I just bought this truck two weeks ago and have been fixing some minor issues that I was aware of when I bought it. It is a 1950 F1 Ford panel van, with flathead V8 239 (8BA) motor, and Holley / Ford 94 Model 7RT carb. It is very nicely restored and the PO took very good care of it.

I had noticed some rich running recently, and had a couple of backfires when shifting down from third to second gear. After that, it was running quite rough and backfiring. It starts easily and seems to idle rich but consistent.

After reading some posts on this forum, I decided to check to see if the power valve may have blown out, so I screwed the idle mixture screw all the way closed with the truck idling and it kept on running, never missing or even slowing down, which I have read is an indication of a blown power valve. These old 94's don't have the back pressure check valve that more modern Holley carbs have that protect the power valve from backfires.

The idle mixture needle was only open a little over 1/2 turn when I bought the truck so it seems a little low to me. I think the carb was rebuilt by the PO recently but not sure of that. At any rate if it was rebuilt, it still could have blown out the power valve since I bought it.

I am not sure I want to rebuild the carb, having never done it before, but maybe the Power Valve can be replaced fairly easily if that turns out to be the problem.

Any suggestions or thoughts?

Thanks

 

This is actually being discussed right now in another thread
https://www.ford-trucks.com/forums/1...l#post14511720 I'd suggest you join in that discussion.

Oh, and Welcome to FTE! BTW, what part of TN are you in?

 

Problem solved. It wasn't the Power Valve at all. I tuned the idle mixture screws using a vacuum gauge, and then checked the timing with a timing light. The timing was off a little so I fixed that. I still had a lot of rough running and muffler backfiring on deceleration.

I removed the old Champion H10C plugs to look at them and they were pretty nasty looking (and #8 insulator was cracked). I have been reading about Champion H10C plugs and problems with them so I put in a set of Autolite 216's. Cranked her over and drove around, and it runs like a different truck. No more backfiring at all, and way more power. It had a little hesitation when I goosed the accelerator, so I put the vacuum gauge back on and readjusted the idle mixture screws until I got maximum vacuum (at 20 inches of mercury!) which took care of that problem. What I learned from that: Before tuning the ignition, check plugs and replace them if they don't look good. It's a cheap way to avoid needless speculation when trouble shooting mixture problems.

 

[QUOTE=jhweigel; Problem solved. . What I learned from that: Before tuning the ignition, check plugs and replace them if they don't look good. It's a cheap way to avoid needless speculation when trouble shooting mixture problems.[/QUOTE]

Good advice.