DVNCI

Hey guys, long time no talk!

I haven't been on here in ages, life got in the way. . . . .

Anyway, I have the 96' Collector Edition with solid rear, 9", roll cage etc - you can see the build thread here: https://www.corvetteforum.com/forums...cs-inside.html

Long story short, I have a chassis that will handle whatever power I want to throw at it. Rear end, clutch, fuel are all ready to go.

Please - no "you should really use an LS" comments, that's not what I want to do here.


I have already engaged forum member "tpi 421 vette" (aka Jim) to start putting things together.

Right now the plan is to do a 396 - I already have a Procharger F1 that I will be intercooling (and probably doing meth as well).

So I think 1000 crank hp is probably realistic - it doesn't "have" to do that much but that's kind of a target.

Jim and I were talking last night, we've already got most of the bottom end components picked out. The remaining questions I have are:

1. Compression ratio? From my research I probably need to run close to 20 psi to be able to achieve what I'm after here. However, I'm wary of going too low with the CR - I don't want to make the car a turd on the street, since that's where this car will spend 95% of it's time.

2. Intake manifold? I'm leaning towards a nicely ported LT4. I would prefer not to do a single plane/fabbed type manifold, but I'm not ruling it out either. The Miniram is an option I suppose, but I've read a few things that seem to indicate the Mini is not great with boosted cars. Will a ported LT4 be a restriction at this power level?

3. Throttle body? Probably leaning toward an AS&M Monoblade here.

4. Injector size? 60s?

5. Headers? I'll be running AFR 227's - anyone using a 1 3/4 header on their LTX? (or maybe even 1 7/8)


Just FYI, once Jim begins the build he'll be sending me pics and we'll be posting them along the way.

mtwoolford

well, unlike conventional small blocks there are no beefed up aftermarket blocks available...or new oem blocks for that matter.

so start with a garden variety two bolt main block, bore and or hone it the minimum necessary, and have it fitted for four bolt main caps with the outer two bolts being "splayed"; not much else you can do?

DVNCI

As I state above, Jim has got the bottom end sorted out (it will indeed be splayed, all high end components, etc) - I'm interested only in the questions above.

mtwoolford

item (2) I've got an LT4 dedicated Edlebrock "air gap" manifold; its a nice piece; you probably have your heads sorted out but the Edlebrock manifold is supposedly matched up to their LT4 heads if that would be of benefit.

Marauderprime

Sounds like a good plan. I don't think your fuel injectors are big enough. Siemens Deka makes an 80 lb. I am building a low boost TPI motor right now, and I am going to be running 60lb injectors with a boost referenced regulator, and they should be ok up to about 6-700 hp (although that would be ragged edge). With a supercharger, even with the intercooler, you will be producing alot of heat at 20 psi, so you will need additional fueling just for cooling (in the tune). I had a twin screw supercharger on top of a 5.4 (i know its a different animal from your pro-charger, but its still an efficient blower) running at around 15 psi through stock exhaust and a cold air intake, and my Siemens Deka 60 lb injectors were at around a 90 percent duty cycle at 650ish rwhp with a boost-a-pump. Do yourself a favor, go right to the 80 lbers for 1000hp.

Also, having had a previous 94 trans-am gt with a 396 lt4 in it, I can tell you that the ring lands get scarry. I have heard that the ring/piston packages have improved in recent years, but when you're talking about a max effort boosted motor, my inclination would be to go with a 383, since the power difference between the 383 and the 396 under high boost would be between 60-80 hp depending on the combination, I would go for the beefier piston for longer term reliability (as much as one can have at that power level). I would rather have a 940 hp 383 that I can put 100 passes on, than a 1000 hp 396 that may have piston issues. (These are of course examples, not hard figures. Please no flames internets).

DVNCI

Good info - thanks!

drcook

You might want to consider some engine coatings. These folks provide some very interesting (and affordable) services all considering what you are putting into that engine.

http://swaintech.com/

http://swaintech.com/race-coatings/automotive-coatings/

http://swaintech.com/engines-run-str...-tech-coating/

rklessdriver

Just some general thoughts.

What fuel? Gonna make a big difference as to how much compression you can run.

I'd shoot for 10.5-11.0 SCR with E85.... Somewhere like 9.5-10.1SCR with C16 and I personally wouldn't even bother to build anything FI with 93 pump gas.

I'd get compression with big chambers and flat top pistons.... run them down in the hole if you have to. Don't fret about quench with a supercharged engine..... it's not important. I'd prefer do everything not to use a big dish and weaken the crown of the piston down to top ring land.

Between your choices I'd go with Meth injection only. Forget about air to air.... waste of plumbing and extra weight to carry around for nothing. Now air to water is the real deal..... but again a lot of plumbing and extra weight, plus constantly filling up the ice tank......

The PC F1 will certainly get you there with room to spare. Which one do you have? F1A-91, 94, F1-C?

With an F1 on a 23* SBC I'd probably shoot for like 370-380 inches with the AFR 227. 3.625 - 3.8" stroke. Keep the bore small like 4.020-4.030 max. You need the cyl wall integrity more than the displacement.

Big engine displacement is really not needed. We make well over 1000HP with only 310 inches in our NMRA Renegade engines using a Vortec YSI (cast wheel) on C16 fuel... even more power with the new billet wheel.... We turn them 9400RPM to get there but that brings me to my next point....

RPM is your friend with centrifugal blowers and HP. I'd cam a street car to make peak power about 7200RPM. Set the shift point at 7500.

Will

dizwiz24

forget ported lt1/4 intake manifolds you need a sheet metal intake manifold .

hogan makes them and you will pay $ 2000 for it, but ive seen before after dynos showing 80 rwhp improvements (on heavy modd lt1 builds). camaroz28 site had some dyno comparison

as&m is a good tb choice

i would say compression no lower than 9.6:1 if you want it to not be a turd on the street. this is where im at on my stock bottom end afr 195 head lt1 vette and it loves 13 psi of boost.

1 3/4" headers are too small, 1 7/8" stepped headers might be a good idea for you

you are going to need bigger than 60 lb/hr injectors - esp if you ever want to do e85

lastly: if you come up short on your power goals on pump gas you should have the extra fuel pump/inj capacity to do e85 and you will make 1000 rwhp.

DVNCI

I have used them before actually - good stuff for sure.

All good info, thanks!

Fuel will be pump gas. This car will be driven on the street 95% of the time. I want to run down to my local Shell, fill up, and head to the track - this is the same reason I don't want to do air to water on the intercooler side. I already have the air to air intercooler and I have a buddy that will help me weld up the piping. Very little weight as far as that goes. So any reason NOT to do air to air other than piping reasons?

Thanks - I'm aware of the Hogan, might just have to bite the bullet . . .

Actually sent you a PM on the headers.



Good info guys, thanks.

rklessdriver

Air to air is just terrible for efficiency at that power level. It's not worth the weight and complexity. The FI guys I race against in Real Street are all Meth injection for that reason. Little more power than 1K but they are limited to the F1, YSI or single 76mm turbo....

I think the LT4 intake will be fine with port work. But headers need to be 1 7/8 or 2 primary.

93 pump gas is horrible.... best of luck with that.
Will

dizwiz24

one thing i BEG you to do on this build is use an optispark. No LTCC coil conversion or x24 conversion.

dont use an MSD or chinese garbage optispark, but rather a bonafide vented factory OEM NOS (mitsubishi optical sensor) unit. (you can find them if you do a little digging across some forums/ ebay and ask the right questions).

put an msd 6 on it (as i have done on mine) to light the spark - even under boost, and quality wires.

i ask this so you can prove out that the optispark (at least a vented oem nos model) is a reliable unit to light the spArk - even at ultra high HP and RPM levels.

an LT1 build is not an LT1 without the optispark

Tom400CFI

I would like to see this too.


The MSD doesn't light the spark...the coil does. I'm still waiting for someone who owns an MSD to test the coil voltage when running.

dizwiz24

i got my recommendations for the ignition parts (msd + oem nos optispark) from greg at blowerworks. there was some benefit to a 'spark amplifier' in a 'boost' application.

the coil im running is an msd . i think its higher voltage then stock but not sure.

Tom400CFI

The coil? I totally agree with that. The coil is where the work is done in the ignition system. The MSD box?? Some have claimed that it feeds the coil 450v (?) I've asked for proof, never seen it. I've looked up schematics...I think the MSD box is nothing more than a gigantic ICM (on/off relay) with rev controls built in.

Would you go measure voltage to your coil w/your car running? Or just key on?

DVNCI

Again, my car is a STREET car first, drag car second.

I just talked to my engine builder, we are probably gonna tone it down a bit, will probably be more like 850-900 or so. I will probably start out with 10-12 lbs of boost to start out with.

LOL too late diz - I have had the 24x system for a while now. But not because of anything to do with spark/igntion/etc - in fact I had one of the original "Dynasparks" and it worked great. I went with 24x for tunability.

Would you have preferred I went the all out LS route like every other Joe Blow these days?

I know your feelings on the opti, that's not up for discussion here. Please keep the comments to the questions at the top if possible.

88BlackZ-51

Jim mentioned the bare bones combo to me and all looks good at this point.

Jim built my 421 and flew to my place to assist in tuning it. You are likely in the best hands or very close to being the best hands for your build.....

You dont see guys spending big money on C4's much anymore. Enjoy the build and the finish product!

blue94

Are you considering shaft rockers?

bill mcdonald

With your fuel choices and boost level, which I think will need to be maybe 25psi to hit 1000, maybe 9:1 tops... maybe 9.5:1 with some meth trickery. But this all depends on displacement, cam, and all parts after the supercharger... Boost is just back pressure and we are not comparing a corvette kit on a stock motor to reference across the board. Boost is what is left over, You need cfm flow.

Don't know. I have no idea why a mini ram would have issues that an LT4 intake would not. I have read about it for years. They are basically the same thing. If the edelbrock has a better design, then move towards that and work on that piece. It has supported this power level. I don't have an LTx engine so I don't really retain much about it. But lcvette has done it. Turbo and e85
It is about as big as they get for our cars. Or you could move over to an LSX part if anyone still does that.

Not enough. 80 maybe with meth injection to back it up. Maybe not even then.

25 psi I would want 1 7/8

I think you should take some time to make some compromises with use.
You want a powerful street car you have to work for it. Pump gas, you have to cheat it. Alternate fuel system, double up injectors, dual tanks, meth injection etc.

Lower compression ratio allows you safety, Lower it more and make the blower pull you around. Pulley it up and run a restriction plate? Use eboost to control a servo valve door on the blower inlet? wastegate to control it?

Thing is, with this power level, all worried about low end power... but the top end is just ridiculous. It is not like it will turn into a 80's corolla if you lower the compression ratio. I mean your lugging it around, you are lugging it around. Boost comes on decently with a blower. You just have to think differently about it.

And yes, you should build an LSX, and put all that money into just getting it running in your car.
Sometimes I think cheaper to buy and LSX wrapped up in a C5.

DVNCI

Yep, you may not remember but I sent you a PM a while back about Jim and your recommendation (among many others here) is what led me to him!

Yep! I forget what brand but we are using a shaft kit.

Thanks Bill

Based on Jim's recommendation, and further research, I actually ordered a Miniram today. It will be port matched to the AFR 227's.

After talking more with Jim, 1000 is probably a bit unrealistic for what is basically a street car. With 10-12 lbs we are guessing it will come in around 800 crank hp or so? Who knows, that's way more than I can use on the street anyway.

Regarding compression ratio, general consensus seems to be around 9.5 or so, we'll probably be close to that.

Consensus on injectors seems to be 80, so that's what I'm going to go with.

And yeah, there is absolutely NO question an LSX would be cheaper, but there is a million reasons I don't want to do LSX . . . . and frankly it just wouldn't be as cool in my opinion. Certainly wouldn't be as much of a conversation piece!