Boy, did I pick the wrong turbo cam

After months and months of waiting I finally got my engine put together and on they engine dyno. Its a 383 with 9:1 cr or so and 250cfm heads running a T76 ptrim with a 3.5" downpipe.

The cam is a 224/218 114LSA. Just to let you guys know with this cam the hp droped like a rock at 6000rpm Within 300 rpm I loose 40 hp or so.

On a conservative engine dyno we made 500hp @ 5700 and 520tq @4700 at 7 psi. It really liked 33 degrees of timing. We should be putting on the boost controller tonight or tomarrow night and crank up the boost to 15 and see what happens.

thats a similar setup of what im building...that seems awefully low though, oh its only 7 psi.i was gonna say id have thought 600rwhp at 10 psi.at least.and u dont rev a stroker like that much past 6K!

is this an lt or ls

is this an lt or ls

'93 Corvette
393ci LT1 with a 250hp shot-o-nos(down for the count)
Working on my "Beltless Boost" project

It's a very conservative engine dyno. The guy took an engine from another shop that dynoed at 630chp and made 525chp on his. I was told it's closer to rwhp than chp. But the real test is when we get it to the track.

It was also raining when we did it so I'm sure the air wasn't perfect. But its a good start.

Ah,gotcha....im building a forged 383 ls1 with 9:1 CR and at 10psi im hoping for at least 600rwhp

I think INTMD8 did some camshaft testing and found that a reverse split made about the same power as a regular split duration cam. He made the most power with a single pattern, and several other turbo cars have had very impressive results from the same.

My understanding talking to Jose and some of the Turbo Buick crowd, is that a reverse split should be used when backpressure is really high (3x boost), a normal split if backpressure is really low (at or near boost), and a single pattern anywhere in the middle.

Mike

Well we decided to turn up the boost last night. It was really weird. The boost would go to 12 or so at peak torque and then start dropping off back down to 10 or so at max rpm.

Am I running out of compressor? Or are the back pressures getting too high once I start moving the air that it won't spin the turbo fast enough?

We did get it up to 14.5psi and the boost still dropped back down to 11 or so, but on that run we popped a head gasket! So much for cometics being the end all in head gaskets. My mechanic thinks that there was too much cylender pressure from the small exhaust lobe and the high boost it couldn't take it.

Any comments from the peanut gallery as to what's going on here??

After months and months of waiting I finally got my engine put together and on they engine dyno. Its a 383 with 9:1 cr or so and 250cfm heads running a T76 ptrim with a 3.5" downpipe.

The cam is a 224/218 114LSA. Just to let you guys know with this cam the hp droped like a rock at 6000rpm Within 300 rpm I loose 40 hp or so.

On a conservative engine dyno we made 500hp @ 5700 and 520tq @4700 at 7 psi. It really liked 33 degrees of timing. We should be putting on the boost controller tonight or tomarrow night and crank up the boost to 15 and see what happens.

What cam did you use before?

What cam did you use before?


When I was messing around with the turbo stuff before I had a 230/236 on a 113. I thought that was going to be too big for my 383 with stock manifolds on it. That cam has 7 degrees of valve overlap in it

When I was messing around with the turbo stuff before I had a 230/236 on a 113. I thought that was going to be too big for my 383 with stock manifolds on it. That cam has 7 degrees of valve overlap in it

What power did you make with it? Who spec'd your current baby cam?

What power did you make with it? Who spec'd your current baby cam?

Don't know about the power, never had it dynoed. I got my cam speced from 4 different people. The first three were Crane, Comp, and Combination Motorsports, but I don't remember the order. The last one was cam motion.


1.) 230/227 .544/.560 lift 114 LSA
2.) 232/232 .539/.539 lift 114 LSA
3.) 224/218 .536/.528 lift 114 LSA
4.) 221/217 .540/.539 lift 115 LSA Cam Motion


Here's the link to the old post
http://web.camaross.com/forums/showthread.php?t=333673

i would think for a good DD cam on a 383 you'd look more for something like 230/228 .580/.580 116,because the reverse split will help stop any reversion since you have stock manifolds like i do.

I kinda doubt 2 degrees of split is going to make any measurable difference at all.

so what do you think would be good?

I am debating on a 230/224 114lsa...

for a 383 or a 346/8?

for a 383 or a 346/8?

Sorry! Here it is:

383 LT1
AFR210's
Custom T76 turbo kit

no offense its ur decision but you really need to up the exhaust duration so the motor can exhale :)
especially with have AFR's

no offense its ur decision but you really need to up the exhaust duration so the motor can exhale :)
especially with have AFR's

Yeah, perhaps a 230/230 on 116LSA (-1 overlap)...I need to pass emissions and want peak power around 6000-6200rpm.

I called around to some places today asking about boost that tapers off with rpm. One guy told me to check my intake piping, anothere though it might be a wastegate issue, and a few people told me that I need a bigger turbine. I wonder if that would help me compensate for having a small exhaust lobe. I've got a P-trim with a 1.0 now, I've got a 1.15 housing sitting on the shelf. Maybe I should give that a try.

Im running a 224 220 114, and it seems fine. My dyno drops up high, but that is b/c im running off the compressor map with the TO4E.

Im running a 224 220 114, and it seems fine. My dyno drops up high, but that is b/c im running off the compressor map with the TO4E.

Your hp peaks at 5k then falls off. Tough to tell if its the turbo or cam..

I think 224/224-114 would work well, or 230/230-114 would be fine too. One of Jose's customer's made 1000 rwhp with a 218/218-114 cam.

Mike

If I was going to get back into the engine again I might go with the 218 218 or 220 218 114. Seems to make the power, and at the same time tame the part throttle/idle some.

Correct me if I'm wrong, but with forced induction, wouldn't it be better to go with a cam with a longer exhaust duration? :confused:

Correct me if I'm wrong, but with forced induction, wouldn't it be better to go with a cam with a longer exhaust duration? :confused:

For supercharging that's the theory, but for turbocharging less exhaust duration to keep velocity up before the turbine. That's the theory anyway.

Higher velocity past the valve doesn't translate into higher velocity into the turbine wheel.

for a turbo app read this
http://www.forcedinductions.com/help.htm
mainly on the section about a cam choice near the bottom