I'm about to start my winter rebuild for the autoX car and I sourced a B20 block. The last engine build two years ago was a fairly budget GSR build (PR3's, ARP fasteners on otherwise stock bottom end). This time the plan is to build for some real power, somewhere in the 230whp+ range with good torque delivery. I've already go a nicely hand ported P72 head with springs/retainers, Pro 2's, Ultra street intake manifold and 70mm TB. Header will be last, but I'll cross that when I get there, right now I have some questions about the short block.

1.) I've got another spare GSR short block I would like to rob the girdle and respective main caps from. I know I'll need to have it line honed but someone put my mind to ease that that is for the best because I've always been told you don't swap mains from another motor.

2.) I had been strongly considering having the CSS put in to help cylinder stability with RPM. I'd like for it to be 85mm, but I may go 84.5mm if I CSS so I can rebore later if necessary. Is the CSS recommended for an NA setup that will see trips to 9K with most of it's life spent over 5K?

3.) If the CSS isn't necessary for my goals, how reliable (obviously with a good tune) will 85mm be? Plan is somewhere around 13:1 CR on E85.

Anything else anyone can recommend? I'm open to suggestions on piston and rod choice, but likely will be the lightest H beam (since I beams are twice the price) and piston that will hit my compression goal.

 

Yeah, loose the pro2's if you want mid range tq. They suck. I know first hand. I have some Crowers that **** on my junk2's. Junks are for sale if anyone wants them. CSS is a waste of money for Na. Don't hammer on it when in very low rpms, should be good.

 

I'm look at doing the same b20v build, but with just 12.5:1 compression pistons, I/H/E, ARP rod/ main bolts, its just a budget build since I feel like the single cam in my car is about to let go soon..

In for more info on your build and process though!

 

I've seen a lot of dyno's that show the Pro 2's make good mid-range, like 4-6K. On my current 11.5:1 B18C they definitely lost down low compared to the Edlebrock's I just took out but I gained another 700rpm at least of usable power up top. The 4730's had great pop on the smaller displacement/CR motor but ran out of steam over 8K. I know cam tuning could've helped but I lack access to a dyno within 4 hours of travel.

I recently finished a very similar build for a friend who was in college. We bought some 12.5:1 pistons for his stock rodded B20 and put his B16 head on it, ARP rod bolts and head studs, and he picked up some Crower stage 2 NA cams. Unfortunately, he graduated before we could get the car running (motor's hung needs wiring finished) so I haven't been able to use it as a yard stick measurement compared to my current GSR. His was a total budget build, but should be stout...I just wish I could ride in it before I have to start ordering stuff for mine!

Edit: Looking at light weight rods, I see Brian Crower offers their Sportsman rod that's 426g. That's much less than the Manley H Beams at 505g and the much more expensive Carrillo SA rods at 487g.

 

Skunk2 Tuner 3 or pro 1 cam shafts would be a better cam choice along with a plenium spacer for the manifold, You should deff hit your target power goal and have good mid and top end.

Just cause some peopel had bad experience with the cams dont let it deter you from the brand itself. Too many factors come into play with cams, Some people pick the wrong cam for there engine setup and some dont degree the cams for full power potential as well resulting in the power loss or low power figure.

Not to say the member above diddnt choose the correct cam or degreed his cam obviously the crower cams worked better for his setup. My point being is every engine is diffrent.

Theres a good thread in the faq on how to build a reliable LS/b20 vtec engine. todays after market support for the B series is more than ever.

Skunk2 just released there Ultra series cam shafts which are making head lines in the scene! There making awsome power on peoples setups compared to the leading compedtors. So dont count Skunk2 out the game as far as cam shaft desighns for the B series. Obviously i support them but im just stating my humble opinion.

 

Oh I don't. I've seen too many people making good power on their cams. I mean actual dyno curves, not just peak numbers. It was a toss up between the Pro2's and Rocket's m24xx, but ultimately the split rate of the Skunk2 won me over vs the straight rate of the Rocket's. The primaries are huge on them, and I think will benefit from the extra compression and displacement.

This isn't intended to be a budget build, I need to make power. All my competition in class nationally will be K or forced induction...or both! I feel like the tractability of NA and the lower weight minimums will be beneficial. The suspension is sorted, the trans is, and I'll be adding aero this winter as well...some real power to back everything up will be nice finally!

 

with that c/r and ethanol I dont think the css is necessary, but screw it for $350 you have peace of mind. Ive never liked the b20 sleeve design. Ill be doing it to my gsr block 1mm over same c/r and fuel.

Never hurts to bullet proof something.

 

I agree with that last statement. My only concern is, if it's going to fail I think it will be between two cylinders. I'd hate to spend the time/money to have it done only for it to crack where it can't help anyway and then instead of being out $100 for the B20 I'll be out $600 (shipping and all).

 

With my experience, pro 1, 2, and 3 have excellent off vtec power. Way better than a crower cam would. Pro series is a hard profile to beat Especially pro 2 and 3 . Found out from personal experience that even pro 1 is pretty good even if advertised specs are off. They provide flat torque curve and very snappy response.


My vote for the OP is pro 2 as planned.

 

Since you said this isn't a budget build and making power is the main goal, have you ever thought about a stroker build?

 

If you really want to go all out on the block:

Use the GSR block
B20/LS crank
B20/LS aftermarket rods
Sleeve the block and bore to 85mm+
13:1+ comp, possibly higher depending on fuel (with methanol, 15:1 wouldnt be impossible)

At this point, you are looking at north of 250whp. You will most likely need to look very hard at your intake manifold and header to see if they will help or hinder the powerband you are trying to create.

 

This looks more like a dead build than a autox build. Look into classing in your local region before you go crazy building an engine .

 

Why not just build a K series why stay with the B series did i miss something?

Build a efficiant N.A K series or even slap a kraft works SC on a stock block K with some supporting mods and start stomping some ***! even a all motor 300+WHP K will be a great setup to compete with the rest. **** even a budget n.a K setup will be competative.

But if your stuck wanting to stay B series id look into a high comp 2l B with a ported head using the skunk2 ultra race manifold and ultra 1 cams and good header out to a 3'' cat back on e85 will be competative but thats just me my opinion means nothing its just a sugestion. Theres still lots of racers using the B series but its not a secret the K makes more power period.