Some cam discussion

[Jay 02 TA ws6]

If I do what I am intending to do next spring... I will be doing a 383 stroker and heads/cam.

Since I'll have a little Corolla by then, I'll be knocking around the idea of going pretty aggressive with it. I don't want to completely lose road manners, but I am willing to sacrifice fuel economy more than I was last time I talked about this...

So, I am starting to think about the T-Rex cam now... but I want to leave my options open to throw a Procharger on down the road too. I'm guessing there would be other cams that would be better for forced induction...

Any thoughts as to how the T-Rex would respond to being supercahrged? What kind of lift/duration/LSA numbers should I be looking for in a cam if I want to supercharge it?

Also... let's use this thread for some general cam discussion, too... if you have any questions, ask them here

[fastTa]

They make a nitrous and blower version of the T-Rex. The 110 LSA of the original T-rex would let half the boost go out the exhaust during overlap.

Jay, it's going to be dependant on which head unit you decide to go with, how much boost, cfm, final compresion ratio, head flow characteristics, etc. But generally speaking for most blown LS1 small cube motors, you want at least a 114 LSA up to 10-11 psi, and if you plan on making more I would go with a 115 LSA.

There is a guy here in locally with a H/C '00 Z28 with a F1 and 17 psi pulley and I watched him make 818 to the tire through a T-56 and 12-bolt couple weekends ago. His cam was I think a CMotorsports grind 240/244, 115lsa. Not sure on the lift. The car made a very streetable power curve too!

Jason 99/TA from Thunder Racing just made a 11.08 @ 125 pass on the t-rex with stock heads. Here are his only mods:
All bolt-ons
Stock "241" LS1 heads
Thunder Racing TReX cam
Moser 12-bolt/4.56s
RAM 910 clutch
M/T 28x10.5x15 ET Drags
Futral Motorsports built T56 w/ upgraded internals

[Jay 02 TA ws6]

OK, so I am getting it that LSA is the overlap... if it is under 110 or so it gives it a lope, and it will have poor fuel economy because the exhaust valve will be pretty open during the intake stroke, and the streetability will be lacking...

my question is, why does this create strong top-end power?

[fastTa]

Jay, here is some pretty good reading on some cam and timing basics.
http://www.compcams.com/Technical/TimingTutorial/

LSA (lobe separation angle) is the measurement of the angle between the peak of the intake and exhaust lobes. So the higher the angle(LSA), the further apart the valve events take place and hence less overlap. The lower the LSA the opposite.

The reason for allowing the intake valve to open while the exhaust stroke is still moving towards TDC is because as soon as the exhaust valve opens, all of the hot expanding exhaust gases are rushing out the exhaust port at a high rate. This creates a scavenging effect which in turn helps to pull in even more additional a/f into the cylinder than the engine could otherwise do without the aid of the valve overlap and the scavenging effect.

[fastTa]

Originally posted by Jay 02 TA ws6

my question is, why does this create strong top-end power?

The higher your RPM's, obviously the higher the piston speed becomes. The higher the piston speed, the greater it's "pump" capabilities become. So a cam with a higher duration really takes advantage of a motor that it is spun higher.

[Kevin - Blown 95 TA]

LSA=Lobe Separation Angle. Less LSA generally means more overlap, but it also depends on the profile of the lobes. At high rpm, the momentum of the exhaust helps fill the cylinders...


I see as I'm typing this thet the other Kev beat me to the punch...

[fastTa]

Kev....... are you sitting on the couch in your birthday suit again with a beer in your hand?

[Kevin - Blown 95 TA]

Originally posted by fastTA
Kev....... are you sitting on the couch in your birthday suit again with a beer in your hand?

pants - no shirt, iced tea - not beer. Couch - 'fraid so, but I did work today, hit the gym, and ran afterwards. No wifey tellin me what to do...

[Jay 02 TA ws6]

Man, the more and more I think about this, the more confused I get as to what I actually want to do...

It seems like that F1 blower setup with the 383 stroker would be wildly expensive... and the more and more I think about it, you really start to run into decreasing marginal returns up there...

I mean, I see little reason to pay $20K more for 800rwhp over 600...

what about this?

383 stroker with high compression pistons and a mild head/cam upgrade (so I don't run in to clearance problems)... anyone try this route?

[fastTa]

How much power do honestly think would satisfy you?

I mean if you just want a mean 600 N/A LS1 there are lots of speed shops that offer 348, 382, 409, 422, 427, 434 cubic inch complete ready to run shortblock packages for under 6K. Basically you would just need heads and TB. So for less than 10K you could have a pretty bad ass N/A LS1.

BTW normally when a 346 inch LS1 is stroked, it is normally made to be a 382 not a 383.

There are more and more streetable N/A LS1's turning 500-550+ at the wheels.

It is just going to come down to how much power you really want and would be happy with.

[Jay 02 TA ws6]

Well, of course my power wants are pretty endless... but the vibe I am getting here is that 600 HP is quite a hurdle to get over.

It seems like at that point, you can either go forced induction and drop sickening amounts of cash... or you can go BIG cam and super heads and make your car totally undriveable... neither seem worth it to me.

So I guess 600 would be a good goal to shoot for.

[fastTa]

510-530RWHP (through a 12-bolt and T-56) is a reasonable goal with a good set of ported LS-6 heads and moderate cam. Do a search for LS1 shortblocks and you will find alot of pretty good deals.

Here is one the most populat h/c packages on the net because of it's very attractive price:

http://www.ls1f-body.racenet.net/valvetrain.php

With a fully ported set of LS6 castings a cam in the high 230 low 240 range, a good lid, good LT's, a LS6 intake, 90mm TB, and a very good tune, 510-530 RWHP is yours.

[Jay 02 TA ws6]

Thanks for all the feedback, I really appreciate it.

One more question... in the situation you just described, are those power numbers with or without the stroker that I am considering?

[fastTa]

These numbers would be with a big cube LS1/LS6. I would go with a large cube LS1 stroker. 409 or bigger. I have seen some wicked numbers with 422 and 427 inch LS1/LS6's.

[fastTa]

If really want to talk to an LS1 guru about your goals, give Sam a call at Combination Motorsports. He knows just about all there is to know about LS1's. Tell 'em I sent ya.

708-798-8504

EDIT: I'm out to get a few coldies, and chase some tail
Look forward to continuing our discussion later Jay.