rossjmu

Hey guys looking for some opinions on my hopefully-soon-to-start-if-it-would-ever-warm-up-a-little NA build for a dedicated CRX autocross car.

Car background: '91 CRX Si with a stock OBD-1 LS swap.

My plans are to completely strip the car down and strictly use it for Autocross. It will never see the street. I don't care how it idles, I don't care if it can pass an emissions test or not, and it certainly doesn't need to run on pump gas. What I'm looking for is good throttle response, torque, and mid-range power suitable for autocross style racing. I wouldn't even know what HP number to say I'm shooting for.

Parts I already have:

Stock bore GSR Block, fresh B16 head with valve job, port and polish, titanium springs and retainers (forget the brand at the moment), Skunk2 IM, Toda cam gears, ARP bottom end bolts and head studs.

I would like to do a high compression motor (again, race fuel is fine) with no more than an 82mm bore (don't want to have to sleeve the block). I have no idea what pistons to look for and these seem to be my stumbling point right now. I was thinking a Bisimoto header but am open to any suggestions. For cams the Skunk2 Pro2s look like a good choice. Injectors: what size should I look for? For engine management I was looking at picking up an ECU with Hondata s200- does it matter which ECU as long as it came from a VTEC B-Series motor and same OBD gen.? Trying to get an idea of the major parts I still need to purchase

Also, would it be a good idea to use the LS crank/rod to get a little more stroke?

Thanks!

solorex

Stock B20 with ARP rod bolts mated to a short ratio tranny. Get some seat time with this and then put some Crower 403's in it mainly to get some more revs out of the engine. Lots of usesable torque and a cheap build.

rossjmu

Stickin with the GSR block. Tranny I already have is from an SiR Civic with an LSD. Very short ratios.

jdm_ef9

LS crank will net you the needed torque/hp for low rpm.

DC-2uned

^And you would never think 1.8mm could make such a diffrence, but it does. My 81.5x89mm LSVTEC doesnt make 145wtq for nothing.

rossjmu

Sounds good I'll plan on using the LS crank and rods and get everything balanced. What pistons should I be looking at to use with that crank/rod combo and the Pro2 cams? Looking for the most compression I can get without smashing valves.

jdm_ef9

We used a custom Wiseco piston in our LS crank'ed b18c. I had the pin moved so we could run a 10cc dome with those PRO2's. If you wanted to run a smaller dome you might be able to get away with a "shelf" piston. Just need to do the math and see what you need.

BTW... I have a lightweight eagle LS crank for sale if your interested. It has been balanced to 10k.

rossjmu

You going to give me a deal since I just bought the Pro2s off you?

andrewk

I would also check to see what class you're thinking about running. don't want to get stuck with a bunch of awd turbo beasts or tube chassis cars. each class has a certain set of rules.

i just built a oem gsr but with a 81.25x89 gsr block using the ls crank/rods and oversized itr pistons. should be a beast once i get it running properly.

jdm_ef9

Hmmm... shoot me an offer!

rossjmu

I really don't care much about what class I'll be running in. This project is for two reasons: 1) A learning experience on putting together a car (never gone this in-depth before) and 2) For fun. I know I'll be in some type of open modified class because of the engine swap, but I'm ok with that. When I AutoX'd before I was never too concerned about my time compared to others, I was just there for the experience. After I get some more seat time and want to get serious about the competition I'll work on something else and worry about the car class.

junkyard racer

stock b series with vtec, tires/wheels, good suspension, brakes and learn to drive. My old auto-x car (EG) had top notch everything, to include a 200hp b16 and I got smoked by a nearly stock B series eg.

If you think a built engine in a honda will earn you anything at a auto-x you need to reconsider. Put your money in track time and tires.

rossjmu

Thanks for the advice but there's more to this build than not getting beat by stock-class cars.

rossjmu

Question on using the LS crank: do I need to use the LS main caps, and should I have it line honed? Anything else to know about using the LS crank and rods besides blocking off the oil squirters?

4piston

For Street Mod right?

Not sure if this is in the budget, but I'd do a 92x87 motor at 12:1, a pretty standard ported GSR head with nothing too big on port volume, and some off the shelf camshaft good for midrange. For throttle response, some 50mm Kinsler ITBs.

Low budget, some 84.5mm 12:1 pistons, Eagle rods, stock crank, LS head with a Crower 404 or something like that....and ITBs The throttle bodies make great midrange and have excellent throttle response.

I have never driven a Street Mod Honda, but I have run SM in my EVO and I know I'm always begging for more low in power right off the corner and that is with over 400wtq and a fast spool. I have driven ST Hondas, but never a SM Honda and they have zero power and it is all about momentum. Set it up to have acceleration from 3000-6000 rpm, and anything beyond that is momentum so it doesn't matter. Everything for you is going to happen in 2nd gear for the whole course, so keep that in mind. You probably want to be able to go 65mph in 2nd.

rossjmu

Sleeving is out-of-budget for the time being, so are ITB's

Are aftermarket rods really necessary on a NA build?

Frankacura

I agree
Take a B20b 98 JDM 9.3CR and get the bloc decked at 0 wit pistons, get the head shaved by .020 and you have 9.8:1CR add Crower 403 and double springs, Si-R or type R IM and there you gonna feel TQ (150) at every RPM till 7500 185Whp
I run a Stroked B20 on LS cams and i have 140tq at 2000rpm and 148tq at 4700rpm for 160whp@6500rpm (B18b cams)
Ran 1/4 on street tires at 13.9 in integra 95 2550 wit driver

Frankacura

Rods bolts only (ARP)

Natural Aspirations

What makes you think ARP rod bolts are better than OEM Honda rod bolts?

Frankacura

Cause wee stretch a couple of OEM one but probleme solved wit ARP
The LS rods studs are not the same size that the vtec one.
they much smaller so make it safe and put ARP
Hy rpm is hard on them.
But 7600rpm is not hy on nonvtec crower 403

rossjmu

Can anybody answer this question?

PyroProblem

Use the maincaps that are machined to the block. You SHOULD have the line bore checked and corrected if needed. That and plug the squirters and your good!

rossjmu

When you say use the main caps that are machined to the block, does that mean I can use either?

jdm_ef9

Use the main caps that go with the block.... if you have a b18c block, use the accompanying caps.

rossjmu

Thank you. So will I use main bearings that correspond with the B18C block or the LS, or are they the same?

*edit: A quick look on ACL's website looks like the main bearings are the same for the LS and GSR, with the rod bearing's being different.