My dyno numbers are with unported stock heads and a CC306. Sounds like someone really messed up your heads, flow characteristics or something.

 

my question - do you have stock injectors?

 

Your 383 must have had alot more torque... how high did you spin it?

Here is the flow sheet for the heads for comparisson (SF 600):


(personal info blacked out)

 

No I've got some LT4's tuned from pcmforless but that are maxing out in the high RPM so some 30#SVO's are going in soon.

 

that will probably help your high-end power than

 

I don't think it will do much in terms of power though?? I mean the injectors are running at up to 97% but it seems to me as long as it's getting the fuel then it will make the same power? correct me if I'm wrong? Maybe I'm not understanding... I am still going to change the injectors so as to not put too big a workload on the ones in there right now, but I was under the impression it's not really affecting power.

Also I have some logs from datamaster of som WOT blasts if someone would like to take a look to see if something is off. I'd appreciate it alot.

 

Question is how did he flow these? There are many ways to make a flow bench show better numbers than what they really move.

 

My 383 made 370 torque to the wheels, and made max power at 5400. My combo was clearly less than optimal for the cubes.

I looked at your head flow chart and it looks like your heads flow the same as mine did, I had AFR 195 "race readies" 70 percent CNC ported. I just went off the website at AFR and they claimed it would flow 262.

Cam was a Comp 503.

The only thing I can think of now is your tune?

 

In that case maybe you're right there really is a problem... or like MeanGreen97Z said I got ripped on these heads.

Thing is, years ago this was only supposed to be an exhaust/cam kit only project, but I figured if the car is going to be down anyway, why not just bring the heads to someone around here for porting and this place was recommended to me by a good friend of mine. Lesson learned I guess next time I will go with someone reputable for the heads like Lloyd or AI.

 

Yeah for the tune I realize a dyno tune is the best thing but the car has been running pretty smooth with the mail order tune.

Also the fuel injectors and valvesprings are on my to-do list for sure.

 

What is the matter with the valve springs you are running now?

 

Nothing mechanically wrong with them, just that judging by the way the torque just drops in the high 5k-low 6k RPM range, something seems not right. Where my hp peaks, the torque falls off dramatically. I just thought that maybe if I put more spring on it it would help the top end? What do you think? Lloyd used to use the 612's but on cams with less duration, less lift and in a lower RPM range (6200 max.) than my car is operating right now. Also my cam has the agressive XE lobes so these springs probably aren't the best choice for this cam.


Maybe something else could be off though, I'm open to any suggestions before I throw parts at it if there is anything else that could explain a significant drop in torque like that.

 

That isn't valve float. There's no way the valves can start floating and then recover. Your upper rpm curve looks fine. If you say there's a dip in your A/F ratio then that should be the first place to investigate. If you want to know what springs to use then call the cam manufacturer. That's your best bet.

 

After looking at a few dyno charts though, seawolf mentioned that the temporary drop in torque in the mid range could be normal, and I've seen what he is talking about on other dyno sheets (ie the slight drop at 4000-4500) apparently due to the overlap in the cam?

I was referring more to the torque curve after the HP/TQ crosover point, where the graph shows a loss of about 30+ WTQ up to 6300. I thought that could be valve float. Good Idea for the springs I will contact comp cams and also valvespring manufacterers (crane, PAC) and ask what they think is the best spring for my cam.

 

The two dips look awfully deep. I don't know if I would accept that answer.