Whered my torque go?
Whered my torque go? 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. 
Launching!
Joined: Apr 2005
Posts: 263
Likes: 0
From: Abilene, TX
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.......
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!
Originally Posted by 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.......
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]
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]
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.
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]
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]
Trending Topics
Originally Posted by 01tam6
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]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.
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
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Launching!
Joined: Jun 2005
Posts: 202
Likes: 0
From: longview, tx
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.
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.
Originally Posted by 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.
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.
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
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.
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.
Originally Posted by WS6FirebirdTA00
did you try any lower timing values in there to see how it reacted to it?
Originally Posted by gomer
The first pull on the car was stock 01/02 timing and we worked our way up from there. More timing made more power.
Originally Posted by WS6FirebirdTA00
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 