4x4Wire TrailTalk

carburetor/motor help!

Posted By: yotaman1224

carburetor/motor help! - 09/10/09 05:56 AM

so i got this here 1976 jeep cj5 with the 4.2 258 motor and i bought a carburetor cleanin kit and it had a bunch of wrong stuff and i just ran the number on the carb and come to find out its off a older ford 300 straight six motor so now the question is could i have a 300 six ford motor bolted to my jeep 3speed and tcase or is it more likely that the threw a ford carb on my jeep motor????????
Posted By: BigJim

Re: carburetor/motor help! - 09/10/09 07:00 AM

Quote
so i got this here 1976 jeep cj5 with the 4.2 258 motor and i bought a carburetor cleanin kit and it had a bunch of wrong stuff and i just ran the number on the carb and come to find out its off a older ford 300 straight six motor so now the question is could i have a 300 six ford motor bolted to my jeep 3speed and tcase or is it more likely that the threw a ford carb on my jeep motor????????


It is a common swap to change out the Jeep carb for the Ford six cylinder one. It is uncommon to actually install a complete Ford engine. In fact I've not heard of the ford six cylinder in a CJ.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: BobRowe

Re: carburetor/motor help! - 09/10/09 08:16 AM

It's not likely that you have a Ford 300 I6 in your Jeep, because that motor is longer than the AMC 258 I6. Plus, the tranny fitment would be a problem. Anyone wanting more cubes than the 258 typically installs a small block AMC or Chevy V8, which are actually shorter.

It's much more likely that a PO swapped out the 258 carb for one from a Ford 300. that's relatiely easy to do.
Posted By: yotaman1224

Re: carburetor/motor help! - 09/10/09 03:46 PM

would this result in increased performance? should i stick with this carb or get the right one?
Posted By: BigJim

Re: carburetor/motor help! - 09/10/09 05:17 PM

That particular motorcraft carb works pretty good on the jeep engine. It seems to give a bit less economy. But it is the easiest of all carbs to work on. It is simple compared to the stock carb.
If you observe closely there should be a home made adapter piece between the carb and the jeep rod that opens the carb. As there is a difference in how the two carbs have their opening pins. If this adapter isn't made well the carb won't open all the way.
Many guys have installed the wrong carb on their Jeeps and they run way too rich. YOUR carb should have a --108-- stamped on it somewhere. (I think that is the correct number, I havn't done one in several years) If the number is other than that the carb is too large for the Jeep engine.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: yotaman1224

Re: carburetor/motor help! - 09/10/09 05:37 PM

i ran the number on the carb and its off of a 1981 ford f150 with the inline 300 six the number was 7394 ill look for the 108 but i just went and got the right rebuild kit and some new spark plugs ill let you know what happens
Posted By: BigJim

Re: carburetor/motor help! - 09/10/09 07:42 PM

Quote
i ran the number on the carb and its off of a 1981 ford f150 with the inline 300 six the number was 7394 ill look for the 108 but i just went and got the right rebuild kit and some new spark plugs ill let you know what happens


That sounds like the correct carb.. The 108 will be CAST into the carb.. I'm remembering it is on the bowl on the side near the choke stuff.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: yotaman1224

Re: carburetor/motor help! - 09/11/09 05:19 AM

got the carb kit for that model truck and now its runnin like a bat outta hell no hesitation lots of power, and i found a 107 cast ont the butterfly valve???? but yeah after takin it for a ride now the new fuel pump that is on it is crappin out im gonna go for a electic unit
Posted By: 4x4Wire

Re: carburetor/motor help! - 09/11/09 06:00 AM

My memory is fuzzy on those year engines and fuel pumps....

But, is that one that has the level actuated by the revolution of the cam?

If so, due to age, you could experience wear on the cam lobe which will impact fuel delivery.

BTDT with an AMC 304. I want to say the 258 has a similar setup.

Remember:
Jeep = Just Empty Every Pocket and you will have Just Enough Extra Parts.

and, you can say - Fix It Again Tony
Posted By: yotaman1224

Re: carburetor/motor help! - 09/11/09 06:08 AM

lol yeah thats what i hear (just empty every pocket) it does have the lever action pump with the revolution cam and since the fuel pump is brand new i was figuring that cam is the problem im thinkin about just orderin a couple cheapo inline fuel pumps of ebay (so i have a spare) and makin some cheazy block off plate
Posted By: 4x4Wire

Re: carburetor/motor help! - 09/11/09 06:21 AM

If you go with electric, pay attention to the pressure. I do not recall the source, but there are some write-ups about electric fuel pumps replacing manual pumps.

You would need to do a google search.
Posted By: sunder

Re: carburetor/motor help! - 09/11/09 06:36 AM

The fuel pumps have 1 way valves in them. If you just put an electric pump before the mechanical pump, it will push fuel to the carb no problem and you can leave it all well enough alone. Then again... If you don't want it to look that ugly under the hood a block off plate will fix that right up...

If it were me, I'd install the electric pump in line with the system just to prove to myself that there was a fuel delivery issue before I removed the mechanical pump.
Posted By: BigJim

Re: carburetor/motor help! - 09/11/09 04:33 PM

If it were me I'd leave well enough alone! A lectric pump needs a few things you won't be able to install in there. Like a roll-over switch..
As cheap as mechanical pumps are, just install a new one of those and forgetaboutit!
One day that Jeep may just get into trouble and start squirting fuel out when you don't want it too. I advise staying with the mechanical pump.
Big JIm
Posted By: 4x4Wire

Re: carburetor/motor help! - 09/11/09 05:44 PM

I am leaning to the simplicity is better concept myself.

Just remember, when messing around with fuel lines, always use NEW rubber hose....

When in doubt replace that hose....
Posted By: yotaman1224

Re: carburetor/motor help! - 09/11/09 07:26 PM

the pump is a brand new one and it was workin fine and then i got stuck in the mud and i got pulled out and i was wrappin the strap back up and the jeep was idling and all of a sudden it just shut off, and now the fuel pump isnt pushin enough
Posted By: 4x4Wire

Re: carburetor/motor help! - 09/11/09 07:45 PM

Any fuel lines bent???
Posted By: BigJim

Just for kicks and grins - 09/11/09 08:42 PM

Yoto tell us how you know for sure the pump isn't pushing enough fuel? If it is pushing any fuel, after a minute or less of cranking it should at least pop and crackle.. Have you poured a bit of fuel into the open carb to see if it runs thataway?
You do know that it pumps squirts out and not a full stream of fuel..but the squirts are plenty to keep her running at full speed. There should be about 6 pounds of pressure.
Big JIm
Posted By: MartySoCal

Re: Just for kicks and grins - 09/12/09 03:12 PM

Like BigJim said, I'd stick with the stock replacement mechanical pump for a carb'd engine, it will last 10 years or so and cost under $20. The late 258 fuel pumps include a roll over valve in them.

I would add that you should carefully inspect all of the rubber hoses on the suction side of the pump all the way back to the fuel tank sender, any small crack in the hose or a loose clamp can allow the pump to pull in air instead of fuel. It may also be seeping fuel. If the rubber hoses are over 10 years old, replace them, they don't last forever! Usually, the stampings on the hose contain a date code. I'd almost bet that your rubber hoses to the tank are from '76!
Posted By: BigJim

Re: Just for kicks and grins - 09/12/09 04:19 PM

Marty are you saying the newer intank pumps have the rollover protection right there in the pump itself? I hadn't heard of this happening before your post.. I wonder how one resets a device like that?
I'm gonna have to find a schemetic and look at one of those.
Big JIm
Posted By: yotaman1224

Re: Just for kicks and grins - 09/12/09 04:24 PM

when i spray carb cleaner in the carb it will fire off and run i hooked up an electric pump that says its 5.5 to 9 psi and it was runnin good but as soon as i floored it for a little bit its like the carb ran dry???? i think im gonna try the mechanical again with a boat gas tank and some fuel line
Posted By: 4x4Wire

Re: carburetor/motor help! - 09/12/09 05:19 PM

One thing you may want to try is disconnecting the fuel line at a convenient spot and blow air back into the tank.

With a 76 model, there could be some interior tank rust or other crud that is partially plugging the fuel pick-up tube in the tank.
Posted By: yotaman1224

Re: carburetor/motor help! - 09/13/09 02:02 AM

^^^thats exactly what i did today and it still wouldnt run so i hooked up a fuel cell in the back and now its workin so im guessin the fuel tank sucked up some [censored] thanks for all the help guys!!!!
Posted By: BigJim

Re: Just for kicks and grins - 09/13/09 03:41 AM

If you have enough fuel in your tank? It sounds like a split in your rubber hose is causing air to be sucked in the line. Common problem with the hose on the top of the tank.
Big Jim
Posted By: yotaman1224

Re: Just for kicks and grins - 09/13/09 05:55 AM

could be it had 8 gallons in there had enough gas lol but all i did was take off the rubber hose from the hard line back by the gas tank and put on my own and put it in a boat gas tank and it worked so either the pickup on the tank was clogged or it had a split in the line?
Posted By: 4x4Wire

Re: Just for kicks and grins - 09/13/09 10:45 AM

I would opt for a clog in the line.

A split in the line would have spilled fuel.

Working on that issue now with my YJ... Replacing rotten fuel lines.
Posted By: sunder

Re: Just for kicks and grins - 09/14/09 12:05 AM

I've had split in old rubber lines that didn't leak but did suck air when the pump was running full bore. Apparently their is a higher vacuum on the lines from the pump, than pressure in the lines from the hydrostatic head in the tank. No gas leaks, but the lines suck air...
Posted By: yotaman1224

Re: Just for kicks and grins - 09/14/09 02:00 AM

it was a clogged pickup in the tank too old of a tank and ran it dry too many times lol
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