Carb size for a 1997 F700

[TooManyTrucks!]

I bought a 1997 f700 about a year ago. It was a propane powered truck that got converted by my friend in the middle of the trip after not finding a propane refill anywhere close by and running out of fuel cause the gauge on the side was stuck on full.

My friend placed an Edlebrock 750 on it and we were able to get home without too much of a problem even though the truck's axle was stuck in low the whole time.

It back fires under a load often, so could the 750 be too much carb for it? It is a rebuilt Jasper 429. I heard Industrial Ford truck motors need to be a four-barrell.

 

[sle2115]

I bought a 1997 f700 about a year ago. It was a propane powered truck that got converted by my friend in the middle of the trip after not finding a propane refill anywhere close by and running out of fuel cause the gauge on the side was stuck on full.

My friend placed an Edlebrock 750 on it and we were able to get home without too much of a problem even though the truck's axle was stuck in low the whole time.

It back fires under a load often, so could the 750 be too much carb for it? It is a rebuilt Jasper 429. I heard Industrial Ford truck motors need to be a four-barrell.

Couple of things, if it's truly a 750, it's a four barrel. I don't know of many 2 bbls that will flow 750cfm, and before anyone starts saying "I've seen one..." I know they are out there, but they are rare. Not only that, if it's flowing 750 cfm through a 2 bbl. it should be fine anyway. Most of the carbs I worked on them were 4 bbl. Holley/Motorcraft carbs. They mostly had govenors on them as well. Do you see a lot of black (rich) smoke with it running down the road? If not, you probably need to run bigger jets as it's running lean. The last SBC I built did this with a 750 on it as well. Wasn't that there wasn't enough carb, it was that there wasn't enough fuel. Some pretty hard running motors use a 750 with no problems. Have run them on 700 HP big blocks with jetting changes to meet street class conditions. I'm also guessing that the motor is limited or should be on RPM, meaning you wouldn't be turning near the RPM's we did. It's hard to diagnose from here, but I'm guess it is running lean. Is it popping back through the intake or out the exhaust? That will kind of tell the tale. Running rich sounds like a blubbering in the exhaust (excess fuel is burnt off in hot exhaust), running lean will cause pre-ignition when the air fuel enters the cylinder and will pop back through the intake (fuel is ignited as the intake charge enters the cylinder with the intake valve open). Hope that helps.

 

[TooManyTrucks!]

I made a mistake, it is a 4 bbl earlier in the post. I meant to say that the 429 was explained to me as having to be a 4bbl or it gets quite cranky at having anything like a 2 bll on it.

This is the second 750 I had to put on it. I had the first one stolen the night before I went to move the truck. My friend believed that the second one sat in the box and perhaps some of the gaskets dried or froze up. I believe along the lines that the power valve or whatever it called wasn't functioning right.

The RPM gauge only goes to like 4k or so on the dash.

http://www.teamc.com/edelbrock750cfmmanualchokecarburetorede-1407.aspx
The reason we got this brand was cause Pepboy's had it in stock. Should I have something smaller like a 600cfm on it?

It sounded more rich than lean at all. All the popping was from the exhaust. Sometimes with a small explosion of fire for a split second.

Since I didn't have a fuel tank, (it had a 35 gallon propane tank on the side from being propane powered)I bought a fuel caddy cylinder for about $100 and ran hose from the back rails to a cheap electric fuel pump wired to be on when the ignition is on.

It is an air braked truck chassis with no 2800 gallon tank on the back.

 

[sle2115]

Well, light the fires, but in my opinion, you got a much better carb than a Holley, and there is no power valve in that one. It's a pretty simple design and one I put on the last few motors I built for street aps! You can play around with metering rods and jets for little money. They aren't that expensive, but that carb is not governed, not that it is an issue.

 

[TooManyTrucks!]

I got the truck off a propane dealer near Monticello, NY (somewhat near Woodstock). He bought it for the extra-large tank on the truck's frame. He removed the tank and found it was too big for the configurations he had on his fleet (of mostly Diesels). The propane guy put it up on eBAY in not the best category and I got it for $820.00! It had brand new 22.5 ****** tires all the way around. Not to mention the Jasper 429. I still have all the propane carb stuff for it.

When driving it home, the s-cams on the breaks became an issue, so I had them fixed at a truck stop. Which was like $1300 cause the ways the wheels were set up, they had to remove way more stuff. They are Bud Wheels.

The split rear is one of those worm gear applications and stuck in low. We tried to bypass it electrically but no dice with that. So I was told I take the unit off and either get it fixed/rebuilt/swapped and I should be fine.

Is there anyway that I could find the compression ratio, hp, and other figures for this rebuild? If I called Jasper would they tell me?

Where would I get the Jets for it? Edlebrock or is there more universal generic stuff that can work?

Thanks for all the help also.

 

[JLDickmon]

Your Edelbrock is most likely a Carter AFB knock-off..
Carter jets, plungers, plunger springs, and metering rods will work.

 

[tractorman86]

you can get most all the parts at a napa, checker/shucks/kragen, or i would think at a pepboys. they are a relatively trouble free carb.

 

[sle2115]

Yeah, I don't know of anything Edelbrock used but Carter, they even use the Carter numbering system, or did!

 

[typ4]

The timing might be retarded a bit also these trucks had manifold vacuum plumbed to the distributor ,so when you accelerate it retards it backfires because of the larger carb, The factory holley was about 370 cfm and governed. Hook the advance up to the small port on the carb front that has vacuum under accel and set initial timing to 8 degrees and see how that works. Then mess with the jets, edelbrocks are a little fat out of the box so it might be ok. You can buy a metering rod and jet and spring kit for cheap thru summit or jegs.

 

[Alex S]

actuly propane powered trucks have way more timing advance then gas (propane burns slower) so i would really keep my ear out for pinging and get a timing light on it soon, also the timing curve is also steeper

 

[sle2115]

edelbrocks are a little fat out of the box so it might be ok.

That is what everyone told me as well...unfortunately, I've experienced the exact opposite on everyone I've installed...engine making a big difference, but none the less, we were to the point that we richened everyone a step out of the box with very good results.

 

[MUDKICKR]

i have a tuning kit for that carb. let me know if you still need it and i can sell it to you.