I have a 1968 Ford F-100. It has the stock 360 FE that was rebuilt with less than 8000 miles. 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 ***** now but I feel uncomfortable with the timing.

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)(LINK---> NAPAONLINE® ). 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. Thanks for any help and I appologize for the jumping around with the info.

Sam....Thanks FTE!

 

late timing i'd say !automatics from 8degs-12 hp.like 330 hp. 390-68 mustang 4 banger! did this condition start after rebuild if so timing chain or eng. wasn't degreed properly it shouldn't even start passed 12degs> or bulk like a bull -huffing and puffing if it started later say5-8000 mi jumped timig chain and look at the dist.for mechanical faults/then go to a new carb it will be good upgrade anyhoot >i'd look at mechanical timing first that's what it's telling me /ps higher cfm go to a higher base t bone plate/or manifold to compensete for higher flow carbs /but the holly should be ok and more tunable >good luck you will figer it out keep at her

 

Instead of buying a Holley, or a rebuilt carb, there is another option.

Here's the original, and it's brand new...old stock (NOS).

C8TZ9510N .. Carburetor (Autolite/Motorcraft CA606) / Obsolete

Fits: 1968 F100/350 360.

GRIESEL MOTOR CO. in Okarche OK has one.

Ford was forced by the US Gov't to sell Auto-Lite in 1972, because the Gov't claimed Ford had a monopoly on auto parts.

Ford then started Motorcraft.

All the parts and the part numbers are the same.

 

don merke

It was difficault to read your post but I think I understand what you were trying to say. 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.

Numberdummy

Thanks for the heads up on that factory carb. I'd definately be interested in that if the price is decent. Hope the price isn't too bad. New carb is $400 and rebuilt is $200. Word on the forum is that rebuilds from the popular parts stores are junk. So a factory carb is right uip my alley in that sense.

Anyone else have anything they would like to share?

I just want to say thanks to FTE...it's been a good place to come for info and such.

 

Does it run fine with timing at ~12 degs? Idle fine? Then why spend the money on another carb. A rebuilt, like mentioned, is a waste of time unless you have nothing else. A new carb will likely be better, with less chance of vacuum leakage around throttle shafts, but over time it will just return to what it is now.

Guess I wouldn't split hairs over it.

 

The original carb has been on there for over 40 years...since 1968.

How long will it take a NOS carb to arrive at the same condition?

Decades.

Unless the truck is driven daily, the NOS carb will last a lifetime.

 

Absolutely Bill. Don't disagree at all.

I just wonder if it runs fine, why worry about it.

 

Freightrain

It all depends on what your idea of running fine is. Yes, i was able to drive the truck back and forth to work for the last 8000 miles. There isn't alot of power (I mean slow just from a take off standpoint) and the fuel mileage has dropped off this winter as well. I get 200 miles to a tank the first summer and I'm lucky to get above 150 now. Tank is clean...rebuilt trans...a nice clean truck. Drives like new....except for the slowness and what I beleive to be really poor fuel mileage because of the carb being goofed up. But, honestly who buys these things for fuel mileage...I'm just looking for dependability and wanting to tow my car hauler a few times which would require a little more power than it is giving me at the moment.

I payed with my hard earned cash to rebuild the engine and to have a reliable truck for years to come. I don't want to hurt my investment because of failure on my part to do the homework and getting the truck to run in tip top shape.

Numberdummy

You almost sound like a salesman there for a brief moment....haha. But I aggree with you. 40+ years on a truck and it may have been gone through once that I know have before I touched it.

 

I agree, if things are noticably declining then it's time to look into finding the source. Your intial post didn't mention anything other then tinkering, so I was wondering why spend the money. It's clear now you've got issues.

What 4spd auto does it have? AOD?

 

Freightrain

I apologize for not mentioning anything but the tinkering. I beleive in the "don't mess with anything unless it is broke" method. But, knowing it is a machine and if one part of tha machine isn't up to par it has an effect on the life of the rest of the machine. Everything must work in unison. As well as I am trying to learn more and more. Guys that know this old stuff are getting scarcer and scarcer by the moment. I have a C6 auto from the same era.

 

C6 = 3 speed Cruise-O-Matic first offered on F100/350's (with 360/390's) in 1968. Some cars got it in 1966, hence the C6 designation.

First year for the AOD: 1980 cars / 1982 F100/350's, Bronco's, Econolines.

 

No problem. That can be the problem with communicating over the internet.

That C6 is only a 3spd, not a 4spd(OD) like you have in your signature. I was wondering where you came up with a 4spd automatic for it. I'm guesstimating you were getting around 13 mpg(at about 200/tank) and dropped to 10 mpg(150/tank). 13 mpg is pretty good for these motors, as it takes a light foot and a well tuned FE to get that. My 352 got 10 mpg all day everyday with 150K miles on it.

 

Unfortunately a previous owner changed it from a 3 speed on the column to a 3 speed auto. In turn changing the steering column to a auto/power unit as well as changing the pedal assembly under the dash. I'd love for it to be all manual. A relative of mine just picked up a 68 F-100 as well over the summer and it has manual steering and a 3 speed on the tree. I want those parts! But I'd need a differnt bellhousing I believe as he has a small block 302.

 

Oops...I need to change that...my goof. I'm gonna change that when I get home. Yeah I was getting about 12 MPG over the summer. So I must have been doing something right. And yes I drive her easy. I know it'll take a beating but I like to take care of my stuff. But, I still get on her every once in a while...haha..just to clean her out.

 

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

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.