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Old 09-28-2005, 03:14 PM
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how much boost will a goodwrench 350 take??

Ok ive gone and done it again, after a venture into dieselturbocharging which ended up costing me a toyota puckup after hitting 30 pounds of boost, ive decided to try somthing ive wanted to do for a long time.. turbocharce a smallblock chevy....

the project car is a 79 malibu 2.dr with a 267 smallblock... now i know what everyone is going to cry now... junk junk.. but my question is this how much horsepower and boost could i safely squeeze into a new goodwrench 350, you know the 249 Hp thing that retails for 1350 USD... i have single turbo header system and i have my dirty hands on a garett GT-40 turbo with intake a/r 0.58 and exhaust a/r 0.84, the turbo will support up to about 780 Hp and 25 pounds of boost if staying within max efficiency. so i have the potential to detonate the engine at will.... but where do i stop if i dont want to find out the hard/expensive way what it will safely handle??

9 lbs??

11 lbs?? with intercooler?????

any input please

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Old 09-28-2005, 06:20 PM
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depends on the compression ratio... either 9.1:1 or 10.0:1. you dont want to raise your effective C/R above 12.1:1. which means a 9.0:1 CR with 4psi boost will be 11.4:1 effective CR. now a 10.0:1 CR with 4 psi boost will raise the effective to 12.7:1 CR effective. basically, the lower your CR the more PSI you can run. and another thing is when you add boost you need to add fuel so you dont lean out and burn up your pistons. and the last thing is you will need to run a much higher octane fuel. other then that, thats about it.
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Old 09-28-2005, 06:30 PM
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Quote:
Originally Posted by 97Z28
depends on the compression ratio... either 9.1:1 or 10.0:1. you dont want to raise your effective C/R above 12.1:1. which means a 9.0:1 CR with 4psi boost will be 11.4:1 effective CR. now a 10.0:1 CR with 4 psi boost will raise the effective to 12.7:1 CR effective. basically, the lower your CR the more PSI you can run. and another thing is when you add boost you need to add fuel so you dont lean out and burn up your pistons. and the last thing is you will need to run a much higher octane fuel. other then that, thats about it.
The listed ratio for that motor is 8.5:1
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Old 09-28-2005, 06:36 PM
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That engine has cast el-cheapo pistons. 5psi max unless you want to toss $1300 away in a very short amount of time.

Larry
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Old 09-28-2005, 09:27 PM
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Like Larry said, the worst thing is those cast pistons. The other internals would be fine, but with cast pistons you have to be careful. I have heard of engines running for a little while at close to 20 psi on cast pistons, but they will break eventually if they dont melt. If you keep the AFR in the high 10s under boost it will help keep combustion temps and EGT down.

That GT40 is a damned fine turbo and perfect for a small block. If you could replace those cast pistons with some cheap speedpros it would really help alot. The limits of pump gas are dependent on alot of things. For a small block 12psi with 8.5 CR is not a problem at all as long as you control AFR. With the cast pistons you would be pushing it, but it is doable. You can run more boost with a turbo than a roots blower so the 8-10 psi limit for that type of engine can be pushed up a little. I took a ride in a truck that a member of this board has with a GN turbo engine pushing 23psi on pump gas, but he is running a nice intercooler and water injection kit that allows it to work.

The problem you can run into with trying to run low boost at high RPM on a small block is that the compressor really gets off its map and effciency drops off pretty bad, but it can be done. That turbo is pretty versatile and about perfect for what you are wanting to do.

As past the pistons, as long as you keep RPM reasonable the bottom end should be fine. The turbo really kindof cushions the bottom end parts and as long as you dont detonate it or let it RPM real high it should hang together fine.

The carb will be fine, but I would get a WBO2 for tuning and do some homework on carb mods. It is cheap and straight forward for a plain jane Holley DP.

Chris
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Old 09-28-2005, 09:59 PM
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ok... 1 thing.. how do yall know whats in this motor. he hasnt given part numbers or anything. and the GM 350 crate motors that i looked up come in various configurations. so how can you definitely tell what he has without asking????
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Old 09-28-2005, 10:02 PM
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Quote:
Originally Posted by 97Z28
ok... 1 thing.. how do yall know whats in this motor. he hasnt given part numbers or anything. and the GM 350 crate motors that i looked up come in various configurations. so how can you definitely tell what he has without asking????
The parts dont really matter and are not that different. Pistons are the only problem. Stock parts other than that are fine as long as he keeps RPM decent.
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Old 09-28-2005, 10:04 PM
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ok... i dont want to start anything... i was just curious. what about the CR???
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Old 09-29-2005, 10:33 AM
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Quote:
Originally Posted by 97Z28
ok... i dont want to start anything... i was just curious. what about the CR???
Obviously the CR is a question. Most of the GM engines come with vortec heads these days for not much more money. I think those engines are around 9.5CR which is a little high. If he does the piston swap and uses a dish piston he can get CR right where he wants it. 9.5 is still not a deal breaker and will handle boost okay, but will just have to be a little lower boost to keep detonation at bay.

Another thing is the cam profile. I would be interested what it is. Typically they factory cams are low duration with wide lsa which is perfect for a turbo setup. If you get a bigger turbo oriented cam it will make alot more power, but for what he is trying to do the small cam might keep from breaking the stock bottom end since it will not rev past 5k very easily. My engine will rev very easily with the bigger cam and the turbo really makes it like RPM. When you start turning over 6k with boost and make bigger power that is when the bottom end needs some real attention.
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Old 09-29-2005, 02:57 PM
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The Goodwrench replacement motor he is speaking of has 195 INT 202 exh
duration with lobe centerline of 112. Basic 1250 dollar motor, good torquey truck motor. Right at 8.2 to 8.5 c.r.
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Old 09-29-2005, 06:35 PM
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Quote:
Originally Posted by USA1
The Goodwrench replacement motor he is speaking of has 195 INT 202 exh
duration with lobe centerline of 112. Basic 1250 dollar motor, good torquey truck motor. Right at 8.2 to 8.5 c.r.
Well, that is even better. It should make good boost off idle and right up to about 4500 RPM. It will hang together just fine at that level.
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