408" with 6-8 lbs boost
- Thread starter m880
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harrisonm
Well-Known Member
I guess my first question would be how well built is it? If Mike from MRL built it, I'd bet it would be no problem. However, how was yours built? Was it professionally built by experts like at MRL? What is the current compression? I think I remember reading that builders might plan the compression to be a little lower if the motor is to be boosted. What quality of parts did you use? Big difference between a cast crank with budget brand bearings, pistons and rings and all top drawer stuff. And finally, how carefully was it assembled? There is a big difference between file fitting piston rings and checking bearing clearances carefully with micrometers and using plasti gauge and just throwing parts in. I am sorry, and I do not want to insult, but I'd think these were fair questions.
SLOPAR72
Well-Known Member
What is your goal with the car? What direction you headed with it?
JW
JW
Woods74
Broke Senior
An eye for detail doesn't have to be paid for.. In fact I'm tired of hearing the only way to a good build is to buy it. Now, good machine work is another notion; If you wrench, a quality job should be part of your DNA by now. If your confident in your build it will be fine. These blocks are tough. 6-8lb's is conservative. Cubic inches don't add boost.
As it was said before, there IS a difference between RPM and LOAD under boost
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Matts440
Well-Known Member
You should be fine with that low of boost. And I agree pro engine builder might know tricks to get every last horse power out but I've always built my motors, plus most pistons companies have the ring gap for boost applications on their paper that comes with themail, if not a simple phone call to the manufacturer they can tell you as well. I'd just get all forged internals just in case later on you want to turn up the wick a bit.
SLOPAR72
Well-Known Member
I would do the 365. You can put good internals in it and crank it up. It will be a handful even at a 365. Opinions will vary and that is mine...
Good luck,
JW
MiradaMegaCab
Well-Known Member
What fuel will you be using? E85 or pump gas?
Typical 408 stroker kits have a hi comp ratio for boost. W/M injection will help with this issue.
A custom piston for the 408 with a huge -40cc dish would be needed to drop the CR .
I run a 387ci 360 with a 3.79 stroke K1 crank. 2.1 rod journals , .927 pin, K1 6.125 rods. An off the shelf -30cc Diamond 2618 Forged piston from a 383 stroker chevy with slightly modified valve pockets, only $8 extra charge. 2618 alloy is great for handling boost.
I'd recommend using full Grove main bearings to provide full time oiling to the rid bearings. I'd also recommend ARP head studs and a serious head gasket. I use SCE copper head gaskets , my heads are O-Ringed and have a receiver groove cut in the deck of the block. That will hold any cylinder pressures.
Typical 408 stroker kits have a hi comp ratio for boost. W/M injection will help with this issue.
A custom piston for the 408 with a huge -40cc dish would be needed to drop the CR .
I run a 387ci 360 with a 3.79 stroke K1 crank. 2.1 rod journals , .927 pin, K1 6.125 rods. An off the shelf -30cc Diamond 2618 Forged piston from a 383 stroker chevy with slightly modified valve pockets, only $8 extra charge. 2618 alloy is great for handling boost.
I'd recommend using full Grove main bearings to provide full time oiling to the rid bearings. I'd also recommend ARP head studs and a serious head gasket. I use SCE copper head gaskets , my heads are O-Ringed and have a receiver groove cut in the deck of the block. That will hold any cylinder pressures.
Boost and CR are not mutually exclusive, it just means you really need to be on top of your tune if you don't want to blow it up.
Built many engine's,probally 40 gas burners and 75 or so Detroit and cummins and 3 cat diesels..only turbos and superchargers though were on diesels.My second car in 75 was a 70 Dodge Challenger, been Mopar or no car ever since.This is to give me something to play with while I build my 73 duster if my pain will cut me some slack. I'm just thinking that the extra load on the longer stroke with boost might not hold up well,but I could very well be wrong. I like the idea of boost because I can keep the 3.54 gear and pathetic gas mileage or go n/a strokers and 4.10 have horrible gas mileage.
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The added torque from the stroker adds stress to the block. I still wouldn't worry.
Not to knock an awesome build, but why such gearing in something with probably about 700hp?
Actually, why would you want 700hp on the street in the first place? 500hp is HUUUGE and more than enough to blow almost anything into the weeds *if* you have traction.
I would go 408ci and not worry about the turbos. You will have an easy 450hp, probably more like a lazy 500hp if it is built well with even mild components correctly matched, and you won't have to worry about the expense of a turbo setup and the headaches that come with dissipating that much heat from that many components.
- boingk
Actually, why would you want 700hp on the street in the first place? 500hp is HUUUGE and more than enough to blow almost anything into the weeds *if* you have traction.
I would go 408ci and not worry about the turbos. You will have an easy 450hp, probably more like a lazy 500hp if it is built well with even mild components correctly matched, and you won't have to worry about the expense of a turbo setup and the headaches that come with dissipating that much heat from that many components.
- boingk
Why, if I have to explain, you wouldn't understand why 700 is better than 500.
The key lies within your own words here; "BLOW ALMOST ANYTHING AWAY"
Everything else you need not worry about. I'm SURE he will get a grip on things and handle it. You needn't worry.
nm9stheham
Well-Known Member
6-8 psi boost is pretty low... it was the boost used on the production Buick turbo'd V-6's in the mid 80's. I would go for it; the better mileage rationale makes sense to me. The comments for the CR are good, IMHO.
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nm9stheham
Well-Known Member
Well said! Thank you.
SLOPAR72
Well-Known Member
And there you have it.... I had my hands the V6 Turbo Buick stuff in the 90's...... Your Boost level of less than 10lbs won't even scratch the surface of the power potential. Even at 365 inches it would be a beast.... Cool the air charge properly and with good tuning you will be riding. I like the idea of a Block Girdle, Head Studs, and really good head gaskets.... I could go on and on but would be boring banter Lol....
JW
there was a member running 935 rwhp on a twin turbo stock block 416 I believe .
Pump gas,e85 is unheard of here in escambia county FL.
Your choice of cranks is my prefered choice in stroke,3.79" but not a cheaper stroker crank option in the 3.79".
The off the shelf pistons may make it viable though.
Great reply
D
Did I say anything about 700 hp? I looked at my post and can't find any h.p #s mentioned.
500 hp 408 stoker and 8 pound of boost could easily add another 200 hp. That's where my mind when.
Have you done much research on what it will take to boost a chry sb eng.
I spent 2 year researching it for my 340......In the end, decided it was way too rich for my blood. Built me a high compression 408. If you have good welding skills, it will be much cheaper!
Every one i talked to said dont' build your first boost eng with a eng that you care about. You will burn up at least one in the learning curve.
Then there's the throw everything a way and go fuel injection........there is even more dollar sign.... and lots more learning, in my case.
just food for thought, not trying to change your mind
Have you done much research on what it will take to boost a chry sb eng.
I spent 2 year researching it for my 340......In the end, decided it was way too rich for my blood. Built me a high compression 408. If you have good welding skills, it will be much cheaper!
Every one i talked to said dont' build your first boost eng with a eng that you care about. You will burn up at least one in the learning curve.
Then there's the throw everything a way and go fuel injection........there is even more dollar sign.... and lots more learning, in my case.
just food for thought, not trying to change your mind
Nope, but a decent 408 will make 500hp and half a bar of boost on top of that kind of engine will push power to somewhere near 700hp if you can keep the charge cool enough.
- boingk
Because just imagine the look on a Hellcat drivers face when they can't pull away from freaking Durango!! And the look on the many mustang and camaro owners that get BLOWN away by a Durango.
barnett468
Well-Known Member
If you want strong bottom end with a turbo and dont want to rev to the moon, you should build a 408.
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