derv3tt3

My 78 vette auto w/shift kit,dual exhaust stock manifolds 336 gears q-jet & street tires.First 383 268 high energy cam ,Chevy 624 heads w/202's 76cc,Weiand 8000 intake. Best time 13:93 at 98.68.
Second 383 edelbrock rpm performer heads 70cc, performer intake,268 extreme energy cam.Best time 14:24.
So why am i going slower?Shift point 5500 for both engines.Any help out there. Thanks

RaC3R

What is your MPH in the 2nd run? I'm no expert but your MPH in the first run seems kinda low for a 13.9X ET. Not sure what any of this means, just a thought. Good luck :).

mountainmotor

Like above post,what MPH so can tell what hp you are making.

First thing if mph is down that comes to mind is timing not dialed in,different valve adjustment,intake leak"minor" that is not apparent while running.

Did you change air filter assemblies from first motor?

If you port matched the manifold to the new heads,was work performed to the floor of the manifold runners?





[Modified by mountainmotor, 6:44 AM 2/22/2002]

Ganey

More info. needed & it would be better to look at all info. on timeslips as well.

Matt Gruber

check fuel pressure and or A/F ratio. if OK at 100 mph, the intake is too small. the weiand 8004 flows much better.

might check exhaust back pressure too.

derv3tt3

The weiand 8004 flows better than edelbrock performer?

derv3tt3

Can't find my time slip for the 14:24 run.I also have a best time with the wife's 94 which was 13:939 and mph was only 99.32

Matt Gruber

now there is a good new topic for you:
WHO HAS THE BEST 1/4 MILE with the preformer 2101. Anyone running 12's?
the 8004 is way bigger; i have both

derv3tt3

Is the Weiand to big for me? I don't have headers.

Matt Gruber

it's just right. but inspect it carefully, mine needed 2 hours of porting due to casting shift.

what fuel pump are u running? some guys think they can run a stock pump :lol:

derv3tt3

Is the Weiand 8000 the same as 8004 but has egr? Yes i'm running stock fuel pump.Ideas for a good pump?

John Dirks

I'm running a stock fuel pump on my 383 too.
What pump do you all recommend?

mountainmotor

I guess we are not going to get the mph we asked for so:


From what I remember about Edelbrock is they came out with a Performer that was good,changed designs to one that was better and then went back and changed for the worse with the one that is available now.A long thread about this awhile back at Chevelle site. A guy there really knows his stuff on the history of Edelbrock.

I like the 8004 as well.Like the Stealth better and the Offenhauser 360 better than all of them including the RPM

[Modified by mountainmotor, 7:39 AM 2/23/2002]


[Modified by mountainmotor, 7:43 AM 2/23/2002]

blue_stingray

just from looking at your mods, i'd say your biggest "power hurter" is your stock exuast manifolds-- bigger engines like to breathe- especially with those RPM heads. stock isn't going to cut it, you need at least 1 5/8 headers with short collectors. also, what size is your exuast tubing? are you running cats? what mufflers?

another obstacle is your Q-jet. unless you retune them for performance, they slow you down big time, even a carter/edlebrock 625 will do you better than an untuned Q-jet.

those are my just my opnions based on what i have done to mine. if you wanna go fast, you gotta loose stock, and everything has to match and work together. it seems like your 383 is struggling to breathe.

Matt Gruber

my 72-355 leaned out by 45mph in 1st. i tried another stock pump, was slightly better, finally i wised up and got the GMPP pump # 6415325 from Scoggin 1-800-456-0211 $29.25. Pulls strong to 56 in 1st and 90 in 2nd, in way less than 1/4 mile. I can't imagine a 383 with a stock pump. But it would use less gas(while melting a piston) in a longer race.
Most guys here are big spenders and get a $50 pump from Summit or Jegs
for tuning, see my article: http://community.webtv.net/MATTGRU/AFtesting

derv3tt3

Stainless 2" dual exhaust no cats ,not sure about mufflers they came with the stainless.Dosen't headers cause more heat?The addition of performer heads have really caused the temp to go up under hood.

Guest

Derv,If you want to go fast get a 65 250 HP.Heh heh. Chuck :lol:

derv3tt3

Are u ready to line them up this year Chuck?

blue_stingray

i wouldn't worry about under hood heat too much unless you know you have a bad coolant system. i had the RPM heads on my 355, with headears, 2 1/2 inch exaust (no cats) and flowmasters. my average time was 13.2 at 107 with 3.36 rear and 625 carter. i had to remove my machanical fuel pump and install a gravity fed electric cause i was experiencing high rpm stuttering. i can pretty much bet that if you at least get headers, you'll see a big drop in those times.

mountainmotor

Quote:
"The addition of performer heads have really caused the temp to go up under hood."

Above in a reply by me I talked off difference in tune up from other combination.If the heat is up as you say,your timing is slow I suspect.Also suspect possible intake leak .Spray WD 40 around manifold/head area to see if idle picks up.
Certainly as others have said you will benefit from a good fuel pump and headers will pick it up some but I seriously doubt the lack of headers has slowed you down .You have changed to small dual pattern cam that to an extent should work better with the iron ex manifolds.

We have 2 members running 13.16 and 13.22 with Small Chevy and iron manifolds.Modded Qjet on one-Holley 750 on the other.350 auto trans/both cars/both are 1975 year model-cammed by some guy called CH Racing?