Turbo Camshaft Theory

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RustyRatRod

RustyRatRod

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So most of yall know I am building a turbo slant 6 for Vixen. My project "Cheap & Nasty". I would like to discuss turbo camshaft theory. I know that normally, turbo engines use a wider LSA than N/A engines. Usually on the order of 112 and 114. However, I've been reading a lot lately on turbo cam theory and it seems that has changed with modern turbo technology. So my question is, is there any reason I couldn't run a camshaft with say a 108 LSA with a turbo and tune it accordingly? I'm not asking regarding the Cheap & Nasty project. This would be for the next project after Cheap & Nasty, after getting my feet wet and getting familiar with turbo tuning on the stock 225. Any input is greatly appreciated. Thank you. Drive through.
 
Minimal overlap due to exhaust pressure being much higher and greater reversion. Also little to no need for a muffler, (hence the original corvair turbo mini-muffler). Stock spec cams work well.
 
I have a .257/.267@050 108lsa solid roller in my stroker.. turbo doesn't seem to care. Although that was with the carburetor. I like Richard Holdener's ideology. Every cam is a turbo cam. Whatever the engine does na, will reflect the same style curve with boost, just at a higher horsepower level. (Although linear boost curves from centrifugal superchargers can skew that a bit.). But I do see where minimal overlap can help with building boost and driveability, but not necessarily better power production overall.
 
For what it is worth, my "old" 170 turbo slant used a very mild Crane cam. I would have to dig for the full specs, but it was the S-264. 264 adv dur, I think 224 @.050, and .434 lift.
 
Charrlie_S said:
For what it is worth, my "old" 170 turbo slant used a very mild Crane cam. I would have to dig for the full specs, but it was the S-264. 264 adv dur, I think 224 @.050, and .434 lift.
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And I just got back from a grocery run with Charlie's old "turbo" cam. Ok, I'm exaggerating - the grocery run was about two hours ago.

They're still in production and you can view the cam card here: https://www.compcams.com/high-energy-220-220-solid-flat-cam-for-chrysler-170-225-6-cylinder.html It has a 110° lobe separation angle. The more efficient your turbine, the less important it is to run a wide LSA. The wide angles were due to the high back pressure from earlier turbos. Newer designs have exhaust manifold pressure closer to intake pressure.
 
****, maybe I should rethink trying to help so many people.
 
RustyRatRod said:
****, maybe I should rethink trying to help so many people.
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We made a mistake around '90-'91 & put a 'special' turbo cam from Comp in the '70 AAR that was running a Rotomaster, it turned it into a lag pig, had more intake #'s kinda like the reverse-pattern Dutra tried on the Slanty. Use a small intake, lots of exhaust duration w/a wide LSA, crank it up....
 
Killer6 said:
We made a mistake around '90-'91 & put a 'special' turbo cam from Comp in the '70 AAR that was running a Rotomaster, it turned it into a lag pig, had more intake #'s kinda like the reverse-pattern Dutra tried on the Slanty. Use a small intake, lots of exhaust duration w/a wide LSA, crank it up....
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I think I'm just going to go with the stock cam. I've pretty much decided not to put the turbo motor in Vixen. I'm going to pull the 331 hemi out of the rat truck and put it in that. Whatever I've touched slant 6 wise has gone well. This truck has sat for too long. I need to do something with it.
 
Every cam is a turbo cam. Whatever it does for the engine NA it will do for the engine on boost. Choose it the same way you would for any other engine as the cam will move the power around the same way when it’s turbo charged. There is no such thing as a “turbo cam”
 
TT5.9mag said:
Every cam is a turbo cam. Whatever it does for the engine NA it will do for the engine on boost. Choose it the same way you would for any other engine as the cam will move the power around the same way when it’s turbo charged. There is no such thing as a “turbo cam”
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Yeah yeah. I've seen the videos. I just wanted personal opinions, das all.
 
When I built my last/6 I floated the idea of putting a turbo on it, and the guys at the/6 site suggested that I build it differently than what I'd do with it if keeping it N/A.
They suggested a different cam and if turbo-ing, not to shave the block/head, and some different cam specs than if not. I'd have to dig and find the posts.... I'm sure they're pages deep by now, it was a few years ago.
 
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