jimbob

iTrader: (4)

As a comparison (take with a grain of salt). Buddies 402 with stage 1.5 5.3 heads (from TSP), 90 Fast (unported), 1 3/4 headers into 3 inch, 85mm Maf and 10.8 to 1 compression. I specked a cam for it that was 236/242 and the motor made 460 (SAE) thru a 9 inch and unlocked 4200 stall. The car ran 10.92 first pass (full weight, plus roll bar). I would expect with manual and stock rear end in there that 500 rwhp would not be out of the question.

So mixed parts can work if they work good together. I mean stage 1.5's...come on, that is a small head and valve size for a 402. They should be very close in flow and size to your old LS1 MTI heads. I would almost believe that you have some cyl sealing issues, or head sealing issue (as discussed above) at that low of hp.

stumprrp

iTrader: (2)

that single 3 inch exhaust is a choke point as well, with open headers i bet it would gain 25-30 RWHP and TQ. 5900 peak doesnt seem to unrealistic with a 244 cam and 427 cubes, maybe a tad low.

Detoxx03

iTrader: (14)

Port the intake or sell it and get a 102, bad choice of heads for such a nice motor, cam is too small for the cubes you have, and lastly your exhaust is holding you back.

SpinsB

iTrader: (5)

I totally understand the restrictions of the headers and exhaust. I had those years ago when I did the motor and just didnt know that they wouldn't let this motor breath the way it needs to breath. Outside of 1 7/8 headers and say kooks new 3" true dual exhaust what should I look at as far as the set up i have now. Im not against getting a bigger lid maf tb and intake but keeping with what i have now what would b next.?

SpinsB

iTrader: (5)

the tuner did say the cam is a little small for this motor he mentioned going with a TSP ls7s cam or the ls7r. ?? thoughts on that and with what heads?

jimbob

iTrader: (4)

what is the SCR and DCR of that combo....? it maybe too low with that size cam...
I would also shoot for an ABDC @ .05 of 53 to 54 degrees. This will allow 6300 (rpm power peak with the plastic manifold and your cubic inches)....

odarabla

iTrader: (1)

You need different heads and a cam that will match your setup and what you are trying to do. Also I would look into different headers, lid and maybe port the intake. I am building a LS2 402ci engine with trick flow 215cnc heads opened up to 4" bore and bigger intake valves. Ported Fast 90mm intake with the NW trottle body fast 42lb injectors. My cam that was speced for my build by EPS was a 246/255-613/632@113+2..

odarabla

iTrader: (1)

Man call Geoff at EPS and have him custom spec you a cam for your build..

Johnnystock

iTrader: (6)

I would not say the FAST 90 is the big problem; its still a nice intake and plp were running stroker way before the 102mm was release. Of course you would gain with a ported 90, and 102mm version would be better but I dont think you should invest there for now.

Get started with bigger headers/4 inch ORY with a cutout or true duals.

Then if youre not happy, call a sponsor for a custom cam for your combo. I think that having a higher torque number with a 6 speed shows that the cam might be just too small...

Brad Hutchcraft

iTrader: (8)

did anyone get a chance to run a leakdown test yet? I honestly think you are being robbed with those cylinder heads and camshaft. Invest the money into your heads and cam, and you will make great numbers, even with the FAST 90 and 1 3/4" headers..

There is so much better technology and port designs out today.. I would really consider unloading your heads and moving up to a quality, optimized head/cam combo for this build. You could probably get 1000 dollars out of those heads, 200 out of that cam, and thats really like getting 50% off of your new stuff..

At the very minimum, pull those heads and send them to AI. They will get the most out of your current cylinder heads. As far as the OEM castings, they do amazing work, and at a great price.

Honestly, your 427 is way down on power. Definitely being held back on both the intake and exhaust sides of things, but I think the dead weight is the cylinder heads.

Detoxx03

iTrader: (14)

Get a set of Trick Flow 225 or 235cc heads and let Allan @ Futral Motorsports spec a cam for that beast and you'll easily top your goal. Just provide your goals and specs of your build.

SpinsB

iTrader: (5)

WAY over my head

jimbob

iTrader: (4)

How can he spec out a cam if this guy does not know all the required info. Having been specking out cams before the site was started; I already have him a starting place for the correct valve events with that manifold. "SCR," rod length, peak rpm, gear ratio, intended use; longevity of springs and even cooling requirements/upgrades goes into a correct formula for costumer. Since the Torques numbers are not that far off (for an engine making 500 at the wheels), it more than likely is a combination of things. Incorrect cam events, poor seal on cyl/valves. The other distracters like 1 3/4 headers and 3 inch merge are not going to gain you much on such a low powered engine, seen way too many over the years jump on these only to find 10-15 hp. Not saying they won't help but not the cause of 50+hp loss.

Here's an unscientific was to see if your engine is even close on DCR. Take cranking cyl pressure check. Ls1's on 92 octane like up to 200-210 psi. This is a real general number, so don't shoot the messenger on this one. I don't like throwing this out there as gauges and cranking time can change this number easily. But, if you’re at like 160 then you could be wrong events plus poor sealing engine. Leak down will tell you the condition of the cyls and valve seal. I also don't remember MTI specking cams using SCR and coming up with correct DCR/valve events. They were more of a general off the shelf cam for certain combos.

jimbob

iTrader: (4)

OK, basics...what is the Compression ratio of your engine? and, do you have a cam card? I would expect since MTI (in Houston is now gone) that the grind know longer exist. Just thought I would ask. S1 grind was probably a 4 degree advance? with maybeE 286-292 Base duration..

Brad Hutchcraft

iTrader: (8)

Great post, right here.
Well said, jimbob.

SpinsB

iTrader: (5)

again i didnt ask nor know anything back then like I do now. compression no clue, card for cam nope. @ the time i was excited to be getting a motor with the hopes of big horse power. I understand now that alot of things have to go together for all that to happen. Im working back wards here trying to NOT blow more $$ in the wrong areas.
The motor to me runs very good, never had issues with it. I have never done a leak down test but i will once i replace fuel pump this coming week.

disc0monkey

iTrader: (10)

+1 ^^^ Jimbob.

a custom cam will get you where you need to better for the least $$

basically if you don't have money to get different heads and intake, taylor the cam to what you have

plus you have a pontiac, call that motor a 428 haha

PREDATOR-Z

WADA

427LS7HCI

Needs TFS 245s, FAST 102/102, 1 7/8 headers and a retune

jimbob

iTrader: (4)

Damn, hoped you had a little help for us. Anyway, you can only do with what you got. Heads off could tell you lots Then with all the info such as piston cc's and head cc's gasket thickness you want to use. You could then Get a cam spected to your combo...