rpl8061676

Hey all,

First real post here, but done a lot of reading. Looking for some feedback on a build I am looking at.

I have an 85 IROC, currently has a 350 punched 30 over, 305 heads on it, and stock TPI setup. Built 700R and 3.73's in the back. Comp cam's Xtreme 4x4 cam in it, headers, and that about it.

Have my hands on a donated (free) L31 from a 1997 GMC Sierra, and want to swap it in. Here is my build plan, as well as possible alternatives. Looking for feedback from those who have done any of these as to best route and power for my buck.

Current front runner- Stock L31, stock cam and heads, 1.6 rockers, Scoggins Dickey high flow TPI to Vortec base, high flow runners, and port match the plenum and base. Same headers, trans, gearing etc. (kept same cam due to flat torque curve and low peak power/torque capabilities).

Secondary option- Same L31 and heads, Holley Stealth ram, much larger cam. Obviously would make a lot more power, but requires a lot more cash. At this point I would be into custom tunes just to run, and a substantially higher spend on the Stealth ram.

Third option- Keep current setup, just rebuild as is.

Give me all the good, bad, and ugly feedback.

And yes, I know there are a lot of articles on all of these out there, but it takes so much time to comb through each one for true results (and I have spent hours doing so) that I would love consildated feedback from folks who have done these in one place.

Thanks in advance!

MoJoe

iTrader: (5)

Welcome rpl!

L31/TPI - vortec heads are good. Vortec TPI base is reported to flow poorly. You will have to add an external exhaust-to-EGR supply, which is not available with stock manifolds, but could be added to headers.

L31/StealthRam - much better flow/RPM potential. No EGR provision (if you need to pass emissions).

You probably need a custom tune for either L31 choice.

Either case, you might want to put a larger cam in the L31... Something bigger than the L31 wheezer, with the LT4-HOT cam as a top end. The LT4 cam is probably too big for TPI, which chokes off the higher RPM potential, but could go well with the StealthRam. I've done well here at TGO getting hands on GM roller cams for $100-$125 (no problem to re-use a roller cam).

If you go bigger cam/higher RPM, you will most likely need to address the pressed in rocker studs... pin or machine for screw in (that's what I did), and upgrade springs.

I have an L31, added screw-in studs, beehive springs, SD-TPI intake, and LT4 cam... still un-fired. And I have a 94666492 cam to downgrade from the LT4 cam (Do you want to buy it? If so, I'll need to get my poop in a group and make the swap!)

Cam specs from my notes...
L31 = 191/196. LSA 111, .414/.442 p/n 10241264
492 = 214/220, 270/276. LSA 112 .452/.465 = 2000-5500 GM p//n 94666492 = Crane 2032
ZZ4 = 208/221. LSA ???, .474/.510 = 5500rpm
LT4 = 218/228, 279/287. LSA 112, .492/.492, or .525” w/ 1.6 => 5500-6000rpm

Abubaca

iTrader: (3)

The Vortec TPI base does flow poorly, but it keep in mind that everything is relative. So many guys have done Vortec TPI builds and loved it. Then you get online and everyone tells you that you don't love it and you should feel bad about your build! LOL ....truth is in there somewhere. Seriously though, the flow numbers aren't great. Just barely better than stock. Still, with the heads and a little cam, it can be quite the fun car with the way it makes power so quickly off the line. I was running a zz4 cammed/exhaust/full bolt on L98 with stock heads and a stock base, 5 speed and a 3.27 gear and the car was an absolute blast to drive. Doubt it made 260 to the wheels but you'd never believe that if you drove it. Had another local club guy with the same build, but stock Vortecs and base, and it was noticeably faster than mine. Research is obviously important, but be careful not to get TOO caught up in the numbers.

kenbob

I'm running a L30 stealth ram with a T-56 and 9-bolt with 3.70's. my ZZ4 block is at the machine shop I have a forged crank, H-beam rods, and forged pistons. I'll be running modified 062 L31 heads basically I cleaned up all the casting flash smoothed out the combustion chambers except the 90 degree corners those need to stay rough. So far the L30 with bigger cam and stealth ram put 289 to the wheels but I plan on running a T-76 turbocharger at 6lbs for a powerful daily driver. All that being said it how you drive your car if you want a high torque tight converter cruising machine go tpi if you're like me and like driving around at 2,800 rpm and banging gears at 5,800 then go stealth ram but make sure you get a nice tuneable ECU the EBL flash 2 has worked great for me and Bob at dynamic efi is awesome he will help you through anything. Best of luck