Engine is a 383 stroker 11.5 compression

TFS 215 heads
238/246 .605/.615 @.050" 113 lsa custom cam
LS7 replacement lifters
Yella Terra Ultralite rockers shimmed for a good wipe pattern
7.525" pushrods which give 1 full turn preload
Fast 90mm intake and Throttle
Kooks 1 7/8" primary headers with cutouts open for dyno pull

This thing was spec'd out to peak at 6400 and shift at 6800 yet it is peaking 1000 rpm early and is very saw toothed. Also the torque is dropping off very hard. I read that the stock dual springs on TFS 215 heads are rated .650" lift. Thinking the rockers may be the problem.

Dyno'd with 12.0 afr with 21 degrees timing. 4000 FTI stall unlocked.



Wanted to post on here because I know there are alot of intelligent people on this board and hope that someone can give me their insight.

 

If I had to guess I would say yeah. That is a pretty common chart for float. Are the lifts you are givving actual valve lift?

 

Valve spring lift capability doesn't provide meaningful information. What is the installed height and seat value. Also, the curve is choppy because the smoothing is set at zero. They can replay the curves with smoothing if they have them saved. Float is usually a steep drop with no recovery, yours seems to be losing power steadily with RPM.

 

Yes the lift specs for the cam are valve lift with my stock 1.7 ratio rockers. I do not know the installed height of the springs because I didn't take them off the Trickflow heads. Just took them out of the box and installed them.

This is what i get off the paperwork that came with the TFS 215 heads.
Valve Springs: 1.300" double (140 lbs. 1.800" installed height, 385 lbs. @1.150" open), .650" max valve lift.


Gave the same specs to Pat G when I had him spec the cam.

I do not necessarily know if valve float is the issue. But I am certainly concerned about it peaking so early and low considering the engine build.

 

Sounds extremely close tou our 1221. With the Yella terra rockers I know a lot of guys needed to add spring to control the extra weight. Might want to look into a 1206 or 1207 shimmed up to 1.750 to 1.700. I would suggst a better lifter also, something that can handle 150-190 on the seat.

 

Forgot to add that, running LS7 replacement lifters. I have also been told it may be misfiring due to a weak or bad coil but would it not be noticable to the ears during a pull?

 

That is a possibility too. I'd lookk everything over well before you start to go through parts.

 

I'd agree it doesn't strike me as valve float just looking at the graph. I wouldn't expect it to keep pulling, but rather drop some big HP, shows some peaks and valleys, but not recover and keep pulling like yours is. Set smoothing to 4 or so and see how it looks first...what plug wires are you running? It could be interference being picked up by the amp probe too.

 

Apparently the springs on those TFS 215's sold by Hinson Supercars are different than what are sold on them elsewhere. I checked the receipt and it said 150 seat 450 open pressures so I have thought it wasn't valve float either.

I'm running the 8.5mm MSD wires. How would you go about testing the coils if I didn't have access to an oscilliscope?

Also I am running br7fe's due to having a plate kit on the motor but haven't sprayed the new motor yet. I don't think it would affect it this much though vs some tr6's.

 

Changed off the br7fe nitrous plugs and put in some TR6's instead. Made sure all the plug wires were snapped in tight. Idle was healthier and pulled stronger seat of the pants. Made some passes today. 1.5 60' 11.1@120 Slight break up at top of 2nd and in 3rd. So minor i can't feel it in the car but others can hear it in the exhaust on the sidelines. When it's running right I am expecting 125-127.

 

Pat G just got up with me (spec'd the cam for my setup). He says it's definately a valve control issue in his eyes. Says alot of time Trickflow doesn't have the springs shimmed right and I should either set them to within .050" of coil bind or get some .675" EHT springs which I have been eyeing already.

Think I may get some EHT springs and set them up right. Would rather have the extra pressure to control the valvetrain better.

 

Any more info you this i have about the same thing going on. Mine will pull to 6200 and then fall off. Im going to try to put on the dyno this weekend and see what it does.

 

interested in your findings. Time for a hydra rev kit? though I usually see this used on gen 1/2 SBCs...

 

Working on swapping back to stock rockers with the Thunder Racing shim kit for the TFS heads. Figured this would be an easier route than swapping springs and it falls right in the .600-.650 lift they designed that kit for. Will update this with a dyno sheet next month when I install it.

 

You didn't mention fuel, so I thought I'd throw this in. Last time I dynoed my car, my power fell off at 5500 rpms. Turned out, my fuel line in the engine bay had THREE kinks in it. Not saying you have a kinked line exactly, but it could also mean something else fuel related.

 

Fuel was good, afr was solid 12 all the way thru the pull.