Hey guys. Wondering if you can help me out.
The car, well it just feels slow. It seems more powerful than the stock version before, but it doesn't feel like the numbers it churned out on the dyno. It actually feels really sluggish till I hit about 4k.

I will post the dyno tomorrow when I get the tuner to send me a copy.

Here is the story:

383 Stroker Motor
-3.75"' scat crank
-5.7" GM pink rods
-4.030" Hyper pistons
-Dart 200cc Pro1 heads
These have been slightly ported, flow numbers listed below
-Superram Intake
-52mm Holley TB
-LS1 25lb/hr injectors
-Holley AFPR
-Walbro 255lph Fuel pump
-LPE Longtubes into a 2.5"' mandrel bent Y-pipe to a straight 3" section to 2.5" Magnaflow catback
-LPE 213 flat-tappet hydraulic camshaft
(224/234 .496/.520 w/1.6rockers )
-Magnum 1.6 roller tip rockers

The heads:
Ported and have 2.06/1.6 valves with CC dual springs

My Darts: @28" H20
LIFT---.200.....300......400.....500....600
Intake--138.....197......240.....268....283
Exhaust-101.....152.....183.....206.....210


Ok, so on the dyno (mustang dyno) the motor made, 326rwhp/400rwtq peak. So any ideas why it is acting like this.

I have two theories, but I won't say them till I hear what you guys say. It just really, well its a little dissapointing.

Let me know anything...
Thanks guys!

 

Sounds like a tuning issue. Your torque peak is below 4k I'd guess based on the specs.
Or your car is heavy or tall gears.

 

The 2.5" cat back might be the problem

 

Small cam for a 383.

What did the wideband look like?

 

Didn't notice it was a flat tappet hyd, those numbers look decent with the cam and 2.5" exh (pushing 410 hp at the crank), if it was a roller with those specs i would think you got more in it.

 

Bad tune. Has anyone burned a chip for it yet?

 

Looks ok to me. You aren't going to make lots of peak hp with the superram, it is better in the midrange.

What is your compression ratio?

 

Ok, the tune has been done. It still needs work but the AFR is straight all across the board. (This was taken with the sensor in the tailpipe method however)

The problem with the tune is, I can totally pull codes, using the ground A/B port trick, but I couldn't for the life of us get the tuners laptop to communicate with the computer. (New chip/New Computer/tested wiring...wtf)
But I can't work on that since I am not with the car right now. So I am just looking down other avenues.

The car is aboue 3200lbs w/3.07 rear gears (and I am a brother to you guys...I'm in y-body w/ this motor)

Comp is 10.3:1

I wondered if the cam was too small too? But wouldn't a smaller cam make more torque at low end, this thing peaked, I think, around 4500rpm.

Do you think my heads are too big?

I'm working on gettin the dyno graph, the tuner is sort of being a pain about it....

I just don't feel the torque down low is the issue.
I don' know, I will post up the graph when I get it.

Thanks guys!
I really appreciate it!

 

 

feels slow why dont you go to the track and see what numbers you are making.

 

I have a similar 383, but carbed, vortec heads, 10.9 CR. little bigger cam.
I made about 370ftlbs at 3k. 150 heavier car, same gears but 3spd, I don't hook till past 4500. So slow might be tire spin.

It looks to me like you might need some more timing below 3k. That dip at the beginning doesn't look right.
My curve was almost flat and I have an RPM intake.
Most SR curves are closer to flat that I've seen.

 

My old superram 383 combo dyno'ed about the same rpm. You have to port the superram runners, plenum and base to get it to breath on a 383. You are about 406 fwhp right now.

LPE used to get 440 fwhp from a similar combo but with smaller 170cc intake heads and .7 more compression.

What tranny and convertor? Should be at least 2800 stall if an auto.

 

See thats the thing, I am running 255/16 Kuhmo Supra 712s out back. Not the stickiest tire....cannot make them spin from a roll. Its just plain embarassing.

Its a manual with a Centerforce dual friction clutch.

I am thinking you are right, more timing is the key.

I also haven't ported the MAF, should I get on that?

Ohh and its a 52mm TB too.

So you guys don't think the heads are too big?

 

yeah 330rwhp in a 3200 lb vette will move well. go to the track

see what ET's and trap speeds u turn. if it cranks out 326 on the dyno it will run like 326 rwhp.

i would say u could touch high 11's at 115mph on some decent tires

 

RedGut86 - My opinion is that you have a good combination of parts. Yes, the cam would be better if it was a roller but it's definately not holding you back.

As stated in an earlier reply, it appears that you do not have enough timing at lower rpm. You should be able to have full ignition timing in by 3000 rpm. My guess is that you should have 33-34 degrees total.

www.geocities.com/dzperf

 

I agree with the above post. No way should you have a 2 1/2" cat back. That alone is choking your engine big time. You should have a 3" all the way back at a minimum and a 3 1/2 inch Mufflex would be even better.

 

I'd say the heads are to big, or your cam is tosmall, you pick. 3" exhaust would likely help as well.

 

Wow, first off. Thanks for all the responses and help!


Ok, so I'm hearing mainly:

The primary cause of the spike of power, is probably a timing/tune issue.

Also the exhuast is too small...

Also the cam/heads might be too small...

Well to be hoenst, I will swap out the cam before I swap heads, so if I were to swap later on, any suggestions?

Thanks Again

 

Your head are definately not too big. I like the flow numbers and would opt for a single pattern cam if you were to change it out. I would also convert to a roller if your budget allows.

I'm running a solid roller on my motor and find it to be very streetable. It even passed an Ohio E check.
IMO you have good combination of parts.

I still believe that you have a conservative timing curve or the computer is pulling timing due to false knock. Mine did and now I run without a knock sensor.

 

Get rid of that 3.07 gear! Jeez! A 3.73 will wake up yur little slug issue. Those are some pretty stout numbers and some tuning is needed but, Its all about gearing after that.

 

I did not see it shown above:

What is your fuel pressure @ WOT?

I have a 396 and pulled 340RWHp which equates to about 400 crank Hp. So you are not bad at all. You should pick up a bit more a have better throotle respond if you lean it out a tad to 12.8 to 13.0:1 AFR.

IMHO of course.

 

Fuel is 12.5. Yeah that is a little rich. But it is steady.
So it must be timing.
I believe the chip programmer did it a little rich beause we were using the tailpipe method for tuning and wanted to make sure we were rich not lean with my hypereutectic pistons.

Yeah better gearing would help for sure. I have been reluctant to do so, as I am sure this tranny will break soon and I want to have the right rear gear for the new one!

I am thinking if I were to go to another cam in the future, LPE 219/219.
Thoughts?

 

Bigger.
I put down 355rwhp from my 355ci motor in 102* weather. I'm using a 230/244 @ .050
Use a bigger cam. The 219 is fine for a mild 350, but a stroker will idle like a kitten.

 

Yeah, after I posted that last night I started researching good combos using the 219. I think you are dead on. Bigger would still idle quite well but with much more power. What do you think I should go with?

Mind you, my 224/234 cam is a flat tappet right now, so it behaves much like a smaller roller (correct?)

 

Get bigger injectors, 25 lb/hr injectors are only good for less than 400 flywheel hp right?

 

The injectors are "25lb/hr" at our stock PSI, but they are actually LS1 28 lb/hr injectors. So one twist of the Holley AFPR, I will have better fuel spray and higher flow injectors.

I am curious though, are you saying I need them now? Wouldn't I be going lean if I did?
(Its quite possible I just don't understand)

 

If you decide to change the cam, opt for a Comp custom hydraulic roller. Your heads are flowing 88.8% intake/exhaust at .400 lift. Go with a single pattern grind. My recommendation is 230/230 @ .050 with .544 lift using 1.6 rr and ground on a 112lsa. Install the cam at 109 degrees. This will give you a dramatic increase in your mid and upper rpm. I do not recommend a dual pattern grind.

PM me if your looking for more specifics.

www.geocities.com/dzperf

 

what he said.....