GoatCaptain

iTrader: (2)

Ok i've got a 402 stroker thats only been in the car for 9 months and has about 9k miles on it.

So recently i purchased alot of stuff for the car and was all set to have it installed (ported LS3 heads/intake, 4 inch intake/100mm maf). So when i went up to get my intake and get the heads swapped the shop did a baseline dyno prior to install. This is where the red flag went up, the results on the dyno were 400/408 which after the motor was put in it produced 475/447 so something isnt right. With that said they're different shops and dynos so i expected a difference but not that much. So the shop did a compression and leakdown check for me to see what was up, the results were,



So i decided to hold off on the install until i could get my car back to the shop that built my motor since its still under their 12 month/12k mile warranty with LMR. They've been great to me so i'm sure they'll get this diagnosed and if something isnt right they'll get it fixed. Hopefully we'll get this figured out this week.

LMR said that some blow by is expected since i have nitrous pistons but they want to do their own dyno and leakdown test this week to see for themselves. My car doesnt smoke normally or burn any extra oil than these ls motors normally do. The gas mileage hasnt really changed nor have i felt any massive loss in power in my butt dyno. However the car obviously is putting out too much smoke on the dyno at WOT which isnt the norm for my car.

Recently i had the car up at the shop because of stuttering and some sluggishness which ended up being a dirty maf but since cleaning it i havent had any noticeable problems. But seeing that big of a difference in dynos and the leakdown results have me concerned. Since its my first time with a leak down test i figured i'd see what you guys thought of the initial results.

Here's the dyno video,



thanks for your thoughts

msydow

hmmm, 75rwhp would have to be a serious weather change or a dyno problem. that sucks dude. you said it had nitrous pistons, but were the rings gapped for nitrous and are you spraying it now?

GoatCaptain

iTrader: (2)

the motor was set up for nitrous but i'm not spraying yet. So as far as gaps go they set it up for eventual use of nitrous. Either way the power shouldn't change that much cause the rings and gaps shouldn't have changed since the original install, so the power shouldn't be that far off. The higher dyno numbers where done in the summer time and the more recent one was last week in cooler dryer weather. I'm hoping for a dyno difference but the leakdown test had me worried as well as the smoke during the dyno.

the only changes to the motor were i got rid of a vararam and i'm now running the stock air intake until i get the new 4 inch one installed.

hymey

Even thrasehed 200000km LS engines with cams run a good number, I would be looking at your cat convertors. I dropped 80hp once partially blocked cats.

midevil1

iTrader: (17)

Smoke didn't look blue too me. You didn't tell this shop that LMR built it before you had them dyno it.? Shops will play games to get work from other shops. Who knows....

SOMbitch

iTrader: (8)

Whole bank with too much leakdown. Somethings up.......

cam

iTrader: (9)

Didnt sound the healthiest to me. Sounds dull up top and not crisp enough. Could be your exhaust ( maybe plugged cat thats worth looking into ) but something doesnt sound quite right to me

GoatCaptain

iTrader: (2)

Well we did the top end conversion and picked up 65 horsepower over the down numbers and 20 over the original dyno before the problem. It was either the headgaskets not sealing right or the old heads had problems.

The original Dyno before any problems were noticed was 467, then on the last dyno it did about 430. Post head/intake swap it put down 485/447 so this fixed it and it feels like a real beast again. thanks for all the advice guys

cam

iTrader: (9)

Nice numbers congrats

Sales2@Texas-speed

iTrader: (5)

Any chance you have or have had a bad front O2 sensor on that bank that is dumping too much fuel, and has washed the rings out?

GoatCaptain

iTrader: (2)

i had a bad 02 sensor before but changed it immediately as soon as the code was thrown. My guess it was the valves on the old heads or the old head gaskets. None the less the swap i just did fixed the problem and got me back to where i should be with my set up. Butt Dyno feels great