I drove the truck up and down about 220 miles crossing the Alleghenies to get to the cabin. I doesn’t want to rev smoothly above 2500 rpm’s or so. Sometimes I hear a blub, blub, blub sound when I’m giving it gas above 2500. I could climb the mountains ok, just keep it below 2500 or so. Today I gave it new points, condenser, and rotor. The old rotor was bent on top, I thought that was going to be it. I pulled all the plugs, they’re all white. The pictures are of 3 and 4. #3 was only hand tight. Am I running too lean? Edelbrock 354 with progressive linkage. I think I have all 3 carbs with .53 jets or possibly .51 jets in the outside carbs. The plugs are at least 2 years old, Autolite 46. The engine is a 239 bored +.125 with a 312 crank. I rpm’s.

  Dennis in Lititz PA

Does the advance seem to be working?  You had an issue with that a couple races ago.

Are the plugs normally that white and has it been driven much since they were installed?


Lawrenceville, GA

What is the elevation where you are?


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Dennis:
The plugs look lean to me.  Is everything the same since you last raced it?  I know it would rpm before.  If you haven't messed with the jetting, I would check the fuel supply system from the tank to the carbs.  /a big vacuum leak would lean the mixture, but it wouldn't idle worth a darn.

John - "The Hoosier Hurricane"

Hard to tell from the picture but it looks like a lot of ignition timing.  I’m basing that on what looks like the color change on the ground strap being close to the base of the spark plug rather than in the curve.  Are you sure all three carbs are getting fuel?  A stopped up or stuck needle seat on one carb could also be an issue.

Lorena, Texas (South of Waco)

It’s idleing around 450 - 500 right now. I don’t think I’ve got an intake leak. We’re around 2400’ elevation here. There’s a lot of miles on those plugs, I use the truck a lot. It does sit over winter because I don’t run any antifreeze in it. Maybe the outside carbs aren’t giving me fuel. I will recheck the timing, I’m using centrifugal only.

I got to post some pictures from last evening, they’re grainy as it was near dusk. Check out the front door.

  Dennis in Lititz PA

Dennis is that your new Mechanic?  LOL

You might drop down to a 45 plug  they are a tad colder..Your's look plenty warm and lean  Normally with unleaded the porcelain should be tan color rather than white. I agree not wanting to rev over 2500 could be a fuel supply problem

I’m home again. In the mountains I replaced the points, condenser, and rotor. Initial timing is at 10 degrees. When I rev under no load, it goes up about halfway between the 30 and 40 degree marks. On level ground about 2300 rpm it would sometimes surge. Sometimes under light load, it would backfire out the exhaust. I’m thinking too it’s carburetor problems or maybe fuel pump. My timing marks on the pully are 0 10 20 30 and 40.

  Dennis in Lititz PA

Dennis:

When you are at 2500 under load, are you getting into your secondary carbs?  The reason I ask, I have had experience with older stock Viton needles getting swelled and softened by our wonderful alcohol laced gas.  Your secondary carbs probably don't get a lot of use in street driving, so the floats keep pushing the needles into the seats and they don't get a chance to drop out.  So when the gas leaves the carbs, the needles don't let more in.  Opening the throttle without fuel would amount to a huge infusion of air.  This is conjecture on my part, but you have been running this tripower for a lot of years without this issue.  Something has changed in your system.







 

John - "The Hoosier Hurricane"

Surging at cruise or under light load is classic lean condition, with backfiring, a lot lean..... Usually you would up the main jets to cure this, but in your case since it has been running in this configuration, something in your fuel delivery has changed or there is a vacuum leak. Conjecture again,  maybe one of the 2 main jets is plugged