01tam6

iTrader: (1)

Alright just had heads and cam put on my 01 T/A. Before the heads and cam my car dynoed 356 hp 372ftlbs. Pretty strong for just bolt ons with great torque. Now I have had a set of PRC stage 2.5 5.3l heads and a F13 112 +2 cam installed with 7.4 pushrods new oil pump, chain etc. Now my car is making 414hp and 365ftlbs of torque. I know that a bigger cam moves the power range up some and all but I didn't expect to lose this much torque. I was hoping for 430hp and 400ftlbs, but wouldn't have been surprised if the torque only climbed to 385-395. Should I have went with a smaller valve head? Another thing my first dyno was on my factory 16in wheels and this one was on 17x11's so that hurt me some. A/f is a fairly flat 13.3-13.5. At 2500 rpm I lost 50ftlbs! At 4000 I lost about 40ftlbs. The car does run better up top but it takes till 5500 before you can feel any difference. Install and tune was done by a very knowledgeable person with ALOT of experience. BTW the car has 24k miles on it only about 6k since my last dyno. So where did I go wrong? Mods in sig.

slpss9723

Don't know.....i went 411/385 corrected with just an F14 112+4 and bolt ons through 3.73s, torque peaked at about 4850, but the curve is pretty flat from 3200-5000, then it starts falling off......that doesn't make any sense to me since our cams are fairly similar and you have heads to boot.......

PREDATOR-Z

Well, I would say you're running a bit lean, try fatening a little and see if it improves.
Also, what was your lifter preload?

01tam6

iTrader: (1)

The curve on mine looks pretty flat too its just way low! Looks like I was making about 12ftlds more than you when both stock. You add a cam and I add heads and cam now your 20ftlbs more than me!

01tam6

iTrader: (1)

Actually on the first pull I believe my car was in the mid 12s as far as A/f goes and made less hp and tq. Sorry don't know on the lifter preload. Thanks

QUOTE=PREDATOR-Z]Well, I would say you're running a bit lean, try fatening a little and see if it improves.
Also, what was your lifter preload?[/QUOTE]

LSGunZ28

iTrader: (8)

You changed your heads you said... it might have affected your compression ratio, which can give you less torque, typically, your compression ratio was probably less than it was with the older heads. I may be wrong, but this could be the problem.

01tam6

iTrader: (1)

Actually I gained compression on the head swap. I believe my old heads had 3-4cc bigger chambers than what I have now.

QUOTE=LSGunZ28]You changed your heads you said... it might have affected your compression ratio, which can give you less torque, typically, your compression ratio was probably less than it was with the older heads. I may be wrong, but this could be the problem.[/QUOTE]

LSGunZ28

iTrader: (8)

[/QUOTE]

that is certainly odd...

I cannot think what the problem is, especially you losing torqu and it being moved higher, usually it just moves the powerband, but no loss....

I honestly cannot think of why this could have happened. sorry dude

krexken

Weird. Almost sounds like the cam timing is slow. What rpm does it make peak hp at? Was the cam degreed when installed? As stated above, I'd check lifter preload also. No doubt the bigger rims are hurting it some.

01tam6

iTrader: (1)

Peak looks to be about 6200 and stays pretty flat to 6500 where it was shut down. Sorry don't know if it was degreed in. Thanks.

01tam6

iTrader: (1)

I am going to try a few things. First while my car was idling today there was a rattling noise coming from underneath, turns out the y-pipe is hitting the tunnel brace. Maybe causing false knock? I am going to use a pyrometer to check the temps at the headers to see if I can find maybe a dead cylinder or something(I did check over the wires already). Also my A/C compressor or other pulley has been making a whining noise lately so maybe that is putting some drag on the motor. I think I will try these things, get a cutout, and redyno just to see if there is any difference.

WS6FirebirdTA00

iTrader: (33)

what kind of timing are you running WOT? what kinda plugs? did you get any KR on the dyno?

WS6FirebirdTA00

iTrader: (33)

might be a good idea to do a compression test as well just to be sure. with that cam on a +2 i would have thought like you that the power should have been near 430 and torque near 395ish

magius231

iTrader: (8)

yes the banging is probably pulling timing, have you put a scan tool on it to see what is going on? Thats your best bet, it will show if theres any timing being pulled as well.

gomer

iTrader: (13)

Sorry that I'm just getting in on this thread guys, but I was away from the board all day yesterday. I did the install and tuning on Chris's car. I was really surprised at the outcome of it also. I've been trying and trying to come up with a reason for the low power on his car. I was really expecting 430ish rwhp and 385rwtq at the least. To answer some of the questions in the thread. I had it slightly rich initially and gained a little power by having it 13.0 thru the midrange and leaning it to 13.2-13.3 on the top. The car has 28-29* of timing in it. All dyno runs were logged with HPtuners to verify that there wasn't any knock retard or anything else that would effect the pulls. The lifter preload was checked when I did the install and came up normal. His heads were unmilled 5.3's and the F13 came with a cam doctor printout. I'm very sure the cam timing is correct due to the power peak occuring at 6300ish rpm. At the time of the install, I installed new plugs in the car and reused his stock plug wires. The heads didn't come with a flow sheet when Chris brought them to me, but I have the serial numbers off the heads and will get with TSP on them today.

WS6FirebirdTA00

iTrader: (33)

did you try any lower timing values in there to see how it reacted to it?

gomer

iTrader: (13)

The first pull on the car was stock 01/02 timing and we worked our way up from there. More timing made more power.

01tam6

iTrader: (1)

Thanks for answering some of these questions gomer. We'll figure it out.

WS6FirebirdTA00

iTrader: (33)

let us know if u guys find anything. best bet would be take it to the track, if its fast its fast, doesnt matter what the dyno tells you

gomer

iTrader: (13)

I dyno about 5-10 cars a week on this dyno and I was really expecting it to do alot better. Even driving the car around.. I can tell it is missing the midrange that it should have. I'm going to get the car back from Chris, do a compression/leakdown test, change plug wires, pull the front cover and verify the cam timing, then if I don't find anything.. pull one of the heads and have it flowed.