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wrong cam for turbo?what should I go with?

 
Old 07-23-2004, 12:05 AM
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v8, im not picking sides on this, but how much can you type on here? I dont have that kind of time
damn
ed
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Old 07-23-2004, 01:07 AM
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Originally Posted by V8_DSM_V8again
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With just 230* duration single pattern...

Tell him he should have run a 234/226 and watch him laugh and blow your doors off...

. YOU DONT mother trucking need a big cam anyone suggesting t-rex like duration is something illegal..

What I mean by a good cam for a restrictive manifold is like 220/230 ish... or so depending on the size and RPM range of the motor maybe slightly smaller or slightly bigger...
Where did i say go with a Trex cam for a turbo car? Anyways as i said before u believe in something and I believe in something else that was tested infront of me with great results. As was said before, there are guys with Turbo LS1's that tried all kind of cams and the best were reverse split cam. I said 234/226 because the guy asked for a cam that is mean with a turbo. If u read my first post again u will see that i did tell him he can go with a 230/222 cam. A T76 wont have any problems feeding the LS1 the boost it needs and it will make more power, faster spool and response than a 220/230 cam for the reasons i stated before in my posts. The guy who wanted an advice can make up his mind after reading this thread. You stated your point of view and we stated ours.
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Old 07-23-2004, 02:54 PM
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Originally Posted by 69firebird
v8, im not picking sides on this, but how much can you type on here? I dont have that kind of time
damn
ed
You have no idea how many W.P.M I can type, how many years of education I have, how many different engines I have worked on or just how much work I cram into each day......

Originally Posted by ls1power
Where did i say go with a Trex cam for a turbo car?
That was'nt directed exactly at you... It was more for the "I want a 1800 RWHP Z06 no make that AWD Z06 with a C5R block and a 4.25" stroke and two huge turbos and a TREX cam" Kind of people. It would have like a 1000 rpm wide powerband or something...

I do think the intake duration on your suggestion is too big.. I guess if he wants lope for lope sake and is a poser who'd rather sound mean than make more hp it is ok.

His exhaust manifolds don't flow so good... So you compensate for it by using more exhaust duration and limiting or eliminating overlap...

Alot of low 11's and 10's turbo buicks run 208/208 or 210/210 or so..... I use the buick example because it is a GM pushrod actuated engine with alot more turbocharged cars running around... It is a lower reving engine... I'd add about 10 degrees on each side for an LS1 due to how much higher you can rev it.

Here are some cams I think would work for him

http://www.crower.com/pdf/35.pdf
Stage II and III crower.. NOT so much the III but the II.

II= 114* LSA 217/226 .553/.575
III= 114* LSA 226/232 .556/.556

Turbocharging stretches a cams powerband.

Stage II RPM power range 1500-5800... Since its turbocharged it will actually be a nice fat power range from spool to 6800. Power wont taper off hard untill 7300.

If you have a raised rev limiter, shaft rockers, titanium retainers, lightweight valves etc to wind her higher then go with stage III.

Stage III RPM power range 2000-6000.... Again since it is tubo equiped the powerband will be spool to 7000 rpm without a sharp drop off untill 7500 rpm...

The stage II will pull alot harder on the street..

In the catalog Comp has a 216/220, 220/224 and 224/228 all at 114* LSA.... I'd actually ask them what is available now.. For a young yet popular engine like the LS series they have alot going on in R&D and new options not in the catalog.. Also the custom shop has some really trick stuff that works.

Even proponents of reverse splits recomend alot less duration on a turbo set up..

Originally Posted by Pro stock John in another thread
For a turbo grind, Terry @ Cam Motion likes reverse splits, to keep the intake valve open as long as possible.

But he also cautions that turbo cams tend not to be as big as supercharger cams.

So a 230/236/115 +2 like mine does not necessarily translate into you getting a 236/230/115 +2. In fact, he said that going with intake duration over 230 might (emphasis on might), result in slower spoolup of a turbo setup. Again keeping in mind that duration makes power, you may find that a 230/224 is the biggest cam you may want to run.
I also think that unless the valvetrain and everything else has been optimized for a raised rev limit and a higher powerband even the 230/224 is too big for most peoples std displacement.

The case in point is that on a naturally aspirated LS1 if 217* intake works for a 1500-5800 range and 226* of intake duration is good for 2000-6000 range and a turbo adds about 1000 rpm to the range of the cam why would you need anything bigger... Of course really BIG cubes and or high RPM goals excluded of course...

So in either case the split forward or reverse is'nt that much... 10* there is'nt a ton of duration on either side of a good turbo cam forward or reverse split as compaired to a who cares its a trailer queen car with a 8-71 supe and a 262/258 cam. It probably really just comes down to if the overlap or "non overlap" (-overlap) is right for the intake to exhaust pressure ratio in your desired power band. It is also not so much the amount of duration on either side but having the right intake closing point to match the desired RPM range. The other specs like the exhaust closing point etc go down the list in priority but the intake close point is #1.
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Old 07-23-2004, 03:07 PM
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Some day we might be discussing how a 240/248 cam made great power in a 348ci FI car... who knows... we have never found the upper limit of what works.

When I picked my camshaft, I used the "duration makes power" standard and balanced that will engine reliability. I can only spin my hydraulic setup so high, so whatever I picked had to work up to 7300. I went 230/236//115. But that's not to say that 234/240/113 would't make more power and still work below 7300 rpms, I have no idea. But I will say my combo pulled to 6900 which is as high as we pulled it so I don't never know how high I should shift it.

Keep in mind that the cam grinders have also gotten a lot of feedback from us dsmv8. Chris Mays at Comp Cams is a name you referenced and he has suggested grinds but has also requested technical feedback.
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Old 07-23-2004, 04:30 PM
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Chris KNOWS his stuff... He will ask what about EVERY aspect of the engine, turbo sytem, intake etc.. The split patterns really just compensate for a flow differential on a given side of the engine.. If the car was built with an intake and exhaust system designed for alot of flow and a properly sized modern high efficiency turbo just run a single pattern...

That 230/236/115 you have would be a good cam too.. Bennett used a 236/236 on a car that really could function very well as a daily driver while making 700hp on 93 octane swill.... I could definately see a turbo car where the exhaust side at 236 would be good but with a 230 intake... Perhaps a lower RPM engine like one with a longer stroke but a bit less bore and much better heads... Sounds like a std LS1 (346) with its 3.64 stroke and 3.898 bore as opposed to the 4.03 x 3.25 (331)

I would'nt blame anyone for running your 230/236//115 cam on a SC or Turbo car...
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Old 07-23-2004, 04:32 PM
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Originally Posted by V8_DSM_V8again

That 230/236/115 you have would be a good cam too....

Its a good cam for a SC'd car. I have 224/230 114 for my car which have D-1SC blower.
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Old 07-23-2004, 04:57 PM
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I talked to Chris about a cam and he suggested a cam in the 240/24_ range and I was concerned about whether it would need to be buzzed over 7300, but I'd like to see someone try one... He does a lot of cam spec'ing for racers in organizations like NMRA and PRO.
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Old 07-23-2004, 10:17 PM
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who are you talking a bought Chris Mays? he does all my cams and my new turbo cam and he says shorter duration on exhaust so go figer
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Old 07-23-2004, 10:28 PM
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It's all about the entire engine package...

I know he was running a one off 203/211 setup on his 1991 GSX....

I'm sure he has a reason why a reverse split is needed... Probably LT1 Valve angle flow restriction...??? Something about your setup makes him suggest it.. If it is coming from him it is right.. I have seen him suggest Forward splits, Reverse splits, and standard (even) patterns... It all depends on the rest of the setup..
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