99C5JA

I need some opinions on why my particular setup just doesn't seem to perform. I got the car in '01 and have been steadily modifying it and I can't figure out what I am missing here.

The first round of mods was a TR 227/224 cam (.569/.563 114 LSA), LS6 intake and a set of FLP Longtube headers. The setup made a predictable 375rwhp and 350rwtq. I was pretty happy with the results and the car ran good.

The second round of mods was a ported TB, Absolute Speed stage 2 241 heads (306cfm intake/230cfm exhaust @.600), and a RAM 980 clutch. The combo made 418rwhp/382rwtq. Again I was pretty happy with those results. Seemed about right for that cam and those heads.

The third round consisted of installing a Futral F13 cam: 230/232 .595/.585 112LSA no advance. Having seen great results from this I was disappointed when the cam only yielded 427rwhp/390rwtq. But I figured perhaps the heads, which were from the early days of LS1 head work just weren't up to task.

Which brings us to the last round of mods. I bought a set of TFS 215 heads. From all the results I've seen with these I was expecting to see some big gains. Instead I got 5rwhp/5wtq which was disappointing to say the least.

So I'm not sure where to go next. The car has had it's last 2 tuning sessions with Dan at FLP, so the tune is not suspect (it runs hard and drives great). I asked him if it looks like there was any valvetrain instability and there doesn't appear to be. I triple checked my pushrod measurements when installing (ended up with a 7.5" pushrod since my TFS heads are milled to 61cc).

My gut tells me I am looking at a restriction someplace. The cam and heads should have each yielded at least a modest gain, but instead I'm only seeing minute changes. The exhaust with Corsa Indy's and catless Longtubes doesn't seem likely. The cam isn't huge, but judging from others results and the specs I would think it should support some decent power. My only thought at this point is that the stock MAF/airbridge/TB and the LS6 intake are starving the engine of air. But before I contemplate sinking more money into this thing I'd really like some opinions on what could be holding this combo back.

mvvette97

iTrader: (18)

interesting, I would like to also hear some info on this. Here is a bump.

m6speed

iTrader: (11)

fast 90/90 w/throttle body could open things up some. do you have full bolt ons? pulleys and so on?

99C5JA

Nope, didn't go the underdrive route. With the amount of juice the Vette sucks it didn't seem like a great idea.

m6speed

iTrader: (11)

eh, it just frees up some hp, you can get the alt pulley to compensate.

99C5JA

Yeah I know. It just wasn't a mod I decided was a must.

m6speed

iTrader: (11)

hmm well either way the fast 90/90 and tb should net you close to 25rwhp. x pipe or cutout could help a bit.

Zosickness

How much seat of the pants feel could you tell between mods? Corvette's are not dyno queen cars with our IRS. If you could feel the difference I wouldn't worry about the numbers. Do you have any track times to compare? What kind of dyno were you using? Are the numbers corrected? There are two dyno shops in my town. If I just want to get high numbers I use the dynojet. I decided I just wanted to know what I was really putting down, so I went with the mustang dyno. I can tell the difference my mods made. The dyno numbers don't show it. 422RWHP/365RWTQ 04 Z06 MS3(.603/.609,237/242 112LSA) , Kooks LT, PRC Heads, Blackwing, ASP underdrive

99C5JA

The numbers are corrected. It was on a Dynojet. The TFS heads felt stronger in the lower rpm's. Throttle response is certainly crisper. Haven't made it to the track yet to compare. In the end they are only #'s, but a guy likes to feel all the $$ he just sunk into the car was worth it.

99C5JA

That is where I am leaning. The car has an x-pipe. Cut outs don't do much on the C5. Just going back to the basics it seems like either the intake or exhaust is the culprit (old hot rodder adage she only puts out what she can get in). The exhaust isn't real likely so I am left looking at the intake side of things.

99blancoSS

iTrader: (115)

A 90/90 isnt a cure all for low dyno numbers. Ask me how I know. Added one and it didnt change a damn thing.

99C5JA

I'll be the first to admit that a 90/90 setup hasn't seemed worth it from the results posted. But I'm just coming up blank with how a bigger cam and better heads don't make power. The dyno's between the ported 241's and the TFS heads are damn near identical all the way through the rev range. I don't know what else it could be except a restriction at either end.

99blancoSS

iTrader: (115)

I'm in the same boat but with an fbody. I added stepped headers and bigger Y and a 90/90 and a meziere and gained nothing with a 234/240 .627 . 641 112 lsa cam and my Terminator heads.
Put down the same numbers with prc 5.3 heads tr224 cam and an ls6 intake and a smaller Y pipe.

99C5JA

Was it on the same dyno? And I am guessing you put on the 85mm MAF too.

99blancoSS

iTrader: (115)

same dyno but my stock maf, was told the 85 wont make a difference.

99C5JA

Bumping to see if I can get some more input on this.

PortPros1

You should be in the 450 to 465-rear wheel HP range, I have done many head and cam packages on this cars.
Depending on the cam we see consistent numbers with ported 243's, TFS, Dart etc, heads in this range.

You have a restriction, but from what your saying I don't think it's the throttle body or the exhaust.

Give me a call I would be happy to go over some options with you.
Advice is free.

Harold
Port Pros LLC
512-257-0222

99C5JA

I appreciate the offer Harold. I may take you up on that.

99C5JA

Well you'll only flow as much air as the smallest link in the chain. Since you have gone as far as you have I'd stick an 85mm in there.

99blancoSS

iTrader: (115)

I'm thinking about it. The problem is everytime I take it to the tuner its beaucoup $.
Changing out the MAF will require some ECM work and I have to pay for that. I'm getting a 0121 code as well and I've already repalced the TPS but the TB blade opens all the way so it's not restricting. Damn frustrating I'm sure you know what I mean.