Ls1 Turbo top end setup questions
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Teching In
Joined: Jul 2015
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Ls1 Turbo top end setup questions Hello,
So after heads failure on my ls1 76 trans am i decided to go turbo.
Soo here is a little about my engine. Its an stock ls1 aluminium block with a set of high compression ported heads (took it off already). It has a big loop cam (i bought it with the cam so idk the specs), it was converted to carburetor setup with a high rise intake.
So would it be a problem to run turbos with big cams?
What heads specs would be preferred with turbo setups?
I am thinking of keeping the carb and go with Blow through carburetor for the turbo set up so would it be hard to tune it?
Thank you
So after heads failure on my ls1 76 trans am i decided to go turbo.
Soo here is a little about my engine. Its an stock ls1 aluminium block with a set of high compression ported heads (took it off already). It has a big loop cam (i bought it with the cam so idk the specs), it was converted to carburetor setup with a high rise intake.
So would it be a problem to run turbos with big cams?
What heads specs would be preferred with turbo setups?
I am thinking of keeping the carb and go with Blow through carburetor for the turbo set up so would it be hard to tune it?
Thank you
No but it helps if the cam is specced so the valve events work with the turbos. The one in my 408 was ground for twins and is fairly large at 235/247 but idles fine and has no issues putting down the road in 6th gear at low speeds even with a single plane intake. Part of that is also in the tuning.
Depends on the fuel you have available. Most will recommend 317s. That's what I use and they work well plus they're probably the most produced head so they're fairly cheap.
Depends on how well you can tune a carburetor and how much headache you're willing to put up with.
What heads specs would be preferred with turbo setups?
I am thinking of keeping the carb and go with Blow through carburetor for the turbo set up so would it be hard to tune it?
On The Tree
Joined: Feb 2016
Posts: 102
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From: Leeuwarden
In order to determine the heads you'll need you need to ask yourself what's your goal. When your goal is clear you can start to determine what you'll need to get you there. High hp will need a big(ger) turbo. A bigger turbo will need a lower c/r. Lower c/r will mean less grunt at lower rpm.
Keep your chamber as small as possible. A stock pair of 317 heads will give you a c/r of 9.3, that's appropriate for a fair amount of boost. A pair of polished 241 heads will give you a c/r of around 9.8, good enough for an application with mild boost.
Keep in mind that using a big cam will lower your dynamic compression ratio and will cost power at lower rpm also.
Good luck!
Keep your chamber as small as possible. A stock pair of 317 heads will give you a c/r of 9.3, that's appropriate for a fair amount of boost. A pair of polished 241 heads will give you a c/r of around 9.8, good enough for an application with mild boost.
Keep in mind that using a big cam will lower your dynamic compression ratio and will cost power at lower rpm also.
Good luck!
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Joined: Mar 2014
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From: Ohio
A big cam isn't the problem, overlap is typically the problem. Exhaust pressure in a turbo setup is usually higher than intake pressure, so when both valves are open, the exhaust will want to backflow through the intake. The more overlap, the more reversion you might see. This usually kills top end power, causing people to complain about power falling off too hard.
I'm not too keep on the whole low compression idea. I was skeptical coming into my current build because I typically run 8.0:1 - 8.8:1 compression on turbo builds, so 10:1 was new to me. It works fine. I just tore it down for inspection and lifter replacement. Not a single sign of detonation even being driven at 20 PSI daily and hitting 30 PSI on pump gas on 2 occasions. That being said, 317s are cheap and easier to come by than the 799/243 heads, so why not. 317s certainly aren't the most common. There are far more 862 or 706 heads out there, since there are far more 4.8s and 5.3s than 6.0s.
I'm not too keep on the whole low compression idea. I was skeptical coming into my current build because I typically run 8.0:1 - 8.8:1 compression on turbo builds, so 10:1 was new to me. It works fine. I just tore it down for inspection and lifter replacement. Not a single sign of detonation even being driven at 20 PSI daily and hitting 30 PSI on pump gas on 2 occasions. That being said, 317s are cheap and easier to come by than the 799/243 heads, so why not. 317s certainly aren't the most common. There are far more 862 or 706 heads out there, since there are far more 4.8s and 5.3s than 6.0s.
