99C5JA

Long story short I dyno'd last fall with a Futral F13 cam (230/232 .595/.585 112LSA no advance) and Absolute Speed stage 2 241 heads (306cfm intake/230cfm exhaust @.600) and made about 420rwhp and 380rwtq. A small gain from the previous cam, a TR 227/224 (.569/.563), which netted 416rwhp. So I decided that the heads were holding me back.

So this spring I installed a set of Trickflow 215's milled to 61cc. Here is the result:


Yup 5rwhp/2rwtq 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.

Sharpe

iTrader: (7)

Well, what did Dan say?

98SS2836

iTrader: (6)

do a compression test on all the cylinders. You really need a fast 90 to make that combo shine.

BIRDONNOS

iTrader: (3)

installing 215's on my car tommorrow, wanna keep track of this thread

99C5JA

Dan said he couldn't see anything obviously wrong. No sign of valve float. Car acted fine from what he could see. Drove fine when he took it out.

NEVRLIFT

A ported FAST will get you about 15-20rwhp. A Callaway Honker will also get you some more horsepower. I read one article in a 'Vette magazine where an H/C FRC gained around 10whp with one over a Blackwing. A Vararam will do well too.

miami993c297

iTrader: (6)

The swap from a Stage II 241 Heads to a set of TFS 215 milled to 61cc gave you a gain of 5 rwhp?????

Something must be wrong there, don't you think?

Christian

Vengeance Racing

Call Vengeance we will get you squared away.

Brian Tooley Racing

iTrader: (13)

I have seen 2 poor results with TFS heads, yours and a guy with a C6 Vette LS2 and TFS 225 heads, the only thing in common is both combinations had YT roller rockers...

I would take the advice of Mike above...

SEB

iTrader: (12)

I am running the TFS 225 Heads on a 347 Motor with a 648 - 652 Duration Cam on a 110 Lobe Sep at 650 lift, Nick William TB, FAST Intake (ported), Kooks 1 7/8 headers Stepped 2inch on 3 1/2 Collectors with a 3 1/2 inch Custom X-Pipe with Elec Waterpump & pulley through a Stage 3 Built 4L60E Trans with a Yank PT 4400 converter,on a 12 Bolt.

Any thoughts on what I can do to help out this combo. I am looking to make 440 RWHP


Sorry to the thread starter. I didn't mean to Hi Jack your thread

Seb

ATVracr

iTrader: (5)

It would have picked that up with his old heads also.

ATVracr

iTrader: (5)

Thats a big *** cam for a 347.

I dont think it needs to be that big to make 440rwhp.

JakeFusion

iTrader: (7)

Isn't the "stock" pushrod length 7.700" for use with the TFS heads? If so, why would you go to a 7.500" which is .200" shorter? Even if you mill the heads .18" ~ 61cc, you'd still need 7.675" pushrods. Do the YTs require a different length pushrod?

JakeFusion

iTrader: (7)

High stalled A4s simply don't put down good dyno numbers. Unlock it and run it - it should be close. Also, you gave lift numbers, not duration for your cam.

SEB

iTrader: (12)

248-252 duration.

I am wanting to make good TQ & that is why I am going with a 110 lobe sep. It just going to be really hard to tune from what my tuner says.

Looking to run 6.80 @ 101 mph in the 1/8 mile. The car is Full weight at 3600 lbs,,,,

Am I setting my goals to high.

Also I am wanting to run the Jessel rockers

99C5JA

I suspected the rockers on the dyno, but we just couldn't see any signs of valve float. Would the rockers be effecting the whole RPM range here? I would have thought rocker instability would have shown up in the upper ranges and not throughout the whole curve. I'm certainly willing to change them.

99C5JA

I can't see the rocker brand effecting the length of the pushrods since they all must maintain the necessary geometry. I triple checked the measurements before ordering the pushrods and after ordering found another member with the same heads milled to the same cc size also running the same pushrod length.

LS1curious

To much overlap in the camshaft. It'll kill Tq and HP with a head that efficient.

SEB

iTrader: (12)

When you say overlap. Please explain. I am confused?

99C5JA

Overlap refers to the time when both valve's are open. The lobe separation angle and duration determine overlap. Smaller LSA's will increase overlap which can be bad or good depending on your setup.

Not to be rude, but can you please continue this discussion via pm's or with a different thread? It's hard enough trying to get a handle on what the heck is wrong with my car without two different conversations going on.