cam help for twin turbo motor

**79centurion** · 01-17-2012, 12:19 PM

I am getting ready to swap the cam in my motor but not sure if its a good idea. The cam that is in it is a comp cams blower cam that is a hyd. flat tappet. Part number is 11-400-4. Its specs are intake 226, ext 218 at .050.
intake lift .525, exhaust .514.
115 lobe and 111 intake centerline.
Valve timing at .006
intake opens 27 btdc closes 69 abdc
exhaust opens 73 bbdc closes 15 atdc

The other cam I have is a custom ground cam that I was using for a nitrous motor. Its a solid roller.
Intake is 242, exhaust 248 at .050
113 lobe and 113 intake centerline
valve timing at .050
intake opens 8 btdc closes 54 abdc
exhaust opens 57 bbdc closes 11 atdc

The enigne is a 468 twin turbo with 91mm turbos with 1.23 ar. 990 heads and around 8:1 compression. It is intercooled and was a motor setup for speed skiing. I was told it made 1,000 hp on 12lbs of boost. Never dyno'd the motor though. I am in the process of swapping into my jet boat. Should i swap cams, or keep the cam that is in it and up the boost if I need more power?

**cstraub** · 01-17-2012, 12:55 PM

Blower cam and a turbo cam are 2 different animals. Do you have the flow numbers off the heads?

**79centurion** · 01-17-2012, 01:10 PM

Heads are unported other than cleaned up the opening to match the intake. Here are specs from chevy hi performance

ValveLift Intake Exhaust Exhaustw/pipe
050 ****** 32 24 24
.100 ****** 69 53 53
.200 ****** 125 101 103
.300 ****** 183 134 140
.400 ****** 233 163 176
.500 ****** 254 180 198
.600 ****** 292 185 204
.700 ****** - 186 207
.800 ****** - - -
~E/I ****** 70% 75%

**79centurion** · 01-17-2012, 01:13 PM

I also just read the info on the cam and it is a turbo cam. It was under the blower/turbo cam, but says it a baseline turbo grind helps increase boost

**cstraub** · 01-17-2012, 01:43 PM

Based on those flow numbers and making peak power about 6400 rpm

700/660
249/249 @ .050"
112 Lobe sep

**79centurion** · 01-17-2012, 01:57 PM

Thanks Chris. I think i am going to try to use my nitrous cam then and put 1.8 rockers on the intake side to move the lift to .685 intake, and .654 exhaust. If I had the money i would do another cam, but cant afford to buy another one at this time

Dan

**Unchained** · 01-17-2012, 02:52 PM

If the smaller cam is already in there you might as well give it a try if it's in good shape.
Less lift and less abuse on the valve train would be the direction I would go.

Once you get it running you're probably going to be looking for ways to tame it down, not get more out of it.

**79centurion** · 01-17-2012, 03:53 PM

The small cam is in it, and looks new. It only had a few hours of run time on it. I do have 1.8 rockers that I can put on the small cam to help it breath better.

Dan

**ap67et10** · 01-18-2012, 09:01 AM

Originally Posted by 79centurion

The small cam is in it, and looks new. It only had a few hours of run time on it. I do have 1.8 rockers that I can put on the small cam to help it breath better.

Dan

That's what the turbos are for! Haha...it's gonna be a beast, if you don't have exactly what you want leave it alone and run it to see how it does. At least that's what I would do.

Andrew

**Unchained** · 01-18-2012, 03:56 PM

Food for thought,
Each one of those 91mm turbo's will flow (a lot) more than the 2 that are on an old school Gale Banks turbo setup.

**jimsplace** · 01-18-2012, 07:35 PM

I don't want to jack this thread, but I have essentially the same set-up, that is same cam and same heads turning about 6700 rpm, but with the Rajay 301-E10 turbos. Would the recommendation be the same as has already been posted. I am planning to switch to a hydraulic roller cam, any recommendations.

**79centurion** · 01-18-2012, 10:11 PM

Unchained, so you think I should keep the smaller cam in then? It would work for me since its in there. Just didnt want to have to pull it apart and do it all over again. Also the would have to reprogram. Really 1,100-1,200 hp is more than enough.

Jimsplace, do you know how much hp you have? How much boost, and if in a jet boat what impeller?

**Unchained** · 01-19-2012, 04:26 AM

Originally Posted by 79centurion

. Also the would have to reprogram. Really 1,100-1,200 hp is more than enough. ?

It may be a challenge to bypass enough exhaust to run it that low.
I don't know the specs on the turbine wheel and housing but I would estimate that each of those turbos will be capable of 1200 + HP.
Did you look up a compressor map ?

Post up all the info you have on the turbos and maybe we can match a compressor map up to it.
Measure the turbine exducer also.

This is a common direction with a turbo program, to try to optimise things to make more power during assembly.
Then once it's up and running and you see what a monster you created you then want to turn it down.

If I had it to do over again I would have used an aluminum small block.

**jimsplace** · 01-19-2012, 08:51 PM

Originally Posted by 79centurion

Unchained, so you think I should keep the smaller cam in then? It would work for me since its in there. Just didnt want to have to pull it apart and do it all over again. Also the would have to reprogram. Really 1,100-1,200 hp is more than enough.

Jimsplace, do you know how much hp you have? How much boost, and if in a jet boat what impeller?

I recently purchased the set-up and don't know the horsepower or the PSI. It is not in a jet.

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cam help for twin turbo motor

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