Timing & Carb question...

[1968 Ford F-100]

I have a 1968 Ford F-100. It has the stock 360 FE that was rebuilt with less than 8000 miles on the clock now. My issue has been like this ever since the rebuild. Everything was replaced except for the carb I rebuilt. From what I have been able to determine is that it is a Motorcraft/Autolite 2100 (not a 2150). I started with the idle mixture screws at 1.5 - 2 turns out. The needles aren't all goofed up from over tightening. I have a vacuum gauge hooked to full manifild vacuum. When I start the truck and set the mixture to the highest vacuum reading I will get about 15" (this is with the truck up to full temp). According to my gauge that indicates "late timing". From what I've read on FTE...the timing from the factory was 6 degrees BTDC. It has been recommended that these low compression 360's can be set between 10 & 12 degrees BTDC keeping an ear out for pinging. Now, with my timing set at 10-12 degrees BTDC and with the carb mixture screws adjusted I can get 15" on my vacuum gauge....which is the highest reading I can get but, my mixture screws are out 4-5 turns. This is not good I feel! So, I have checked for all vacuum leaks and such multiple times. Everything is good. Been running at those settings since I got the engine back last summer.

Well, I wanted to fiddle with it to get a better vacuum reading. Thinking my carb was the culprit. A rebuilt carb is around $200. I'm not really wanting to go to a 4 bbl carb and intake. I like the ol' 2 bbl and originality. On a side note when I turn off the truck, after a few moments fuel will seap down the throat of the carb. I beleive it is boiling the fuel out. I could be wrong. So, I had to bump the timing to 20-25 degerees BTDC to get 20"-25" of vacuum which seems a lil high to me. I listened for pinging and such. Sounds good and all....just not comfortable with the timing being cranked up so far. It's got some balls now but I feel uncomfortable with the timing.

I was reassured by the guy that actually rebuilt the engine that the timing was set straight up..meaning "0" on the timing set. If I remember correctly the timing set didn't have the option of setting it different. It was a double roller but I beleive it could only be set at "0".

The engine is bored .030 over with a new set of pistons as well as "Police Interceptor" valve springs installed and a stock replacement cam. Other than that the engine is as stock as can be. I checked to make sure the harmonic balancer hadn't spun...it is dead on! The engine has a rebuilt distributer from NPD (dual vacuum port). I also disconnected and plugged the vacuum line to the distributer before attempting to adjust timing. no vacuum leaks what so ever. I have a petronix ignition set in the distributer. My timing doesn't jump around when pointing the timing light at the pointer.

The only thing I can see that is bad is that I have to turn my idle mixture screws out 4-5 turns to acheive maximum vacuum. My vacuum gauge doesn't jump around...hold very steady. Also, with the carb settings my plugs aren't black and sooty...they actually look just right. Very strange. Again I am looking to stay with a 2 BBL carb. I'd hate to have to spend $200+ on a carb but I think considering my idle mixture issue I think I'm going to have to bite the bullet. Atleast then I'll more than likely know whether it was the carb or not. I really hate throwing parts at the truck. I'd rather do some investigation work and figure it out rather than blowing money on what may not be the problem.

I wanted some opinions on my delema. I'm thinking of springing for a new carb. The only thing is that once you buy it and install it's yours for life. Also, NAPA is the only local parts store that sells a 2100 (Holley is what they offer). It's the only one I can find that has a manual choke and is extremly close to my carb. Also, I know different CFM 2100 carbs are available...1.08 to 1.38 I beleive. Should I find one that matches my CFM? I know there is more I want to ask but I figure I should take it easy. I love this truck....just trying to learn more and I basically got it because I know if I take care of it, it will last another 40 years and it sure as he** beats a car payment. Oh, and I have to use it to haul a car hauler and a few cars here soon so I am not wanting detonation/pinging to accure under a load. Thanks for any help and I appologize for the jumping around with the info.

Sam

[warponyxlt]

if its a motorcraft two bbl check the size of your jets i think they should be 53f thats a good size also the idle mixture skrews sould be only about two and a half turns out

[1968 Ford F-100]

Yeah...thats what I was thinking on the mixture screws. I found a reputable rebuild shop for my carb and can have mine rebuilt for $160 and I can get it back in a day. I'm thinking of going that route. I'd still like some feedback if anyone has any. Thanks again....love the site.

[warponyxlt]

dont pay that much to get a carb rebuilt man! just take it completly apart an blow the circuts out with compressed air clean the venturi's out the power valve accelerator pump the needle and seat and that little screen under the seat assembly. that is wat u need to do them rebuilders are full of it the two bbl ford is the most simple carb there is get a kit and do it your self you will notice that you use only half the stuff it comes with seriously just clean it good! that is all. I learned the hard an costly way that showed almost no results check every thing twice and put every thing back in its place be sure to clear the squirters on the top of the throttles those make dead spots.

[fordman]

that was a real detailed writing that you done on checking out this and that. butt he only thing i can see that you are saying is that you are worried about the manifold vacuum and the timing. but you didn't sya why you were worried about this.

Is the truck running bad? if so what does it do? i'm sure your not trying to adjust the carb to fix a flat tire. please give the symptoms of your problem and not someone elses advise on what you are suppose to be adjusting. that will give us a better way to help diagnose your problem.

[1968 Ford F-100]

Ok, my problem with the truck is that I have to turn the idle mixture screw out 4-5 times to get the truck to run smoothly and that when adjusting for maximum vacuum I can only get 15", which according to my vacuum gauge is "late timing". The only way I can get 20-25" of vacuum is to bump the timing up to 20-25 degrees BTDC. This is WAY OVERKILL. I should be able to run the truck at 10-12 degrees of timing on a stcok engine. The truck has no power at this setting. Yes, I am aware that it is a low compression 360 and not a 390, as well as having a 2BBL carb to boot. I know I can't expect some tire burner...thats not what I want. I definately have carb issues if I have to turn the mixture screws out 4 turns before it runs halfway decent. At 2 turns out the truck will want to sputter...and die if I don't back them out more. It starts to run ok at 3 turns out (atleast not sputtering). I ran it at 4-4.5 turns out for the past few months without issues, other than the vacuum being 15" and having no power. Hopefully this helps with what kind of troubles I am having.

Looking for some pointers. I'm wanting to fix it myself and learn something along the way. I've been doing alot of reading and I realize I have to take everything with a grain of salt. I beleive I have the tools to help myself out. Maybe just need a little direction or ones opinion as to where I might diagnose the issue.

By the way I already rebuilt the carb doing exactly what was said in earlier posts. These carbs are very very simple and easy to do. But I am aware of improvements that can be done and I am not wanting to goof and ruin the only carb I have to run the vehicle. And besides, the major issue with my carb is the mixture screws and I don't see that there is alot that I can do myself to remedy that issue as of yet. I am open to suggestions.

Thanks

[fordman]

ok i see now. you mentioned you had looked for vacuum leaks. does your truck have power brakes? if it does one thing that can happen is the power brake booster can go bad and create a vacuum leak also. one way to tell is if you hear a hissing sound when you push on the brakes. a few ohter thing sto consider are the carb base plate gasket. the carb bottom spacer to the engine being matched with your carb. there was a recent thread on that subject. loose bottom throttle plate bushings. or its still dirty carb some place. those are all possible vacuum leaks. the dirt in the carb thing could be there. did you soak the carb when you rebuilt it?

[1968 Ford F-100]

Fordman

My truck doesn't have power brakes. The only vacuum lines I have are to the C6 auto trans and for my distributer. All these are brand new lines and I have even changed them to double check. I've checked for vacuum leaks around the intake and carb to no avail. I have also heard of intake/spacer/carb plate gasket issues as well. Maybe you can point me to the thread incase there is something I am missing. I didn't dip the carb when it was rebuilt. I heavily cleaned it with strong carb cleaner and blew out the passages as well. I completely stripped everything except for the throttle shaft and butterfys. I am leaning toward a dirty carb or bad throttleshaft since the carb is orignal to the truck. Alot of guys are telling me.."why pay all that money to rebuild or get a rebuilt carb when you can do it yourself for a few dollars?". This is exactly the reason why....bad throttle shaft.....carb not being soaked...etc. And besides, I already rebuilt it and abviously either my work wasn't good enough or things are wore that I am unable to determine. But, you are making some good points Fordman. I appreciate the input.

Thanks

[fordman]

you can take the throttle shaft and see if it moves any up or down around in a circluar motion or whatever to see if its worn at the bushings. if the spacer plate is warped you can try and use more than one gasket to make it seal. here is that thread i was thinking of. http://www.fordification.com/forum/view ... =3&t=38604

[My427stang]

I wonder if your balancer ring moved and you arent really at the timing you think you are.

The right way is to get a piston stop, find where it hits the stop, then 1/2 between is true TDC.

The lack of power sounds like retarded timing, however, I wouldnt worry too much about the vacuum reading as much as how the truck runs.

[1968 Ford F-100]

Fordman

I need to take a closer look at the throttle shaft. I can't remember if it was loose when I rebuilt it. But regaurdless...my mixture screws have to da** near fall out to get a good fuel mix I believe. But that may be a result of a warn throttle shaft which makes a vacuum leak. I'm really afraid of running it too lean.

My427Stang

I actually thought of the balancer ring turning...I checked to make sure my piston was at TDC exactly and even pulled the valve cover off to double check compression stroke. It is DEAD on. I know...stumping me guys. But you all are making good points. So your saying my vacuum reading isn't how do you say "gospel"?...haha. In other words writen in stone. It can vary? I figured since my application is fairly stock that I could use the gauge to tell me what I was looking at. I think I am going to doble check that balancer again...never know. Maybe I missed something.

Thanks

Any more input is appreciated.

[peanutman]

I just done away with my dual port vacuum advance, you may check both diaphrams in it, one of mine was bad. Also my vac advance hoses ran to a gadget called a de-acceleration valve which does weird things to your timing for emission sake. I talked with a old mechanic and he said to do away with de-acceleration valve, they used to pull them off years ago, and plug the vac port closest to your dizzy and run your other dizzy vac port to the carb.

Plug any other ports in intake . My 302 was doing something simular right after i rebuilt my 2100,But more running rough if timing was set at 10-12. I think rebuilding my carb brought the bad vac adcance to light.
Since i done this my timing is set 10-12, she runs great and no more heat soak problem.

Also someone told me to put 2-3 wooden cloths pins on my fuel line close as i could get them to the carb to help absorb heat, i did. Don't know if it thats what worked but one or the other solved the heat soak problem.

But yes i thought i had bungled the carb rebuild as well. When you buy a rebuilt carb all you are paying for is the shine, they only replace what you or i normally would. If you buy a carb buy a new one, you may not be able to get an autolite carb but you are also not buying someone elses old problem.

[warponyxlt]

ill sell you my 2 bbl moter craft cause i just aquired a used edlbrock intake and carb today

[sgs]

My first guess was also that there is a problem with the balancer. Something doesn't seem right. It should ping like crazy if it's really that advanced and it should run on when you shut it off and start hard (turn over hard) when hot.

I had a carb that was boiling the fuel out of it during the winter in Wisconsin. We replaced the base gasket with a thicker one and the problem stopped. I would have bet big money that wasn't the problem but it was.

sgs

[1968 Ford F-100]

Fordman

I took the carb off tonight. Apon closer inspection tried to move the throttle shaft end-to-end, front-to-back, as well as top-to-bottom. Absoultely no play what so ever! I was surprised. Now...for the he** of it I decided I got it off, I should clean it out and reinspect and recheck my work as well as the rebuild kit instructions. Well, guess what....I'm not sure if this would exactly cause anything but, one of the orifice tubes has a crack in it starting at the bottom and going about half way up....playing connect the dot in a straight line with the holes that are in the tube. Hopefully that makes sense to you all. Then, apon looking at my rebuild kit info and as well as doing some reading online, there is supposed to be a checkball (steel ball) underneath the pin that is inside the bolt/screw that holds down the venturi. I read they can rust and stick. Guess what....mine was gone! I found 2 in the kit and placed one in the hole and carefully tested to make sure everything was right before I tightened. Everything went ok. I proceeded to clean and blow out the carb. Put it all back together, bolted it back on the truck as well as hooking everything up. Now, I still have the issue with my vacuum. It will hover at 14-15" of vacuum. NO MORE NO LESS! Seems pretty good if my vacuum gauge didn't say late timing. Oh, just for referance my mixture screws are at 3-3.5 and my timing is at 12 degrees BTDC. So the check ball may have helped. But I don't think so.

I also checked and rechecked my balancer. That thing is dead on, original and in great shape. I've seen far worse ones on other running vehicles. Mine has no cracks in the bond between the outer ring and inner area. So, the only problem I have at the moment is the 14-15" of vacuum and when I turn the engine off, you can hear the fuel bubbling (or boiling) in the bowl and then it pushes the fuel out of the venturi after a few minutes. I have started the engine, shut it off and then pinched off the fuel line between the fuel pump and the carb to eliminate the pump as a culprit. It still pushed the fuel out. So I now know it is my carb. The rebuild kit says the "wet level" should be at 31/64. The ruler that is included is in 1/32 scale. Thats jist before one inch I believe. I'm not good with math. But basically I understand that they are dividing an inch into 64 equal parts. I also understand you have to be atleast 1/4" away from the side if the bowl as to allow for the liquid tension on the side of the bowl. I do have the plate between the carb that coolant goes through (factory item). Since it is factory it I would assume there is a way to have this and not boil the fuel. But I'm probably asking for a miracle...ha

Peanutman

I have the timing retard port plugged off on my distributer. The only one that is plugged in is on the end and that is to ported vacuum on the passenger side of my carb. And the diaphram is in good shape. I did notice that when I put my thumb over or take it off the hose I use for my vacuum gauge (manifold vacuum) that the engine doesn't run any different. Which leads me to believe that there is a vacuum leak somewhere. Maybe?

Sorry guys...not trying to be difficult or get math lessons...haha

Any help is appreciated....and thanks for all the input so far.