al a

iTrader: (6)

HI
I brought a 383 lt1 for a corvette guy and He made 378 hp. The motor has tpis afr heads. and a zz9 cam Duration at .050 212 /226 Lobe center of 112 .with 30lb red top injectors. Now I dyno the motor 4 times it made 320-322 rwhp. A/F 12-1 The motor feels lazy when reving it and sounds like it has a monster cam in it. I did a compress check and the compression was around 230 psi.I did a leak down on it when i frist got it and it was good. I"am lost . Could i have some bad injectors or a cross injector wire. I got new plugs the opti new ebay AC delco , no skips ,no codes, Ruff Idle . I was also getting knock at idle with race gas 0-5 degrees and i had the tuned out.Auto car also .I dont know where to look. and nobody wants to work on a LT1 . PLEASE HELP Al

Nostang

iTrader: (4)

Did you get the car tuned for the 383? Was the 379rwhp through an auto or manual trans in the vette? What AFR heads are on the motor, 195cc? That cam should barely have any sound to it at all through a 383 as it is very mild (too mild IMO for a 383 with decent heads). What year is the car it is in? You should not be getting knock at idle. Also, you should have a 3600+ converter to really get the car into it's power band. If you are running a stock converter that would def hurt performance.

al a

iTrader: (6)

I have a 2200 stall he is the dyno sheet. I have a madz28 tune sent to him twice Great guy.The idle is ruff, His car was a corvette auto mustang dyno.

here is the 2nd dyn sheet with the 12-1 A/F

AChotrod

iTrader: (17)

Sounds like the last guy that dynod it pulled some tricks to get the power up. Motors dont just loose 50hp unless its blown or detuned pretty good

Nostang

iTrader: (4)

Your A/F ratio looks a little rich. I would try and shoot for 12.6-13.1 and see how it performs. If the idle is that rough try and see if you have a vacuum leak somewhere or the rubber boot is on correctly between the MAF and the throttle body.

ScreaminRedZ

iTrader: (3)

Yeah, that idle situation definitely sounds related to me. I think if you chase that problem down then you'll find your answer. What kind of dyno and what was the set for the motor in ther previous owner's Vette?

96capricemgr

iTrader: (1)

Maybe down a little but sad fact is the TPIS stuff sucks in a big way. Friend has their TPIS heads on a 383 built by someone associated with the company and has tried a few of their cams currently the 239/239 one and with a M6 it does not make the 379 the previous owner told you yours made.

Usually if there is a mechanical problem dyno graphs will look pretty rough, your's isn't.

When the same heads were on his stock shortblock with an A4 in him Camaro it ET/mph'd the same as my cam only(zz4 cam) Caprice and at that point he had that little cam you have and my Caprice dyno'd 290rwhp on a Superflo.

Again point being the heads just suck, I don't see any major problems with the cam specs.

You may well find a little power when you find the source of the rough idle but not 50hp.

jasonisdn

iTrader: (1)

zz9 cam is crap. on my first setup i ran the afr's and zz9. it made 320's rwhp on the factory shortblock. i also had a few lobes get worn down on the cam. TPIS is junk.

C_Rules

iTrader: (7)

if you have a laptop shell out the $200 for a datalogger and the aldl cable. it'll make it easier to diagnose the problem if you know what to look for.

you know what's funny though if you take into consideration the drivetrain loss of an automatic which some say 18% is the max loss you would get the 379hp he told you the car made. 321rwhp * 1.18 (drivetrain loss adj facotr) = 378.78fwhp

ABA383

iTrader: (1)

I hate to say it but it does sound like a "happy" Mustang dyno...Its very easy to change the effective roller weight on a Mustang dyno to produce inflated numbers...I have also not heard great things about the LT1 AFR heads or the ZZ9 cam...I make 375 rwhp on a calibrated Mustang dyno and I guarantee that nothing about my motor is lazy anywhere...

--Alan

PNYKLR-TA

iTrader: (1)

he told you the fly wheel horses not the crank haha god i hate when people do that!

jasonisdn

iTrader: (1)

might want to rethink that, a little

al a

iTrader: (6)

I do have 4.11 hears in my car.Does that make it read low?

94LT1Bird

iTrader: (4)

that is a TINY CRAPPY CAM....and ya....those maybe flywheel numbers....but they might be to high for that even

C_Rules

iTrader: (7)

your pm said your timing was 42 @ WOT. most people run in the 32-38 range with their LT1s. i'd say switch your timing to 34 and see what that gets you. you can then increase it to 35 and 36 to see if you make more power.