Inliners International Forums General Discussion Hi Performance cam suggestions

Looking for a few rough ideas from some people who have done a turbocharged 250. I will end up talking to a company (probably Crower or Crane for example) for more exact figures, but I would like some ideas before I call them. The motor will be for street/strip use, more street than strip. The transmission is a stock TH350 with a stock converter, and the rear end is a stock GM limited slip, for now. The motor will have lump ports roller valvetrain, and shooting for 8.5:1 comp. The boost will be around 5-8 psi for the street and maybe 10-12 for track use.
These are some rough figures that I have come up with as I am just trying to figure out as much as possible before I begin the build. Although everything is subject to change.
Thanks for any help.

There are so many combinations,,,,,

About .500 lift intake & exhaust
204 duration @ .050 int. & exh.
With a 114 lobe center.

You should get a torque converter that will stall to about 2400RPM

MBHD

rob, i have recently done a 292 turbo and here are the specs from my cam. cam is custom ground by comp for a turbo setup. the specs are .521/.512 int/exh, duration @.50 are 218 int/ 212 exh, lobe separation 114 cam # is C62 5432/5211 H 114. for the 250 you may want to take a little duration out. also keep in mind my part # is for a 292, fuel pump is in a different location. i run a stock torque converter and it works just fine. the cam idles very smooth and has awesome torque. what kind of a hookup will you use for the turbo? a manifold or a header? carbed or fuel injected? will you use a intercooler? what chassis is it going into also. tom

tlowe:
My brothers, Uncle and I hand fabricated a header specific for this project. The turbo is a suck through carb off of an early '80s Buick V6. Therefore no intercooler, and it is going into a 1964 Pontiac Acadian. The Canadian version of a Beaumont. Virtually the same car, just slight changes.
Thanks for the help

Isky also offers the following turbo cam:

Cam: Isky 231-TA TURBOCYCLE-A
RPM Range: 1000 – 5000
Duration: 264 / 252 @ 0.007
Duration: 208 / 194 @ 0.050
Lift: 0.525 / 0.525
Lobe Separation: 114

tlowe:

with you specs, the maximum power came in which RPM?

edy, right now the highest rpm i have achieved is about 4500 rpm. i had a issue with too small of fuel injectors starving me of fuel around that rpm. i was using 6 42 lb injectors. now i have 60 lb injectors and can't wait to get them in and test it. i hope to be able to support full power to 5000 rpm and really not any higher. 292's , from my experience have bad harmonics around 5200 rpm. i have mine balanced and have a good balancer also. so to answer your question, max power 4000-5000. that is also at 15 lbs boost. tom

tlowe I.I.#1716:
you made the point of stating the fuel pump is in a different location on a 292 than a 250. But is that the only difference between the cams? Other than that will the 292 cam fit in a 250 block, is what I am asking. I already have an electric fuel pump so that does not bother me.

if you run a electric fuel pump , then you will be fine. keep in mind, if ordering a new cam, get it for your motor just in case a fuel pump is needed later. tom

yes a 292 cam will fit.Also keep in mind when you buy a cam for a 292 Or a 250,230,194. The cams will act differently. A cam Odered for a 292 Will act Bigger in a Low deck/194,230,250 As a cam For the Low deck/194-250s will act smaller in a 292
How true this is Im not 100% sure but that is my understanding.

Larry,
I believe tall deck, low deck does not make the difference, it's the cubic inches?
That's what make a cam made for a 292,act too big for a 194-250 & vice versa.

Same difference The low decks are the 194-250s
Tall deck is the 292

The bigger the motor the more duration it will accomadate before the cam gets "lumpy". If you put a 220 deg @050 cam into a 292 it'll be relatively smooth, take the same can and put it in a 194 and it'll be really lumpy.

Smaller motor have less volume to fill whcih takes less time to occur.

Thank you efi you said it better then i did.

one thing i noticed is that most of companys in the us (comp, crower and etc) when advices a camshaft for a turbocharged application, the exhaust side is always smaller than the intake side! for example tlowe´s cam (@.50 are 218 int/ 212 ex) and in Brazil the mechanics always advices the exhasut side to be bigger than the intake!!! i wonder why this!!!

edy, keep in mind i am not a expert on cams. my specs were recommended by comp cams. but here are some theory's. turbo grinds need/want less overlap of the intake and exhaust valves because of the pressure build up ahead of the turbo in the exh manifold. if there is a large overlap then the pressure would also have a better chance of making it back up the intake. this is also more of a moderate street grind, not for high rpm. maybe that is the difference. tom

Tom

I asked comp com a camshaft for maximum power @7000-7500 RPM with my turbo. they gave me this:

264/260 at @.050 115 lobe separation.

the exhaust side is shorter than intake too!!!

well there you go. they do know how to make a cam and i would consider them experts. i believe all the turbo grinds from most manufacturers are like this. this is a quality that is turbo specifec. tom