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Discussion Starter · #1 ·
Help, I am having problems with my motor not wanting to drive when it gets to normal operating temps. It idles fine and rev's fine when it is cold. As soon as it gets hot I cant get it to idle past 2k RPM without it stumbleing.

The engine has an updated cam (.050 = in.226'/ex.235') and the carb is a holly 750 4bl. It also has 4V heads. I know that the car had some sort of ignition system when it was new. But when I got the car back (it was stolen for 18 years) it had no engine in it. So the engine is hooked up with power going directly to the coil and the neg pole from coil goes to the distributor.

As I stated, the car was stolen and I have put tons of cash back into it to get it this far. I really want to drive it...soon.
 

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Discussion Starter · #3 ·
Ok, I replaced the original distributor with an MSD HEI and also installed an MSD 6AL ignition box.

Got everything in and it somewhat cleaned up the problem. I took out the plugs and they were black. So after replacing the plugs, I drove it for an hour. During that hour I noted that whenever I put a load on the motor it would stumble. Like going up a hill in high gear it would stumble.

After that hour, I pulled the plugs and again --- black. The person who built the cam told me that a 750 is perfect for that motor. So, should I now replace the coil or go with a new carb?

Thanks in advance for all the help.
 

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Now that you have the MSD distributor and 6AL box, did you replace the coil??

Black plugs can indicate a rich mixture or weak spark (bad coil).
 

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Discussion Starter · #5 ·
Yes, I replaced the coil and the carburetor yesterday. Not sure which one fixed the problem. It seemed to run much better and does not stumble like it did the other day.

I was using a new petronix coil before. Now that I have the MSD set up, I baught a new Blaster 2 coil and it seems to be doing fine. The carb I switched from a Vacumn secondaries to a double pumper. Both are 750cfm.

The distributor is a mechanical advance. What should my initial timed advance be set too, prior to the distributor making any advance?

Thanks for the help.
 

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start with 8 degs and then drive it, especially under load and see how it feels. Also see how it starts up. To much advance will sound like a weak battery. Just advance it 2 degs at a time till it runs poorly or pings underload and then out it back a little to where she likes it. Engine combonations and driving conditions require different settings.
 

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This is what I run on a 351 C with closed chamber heads, 36 degrees total. I have the distributor set up with 16 degrees of initial timing and 10 degrees of mechanical advance (that would be 20 degrees at the crank). If you have open chamber heads you probably don't want that much initial timing.
 

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Your old carb had a blown Powervalve and was really giving her too much fuel.

Glad to hear she's running better!

FE
 

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On 2006-09-13 18:42, 2800R wrote:
This is what I run on a 351 C with closed chamber heads, 36 degrees total. I have the distributor set up with 16 degrees of initial timing and 10 degrees of mechanical advance (that would be 20 degrees at the crank). If you have open chamber heads you probably don't want that much initial timing.
Opposite - you'll want more. I use 18 now, was at 20 initial. Opens are very slow.

If that 750 is a 3310 and it's stock, you'll probably also want to go down on the primary jetting to 70. The 3310 comes out of the box set up for a 396 chebby.
_________________

1967 Falcon 4 door w/351C - Owner built, owner abused.
70 Mustang 302 / 06 Ranger, 04 SuperCrew parts hauler
http://raceabilene.com/kelly/hotrod

<font size=-1>[ This Message was edited by: ckelly on 9/14/06 9:36pm ]</font>
 

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Discussion Starter · #10 ·
I think I am gonna go back to a vacuum secondary 4V carb. Dont know the number on the side of it cuz it is going through another rebuild. The good thing is that the double pumper I have on here now will work until the carb builder guy gets my original carb running.

As for the distributor; I had 20 degrees initial set and the distributor will add 28 degrees if I choose. I know that is way too much, that is why I have not climbed on the gas since figuring out the carb problem. But it runs good with that much initial timing. The bad part is I did not build the motor and dont know what the cam is set to. I am guessing that it is set to zero because the #1 pops when the harmonic shows zero. Soooo the question should be what is the max initial timing be if cam is set to zero.

Also, I have a T-5 in it and I get a little more vibration when starting off in 1st gear than I do in my '90 GT. Any ideas??

As always, thanks for the help.
 

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Discussion Starter · #11 ·
Finally figured out what the problem was. After swapping tons of carb parts we got to the last part. The main body of the carb was bad somehow. After swapping the main body everything worked great.

I still have that vib when starting off. Any ideas?

Thanks
 
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