I need a good recomendation on a good turbo cam for my setup. here is what I have:

Built forged 408
L92 heads (823 castings) Ported
Ross pistons making compression ratio 10.25:1
GMPP Single plane intake
92mm throttle body (Fast)
Will replace injectors (Again)
Rear mount turbo kit with PT76GTS turbo with .81 AR turbine section
Upgrading fuel system to Daul intake pumps as we speak.
3.70 Moser 9" rear end.
Front mount intercooler.
Current cam is a Chet Herbert 230/240 at .600 lift cut on a 114 centerline (I am very unhappy of this cams performance and am looking to replace it)
3600 Stall converter, A4
running AC and Power stearing still
Underdrive Harmonic balancer

I am looking to make 700-800rwhp. I do not want to go overkill with the cam. i would like something that will make a good daily driver and work with the turbo (let the turbo do the work).

Thanks guys.

 

ZThe car is 4000lbs with me in it.

 

I'm curious what the experts will recommend too. I'm looking for a cam for a SChrged LS3 vette. I'm thinking 225/230/.600 on a 117 LSA. I don't think you need a whole lot of cam when you're blowing hard on the intake side. I've heard of FI engines making big numbers with the lowly LS6 cam. Ears open here.

 

EPP's FI cam

 

Cam you have doesnt sound too bad...in what area do you think it isnt performing ??


And 10.25:1 CR ?

 

Car will not turn better then a 12.77 in the 1/4. Tuned it over and over and it will not pick up. I think it is only making anout 370 to maybe 400 crank hp, wich is a joke for what all it has. There is something wrong, I just checked the camshaft timing and it is right on the money for what the cam card says. I was realy hoping the cam was going to be off. This freaking thing is a joke!!!

 

Comp Cam is suggesting a custom grind...246/256 .595/.595 on a 114. I think the lobes would be 3656/3662-HR114. What do you think? Too big? Too much valve overlap? If I change springs something like 247/257 .624/.624 on a 114 Lobes 13022-130??-HR114.

 

I have had great luck with Speed Inc's Turbo cams. I would look at thier TU1 or TU2.

 

More importantly, what trap speeds are you seeing ??

ET's are far more dependant on traction.

If you dont have traction, or gearchanges are very slow...ET's and traps will suffer. But trap speeds are a far far better indicator of potential power, that ET's ever will be.

 

Keep in mind this is NA. I am now installing the turbo. 1.8 60 ft best and 105 mph max trap speed. Like I said before, **** for power, my factory 346 with just an MS3 cam out runs this thing. The 1.8 is with a set of slicks and I can see no wheel spine on my data logger. I have ran the car from 10:1 afr all the way up to 13.8:1 and the timing from 22 to 32 total. The best trap speed, 60ft, and et are all at 12.8:1 and about 29 degrees of timing. It still only pulled a 1.8 60ft, 12.77et, 105mph. What a joke!

All I can figure is it has to be the cam. Last night I checked the cam timing all the way around. It is right were the card says it should be and all events are happening were they are supposed to be happening. I looked up Comp Cams lobes last night to compare them to these lobes,,, looks like these lobes are a very lazy lobe, something you would see in a 1969 hydrolic grind, here are the specs...

Duration @.006" 292/296
Duration @.050" 230/240
Valve lift 593/602
Lobe CNTR 114
Valve Overlap 7 ...............Valve Overlap 66
Valve Timing @.050" .........Valve Timing @.006"
IO BTDC 1 .......................IO BTDC 32
IC ABDC 49 ......................IC ABDC 80
EO BBDC 54 .....................EO BBDC 82
EC ATDC 6 ......................EC ATDC 34

If you compaire this lobe to the XE-R Comp lobes, man it is a very slow ramp rate. I just wonder how much of a difference a XE-R lobe would make as compaired to the one I have. An XE-R lobe with the same duration at .006" would look like this.

Duration @.006" 291/295
Duration @.050" 242/246
Valve Lift 610/614
Lobe Center 114
Valve Overlap 16 .............Valve Overlap 65
Valve Timing @.050" .........Valve Timing @.006"
IO BTDC 7 ......................IO BTDC 31.5
IC ABDC 55 .....................IC ABDC 79.5
EO BBDC 57 ....................EO BBDC 81.5
EC ATDC 9 .....................EC ATDC 33.5

Same duration @.006" lift but a much faster ramp rate.

The XE-R lobe with the same duration at .050" would look like this.

Duration @.006" 279/289
Duration @.050" 230/240
Valve Lift 592/609
Lobe Center 114
Valve Overlap 7 ...............Valve Overlap 56
Valve Timing @.050" .........Valve Timing @.006"
IO BTDC 1 .......................IO BTDC 25.5
IC ABDC 49...................... IC ABDC 73.5
EO BBDC 54..................... EO BBDC 78.5
EC ATDC 6 ......................EC ATDC 30.5

Any cam experts around?

 

Epp FI, TV1 or TV2 do not mean anything to me, what are the details of the grinds? Lobe numbers please.

 

So do you want a good n/a cam, or a turbo cam ?

You dont need to use big cams with forced induction to get very good results

 

Yes, the pistons are -12cc and the head gasket is a cometic part number C5751-040 so its .040" crushed with the 823 heads, I think it is 10.25:1

 

Again, I assumed you were turbocharged, and 10.25:1 is pretty high CR.

 

I will not be changing the compression ratio. This engine has 282 miles on it now. The goal was to make 600hp crank all motor then use only enough boost to get to 750-800 rwhp. I did not want to run alot of boost. We were thinking no more then 10psi but with the power gap I am seeing it will need alot more boost then that to get the job done. Thats why I am trying to find why I am not making the expected power NA.

 

I guess if I have to I can change to the .051" head gasket, that should get me just under 10:1.

 

The engine is the one in my sign.

 

I strongly suggest you...
1. Figure out what's wrong with the engine before adding a turbo. If you really think you should have 600 hp, then it should be trapping about 125 mph. The lobe ramp rates aren't killing 20 mph.
2. Consider a front-mount turbo. The 408 will already have backpressure issues with the 76GTS, and mounting it in the rear will amplify this problem.

Mike

 

Forced Induction sized this turbo for the 408 at the rear. I really want to do a front mount now, but they advised me against it with this turbo due to back pressure.

I have been looking for the problem, I double checked the cam timing, I have run compresion (155 across the board), I have double checked the pushrod length, and I have tuned it rich to lean and played with the timing back and fourth. I am running out of possible causes. What else could it be?

 

Get that car on dyno. A dynojet preferrably .Tuning on dyno even better. Na should make best power around that 12.8 range and timing can be taken up till not much change happens but knock retard can really kill power so you have to watch scanners .Some engines get false knock had that bad on my lt1 and it sucked like 50 hp out of it when it was getting the false knock.Tuned it out and car was much faster and more consistent.
I would think you should get around 450 to 500 out of the 408 with headers, you compression, decent cam ,decent intake and decent heads. If its not putting out that then something is wrong. Talking rear wheel hp.You are auto so could be a bit lower.What stall are you running. Is the trans slipping? Is it a 4l60 mabye its already past its limits.
What altitude are you at. Na cars get killed by altitude. 105 seems pathetic for your setup NA but if you are at say 5000 feet above seal level maybe not as bad as it would first appear. Are you running on all 8. Good plugs, wires, coils. Any misfires on scanner. What about fuel system fuel pump ok, fuel filter, injectors flowing good?
Not sure what compression should show for your compression and engine.
What about cats are you running cats..could they be clogged?

I would dyno and you should hit 400rwhp for sure na if not 450rwhp. Once you figure it out add the turbo. No point complicating things right now until you figure out whats up with your engine.