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Calling all carb experts

3K views 14 replies 5 participants last post by  markb0729 
#1 ·
Hey guys, just a few quick questions as I dig into rebuilding the autolite 4100 I recently purchased. The carb number is C5ZF-F indicating an automatic transmission application, but all the auto trans stuff appears to be long gone except for the arm that the kickdown cable connects to. That's fine because I am running a manual trans anyway, but are there any ports on the carb that I will have to plug due to the missing auto trans stuff?
Next up is jets. I am will be running this carb on a '68 302 with the stock Ford intake and the C9OZ-6250-C cam so what should I be running for main jets? Can I stick with whatever Ford put in the carb originally (I haven't scraped the gunk off to be able to read one yet), or is there another size I should be running?
Last up is throttle bushings, is this something I should do just as a matter of practice on a standard rebuild or is this not necessary all the time? How do I tell if I need to ream out the holes and press bushings in? I bought this carb as a core so I have now way of knowing wether it leaked or not, but the throttle shaft does not seem to have any lateral play in it.
Thanks!
P.S. if anything I asked is 'common knowledge' or really basic stuff, forgive me, I am still learning. :wink:
 
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#2 ·
It wasn't a cable, it was linkage. But no concern. Just rebuild the carb and use as is. The jetting should be fine unless you are in a high altitude area. Then some tweaking may be needed. Bu you'd be better off with a good rebuild and trying it as is.
 
#3 · (Edited)
Thanks Pete, good to know about the kickdown too. I have always seen it called a kickdown cable, and I've only ever dealt with manual transmissions so I've never seen the setup.
I cleaned the jets up today, and they are different sizes for primary and secondary. The one primary jet I could read said 49 F and the secondary jets read 58 F. Is it normal to have this big of a split in sizes between the two sets of jets? If not what should I order for the primaries and secondaries? I have to order new jets anyway as none of them weather being pulled out very well (they were stuck fast), so I want to make sure I get the right parts.
I inspected the throttle shaft today and I can see wear points on it, but I had less than .001 variance in diameter between the unworn and worn parts. Is this enough to warrant replacement of the throttle shaft and rebushing, or am I within tolerance?
 
#4 ·
Just do a quality rebuild and I'd go with the 49/58 set-up to start. Use the float damper spring on the primary side. I'd also leave the throttle shaft bore alone, for now.

See how it runs and where your AFR's are across the spectrum of operation. Simply swapping jet sizes may resolve one issue but create another. The 4100 is a GREAT carb, when properly calibrated but, as you can see, four DIFFERENT versions of the same 289 engine used four DIFFERENT calibrations and jet combinations, with THREE of those running the same camshaft, pistons and heads. A serious 4100 tuner is going to be doing a lot more work than just swapping jets. If you REALLY need the tunability down the road, consider Summits M2008VS600 which is something like a "modern" version of Holley's 4010 which was, for all practical purposes, a knockoff of the 4100.
 
#6 ·
I'm no carb expert but I'm currently in the process of tuning my C5ZF-D and have done a ton of research. Stock factory jets for a C5ZF-F are 48/58 for operation mainly under 5000 feet. 46/56 for over 5000 feet. Assuming you'll be using the car under 5000 feet, 49/58 is a good starting point. Todays fuels have a lower BTU rating because of the usual 10% ethanol blend (use premium 93 or at least 91 octane fuel) so a bump in the primary jetting is warranted.

Don't get lured into those high priced rebuild kits (especially on ebay). Hands down the best rebuild kit for your C5ZF-F is part number 361D by Standard Motor Products. They have a decent parts diagram and setup instructions included. Its $21 at Rock Auto (search this site for a 5% off coupon). As with most rebuild kits, they ship the wrong power valve (4.5Hg) and it's a crap shoot whether you get the correct base mounting gaskets. The stock power valve for under 5000 feet for the C5ZF-F is 7.5Hg (over 5000 feet) or 8.5Hg (under 5000 feet). Get the 8.5 power valve. You can order one from Mikes Carburetor Parts for about $8 with $3.50 shipping. You can also order a set of 50 and 51 primary jets from them (I doubt you'll go lower than 49 on the primary) just in case you need them while tuning your carb. I think you'll be okay with the 58 jets on the secondaries. You may also want to order an extra float bowl gasket to install when you are done tuning.

Rebuild the carb, install the carb and run the car. Drive it. Idle, Cruise, punch it occasionally for a couple of hundred miles, lets say 200. Barring any obvious hesitation or bogging issues, pull the plugs and evaluate. White=too lean. Black soot=too rich Grey/Tan=Good. At cruise you'll be using the primary jets. Go up or down in jet size depending on what the plugs are telling you. The 4100 requires a bit of tuning but when they are set up right they run great. Good luck!
 
#7 ·
Great information here, thank you so much! I actually have already ordered and received a rebuild kit from Mike's, more expensive than the one you recommended but I've bought stuff from them before and haven't had a single issue with any of it yet so I figured I would go back. The proper power valve should be in the kit from Mike's correct? I understand that I'll have to run the carb for a bit before I can make any tuning choices other than mixture and idle, I just wanted to make sure I was starting at a place where I would have a fighting chance at success. The kit from Mike's only came with a single open type base gasket. From what i have read this seems to be for between the carb and spacer, and then one of the clover leaf gaskets goes between the spacer and manifold. Do I have this correct? Anyone have a good source for the clover leaf (4 holes) style gasket?
 
#8 ·
Can't speak to the gasket question as I make my own and IMO the gaskets
out there available off the shelf suck (particularly for the 1.12 autolites).

As far as the bushing situation, it sounds like you're ok on your particular
carb. You really DON'T want to get into this operation, if you can avoid it.
The replacement shaft bushings available leave much to be desired.....
hardly an improvement and a PITA to install. The last 4100 I bushed
was a 1.12 and I don't plan on doing another. I made the bushings on a
mini lathe and persevered through machining the carb to install them
and then honed them to the specific shaft size for that carb. The job falls
into the category of "only if you absolutely have to" or you have lots of
extra time on your hands.
 
#9 ·
Amen GT289. You cannot just ream the wallowed out holes and press a bushing in. That changes the shaft location. That changes the relationship between the throttle plates and the idle ports and vacuum advance ports. None of that is good for the operation of the carb.

You need either a mill or some specialized fixturing to locate the center of the bore off the unworn areas and then bore a hole that stays on that center.

Not a big deal if you are a machinist, but your not going to get the job done with a vise, a reamer and a hand drill.
 
#10 ·
Mike's rebuild kits are good (repackaged SMP kit). Especially the premium kit. You can check the power valve size by looking at the top of the valve. The power valve for the 4100 is also used for Holley carburetors. The minimum power valve should be 7.5 Hg. If that's whats in the kit then try it. See attached picture.

As others have said, I wouldn't worry about the throttle shaft bushings. I wouldn't attempt to replace, best left to the pros IMHO. You can compensate for mildly worn throttle shaft bushings (within reason) at idle by adjusting the idle mixture screws and at cruise with primary jets so don't worry about it. Follow the tuning procedures I mentioned in my prior post.

Mike's swears by the open mounting gasket for the 4100 so I guess it works. I'm skeptical. Why wouldn't Ford use an open gasket from the factory? Ford uses the clover leaf design for carb to spacer and spacer to manifold. That said, go ahead and install the open gasket between the carb and spacer. If you run into tuning issues replace with the correct clover leaf gasket and try again. As mentioned above, the after market gaskets ALL fit like crap. I tried many makers and could not find one I was happy with. The closest is the FelPro 60059 but that sucks for carb to spacer. It's okay for spacer to manifold (talking stock 66 289 here). That said, I did as mentioned above and made my own gaskets so I could eliminate any gasket sealing issues. I used sheet material from Pep Boys (Felpro also has good gasket sheet material). It was a treated fiber sheet from Nickson Industries and was 1/32" thick (don't go thinner). I used the spacer and carb as templates, cut with X-Acto knife and sanded holes to fine tune.
 

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#13 ·
Mike's rebuild kits are good (repackaged SMP kit). Especially the premium kit. You can check the power valve size by looking at the top of the valve. The power valve for the 4100 is also used for Holley carburetors. The minimum power valve should be 7.5 Hg. If that's whats in the kit then try it. See attached picture.

Mike's swears by the open mounting gasket for the 4100 so I guess it works. I'm skeptical. Why wouldn't Ford use an open gasket from the factory? Ford uses the clover leaf design for carb to spacer and spacer to manifold. That said, go ahead and install the open gasket between the carb and spacer. If you run into tuning issues replace with the correct clover leaf gasket and try again. As mentioned above, the after market gaskets ALL fit like crap. I tried many makers and could not find one I was happy with. The closest is the FelPro 60059 but that sucks for carb to spacer. It's okay for spacer to manifold (talking stock 66 289 here). That said, I did as mentioned above and made my own gaskets so I could eliminate any gasket sealing issues. I used sheet material from Pep Boys (Felpro also has good gasket sheet material). It was a treated fiber sheet from Nickson Industries and was 1/32" thick (don't go thinner). I used the spacer and carb as templates, cut with X-Acto knife and sanded holes to fine tune.
The kit has a 7.5Hg power valve, so I will take your suggestion and run that for a bit and change later if I have to. I also picked up some gasket material today so when my OE style carb spacer arrives I will go ahead and make a gasket up.
Now it will be a while until the engine is ready for this carb, anything special I should do for storage, or is it okay to sit?
 
#11 ·
Thanks for all the replies. Some of the reading i did lead me to the same conclusion that many of you have posted, avoid rebushing if at all possible. If it needed it I would certainly have it sent out as my drill press wasn't going to cut it for proper alignment. As it is, I won't sweat it. As for the gasket I think I'll give making my own a try as the hardware store near me has some of the Felpro gasket material. Some of my jets will clean up, but at least one has to be replaced, I think I'll give the stock .048 primary / .058 secondary jetting a try to start out and adjust from there.
Thanks for all the help, I'm sure I'll be back with more questions.
 
#12 ·
The 4-hole gasket goes between the carb and spacer. Another 4-hole gasket between spacer and a manifold with a 4-hole plenum (like OEM) or an open gasket between spacer and a manifold with an open plenum (like most aftermarket ones).

Pay particular attention to the gasket between the carb and spacer and use the 4-hole spacer with tabs that protrude out at the front and back.
 
#14 ·
Put some gas stabilizer in the gas tank and run the engine for a bit. I use Stabil 360 Marine but any name brand stabilizer is okay. If you cant run the engine, still put in the gas stabilizer you should be fine. Here's a tip when making your gaskets... Use a sharpie marker. Use the spacer to make the outside template and throttle bores for both gaskets. Cut the throttle bore holes for spacer to manifold on the outside of your traced line. Cut the throttle bore holes on the inside of the traced line for the carb to spacer gasket. You need a bit more gasket material for the throttle bores for the carb to spacer gasket.
 
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