Forged 383 with 235/242 cam 278/210 cfm heads only making 380 whp-5500rpm? Help!!!!

[MavsFORMULA]

My camaro in sig, was "dyno tuned" by original owner and madr 382 whp and 400 wtq (at like 5500rpm and 4000 rpm). Its an 11 to 1 fully forged 383 with a gtp stage 2 heads and billet 6 cam. Heads flow 278 and 210 at .600 and cam is 235/242 .580/.600 on a 112 w/ 4* advance. Didn't realize until I got it that, first the cam should pull to like 6800 and seccond with that short block and these heads it should make 440-450whp at 6800. I had solomon start tuning on it and when i asked him about the dyno tune on the car, he said it was basicly a stock tune with about 10* of timing pulled (i think in an attempt to get rid of the knock they were seeing, which was act false) -not to mention the 6-10* of add'l timing being pulled by the pcm. So is there a chance that tune is the culprit of the crappy numbers, or should it still have pulled to 66-6800? Im thinking its getting dyno tuned this week, bc Im starting to question just using the stock o2's and datamaster to log/retune this beast. Im also thinkin this, and the large time between logging and retuning has fouled my o2's again. Got new ones and prob dyno tuning this week.

Basicly want to know if the stock fueling, and close to 20* pulled, could cause these low numbers? Or if i likely have a mechanical problem or it wasn't built to close enough tollerances (or something similar)? Poss valve float, but the graph rounded off-not fell strait on its face. Im also running the dual comp valve springs that are good to .600 and were chosen by GTP for this head/cam package.

The other thing I wanted to ask about, was about the best MPG i have seen is 15 on the highway, with 3.42's/M6. Ive heard of people running similar setups with way better mileage. I talked to a guy with a GM847 and AFRs on a 355 with 4.30 gears getting like 24mpg and 20 around town. Im down to like 10 mpg in the city.

What is my problem?

All help is very appreciated!!
Thanks

Nick

[Pro-jection Eng]

run the timing that retarded will cause the engine to nose over like that at a low rpm. stock fueling is definitely not going to be anywhere close. Also running reduced timing is the easiest way to KILL your gas mileage, because the motor will not be making any torque. Surprised your headers weren't glowing orange running that kind of timing lol.

[joelster]

That cam MIGHT seem big to you, but keep in mind you are running a 383 with good heads. That is a decently big cam for a 350 but it's a moderate cam for a 383. It ain't gonna make power up at 6800 on a motor that size. I'm gonna guess and say it will peak a little over 6grand. That cam you have in your 383 would act very similar to someone running a comp 305 cam (or a similar 220-226ish duration) in a 350 cube motor. It will make power from 4000-6200ish. It won't rev to 6800 the way it sits.

Also, with your mileage issues, obviously the tune is pig-fat, and needs to be addressed. Your car should be a torquey beast with the cubes/heads and cam you have.

[Low N Slow]

I don't see injectors mentioned in your post or in your sig. If you are still running the stock injectors you cold be running out of fuel.

[Pro-jection Eng]

i don't really like that cam for that combo, but I think it'll pull to 6600 or so just might not make that much power up there. Should definitely make more than 380 though.

[MavsFORMULA]

Thanks for all the help guys. Im running 30 lb SVO's on this one. My new tuner is busy all week, so it wont get tuned again till next week. Ill post an update for sure.

Wicked, will you send me a cam suggestion or two?
Keep the help coming!! Thanks...

[Robsquikz28]

You really should have a larger cam for that engine combo.

[MavsFORMULA]

I didn't build it, or the cam would be a custom grind with more duration and prob on a 110 LSA. Will be some day anyway, Im sure. Im going to see my new tuner today. Hopefully retuned and dyno'd by tuesday. Ill post my results when I have some. ff