OK, I have gotten another timeslip and wanted opinions on what is going wrong.

Car is a 91 Formula, 406, World Products Sportsman II's, 10:1 comp, TPIS miniram, Solid roller cam 242/250 @ 0.050" lift, .618"/.600" lift, SLP 1 3/4" headers, Random tech 3" cat, Mufflex 4" exhaust, 700r4 with 3000 Vigilante convertor, 4.11 gears in a 12-bolt, all typical suspension mods (SFC,LCA,PHR,airbags,struts/shocks,no fornt sway bar).

This run was shifting at 6300 rpm:

Reaction time: 0.599
60 ft time: 1.69
E.T.: 12.49
MPH = 111

 

IMHO the car is unbalanced. You have a good sized cam, a LOT of cubic inches, a good flowing intake .... but terrible heads. Those heads would have a hard time supporting a high RPM 350 ... you have a 406 I would suggest some Competition AFR220's or some ported Brodix heads. There's no way that those Sportsman heads even come close to flowing what your setup demands.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Sorry, I forgot to mention....the heads may flow too well. They were ported extensively. They have 2.08 intake, 1.625 exhaust valves, flow over 300 cfm on intake. However, the intake chambers are huge (230+). They made about 660 HP on a 434 carbed motor (dyno test) before I got them.

Also, the car weighs 3650.

 

One last thing...the cam is ground on 114. Is that hurting my power numbers?

 

What have you done to the eprom? Is it still SD?

 

Sorry, there are so many details that I forgot to post.

It is a speed density setup using Accel DFI, I have 36 lb. Ford injectors and Edelbrock 58mm throttle body.

 

OK,, I had a very similar set up (pocket ported Darts – running similar times in a 3850lb car and driver) back in 88 or 89 it was not balanced well at all. I don’t know what’s going on with your set up, but the main “problem” I had was the exhaust ports were opened up to large and coupled with an exhaust – even 1.75” primaries and dual 3” with no cats, I had a huge torque spike,, and consequent dip right past the converter’s flash point. The car would leave hard,, blowing the slicks off then fall on it’s face,, I had to petal the car to get it to leave decent,, and then seemed it took forever to get up on that cam. If I had been running a computer ignition system,, maybe I could have took out some timing at flash,, then added a bunch to help with the torque dip,, then I could have took some out as the engine started pulling on it’s on. Maybe,, it would have helped et by .2 or so,, nothing major like you’re looking for though. Like I said,, I don’t know what’s exactly happening with your set up, but I’d bet with heads capable of 660 horses,, that your exhaust port is larger than the openings of your primary header flange,, which is not a good thing,, especially running into a single 3” cat. I’ve got a little experience building a few 600 plus HP SBCs. 660 horses with cast iron Darts is amazing,, even with a 434 with 13:1 plus compression. Not saying it can’t be done cause I couldn’t do it,, but it’s hard to get the iron heads to flow much over 300 cfm,, and to get 660 horses even on a 434,, either the compression and cam was out there,, and/or the heads flow more than 300cfm. To get Dart IIs to flow that much (and get runner volume of 230cc) the cross sectional area USUALLY gets pretty large and port velocity can suffer. However, most guys running a maxed set of Dart IIs are not worried so much about port velocity (or happy medium of velocity and volume) as they are about just volume,, they usually run cams larger than 270degrees at .050, and run 4600 plus stall converters with a lot of gear,, and never see street duty. So I’d say you need to jack up the compression and throw in a larger cam and more stall if you really want that thing to run right with your heads. Certainly if I were you I’d be looking at making sure what I had was dialed in best I could before changing a lot of stuff. I’m assuming you’ve tuned on the fuel and timing curves and this is the best you could generate. Regardless,, my opinion you’re trying to run way to much head and cam for a single 3” cat,, and the exhaust would be the first place I’d concentrate if you don’t want to re-think your entire set up. I wish I could tell you for sure what’s wrong,, but that’s my best guess,, with no more than you’ve provided. Good luck!!

 

Building on this exhaust idea ... the SLP headers have 2.2" collectors. That's too small for your engine. I am currently in the process of replacing the SLPs with a set of Hooker Long Tubes. I can't imagine running a high-effort 400 without the hooker long tubes. They have a true 3" collector and will flow a lot more than those SLPs. The 2.2" collector is way too wimpy for your setup. Although the collector APPEARS to be 2.5" if you look in the collector and do some measuring you will see that it clearly necks down to 2.2-2.25". That's why SLP supplies 2.25" pipes with their headers.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

It seems to me as well that you need more exhaust, more gear, and possibly a looser converter. I think with the right set up you should have an 11 second car.

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1986 IROC, fully loaded, Mini Ram'd 383, Art Carr 700R4, Accel DFI, 12 bolt rear, etc, etc......

 

Yep, I’m not that familiar with the SLP headers and forgot they neck down into a stock type flange. I can tell you the one thing that just kills a real high powered combination is a “restrictive” exhaust. To run a lot of cubes, heads, and cam and it corked up,, the exhaust has to be up to the task, or you will have wasted your time and money. Anyway,, while the wife’s IROC may not need a lot of exhaust to run 12.50’s (1.625” Headman headers, 2.25” y-pipe, single 3” to welded Dynomax – no cat), no way could my SS run the same exhaust (1.875” headers and dual mandrel bent 3.5” pipes and Borlas). An “extreme” exhaust is crucial in my mind when you get in the 500 horse and over range – which it sounds you should be capable of barring any other problems. And while you might not tell much difference if you swapped cams right now,,, the 114 lobe spread would kill power with a really good exhaust,, especially with a NA 10:1 engine.

 

I agree, you need some 1 3/4" long tubes and a good dual 3" or 3 1/2" exhaust system. Blowing through a single 3" cat will not cut it. I just got my SLP 1 3/4" shorties and they have a 2 1/2" collector, but the pipes neck down to 2 1/4" right after the collectors.
My 67 has dual 4" with 3 1/2" tailpipes and I dont think it has over 600HP, it runs good and isnt getting choked

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91 B4C 305 TPI - SOON TO BE 383
TREMEC 5-SP, STOCK 1-BOLT REAREAND w/342 GEARS, K&N, AIRFOIL
EDELBROCK HEADERS, DUAL CAT TO HOMEMADE Y-PIPE & 3.5" SINGLE PIPE W/ FLOWMASTER, CRANK PULLEY, MSD, FUEL PRESS REG, COWL HOOD, WELD WHEELS
14.1@ 98MPH
-------------
OTHER RIDE
67 CAMARO - STREET CAR, BIG BLOCK, PUMP GAS
350TH w/ATI 10", 12-BOLT w/373 GEARS
10.47@129 1.55 60FT. ON MOTOR - ET-STREETs w/MUFFLERS

 

The only way to find out what's wrong is to put the car on the dyno with your DFI program running and see what's happening in the motor. Maybe you are running out of fuel in places, or are getting knock retard somewhere?

I don't think your exhaust is choking you that much, try checkinf your ignition, fuel and timing.

 

Ignition timing is set for total advance at 36 degrees. No possibility of knock retard, because there is no knock sensor (can't have it with a solid roller)

It runs right around the stocihiometric point on the air/fuel ratio gauge. Probably a little on the rich side because of the lack of a knock sensor. I would rather be rich than lean.


Any other suggestions? I got a pair of Hooker Super Comps and will be putting them on for the October EFI day at Englishtown, NJ. I guess I will post a follow up to let you all know what kind of difference the headers actually make.

 

At WOT you don't want to be at Stoich. You want to be about 12.5:1 A/F ratio. Maybe you just explained it in a way I didn't clue into but I post this just in case.

Stoich (14.7:1) is for cruising around at part throttle for good economy and emissions.

 

That is what I meant, cruising around and at idle it is 14.7 or so. At WOT it runs richer.