TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
I am the proud owner of a very nice '87 IROC-Z. It is a L98/700-R4 car with 72,xxx miles on the body. The motor, however, was professionally rebuilt by the previous owner about a year and a half ago with new pistons, rings, and everything and it runs beautifully (has maybe 2500 miles on it). I am thinking about doing some stuff to the motor this winter and was wondering about how much power I would gain. The car currently has the following mods: Hypertech ThermoMaster computer chip, Hooker headers, Flowmaster exhaust system, K&N air filters, and a B&M Megashifter. At my local dragstrip I ran a best time of 14.2 @ 98 mph on street tires. I'm am thinking about adding the following parts: COMP Computer-compatible cam & lifter kit (duration at 050 inch lift: 210 intake/220 exhaust, valve lift: 0.480 intake/0.480 exhaust, lobe separation angle: 112 degrees), Edelbrock High-Flo TPI system, and a Holley High-Flow 52mm throttle body. How much will this improve my times? Will this cam complement the Hypertech chip well? Would a cam with a higher valve lift of 0.500 intake/0.510 exhaust and lobe separation angle of 114 degrees work well, or is that too much? Also, what would happen if I swapped the stock 3.27 gears for 3.90's or 4.11's? Please give me your input. Thanks.
Dude, running 114 lobe sep. is always better than 112, if you want to get the dang thing tuned OPTIMALLY on tpi. Some guys will argue with me, but what I say is true. Go with pretty much any cam that has 114 lobe sep and higher lift and more duration, and you'll be happy. You should be able to take at least a second off your 1/4 with ease. 113 lobe sep would be OK, but the closer you are to 115, the happier your engine will be (if you keep tpi). And definitely upgrade your suspension/handling with subframe connectors and new shocks and struts, and if your car is lowered, make sure it has the rear end goodies like an adjustable panhard rod and control arm relocating brackets, as well as stronger control arms. Also, don't forget your torque convertor and upgrading the thing with a higher stall, probably around 2500-3000, depending on how crazy you get with your cam.
Thanks guys. And I am currently upgrading the suspension. I've got KYB shocks and struts in now and subframe connectors are in the works. Do u think I'd be able to break into the 12's with that setup though and still have the car be fairly streetable?
for 12s your going to need a large converter and everything you priorly mentioned along with a custom tune.
another way to get there would be to upgrade to a mini ram or lt1 or such intake and put a big stall converter in your car. that would do about the same thing.
if you want to do it with tpi your going to need to port the tpi setup, the cam you mentioned isn't a terrible choice. Then slight a pocket porting job on the heads would get you pretty close. still probably going to want a jump in the converter size.
hold out on the 52mm tb, thats not a restriction, spend your money on a porting kit and port out the plenum (probably siamese the plenum for best results) then port and port match the heads
Last edited by flaming-ford; 08-20-2009 at 10:28 AM.
I'm am thinking about adding the following parts: COMP Computer-compatible cam & lifter kit (duration at 050 inch lift: 210 intake/220 exhaust, valve lift: 0.480 intake/0.480 exhaust, lobe separation angle: 112 degrees), Edelbrock High-Flo TPI system, and a Holley High-Flow 52mm throttle body....
It depends on your tune, a 112 LSA isn't really that drastic, as I have seen L98's running with 110 LSA's just fine. It's the other characteristics of the camshaft that allow for this, that, and again, the state of your tune. Here is a pretty sweet L98 on youtube running a 242/248 646"/648" @ 112....;
.... as for the gears, keep your 3.27's, and get a stall speed converter. If your running a high flow TPI system, this will not be fully enhanced with the stock heads, so upgrade them, as all power is honestly found in cylinder head flow.
