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Old 06-03-2013, 12:33 AM
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Engine Combo- Blown SBC 500hp

Hi all, you guys have been very helpfull so far with the timing issues on my last post.

Whilst I have my engine out & in pieces I thought I'd get your opionion on the rest of my build.

The car is a 77 corvette, weekend driver, 93 pump gas. My goals are 500hp tyre shredding fun, with the occational trip to the strip.

The engine is a 388ci sbc, 9.7:1scr, scat cast stroker kit, dished 18cc 4.060 hyper pistons, 64cc edelbrock e-street alloy heads, roller rockers, flat tappet hydraulic Comp Cam NX274H duration 230/244 @ .05 113LSA, edelbrock mini blower- 4lbs boost (eaton mp122), edelbrock 800cfm thunder carb, MSD didigital-6 plus with Boost timing master & billett dizzy. Timing to be set at 26 initial, 36 total with boost reterd.

Th350 auto trans, 2200 stall, 3.08 rear gears.

Will this be a good combo for the street? this is my second build, first blown. All feedback will be greatfull. Thanks.

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Old 06-03-2013, 05:58 AM
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with a 2200 stall and 3.08's its going to be lame in the 1/4.
The compression ratio is too high to allow much boost.

you will be taking a lot of timing out of it under boost, as it is.
A dedicated cold air induction/ram air induction system will help.

Any time the supercharged engine is breathing hot air it will be much more likely to detonate.
You need to account for that....Cold air and or watermeth injection.
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Old 06-03-2013, 06:43 AM
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I wonder how many time you will have do this over again $$$$$$$$$$$$$$$
until you get tired of trying to exceed the laws of physics.

LOW CR IS BETTER.
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Old 06-03-2013, 07:55 AM
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why not use a set of 210 cc AFRs or something close and a 240 solid roller cam with a street friendly .580 ish lift?
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Old 06-03-2013, 08:54 AM
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Quote:
Originally Posted by vinniekq2 View Post
why not use a set of 210 cc AFRs or something close and a 240 solid roller cam with a street friendly .580 ish lift?
The little 122cid blower would then be a restriction.
The car would then be faster without the little blower on it.

This tiny blower is a waste of time and money on a 383CID engine. Especially one with 9.7:1cr.


The 210 AFR's and the solid street roller would Rock on this 9.7:1cr 388 SB.
(Minus the tiny toy 122 blower)

But that would make way too much sense.
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Old 06-03-2013, 09:03 AM
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You are going to need a 2800-3000 stall converter to run this on the street. Even a little more won't hurt. The blower can only do so much, it's still NA at idle. Been there done that to use an old phrase. I drive mine all the time in almost all weather with a 3000 converter. You won't even know it's there.

I don't think you will be able to run 36 total with 91 gas with your compression even with low boost. I run 34 at 2000 with vac adv and no boost retard and that's the limit with 8.25 cr. and 87 gas. I just burnt the ends off all 8 plugs the first day back on the road after the winter, and that not really pushing it. I have it throttle stopped to just barely into the secondaries and just 5 psi boost.

I strongly recommend you get an AFR gage with an O2 sensor on at least one side. You must let the car warm up for about 20-30 min to get these to read consistantly. Any less and you are just kidding yourself.

Your build is ok for street.. I would have used the 72 cc version heads or 72 cc Victor jr. It won't be the fastest at the track with 3.08 gears even with sticky tires. You have potential to get reasonable mpg but just one hard hit on the gas or one smokey tire cleaner and that goes out the window...haha
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Old 06-03-2013, 09:20 AM
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F-Bird did I forget to tell you that this is only my 2nd build 1st with a blower! I got very little experience with engine combos, thats why I read & research as much as i can.

I live in Perth Australia, not many people over here have experience with sbc's. Let alone the availability of parts....... dont get me started..... and the price......

Anyway, if I have a scrambled mess of parts you can put it down to in-experience, bad advice & poor availability.

Again this is a street build, is it really that screwed up?!?
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Old 06-03-2013, 09:21 AM
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without blower/thanks FB

Quote:
Originally Posted by F-BIRD'88 View Post
The little 122cid blower would then be a restriction.
The car would then be faster without the little blower on it.

This tiny blower is a waste of time and money on a 383CID engine. Especially one with 9.7:1cr.


The 210 AFR's and the solid street roller would Rock on this 9.7:1cr 388 SB.
(Minus the tiny toy 122 blower)

But that would make way too much sense.
Ya,I was thinking that 9.7 was ok ish with 210s and a solid

of course the heads could be machined a little to bump CR if needed
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Old 06-03-2013, 09:31 AM
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Thanks bentwings,

The other idea I had was to lock-out the timing @28, it seems to like the initial at 24 anyway. Wouldn't this also help prevent detonation & also the need for boost retard?

What are your thoughts on this? I'v never driven a car on the street with locked out timing.
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Old 06-03-2013, 10:26 AM
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Just curious.How does your gas compare to ours??. Really don't know that.
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Old 06-03-2013, 10:40 AM
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We have Premium unleaded readily available everywhere, its called ultimate 98, it would be on par with your 93/94. Some suppliers have a blend of this gas which includes 10-15% ethanol.
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Old 06-03-2013, 01:24 PM
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Again this is a street build, is it really that screwed up?!?


ya it is that screwed up..How many more times can you afford to build this engine???? .

drop the compression ratio 8.5:1 or less.

build a simple 350 with a low compression ratio for this blower.

The 388 is a big mistake. Too big CID and the cr is way too high for a blower on pump gas.
Where you drive it-how you drive it does not change that.

Last edited by F-BIRD'88; 06-03-2013 at 01:31 PM.
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Old 06-04-2013, 08:09 AM
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You sound like a broken record F-Bird.... "Less compression more Boost"

I only want to run my blower at 5lbs, I dont want to over-drive the f*#! out of it & increse blower temps (its a mp122, not a 6-71).

Saying that, running 5lbs boost on my 9.7:1 388, gives me an effective ratio close to 13:1, well within the limits of 93 gas PROVIDED my timing is correct.

As for the cam & stall, comp give a power ban for this cam (Nx274h) at 2400-6500. My cam rep who sold this to me said for my engine it would more likley be 2000-6100 due being a 388 bored stroker.

My 2200 stall is from a mild 350, am i right to assume that under the extra torque of my blown 388 this will streach to at least 2500??

So this gives me a cam with a power band starting at ~2000 and a stall of ~2500. Hummmmm..... sounds ok to me.

If I have got any of this incorrect please explain it to me. Thanks.

Last edited by blowme77; 06-04-2013 at 08:31 AM.
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Old 06-04-2013, 10:21 AM
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I do think compression VS boost is just two ways to skin a cat both having their top end limits.

The boost will add to the bottom and mid,but given the correct cam timing and compression a N/A can do that also.

Certainly it is the end user's choice how to get there.

It's logical if you notice that most cams for street blower engines are kind of conservative in terms of overlap.My two cents is why blow a engine and then lose the blower effect in cam timing?.
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Old 06-04-2013, 10:38 AM
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Quote:
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I do think compression VS boost is just two ways to skin a cat both having their top end limits.
Ha! ya wouldn't believe it, I was havin a yarn to a chap today about boost vs compression, his words and I quote; "Theres plenty of ways to skin a cat, but it doesn't matter which one you choose because that cat ain't gonna be happy!!"

Point being tread carefully wether it be boost, compression or timing.
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