New carburetor.
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5th Wheeling
Joined: Apr 2012
Posts: 32
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New carburetor.
I'm getting rather tired of some of my autolite 1100s quirks, and I know over the long run I'm gonna want to replace it. Now, what I really wanted is a two barrel with a vacuum secondary, so basically its one barrel until I need the extra barrel, for the sake of fuel mileage. But I was thinking maybe a two barrel wouldn't hurt my fuel mileage any. I get anywhere from 15-18, but this truck is my daily driver and the last thing I need is to take a hit on fuel mileage as I'm sure you can all understand. What do you guys recommend?
Oh, I suppose it might help if you guys knew it's a 1968 ford f100, with a 240 6.
Oh, I suppose it might help if you guys knew it's a 1968 ford f100, with a 240 6.
Senior User
Joined: Dec 2008
Posts: 485
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From: Fowlerville, Michigan
I'm not sure if anyone makes a "vacuum secondary two-barrel" setup like you described.
A 350-cfm Holley two-barrel should get you good economy and a little power boost over your Autolite unit. They are pretty popular in the junkyard and with a rebuild kit you could save yourself a few hundred bucks.
A 350-cfm Holley two-barrel should get you good economy and a little power boost over your Autolite unit. They are pretty popular in the junkyard and with a rebuild kit you could save yourself a few hundred bucks.
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5th Wheeling
Joined: Apr 2012
Posts: 32
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I once had a datsun with a Weber 3236 on it, and it was a two barrel with a vacuum secondary. Never heard of anyone putting one on a full sized ford though.
Looks like I'll need to build an adapter plate. Now what about air cleaners? I've done some shop work, even change a head gasket or two in my time, but I never have had carburetor problems that a rebuild didn't fix.
Looks like I'll need to build an adapter plate. Now what about air cleaners? I've done some shop work, even change a head gasket or two in my time, but I never have had carburetor problems that a rebuild didn't fix.
Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
I've heard good things about the carter carbs they offered on the 300 ci 6 cylinder, but if you want to put it on your 240 you might have to re-jet and tune it.
What kind of quirks are you having with the autolite?
Sam
What kind of quirks are you having with the autolite?
Sam
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5th Wheeling
Joined: Apr 2012
Posts: 32
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Lets see, can't seem to stop the hesitation. When the thermometer climbs above 85 I don't dare shut it off and above 95 I can't let it idle for more than a few minutes or it vapor locks. Biggest problem though is the power. If everything was perfectly flat around here it wouldn't be a problem. I'm probably going to get a job down "the grade" and it will be a long drive home in 3rd gear every day. At 16 MPG I'm not sure I have to much to lose. Maybe its just a small engine pulling a big truck, but it still sure seems to me that it should at least be able to pull its own weight. I'm not sure how much I'd dare to try to haul with that truck for fear it wouldn't make it up the first hill I came to.
However, for a long time I've also been suspect of my vacuum only distributor as the source of some of these problems. Not advancing properly maybe?
However, for a long time I've also been suspect of my vacuum only distributor as the source of some of these problems. Not advancing properly maybe?
Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
Likes: 9
From: Western Washington
For the vapor lock, maybe you could find a spacer for the carb. They have phenolic carb spacers that work pretty good. Or, maybe your heat riser valve is stuck open? That would boil the carb for sure.
And yeah, your distributor could be a problem. Hook up a timing light and see what your total advance is. If it's too low, that could be your lack of power.
Might be a good idea to check for some vacuum leaks too, they can make a motor generally run lousy. I've worked on motors with big leaks and once they were fixed it ran like a new engine with lot's more power.
Sam
And yeah, your distributor could be a problem. Hook up a timing light and see what your total advance is. If it's too low, that could be your lack of power.
Might be a good idea to check for some vacuum leaks too, they can make a motor generally run lousy. I've worked on motors with big leaks and once they were fixed it ran like a new engine with lot's more power.
Sam
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Cargo Master
Joined: Feb 2006
Posts: 3,008
Likes: 250
From: North Pole, Alaska
First do what Rusty said and then look at Clifford Research for go-parts, carbs, adapters, and intake manifolds for your Six.
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5th Wheeling
Joined: Apr 2012
Posts: 32
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I've had some experience with vacuum leaks myself, and that had crossed my mind, but one thing I never knew how to do is test for them. And how do I know if my heat riser valve is stuck open, would I have to take the manifolds off?
Cargo Master
Joined: Feb 2006
Posts: 3,008
Likes: 250
From: North Pole, Alaska
Spray some WD-40 or starter fluid around your gaskets and hoses while it is running. If the engine revs up, then it has ingested some of the fluid through a leak somewhere. A vacuum leak leans out the fuel/air mixture. The WD-40 gives the engine more fuel so it revs up. That can clue you in where the leak is.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
I have a 240 with the same carb as you with a hand choke. Works fine. Starts right up all the time, runs well in the heat.
Heed the advice of the old timers about vacuum leaks. Do what they say with the vacuum lines plus tightening down the intake manifold.
Don't look to carburetors with more barrels to get much if any more power out of the thing. If you want power your cheapest bet is a 300. Or if you have the skills and can find a donor, go to a small-block V-8.
The problem with adding carbs with more barrels to this motor- and all inline engines- is that the center cylinders get flooded and the end cylinders get starved.
Heed the advice of the old timers about vacuum leaks. Do what they say with the vacuum lines plus tightening down the intake manifold.
Don't look to carburetors with more barrels to get much if any more power out of the thing. If you want power your cheapest bet is a 300. Or if you have the skills and can find a donor, go to a small-block V-8.
The problem with adding carbs with more barrels to this motor- and all inline engines- is that the center cylinders get flooded and the end cylinders get starved.
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5th Wheeling
Joined: Apr 2012
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Of course out timing light is broken, and we don't have any WD-40 or starting fluid. But I appreciate all your advice, it will be heeded. I will check the distributor and look for vacuum leaks. I probably won't buy a carburetor, I'm just acting like my father (and his) going around every decision 5 times. If I do later decide to get a carburetor though, I know which one to get. But if vacuum leak hunt and distributor check don't turn up anything, I'll probably just give up. Maybe my older friend was right on his comment when I told him what engine I had in my then new to me truck, "Not alot of power, but its a good solid engine." Thats certainly been true so far, anyway. You won't see me upgrading engines, the whole reason I bought one with the small 6 is because its my daily driver, and wanted to get more than 10-12 MPG.
I did fix the vapor lock. Turns out, it must have mostly been in the fuel line, because I insulated the fuel line and that has made a world of difference. I still need to fight with it a little on really hot days, but I can always get it going. I'm not stranded for 45 minutes.
I did fix the vapor lock. Turns out, it must have mostly been in the fuel line, because I insulated the fuel line and that has made a world of difference. I still need to fight with it a little on really hot days, but I can always get it going. I'm not stranded for 45 minutes.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
Another way to check for vacuum leaks is with a small propane bottle and a decent length of hose. Crack and bottle open a tiny bit and then wave he open end around component mating surfaces.
Btw, remove the entire hose when checking the integrity of vacuum lines. I had one with a tiny crack underneath and it drove me nuts for weeks.
Btw, remove the entire hose when checking the integrity of vacuum lines. I had one with a tiny crack underneath and it drove me nuts for weeks.