MG-- Sounds like you have a good plan for performance & mileage testing. If the new plugs do not build up soot I would run the 52 jets, better to be a bit rich than too lean. That HEI distributor with a full 12 volts will be one of your better additions to that 360 motor. When you get that choke system working like it should I think your starting will be much easier. Shifting and shift point is much better, sounds like you can live with the 3.00 gears.
On a basic stock 360 I am not sure you will feel any extra performance from header. You might think about running your stock 360 exhaust manifolds & a quality dual exhaust system first and see how it runs.
You might find a Autolite 2100 1.21 @ 357 cfm a little easier than a 1.23 and they are almost the same cfm. Nice work & thanks for passing on the information.

 

I have full 2” dual exhaust now with stock manifolds. I wish it was 2.5” but at least it’s full dual from the manifolds back. Even if the headers don’t make a significant difference now they may help if I convert to a 390? And since my main issue is on the top end when flow is most important they may help a bit now and even more if/when I upgrade to the bigger carb.

Hoping to get the fan clutch in this week and see if that makes any appreciable difference. I’ll be out of pocket for a bit after that but will update this thread with any more progress when I can.

Thanks for all the tips, suggestions and encouragement.

 

Will be looking forward to the new plug reading & the soot issue when you have time to update the thread. Full dual exhaust of any size is better than stock.

 

Years back a member named Kyle Jewell posted that he had found a set of headers that the problem child r/s header was 2 piece. So installation around the r/s motor mount and stand was no problem. I didn't write down any information on them though.

 

I would recommend the 350 cfm it is a great carb and great stock performance by the 500 I ran for awhile it was a monster on my mild modded 390 cam Headers pertronix 2.5" exaust it would go up to around 4,500 although it has a 50 cc accelerator pump and big bore it's more of a WOT carb it's a gas hog and was hard to dial in since you don't have secondaries you can be spot on in low mid range in jetting but it would go lean briefly before it caught up in higher RPM I had a wide band installed the 350 is a great all around carb in a 2bbl and Holly's do use more gas that a autolite or motorcraft .

 

IMO a 460 is a no brainer for power and mileage. I did it in about 1980. Have you tried your truck with smaller tires? I'd bet you'd be surprised in the performance difference and probably the mileage will be better as you'd not be lugging the engine.

 

I'm following this thread and really appreciate all the info the members are putting out for you the coil really perked it up I was 🤔 thinking when you said P.O. put a elec kit but said stock coil that maybe a limiting factor a good spark at WOT is needed today's gas is not good for carburetor IMO it is fuel injected gas and will run great one day then somewhat ok the next may contain up to 10 percent ethenol ? Ok which is it from day to day .I installed a wideband 02 sensor AEM took all the guess work out when your at idle cruise midrange WOT that thing will tell you i also think one step up in carb size will get you closer to what you want but in all my tuning with the 2bbl lots of help from here thanks guys it will always be a 2bbl you can't ask a Sporster to be a big twin or a Honda civic to be a ? Whatever there are limits it's a big block with a 2bbl .another thing at first when I was learning mall this I used to tune my truck in park now I know you do some things in park timing settings etc but idle mixture I do in Drive I'm not cruising in Park and on the AFR it is dramatically different from park to D park it's higher idle more air speed air flow put it in gear less air flow lower idle it gets richer big time seen it on the AFR so I set my idle mixture in gear some may disagree but I'm going by what the AFzr is telling me and it's richer once you drop it in gear .National carburetor sells pretty good rebuilds they might have that next size up autolite maybe try a phelonic how ever you pronounce it spacer under the carb 1" I gained way more top end using it jomar performance sells them although re jet might be required said too much AFR gauge for today's gas 👍.....

 

MG--- Have you install a new set of plugs in your rig yet to see if the get the black soot on them that the old plugs had on them? Still running the 52 jets?

 

I did install new plugs but I had a bit of a setback on the carb. The truck developed a hesitation coming off of idle after the last round of jetting changes when I went down to the 50s. I thought I might have gone too lean but when I looked it over I saw that the accelerator pump was not working up to it's full potential and had a weak shot off of idle. The hesitation was minor and the truck recovered very quickly and drove really well but the hesitation was annoying. I pulled the carb again and I believe the problem was that the float level was too low which uncovered the bleed hole in the top of the float chamber that feeds into the accelerator pump causing the pump not to fill all the way. However, when I manually filled the bowl so that the pump would fill all the way it would leak around the external cover of the pump when the throttle was moved. The pump cover had one screw hole stripped out by the PO but I never worried about it because it didn't seem to be causing any issues but that's where it leaked when the accel pump was working as it should. I think the truck was running rich enough to cover the problem when I first got it and once I got the jetting closer to where it needed to be the accel pump became more important and the hesitation started; however, I cant fix it because of the stripped bolt hole. The carb body is cracked from him forcing a larger screw into the hole without drilling and tapping so I can't even drill it and tap it at this point to try and save the carb. So I gave up on that carb and ordered a 1.23 off of eBay. I know you may think that is too big but that's where I went for now :-) I installed that carb today and I'm pretty happy with how it is running again. I think I still have some fine tuning to do and will do a plug check after I've had a chance to run the truck a bit. I had to open the idle mixture screws several turns once I got it running and it is not quite as smooth right off of idle as it was but WOT is definitely better and it easily hit 85mph today where it struggled to hit 80 before. First gear WOT is good and the sound at WOT with the open element air cleaner is very cool. I know the c8ae-h heads have a mediocre rep at best but it sure sounds like they can move some air under the right circumstances!

My fan came in while we were on vacation and I attempted to install it today as well but the Hayden 2710 fan clutch is not right for me even though that's the one they list for the 71 f100 with 5.9l. It all bolted up but the clutch is too short at 1/5/8" where the solid fan has a 3" standoff block. The fan was pulled to far back into the engine with the clutch causing the fan to hit the crankshaft pulley. My crankshaft pulley has an extra pulley for aftermarket A/C which may be part of the problem. Without that pulley it might have worked okay but the fan would not be fully in the shroud with the clutch so I don't think I would have been happy with it anyway. I've gone back to Hayden to see if they have a clutch with a 3" shaft that might work better.

 

I have thought long and hard about a 460 swap and may still do that at some point. I'm torn between the 460 which from what I have heard is a difficult swap and stroking this engine to something between 390 and 445. The advantage to stroking is that it all fits like it does now so I don't have to do a lot of engineering and I get to keep a lot of the work I'm doing now like the fan clutch, HEI, transmission, driveshafts, etc.

 

I have not tried smaller tires, I like the look of the truck with the tires it has so I will either build more power or change the 3.00 gears to something that gives me the power I want. If I had a set of smaller tires I would try them for sure just for grins but I don't have them so it's a moot point I think.

 

MG-- What jets and power valve are you running in the 1.23 venturi carb? Sure sounds like that 360 likes that size. Maybe a 1.21 or 1.23 was a better match. If you can get it tuned like you need it will be fun to run it like that for awhile. Maybe you can be happy with it. Again i will be interested in what the plugs look like after you run them for a bit.

 

i haven’t opened the carb but the seller told me it had #56 jets in it. I didn’t ask about the power valve.

 

Hi, I am new to the forum and have been reading through the different threads. You seem to be very knowledgeable, and have received a lot of really great advice from some of the other members. Although I am new here, I have owned several older Ford cars and trucks over the years. I currently have a 1968 F 250 camper special with 390 two barrel and c6 auto trans. In post # 31, old28 gave some good advice about checking over every detail of the ignition and carburetion systems. I know you have changed carburetors since then, but you have not said if the plug sooting issue has remained. I didn't see anyone mention checking the carburetor dashpot. If this is stuck or out of adjustment, a surprising amount of fuel can be sucked through the idle circuits when the engine is decelerating, maybe enough to cause the sooting.When I rebuilt my autolite 2100 with a kit from Mike's Carburetor about five years ago, I also changed the dashpot because mine was rusted solid. The rebuilt carb and new dashpot made a huge difference in the driveability of the truck, and my fuel mileage increased by about 1 mile per gallon. Just something else you might want to check.

 

My new carb is also an Autolite where my old carb was a Motorcraft. I’m not sure what the dashpot is? The power valve is new and the choke pull off is working correctly on the new carb. I have not pulled the plugs since I changed the carb. I want to put a few more miles on it before I do.

The ignition is a brand new 65kv HEI system that I put on during this thread along with the new plugs so I believe my ignition is in good shape at this point.

I did some research on the theory of operation of the 2100. In hindsight I probably should have done that first. From what I have read, idle mixture is controlled primarily by the mixture screws with minor influence from the jets. WOT is controlled primarily by the power valve with only minor influence by the jets. The jet’s primarily influence off idle up to the point the power valve starts to open. So my WOT plug chop test is not a good indicator for proper jet sizing. My plan at this point is to try a part throttle plug chop test after running at say 65 for a few miles and see what the plugs look like. I believe at this point that I am lean on the jets. Cold drivability is not good even with a functional choke. It was much better with the old carb. Even fully warmed up the performance just off idle is not as good as it should be. All of this coupled with the fact that I had to open the mixture screws to almost 4 turns to get a good idle leads me to believe I’m lean on the jet’s although I think I’m pretty close. I’m going to order some 58s and see what that does for me.

I used the truck to tow my jet skis to the lake this weekend for the first time and it did pretty good. It’s probably 1000lbs or more and it pulled it well. Not a lot of difference in performance with or without the trailer.