z28mccrory

iTrader: (7)

Im still in the research phase of my build, but this is something that i cant find much info on.

My plan is to do a "budget" (meaning 4 bolt head setup with GM casting heads), and im trying to determine what things will limit me.

After speaking with DrTurbo, i intend to use a GT91

Its been discussed a lot as to weather a 370 or a 408 will make more power. Seems to be the general concensus that the 408 has the "potential" to... but only if the turbo is sized for the 408... and in every application most agree that the same sized turbo will always make more power on the smaller displacement engine.

I wouldn't call my build max effort by any means. I plan to stay very modest with the parts i use, but still think it has the potential to make very good power (800-900rwhp)

Here is a quick rundown of what i have in mind.
-Iron block
-Forged Pistons
-Eagle 6.125 rods
-Stock Crank
-Unported 317 heads
-Mild Cam (even considered LS6)
-ARP Head Studs
-Cometic Gaskets
-Stock Main Caps with stock studs
-LS2 Intake

I already have my valvetrain components from parts that are left over from my 418 nitrous motor (Pushrods, Rockers, Timing Set, Lifters, Oil Pump) etc.

At this point im trying to stay budget minded on the motor, without cutting any important corners.

Obviously in the grand scheme of things a 408 is only a few hundred dollars more than a 370, but is the displacement actually a DISadvantage? Things such as more side loading of the pistons, etc.

Im trying to figure out what the first bottlekneck of my setup will be, what i will come to the conclusion of "Ok... im not going to be able to go any faster because of _______"

I imagine it will likely be the 4 bolt head setup, and pushing water/lifting heads. Which brings me to the original point... since you can make the same power on less boost... would the 408 hold the heads down any better? What if i o-ringed the block/heads?

So there it is... which has greater power potential with a GT91, and what will limit each one.

BigRich954RR

iTrader: (1)

you need to arp stud the mains. I would pin them too cause main mains walked around at 700RWHP but had hi rpms too,

Yes the 408 will hold the heads down better at same power level.

The 408 will have more over all TQ too peak power is best for a auto with a hi stall
So are you auto hi stall or M6 ?

z28mccrory

iTrader: (7)

I dont plan on very high rpms. Likely less then 6500.

I already have a 4l80E in the car. Im not sure how my current converter will do, but i will likely try it.

I also already have a Moser 9" in the car with 3.50 gears.

dudeman

iTrader: (43)

i would suggest a bigger cam and intake. i am going to a 6.0L with forged pistons and rods and same heads. i went with the epp blower cam and a victor jr with an elbow to try and get some extra power.

z28mccrory

iTrader: (7)

Im still undecided on the cam, but i think that the LS2 intake should be fine. ProStockJohn took one to well over 20psi... Mightymouse runs either an LS2 or LS6 intake... tons of big power builds run stock style intakes.

The goal is to just stay very simple and only spend money where it will net gains.

My 418 already has a Vic Jr/Elbow setup on it, and will likely be sold with my 5.3 heads since it was port matched.

BigRich954RR

iTrader: (1)

I would still do the Arp main studs at the very least. would still like the mains pined but not needed. I got alot of main walk at 600 hp at 6500 rpms. and a whole lot at 700hp 7k rpms.

ChevyChad

iTrader: (50)

Well, less boost will almost certainly be easier on the whole head lifting problems. I dunno how much better it would be in the 800+rwhp range however with stock casting heads. Plus, if you go 408, you will need an aftermarket 4.0 stroke crank, so thats substantially more than "only a few hundred dollars more".

I'd also suggest going with compstar rods over eagle, and LS6 manifold over an LS2 (assuming you havent already bought those parts). Also, Dont skimp on the main cap hardware. Go with studs.

OUTLAWZ RACING

iTrader: (9)

I think having the the heads o ring and the block will off set the cost of a 4.00 crank. Oringing will allow you to run a ton of boost.

z28mccrory

iTrader: (7)

Considering a 4" eagle or compstar crank is only $800-900, and even a stock one is $100-200 used, that is indeed only "a few hundred more dollars"

I've had fine luck with eagle... one brand to another of budget rods is just splitting hairs.

LS2 and LS6 are very clos, and again, splitting hairs. I already have an LS2 intake available, at less than half the cost of an LS6.

z28mccrory

iTrader: (7)

Yeah im definitely looking into having it o-ringed. I would prefer to wait untill down the road when i go with an aftermarket casting head, but if it will allow the 317's to get there, then im all for it.

z28mccrory

iTrader: (7)

Can you tell me more about the main walk you were getting?

I never had any issues on my old stock bottom end setup. I was 600-650fwhp shifting at 6800. Everything looked perfect after 40-50k miles like that (99k miles on motor at time)

I assumed an iron block would keep things in place better, especially if i was RPM conscious.


*i should have used multi quote*

camarokid94

iTrader: (2)

what about searching and tryin to find the guy form like norway or something like that sells a pyrimid style ring hes got stock 315 heads and makes 1500 hp.

BigRich954RR

iTrader: (1)

Yes iron moves around less. well at the lower level you could see where the the steel cap was wearing on the alum block from it moving around. Bearings looks good but only had it like this for 30k miles stock 8k miles beating one it .

When i upped the power it was moving around little more which could be seen on caps/block. The bearing had a little wear not much but looked worst then the other motor and these only had 10k on them mostly at the parting lines areas.
AT about 15-25k i pretty sure would have seen copper on the bearings

I will say I really really beat on my engines. I rate my engine in sets of tires i go though and not really miles. I never do burn outs and the second motor had 6 sets of tires 2 drags 4 street/road racing tires.

z28mccrory

iTrader: (7)

Thanks for the info BigRich. ARP studs aren't that pricey, but i've been told i should consider having it line honed if i switch over to them... which starts adding up little by little.


As far as big power 370ci setups go, im anxious to see if anyone who is running one with big power steps in and gives their opinion as to why they stayed 370ci vs go larger. Especially people such as Fireball who went with an aftermarket crank anyway and stayed smaller CI.

one fast zo6

iTrader: (490)

stock crank 370ci is a proven setup. get a good turbo camshaft, it's almost
free power.

BigRich954RR

iTrader: (1)

Well if this is the case drop the 408 idea get the main studs pin the caps line hone the block. install good bearings. Dont waste the time to ring the stock heads for 800 hp even for 900 hp The 317 heads will handle it. might push a little water at 900 but live with that and just watch it.

When you have more money buy new heads pull the motor which is needed to ring the block and heads. Have them cut for rings maybe a freshen up the motor which will be cheap cause it was build right the first time.

30k Worth of parts put together for 500 buck will most likely blow up. 3k worth of part put together for 2k will live a long time at the race level.

The reason you see alot of the stock cranks living at 1500hp is because the whole motor was Machining by a good engine builder.
I do a lot of street racing I live near 3 huge city you should see the amount of cars/engines/money wasted cause some one built a engine drop a lot of cash on parts but went with a crappy machinist shop to save a few bucks.

Not sure of cost on your heads gaskets but might want to do MLS if there cheaper.
I like the rods if you have the money callies are a lot better. But if your trying to save money get the Scat Heavy duty rod. The owner of scat is giving this board a great deal on rods right now.

98Z28CobraKiller

iTrader: (17)

Have a look at this https://ls1tech.com/forums/generatio...ston-rock.html

z28mccrory

iTrader: (7)

I dont want it to be misinterpreted that i will just be throwing this together. All the machine work, and likely the assembly, will be done at Bischof. They did my 418 and they definitely know what they are doing.

My original point is getting a bit off track. Once i begin finding the limits of this combo (even if that means AFR heads with o-rings), is the 370 going to be at any disadvantage? Will it be able to handle more power because of the smaller displacement and prefered geometry (shorted stroke and side loading, piston speed, etc).

Because both motor are the same bore, is there any advantage of the larger stroke? Deck surface and valve shrouding will be the exact same.

Are there any high HP 370 guys out there that began finding the limits of their combo, and thought "Damn... i wish i would have went with a 408"

darooke

iTrader: (13)

I think if you are dead set on the 91mm turbo then go with the 408 for the quicker spool and added tq. I think it is going to be a little laggy with a 370. I have driven pt88 setup with a forged 370 at 18psi (800hp) and i am currently building that setup. I think it is a great combo but there is a little lag so with the 91mm turbo it might be to laggy for you

z28mccrory

iTrader: (7)

Im not dead set on the 91mm turbo, but after speaking with Dr Turbo, its just splitting hairs to go with the 88mm instead.

Honestly my goals could probably be achieved with an 80-85mm turbo, but the 91 is a great bang for the buck. I would rather go too large than too small. The car will see a lot of street runs, so regardless of what turbo i go with, i will likely be using an AMS-500 or eBoost2 to slow down how fast it spools.