Power cutting out

[cobraII]

I took the Cobra to the strip today and had an issue I thought I would bounce off the group. I was running great through the 1/8 (about an 8.45 -8.50). I was keeping pace with a Z06 that was turning 12.3 - 12.4. But a little past the 1/8th I loose power from the engine, if I pull my foot out of it for a second and hit it again I get some power but not much (the car doesnt stall or anything but it cuts out). Anyway I end up running mid 15's because of this (still beat the ricer Honda, but got smoked by the Z06). Anyway I am thinking it might be starving for fuel so I am going to check the float, you guys have any other ideas?

CHRIS

 

[ryan218]

do you have a super charger or turbo?

 

[cobraII]

No just a naturally asperated 351W. The shop that did the machine work and helped me spec the parts (9 years ago) said I should be in the 425 - 450 hp range at the flywheel, but dont know for sure, never been on a dyno.

CHRIS

 

[2muchtime]

doesnt sound like a fuel problem to me..
especially if your running strong rpm's through out the 1/8...
sounds more like an air flow restriction at higher speeds

 

[78CobraII]

I dunno...once that fuel bowl runs dry, power is going to drop off... Letting up on the throttle for a second would allow it to re-fill a bit.

Rigging a fuel pressure gauge at the carb fuel inlet would tell you a lot.

Lots of racers increase the fuel supply line diameter to eliminate this sort of problem. I would think that a plugged tank inlet sock would show as a problem much earlier.

If your fuel pump is factory, that could be the problem also.

 

[itsaMustangtoo]

Yeah , I am with 78 cobra II . Float level could be fine but the fuel pump cannot keep up ( supply and demand) When you let off the gas and hit it you are just getting another accelerator pump shot. You need a fuel pressure guage to check it out. I ran 3/8 inch aluminum line from my cell to the fuel pump on my cobra clone.

 

[cobraII]

You know I was thinking fuel pump this weekend. I have no clue what the volume is on the pump, I think it is an electric standard volume Napa pump I put in back in 98, I think (been to long ago to remember, lol) I am thinking lower volume because I didnt need a regulator. I will have to get a gague on it and see where I am at.

It will be tought to diagnose the issue though since I cant take it back to the track untill I put in an "outward visable" battery cutoff bucause the battery was moved to the trunk. They sugested drilling a hole in the tail light to mount it, I am thinking no way. I also have to behave on the street for 6 months, I got nailed in the 97 SVT cobra on the way back from a mustang show sat. afternoon, 77 in a 55 bu I have a clean record so I can do the diversion program. Anyway Thanks guys, I will see what I can do to get it ironed out.

I went and checked out an online calculator and based on the 1/8th time I was on my way to a 13.27, that would have been fun, fastest I have been in the 97 is a 13.95.

Thanks
CHRIS

 

[2muchtime]

ok so u have an elec pump then..
and 400-450 on a preset pump just might be ur problem. most r preset 5-7psi
just sounds odd that you can run it up to 5500 through the 1/8
with no hesitation from 1st and 2 nd gear..
could even be a fuel line running next to a header (pre attomization)
or diameter of line.
anything is possible with little infomation..
what type of ignition system do u have ?

 

[IMACHU2]

I had a similar problem with my II. I had a Holley mechanical pump that was faulty. I replaced it with a carter HP electric and a Holley Regulator and now I run out of guts before the mach runs out of fuel I upgraded all the lines to 3/8" as well.

 

[cobraII]

For ignition I am running an MSD 6AL with an MSD billett distributor. What else do you want to know? I can see what I remember / find.

 

[Mstng2]

I had a similar problem at the track, car ran great until I hit high RPM's under load. Ended up being a bad coil wire that was arcing under load. Really threw me though because it acted like a fuel starvation problem.

 

[2muchtime]

thats where im heading, i also had that same problem, but with msd coils.
2 different styles to be exact.. been through a 6al to..both conditions made the car feel as if something flipped the choke closed...yet it idled great and
had plenty of power first and second with a very occasional sputter at really
high rpms..once i got into third just bogged at anything more that half throttle unless i was easy with the throttle.. after rebuilding the carb and upgrading fuel issues, it still felt like the choke to me ( the carb was the first thing i checked, making sure the choke was in proper position)...anywho it ended up being the month old msd coil i replaced it again 2 weeks after that for the same problem...
nevertheless....i dont use msd shelf parts anymore..
i will say i like some versions of their distributors and never had a problem with them..

did this problem all of the sudden appear cobraII? has it gotten worse?
what does it feel like? those kind of answers r helpful..

 

[cobraII]

I have not noticed the problem before, but it is hard to find enought road to wind it up that hard. It is exactly like you both describe. I have a new stock coil sitting on the shelf, when I get a chance I might change it out and see what happens.