351 not quite right

AMiller · #1 (**permalink**) 03-02-2009, 08:59 AM

Fired my cobra for the first time this past week to results that were somewhat less than hoped for.

The motor is a 351 windsor that I had built for the car. 375 hp. 400 Torque. The motor was run in on the dyno and adjusted for best performance.

Now almost 3 years later I fired it up in the car for the first time. Exactly the same as on the dyno except Ignition Box. I dont know what was used then but I have a MSD 6AL in it now .

Motor fired up right away. Ruff idle around 1200rpm. A lot of sputtering and popping though and not able to take a blip of throttle. Messed around for a bit but nothing helped. Shut motor off and adjusted the idle up a few turns. Motor poped off and ran beautiful at about 2500rpm. If you blipped the throttle it was responsive but I had the 3000 rpm chip in it so it only reved 500rpm. Tried to back idle off to a propper setting and the motor would go back to its old ways under 2000rpm.

Played with the timing and that didnt seem to help. The car has the Holley on it that it was dynoed with no settings changed. It was drained of gas when I got the motor but I now there was still a little in it that sat over that time.

Possible that there is some sticky, varnish, bad gas in the idle circuit that is causing the idle problem??

Any other sugestions???

Thanks Guys,

Aaron

wtm442 · #2 (**permalink**) 03-02-2009, 09:07 AM

First thing - change the spark plugs and see what happens.

Gas will varnish up in some places in 8 months, never mind 3 years.

Remove carb ... disassemble and let it sit in carb cleaner.

vector1 · #3 (**permalink**) 03-02-2009, 09:09 AM

sounds like idle circuit or low speed circuit in carb plugged up.

Rick Parker · #4 (**permalink**) 03-02-2009, 09:10 AM

Squirt some carb cleaner into the 4 brass air bleed holes in tops of the venturies near the metering plated and bowl vents.

Ron61 · #5 (**permalink**) 03-02-2009, 09:14 AM

Try what Rick said. I had that happen to mine one Winter and it wouldn't run at all. The gas had caused varnish on the valve inside the bowl and once I got it cleaned everything was great.

Ron

AMiller · #6 (**permalink**) 03-02-2009, 09:44 AM

Thanks Guys, got the carb off time to take it apart I guess. I am often humbled by how often I have to go backwards to make any progress on this car.

Rick Parker · #7 (**permalink**) 03-02-2009, 10:20 AM

Focus on the metering plates and air bleeds, not much else to it. Drain old fuel from tank and refresh if you haven't already done so.

Rick Yeager · #8 (**permalink**) 03-02-2009, 01:52 PM

Like Warren said, "First thing check the spark plugs." I have really been burned on that. Then go to the carb

Rick

WildBill3 · #9 (**permalink**) 03-02-2009, 04:15 PM

y only a 3000 chip?

AMiller · #10 (**permalink**) 03-03-2009, 09:52 AM

As for the 3000 chip, having never fired this engine since being installed in this car I just thought that limiting the motor to 3000 rpms might ensure nothing too bad happening.

As for the carb, which is a 750cfm Holley 4160, when I started taking it apart I noticed that none of the float bowl bolts seemed like they were tight, not even snug.

I read a post somewhere about the 4160 being a pretty good carb and pretty simple with the one drawback being they dont store well. Something about the gaskets shrinking and then they will not idle for crap. Sounded like my situation. That carb has not changed since the motor was broken in on the dyno so if the gaskets shrunk a little the bolts might seem less than snug now.

Guess its time to put it back on the car and see if things are better.

Thanks Again.