RideZX-6R

iTrader: (8)

I was expecting this to make AT LEAST in the 450-465whp ballpark or even a little more and it didn't, was wondering if people can look over my mods and see what's missing if anything...

The car is a 99 Corvette 6MT with 4.10s. I will check the compression today and see if its ok, but the bottom end was freshly built (I crushed a valve spring, dropped a valve on my last motor and it crack the block, etc) so I don't think that's the issue.

Bottom End...
-stock 346 with new gaskets, all new bearings, etc.
-2.5cc reliefs fly cut in pistons
-Magic stick 4 camshaft
-Ported oil pump
-Powerbond 25% reduction pulley


Top End...
-TEA Stage 2 heads with PAC 1521s, stock lifters, rocker trunion upgrade with stock rockers - .040 milled = 60.9 cc chamber size = should give approx SCR of 11.1-11.2 to 1
-.040 headgaskets
-FAST 102mm intake mani ported by Vengeance Racing
-LS2 OEM fuel rails
-Cobra 39lb injectors with EV6 pig-tails wired in
-LS2 90mm T-body ported with tb harness adaptor
-Breathless intake and airbridge
-Truck MAF - Tuned with MAF only - MAP is shut off after 400rpm
-1 3/4 headers of unknown origin, got em with the car - has an x-pipe replacing where the cats would be (no cats), but its cut short and the factory h-pipe is welded to it with the factory cat-back


The car made 411whp with 26 degrees of timing in it up top, no knock at all with that, but it knocked with 27 degrees and didn't make any more power so we put it at 26 and left it. A/F was a smooth 12.5 throughout. We thought it might be the exhaust being a bit restrictive so we unbolted the X-pipe and made 431whp with the headers dumped open. Like I said I was expecting more and was wondering if there's something I'm missing.

Also if this should be moved to the dyno forum, feel free to let me/a mod know to have it moved.

BlackScreaminMachine

iTrader: (17)

Well on paper it may look one way (as in not enough) but take it to the track and see what it does. It may very well run like a car making low 400 rwhp but I would post the graph as well.

DONAIMIAN

iTrader: (18)

I would look in to a complete exhaust overhaul seeing as you gained 20rw by going open heads. Most well thought out, high flowing exhaust systems loose no more than 10rw in comparison to open headers.

DONAIMIAN

iTrader: (18)

Also, not running the numbers I would say your compression is in the high 10's. (I'm at 11.3 with 59cc chambers)

RideZX-6R

iTrader: (8)

I knew I forgot something on the list, added that I have the .040 Headgaskets

BlackScreaminMachine

iTrader: (17)

Headers could be a bad design like original SLP's so give that a shot.

DONAIMIAN

iTrader: (18)

Exactly. Seems like everything with the motor is covered. Just a matter of getting air in and out more efficently now. I would also look into a 102mm tb along with a SD tune to get the MAF off the car.

RideZX-6R

iTrader: (8)

SD? oh... speed density?

RideZX-6R

iTrader: (8)

How bad of a design were they? jw

dodson55

iTrader: (18)

what kind of dyno was it on i have seen some that will read higher/lower then they should a dyno is a tuning tool no two dynos will read the exact same times take it to the track and see what it runs before you get to worried about you set up but i would change your exhaust for sure

BlackScreaminMachine

iTrader: (17)

Like could make a 10-30 hp difference. Widely known bad design. I'll see what I can dig up... the only issue is that many people moved on from SLP to places like Kooks, ARH, Dynatech and not many post are out there but like said ill see what I can find.

RideZX-6R

iTrader: (8)

I'm gonna check compression on the car tonight... if thats even/ok, I'm gonna check for vacuum under WOT.

I mean it could be a combo of junk headers and a vacuum leak or something as well.

However the car made that 398whp with the same headers/exhaust and a ported ls1 TB, LS6 intake, and ported 241s before.... soooo the headers can't be TOO bad.

But yeah, I'll take any info I can get

DONAIMIAN

iTrader: (18)

From what I remember about the early design is that they were more of a mid length design. When going to a bigger cam, the need for a bigger and longer primary becomes more important.

BlackScreaminMachine

iTrader: (17)

The big point is if the combo is a matched correctly with better compression to help the cam which is known as a top-end cam there has to be a restriction. IF not on the intake, then there is a cork somewhere.

I have been researching nothing too much but there is stuff out there. A lot of it archived and when you search for SLP anything, you get a bazillion random post due to someone mentioning the brand, not the header....

RideZX-6R

iTrader: (8)

Would the truck MAF be a restriction? just wondering. (not necessarily on the tuning, but the MAF itself - is it too creating an airflow restriction? I know some say have 4in intake from filter to TB and run speed density thru the MAP only).
Thanks for the info guys

DONAIMIAN

iTrader: (18)

I couldn't tell you about the truck maf. Only thing before my throttlebody is the an IAT sensor and air filter. I believe some of the newer GEN 4 motors come with a different design that doesn't run directly through the air tract.