LS7 Build Advice
 

I'm planning for a LS7 build this winter that will be going into my 93 RX7. I was hoping to get some advice from some more experienced minds when it comes to LS Builds. I'll start with my goals and current ideas, and hopefully you all can help fill in some holes.

I currently have a new and bare LS7 block. I looking to get 550-600 N/A whp out of it, being mated to a T56 transmission. I am also looking into the possibility of adding a 150shot later on to meet my final goal of a 700+whp RX7.

The car will be mostly street driven, with some weekend track days. Possibly a few 1/4 mile passes, but this isn't my priority.

I'm hoping you can help with some advice on my rotating assembly and cam selection. I have a friend willing to part with a set of stock (used) LS7 rods/pistons. I've been advised to go ahead and go with forged pistons since I'm building it, but I'm not sure if its necessary for my power goals. I was thinking of using the stock crank and rods, with some forged pistons to help keep the cost reasonable. Will those stock parts hold for my power goals?

Also, does anybody have recommendations on a cam? It will be driven on the street, so I don't want something too aggressive. I've been looking into Katech cams, but am open to recommendations.

Thanks for any help in advance! Much appreciated, and please let me know if more info will help!

On all what is wanted the best thing to do would be to hook up with a good engine builder.......1st.........I can give you a cam that would get 550-600rwhp 236- 248 something in duration on the intake side but that doesn't help...All parts have to work together and if you don't no your parts well enough find a good engine builder. the cam is just 1 factor in the power equation ...Vengeance racing,LME,HKE...etc these are some of the top of the food chain as far a LS engine builders...Callies,Eagle, for crank & rods but if you can get the stock rods & crank your good add pistons and have it balanced. Also I don't think they recommend using LS7 rod with after market cranks...I'll check my Gm catalog.. I would hate to see you waste a very expensive block.....They have several guys with the same combo your trying to do.

JE makes some nice light weight forged pistons for the stock rods. Not sure if anyone else does. If you are going to use the LS7 rods, you will need to use the stock crank for balancing issues. We have seen the stock crank and rods handle up to 1100hp to the wheels on a twin turbo setup. Has been running on the same build for 4 years now. If you decide to go with an aftermarket rotating assembly, I would opt for the stroker route. Normally the rotating assembly is the same price whether you go 427 or 440 so why not go bigger? Using a cam around the Lingenfelter GT19 or CBM 630 size on a 440, we have seen an average result of 560hp to the wheels. It has a very smooth powerband and is still very driveable. More power is easy to make but hurts the driveability...

heres a young Kat on this forum same thing you are looking for; Aka.....gnx7 Build:'93 RX7/LS7/T56 Magnum/Ohlins/HolleyHP/DavisTechTC/2800lbs/575rwhp

In your case, I would run the stock crank and rods with some lightweight forged pistons as previously suggested. That will keep the cost of your build down and should be more than enough to handle your performance goals. As far as cam selection goes, the options are unlimited. There are plenty of company's that make some good off the shelf cams or you could always go the custom route, of course. I would go with one of the raginracin selections like the lethal cam but that's just personal preference.

Thanks for all the help! Much appreciated.

Sounds the same as my prior research has shown. I'll begin looking into more specific piston brands and talk to my engine builder.

Another question, although it may be easy for many of you - but what sort of ECM/harness will I need for the LS7? Will any LS harness work? Does ECM matter, since its going to get re-flashed and tuned anyhow?

Again, thanks for the advice!

LS7 Wiring Harness E38 ECM
Starting at: $815.00 Does ECM matter, since its going to get re-flashed and tuned anyhow? A: This is the only one that will work with LS7 engine the car won't run without it. once your done have it tuned for your set-up.

I have a cam that I used in my 560rwhp build. 4.130 boren4in stroke. Stock milled ls7 heads fast102 with stock tb. Made 560rwhp. 247/252 is sell for 250.


If you going to buy new get with Martin from tick and get the polluter ls7 cam.

My favorite ls7 cam yet and I have tried 4 different ones.

The harness and ECM are totally dependant on how you proceed with your build. If you run a 24x crank you can run a ls1 ecm and harness, I have already done it.

Anybody have experience with the ebay re-flashed ECM's?

Such as...
http://www.ebay.com/itm/Corvette-2007-Engine-Computer-ECM-PCM-12597121-E38-LS7-Programmed-to-your-VIN-/221269789730?pt=Motors_Car_Truck_Parts_Accessories&hash=item3384b50c22&vxp=mtr

When I had decided on the block I went with Cathedral heads since I had a fast setup. The builder recommended the Trick Flow 235 and matching cam. I wanted a cam without too much lift so I wouldn't have to be changing springs.
Worked out well, very driveable with a flat line torque curve.