Kannan08

Hey guys, I'm deciding on building a boosted B20 vtec. I've searched around H-T and found a really awesome guide to building such motors (LsVtec/B20 Vtec) from https://honda-tech.com/forums/all-motor-naturally-aspirated-44/how-build-%22reliable%22-lsvtec-b20vtec-1676914/. And Propz to the writer, it got me started on where to begin. I'm keeping my B16A with a possible rebuild, and I'm on my way to get a B20B block. The problem is I really want to boost the setup, which the posting didn't go into detail. I'm hoping to run about 350+ Hp on the setup to build which may be a overshot but I've seen B20 vtec motors above peaking 460 hp. I was wondering on the specifications relating to sleeve and bore the block, as well as mill and porting of the head. Any information that I'll be able to apply to my build would be greatly appricated, Thanks

Turbo-LS

iTrader: (4)

the block's arent the best for boosting but with forged internals and a really good tuner you should be able to hit 350 on it. otherwise i would recomend sleeves. dont bother porting the head, they flow enough for 800hp just some valve spring and cam upgrades is all you'll really need IMO on the head

DirtyDA9

Yea b20 blocks aren't good for boost, the sleeves always seem to crack in the same place.

Whiterice-gsr

its the longer stroke on them that makes too much side pressure cracking the sleeves it seems to be hit and miss though because ive seen lots of fast b20 vtec boosted cars. go to youtube and type in marcus civic this guys b20 pulls hard and its without vtec. that kind of power is totally doable.

92frostwhtdb2

As far as I know the ls shares the 89mm stroke ,your advice today has been somewhat amusing, anywayz to the op.the b20 has unique sleeve design apart from other bseries motors(if you seach Google theres a good comparison photo somewhere) this uniform type sleeve has a tendency to crack its purely based on luck from what ive seen.I suggest you use the ls block to avoid that variable( not saying the stock sleeves on a ls won't crack you just have a way better chance).

Whiterice-gsr

thats what i mean its so random with the b20 guys some blow some dont.

Whiterice-gsr

in my opinion i would not use a b20 block to boost when it seems to be the weakest of the available choices.

DirtyDA9

They have the same stroke as the LS engine. It's the bigger bore = thinner sleeves.

Turbo-LS

iTrader: (4)

the sleeves arent any thinnner most of the way around its just between the cylinders that thin and usually where is cracks. for 350 and conservative ignition timing it should hold up with some forged internals.

Spawne32

iTrader: (3)

the sleeves are thicker on a B20, its the fact that its a monosleeve that makes it fragile, increased stress on the sleeves due to detonation, or uneven cooling around the sleeve itself leads to cracking along the weak points where the sleeve connects.

DirtyDA9

Gotcha, I was under the impression the ls and b20 were pretty much the same block, the b20 obviously with a larger bore.

Turbo-LS

iTrader: (4)

thats ok its common misinformation about the b20 blocks. you would think its the same as LS just bored larger but that in fact would make the sleeves crank driving it NA i would think lol.

Kannan08

Yeah, I've been reading on the forums on hondaswap, and most of the people who posted suggested that i sleeve and bore out 84+, which would allow boost compression and stronger sleeves

DirtyDA9

Lol yea I always thought an 84mm bore was a little big on a b18a/b block haha, so the cylinders walls would be paper thin.

LOWLUDE22

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Turbo-LS

iTrader: (4)

The hp output difference from 84mm to 81mm isn't very much I always say sleeve it and run 83mm so you have room to spare or even smaller. You won't feel the difference in power from the larger bore size

Kannan08

The sleeves for the B20 come bore 83.75, and with most builds people bore it out to 84mm

Kannan08

Anyone know the average compression ratio a turbo b20/vtec is? I think its 12.5:1?

DirtyDA9

It all depends on what head and pistons you use. And 12+:1 is too high for boost.

Kannan08

I was thinking a b16a head, eagle rods, and CP pistons?

SLIM NOTHING

12:! is being done on boosted cars lol but on those sleeves i woudlnt attempt. i beleive that the effect that boosting has on sleeves is safer then building an all motor high cr and running them sleeves.

at this point yes you can port your head, and no you wont see too much of a differance, save your money. a good valve job, maybe performance valve job is good for you. no need to mill your head. do a 10:1 cr, a skunk2 tuner cam or just type R if you want to save money. dont jump on all these band wagons of having to use certain parts. from my experiance and the experiance of others i have talked to and friends with, it way easier than people put into it. if you are worried about your block send it to benson they are good sleeves fro what you need and will be very reliable and wont break your wallet, im saying benson because they are not as pricey as others. GL

Turbo-LS

iTrader: (4)

Your correct, higher compression all motor engines put more stress on the cylinder walls than lower compression and turbo. Its a more linear rise in pressure and force on the thrust postions of the wall with turbo than with all motor. Yes you can do 12:1 with boost but not on pump gas unless its e85 and on the b20 block i wouldnt trust it

DirtyDA9

Depends what compression ratio CP pistons you buy, they aren't all the same.

DirtyDA9

I know it's being done, but it's so pointless, you have to run Meth injection, E85, and have a ridiculous tune for detonation/pre-ignition, and like 2psi. Pointless IMO. It's probably people that wanted to try something different, or didn't feel like taking their NA build apart to boost it.

SLIM NOTHING

lol meth injection. guess you dont know what your talking about. yes e85 is gonna be needed. i can tell you for a fact that it dose make big deal. 12:1 cr in a 1000+hp motor? world record et in the class? no meth? i think it helps out alot.