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Need some advice for mods to my SBC, ive searched

randy88k5

randy88k5

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I have a fairly new GM crate motor, ~15k, and Im looking to squeeze a bit more power out of it. As of now, all Ive done is add a spacer to the TBI and a K&N (done a while ago). I have a Jet 6-Pack chip ready to go in. I was going to purchase Thorley ceramic headers and an Edelbrock Performer Intake for the stock setup. But now, Im thinking I might want 'new' heads and a cam upgrade (Crane Cams 'Compu-cam').

Ive searched and found info on the L31 heads, L98 heads, and the World Torquer Heads.

This is what I want:
I want a bit more power from the engine alone. Ill deal with the other stuff soon. I want to retain some sort of decent fuel milage (~10-15), and would like to run on 87 octane. I have octane booster for the times I want to change the chip setting.

Questions:
Is this possible within these perameters?
Will the head upgrades cause me to have to use higher than 87 octane?
Will there be quality headers available for me to use that is compliant with the emission stuff?
Would you recommend not to mess with a fairly new motor that runs fine?
Should I run the intake and exhaust upgradeds I originally stated and forget heads?
 
i've been doing some 'poor man' upgrades on my 350 (stock motor, not crate), and this is what i've managed to throw into it;

slightly used 305 heads
slightly used comp cam 270H and lifters (roller rockers came with it too)
exhaust manifold from a Z28

throttle body spacer and the jet stage 2 chips are next in line on my engine mods.. just thought i'd show you what i've done to maybe spur some ideas

:edit:
oh yeah... and took off all the emissions stuff (air injection pump and blocked off the holes on the manifold, and ran some new exhaust minus the cat (i'm in a non-emissions state)
 
Well, Im in an emissions state, but the standards dont seem to be set too high for my vehicle. Even without a tune up and a dead lifter, the old engine still passed.

I could take them off, but since the vehicle was designed to run the stuff, and it doesent rob too much power, I dont mind keeping it. And its a bit more environmentally friendly too, since it is my DD.

Jagged - Are you still able to run 87 without a problem?
 
Headers and intake will give you minimal gains. You can't really go much bigger on the cam because TBI's depend very heavily on vacuum, about 265 or so gross duration is about all you can run. The vortecs make good power and are fairly cheap, but you will have to buy a new intake manifold (I think they make one for the TBI) and new valve covers plus it will bump up your compression significantly meaning you won't be able to run 87. I would stay away from 305 heads, they are kinda the bastard of SBC's. If you want to start making some pretty big gains in power out of this engine, you will have to ditch the TBI. Otherwise, you already listed what you can do to squeeze a few more ponies out of that thing.
 
What exactly is the Jet 6-pack chip?

If it's a "universal" chip, your goal of 87 octane may not be doable...most generic chips increase the timing enough to require higher octane. If it's a "generic" chip, for lack of a better way to say it, they suck.

Hypertech's are the ones I'm more familiar with seeing slammed on a regular basis as being garbage.

L31 heads are going to give you some serious headaches if you want to keep emissions. I *think* you could get a carbed intake and use an adapter for TBI, but you'd still lose EGR.

Both the L31's and L98's came in 64CC chambers (AL L98's 58CC) so IIRC, that will bump compression over your TBI heads. Huge improvement in potential performance though. 9.5:1 or less would be a safe number with L31's and 87, BUT the PROM is all wrong for them. L98's are not as "good", but are still better heads.

No matter what you change PROM tuning is going to net some gains, but the more radical the changes (or larger deviation from stock) the more you will "need" to tune the PROM.

Headers will do nothing but help, but I'd ask for some input on the intake. Unless you change the heads, I doubt the stock intake is hurting you any.
 
I would do a TBI upgrade, something like Holley's Projection Direct Replacement TBI unit.

My plans for my TBI 350 is, Holley's Projection 670cfm, Undecided on Intake Manifold, Voodoo Cam, Possibly Vortec Heads (undecided), Hooker Competition Headers, Flowmaster One Chamber Mufflers, Eastern Tru Performance Catalytic Converters (with flanges so I can replace with a test pipe during mud bogs), and about a 100-125 shot of Nitrous.

Now this is a guess but I would think that the above alterations (minus the Nitrous) would give me somewhere around 275-300 HP then with the Nitrous I would be looking at around 400 HP.
 
Jet 6-Pack chip: 7(only 6 work) way adjustable prom.

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3430&prmenbr=361

I got my prom code, and had Jet cross-reference me a part number, then I special ordered it through Summit. So it is for the correct application.

Finding a prom setting for optimal power shouldnt be a problem. Finding a setting, if any, that would be sutiable and economical enough for DDing is my main concern. I want something that has street manners too.

I think I should just do headers for now, but I would hate to drop $$$$ on Thorleys, and find out I want to do heads too and have to buy them all over agiain. And thanks for the thought on the intake, dyeager.
 
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cam duration is part of the equation when it comes to engine vacume, but an equally big if not bigger part of it is the lobe seperation angle. headers will offer some gain. the manifold is also worth some gain. going to a port injected system will give you some overall improvement over the throttle body system. you stated its a late model crate motor, but you didn't say what heads are on it. are they vortecs?

--Scott
 
clancy84 said:
you stated its a late model crate motor, but you didn't say what heads are on it. are they vortecs?
Click to expand...

Hmm, never thought to look. I would highly doubt it though. I got it through my friend at the dealership as a direct replacement for the 88. I assumed it was the base model block with all the necissary peices for that application. Where would I see the numbers?

When I replaced it, it was for more of a halfway resto/DD type vehicle. Now Ive been bitten by the offroad bug, and Im hooked. Im looking to get a bit more power without getting rid of what I have now, and not destroy its reliability.
 
Mudfrog: you're gonna lean that engine out if you're not careful. Those injectors on the Holley unit are only 60lb per hour...also, that stock fuel pump you have has been said to be only good enough to feed about 270 horsepower. You might want to check out www.xtremeFI.com. They should have products to help you out with both of those problems.
 
i've had the engine together for about three days now... gone through about 27 gallons of 87 octane so far; and so far nothing noticeable, however once i get used to the feel of the engine again, i'll be able to tell for sure.
 
What is your budject and power goals?

Are you looking for hp or tq?

I know you said you were thinking about an edelbrock manifold which is a good mod but will run you 200+ bucks. I paid 200 to my door for my holley 2" projection manifold. Might want to check ebay for one. I know they have holley tbi's for 150( i paid 350 new for my holley 670 cfm tbi)

I would definetly go with headers and heads but unless you want to end up with the stock vortec manifold or go with the 350 dollar edelbrock vortec manifold i'd suggest the world torquer heads.

Match those up with a holley or edelbrock efi manifold and some bigger injectors or holley tbi and you'll be in the neighborhood of 280 hp. A computer cam will net you another 20-30 hp and 25-35 ft lbs of tq.

with the torquer heads you'll gain up to 30 hp on a stock motor and will notice a lot flatter and more power tq curve.
Once you do all this you will DEFINETLY need some computer mods. I wouldn't recomend the six pack of chips but since you already have them, you could try them out on it when your all done and see what you think.
 
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