Also as was said $80 a pop for stock size b23ft pistons is crazy expensive.
A search would probably turn up more info.

[towerymt]

Sonic testing is expensive. B23FT oversize pistons in a cheap/free b23 block may come out cheaper.

I could probably find a B23F block to put B23FT pistons into, but I never actively looked for one. With the larger clearance needed for the forged pistons, a little wear on a n/a block might be acceptable. Especially if you want to set it up a little loose for hard running.

[Kevin Hawkinson]

I could have a B23F block loaded up in the van in 7 hours (it's 1:40 in the morning, and the JY opens at 8:30). They're WAY easier to find that B23Fts, and with no turbo, they're still plenty cheap, too.
OTOH, sleeves are only about $50 each plus maybe $25 each to take out the old cylinder bore and fit a sleeve. So for $300, you can make the pistons as big as you want (up to about 100mm).
If you're sticking with B23-size pistons, and you don't wanna spring for sleeves, just get a B23 block. You'll be glad you did.

[benflynn]

b23f's are out of early 240 na's? i think this might be my next project, now for a 16v

[blu92in99]

b23f's are out of early 240 na's?Yup, 1983-84 240 n/a.


-Justin

[MikeHardy]

is 200CC really that important

[Hank Scorpio]

is 200CC really that important

no. Compression on the other hand is ;-)

[towerymt]

is 200CC really that important
Makes a nice difference n/a. Gotta help on a turbo.

[John V, outside agitator]

200 "gozinta" 2300 how many times?
8.7% increase in volume.
OOOOOOOOOoooooooooooooooooooooooooooOOOOOOOOOOOOOO O :roll:
Freshen, get lighter parts, turn the boost up to 22 psi or a bit more.
Have fun. :-P

[benflynn]

if you are going to all that work anyways you might as well up the displacement and cr, but i would not do it for it's own sake

[croovlov]

That's a lot of different information and opinions. Here's my situation: Not much money. Engine has over 160k. I need to do a trans rebuild- I think that 1st-2nd gear problem is cropping up. I don't get how a normal b23 can work because of no way to get the oil to the turbo and back (some blocks have a boss for return line, but what would that cost to set up? My one attempt to put a b230 into a 240 was a pain with brackets and crank pulley.
~10% displacement increase is still probably 15 HP , and it worked wonders with my 78 wagon and my 82 244, non-turbos. This would raise CR, too. Who sells pistons and rings for such low prices you guys mention? I like Mahle pistons , they seem pretty unbreakable- we used them in a 142 race car back in the 70's and 80's.

I have to say , this group is a treasure chest of info I have never had before. I wish I knew of TB years ago!

Carlo

[Hank Scorpio]

Makes a nice difference n/a. Gotta help on a turbo.

It makes a difference but nothing 1psi wouldn't do either. NA doesn't have this option so yes 200CC is much more important NA.

Now... 7.5:1 CR vs high 8's low 9's in CR is a MUCH bigger difference (off and on boost). Compression choice comes before displacement imo (200cc's wise) if budgets are concerned.

On an NA block you drill the block for the return line and run the pressure side off the oil sender port.

[Hank Scorpio]

if you are going to all that work anyways you might as well up the displacement and cr, but i would not do it for it's own sake

Honestly if you dont have to I wouldn't. Save the money and keep the cylinder walls as thick as possible.

[croovlov]

Thanks to all who took the time to offer help. I will just rebuild a b21ft with .030" overbore and go for the boost . Boost seems to be the consensus for max power. I will use my b230 manifold throttle switch to activate terminal 11 (I read that on another thread) for full throttle and hopefully I can beat a few corvettes!

Thanks again, friends!

Carlo