2 bbl Tuning

[cr_bobcat]

To start with, holy SMOKES the upgrade has been better than I had hoped! For those that haven't been following, I updated a stock setup with a new top end and cam. I have a C9 head that was modified for a 2 bbl conversion, 1.75/1.5 valves, 264/274 110* Clay Smith cam, 1.65 RAU rockers, and a slew of other small changes. It's night and day different.

My problem is the amount of carbon I'm blowing out the tailpipe. I'm using a 1.14 venturi Autolite 2100. I plan on attempting to address this over the winter. My problem is that I know Jack and sh!+ about tuning carbs, and Jack just left town.

The last time I measured manifold vacuum, I got something like 14". I don't know if this is good/bad with this cam. I had to do some "backwoods engineering" (ok....I'm a redneck and find oddball solutions....) to get my carb setup to work. Is this in the ballpark of expected or do I have a vac leak?

If this is normal, do I need a 7.0 power valve?

How should I be jetted? Is there a scientific method of determining jet size? Or am I stuck with trial and error?

Any other Autolite 2100 recommended mods?

On another note, a co-worker has a lift. Will try to get on there this spring to get the header and Arvinode exhaust installed.

 

[wsa111]

What settings are you using on your distributor??? Initial, ported vacuum or manifold vacuum???
I can't advise unless i know your distributor settings.

 

[CZLN6]

Howdy Bob:

Congrats!!!! In adition to Bill's questions add; What main jet is in the 1.14 now? Do you know what the carb came from? Is the tag on it? If not look at the stamped code on one of the mounting legs. The point of knowing this is that the bigger the car/truck that the carb came from the richer the idle circuit in the K cluster. For your use, you'd likely hope for a carb from a light weight Mustang or Falcon.

As usual, carb tuning starts with the ignition. So get Bill's Q's answered first. Oh, and what CR, trans and rear gear ratio are you running. I'm guessing your elevation to be about 700' above sea level.

Although you are not ready for fine tuning the PV, FYI- you do best if you could get a vacuum reading under driving/cruising conditions. Remember the PV number only tells it when to open. How much gas is introduced is determined by the Power Valve Channel Restriction[PVCR]. Again, the size of the vehicle the carb cam from the richer the PVCR will be.

Q- "problem is the amount of carbon I'm blowing out the tailpipe"
A- Is the engine broken in yet? It may take a couple hundred miles for the rings and cylinder walls to take a fit.

Also, FYI- the idle circuit on a 1.14 is a little richer than the later 1.08 Autolites. So, you'll be dealing primarily with the Main Jets sizes, accelerator pump levers, choke setting and low speed idle screws to begin with. Autolite jets are a little hard to come by and the bad news is Holley jets don't work. Jets are available from several sources but narrow down the need by starting with getting the ignition rights first.

Enjoy the journey. It's worth it. Merry Christmas.

Adios, David

 

[B RON CO]

Hi, X2, I guess you mean black smoke, which tells you your mixture is very rich. I would get the most from what you have before assuming you need a leaner jet (you might need a leaner jet). I do my initial tuning with the air cleaner off, and as mentioned timing in a happy place, with ported distributor vacuum all hooked up. With the air cleaner off it is easy to reach the idle mixture screws and the idle set screw on the throttle shaft, and make sure the choke is fully open, and high idle completely off. So go for a lean and low idle with the idle mixture screws turn out 1 full turn. Make minor and slow adjustments, turning each idle mixture screw in slowly until the engine starts to stumble, than back out a little until the engine smooths out. If the engine does not stumble when the mixture screw is turned in, the throttle screw is too far open. So that is the basic carb starting point. If you cannot do these adjustments, and the black smoke is bad you may have a bad or loose power valve, or maybe a carb that has not been rebuilt properly, or an incorrect or faulty float or too much fuel pressure. If you cannot get anywhere with that carb, maybe you could try another carb. By the way, if your engine and cam are not broken in you should not let it just idle while you tinker with the carb. A fresh engine needs to gently rev up and down for a while and not just sit a a steady RPMs. Good luck

 

[drag-200stang]

I found that headers with a free flowing system alone was nite and day difference, it will multiply your mods to date...The change way not be as much because you are helping the scavenging with 10 degrees more duration on the exhaust.
Headers will change your tune, it would be nice to do it once....I prefer long tube but may not be worth the money.

PS can you make a sig like wsa111 I can not remember what ing. you are using. :thanks:

 

[powerband]

do I have a vac leak? If this is normal, do I need a 7.0 power valve? How should I be jetted? Is there a scientific method of determining jet size? Or am I stuck with trial and error?

B RON CO 's suggestions are well founded, especially with a new build startup. If the basic Carb settings can't even achieve basic idle and run, trying an alternate carb (preferably a known good-runner) before getting sidetracked.

Inexpensive vacuum guage is basic to scientific method , but if you are serious, a modern digital AFR Meter will yield real-time fuel ratio or log it for study. With (expensive) performance builds, an AFR meter is a @$150 scientific method helping to making engine-critical decisions.


... a YF 1Bbl is my favorite 'startup-breakin' carb .


have fun

.

 

[chad]

... a YF 1Bbl is my favorite 'startup-breakin' carb .

Got one from a 170…I wouldn't want that for 250 break-in?
(that's the only 'known" running carb available).

 

[powerband]

a YF 1Bbl is my favorite 'startup-breakin' carb .
Got one from a 170…I wouldn't want that for 250 break-in?
(that's the only 'known" running carb available).

A YF from a 170 would probably be Maverick vintage and adequate for 250 start-up/break-in low speed/load operation or swapping carbs as a diagnostic. (IMHO)

havn fun '

.

 

[chad]

Kouwell
I'll try it -cuz an RBS David suggsted is 'just outta da box' & aint sure it's tune.
Thnx!
(I like this ideer).

 

[B RON CO]

Hi, for your information, Chad, as long as the carb matches the intake flange, and is in good clean working condition, it is worth a try. To small is better than too big. Do am honest CFM calculation and see how quickly a bigger carb gets too big. When you learn about bigger venturis and other details yes that is good to know, but we can't always find the "best" part, and that is usually when peak performance is the goal.
Good luck

 

[chad]

sorry ta bust in on ur thread, Cat.
Buy it's kinda related...
U still got the 1st carb? They're pretty easy to swap back'n forth, no?
May B give it a try 2 C a difference & get ur new stuff broke in?

 

[wsa111]

Has the carb. been rebuilt???
Replace power valve with a Holley 7.5" on that big carb. Replace needle & seat, Check float for leaking fuel & making it heaver.Just shake it to be sure it does not leak. Reset fuel level to specs.
Get an A/F ratio reading at cruising speed & change main jets to get 14.5-14.7 A/F ratio. Next get a WOT reading, 12.5-13.1. If the carb. is too rich @ WOT you will have to have a professional install screw in jets below the power valve to lean it down. Another way is to go to a music shop & purchase several small diameters of guitar string wire & place a short length in each orifice below the power valve & retest WOT.
Since its a large carb you may have to either enlarge the idle bleed orifice or better yet install a smaller idle jet. Another job for a professional.
Thats one reason i like Holleys cause all these changes can be modified on a stock metering block or you can purchase one from Quick Fuels Tech. They have the idle jet relocated to a better position on the block to improve a better A/F mixture at idle & the transaction range off idle till the main jets come in.
I still have a 4412-500 Holley with annular discharge nozzles which i had in the small six for sale section, but nobody would get out their WALLET.
I have done many mods as described. I have even done this for some of the Ford Six Forum members.
I do this work as well as distributor recurving. I use an Innovate wideband A/F tester to get the most accurate results.

 

[cr_bobcat]

Thanks for the responses fellas! I'll have to go back through my logs on what I have the distributor set up for. It was an out of the box HRI style distributor that I put lighter spring(s) in. I have it mapped out somewhere but I'll have to find it again. I'm currently running about 15* of advance. Vac advance is connected to a ported source.

I did a full 20 min breakin of the cam at 2k RPM. I didn't modify the pistons or rings, so no worries there on break in. After the 20 min run, I changed the oil. I managed to get about 400 miles in before the snow came and now she's blocked in behind the snowblower.

I got the carb from GottaFish out of Oregon. It's a C5ZF-B with 50F jets and "new slosh tubes". Not sure what that last part means but I assume its the pretty bronze tubes sticking out the top of the unit. I just remembered that I had the handwritten card and that's what it said.

I did have some impressive backfires when trying to start the engine for the first time. I could have blown the PV.

Right now I have 1 mix screw out 1.5 turn. I can only access that one with the VC off. The other one I think I may have lightly seated (or at least very close). This helped me get the idle down south of 1k RPM.

I'm guessing that the 50f jet is way too big for my 200 and that's my issue. But that's just a guess.

Rear end is an unknown. Need to get her up in the air and turn the wheels and count. My guess is 2.7 or whatever was stock for this year.

I'll have to dive back in to see if I've answered the other questions...

 

[cr_bobcat]

65zf-b codes out to be from a Mustang/Fairlane/Falcon with a 289.

 

[CZLN6]

Howdy Bob:

Good get on that code carb. Set both low speed air screws at 1 1/2 turns out as a starting point. IF it won't idle check the linkage to make sure the butterflies close snuggly. I've had to reset the butterflys on the shaft after a complete tear down to get them to seat snug. Don't use the low speed air screws to get the idle down.

How come you have your carb installed with the air screw toward the VC? Most mount the carb the other way with air screws toward the fender.

The next thing I'd do is replace the cheapo Autolite PV with a Holley #7.5 before you change main jets. While the 2100 is more back-fire resistant than the Holley 2300 it can still happen. You'll want a Holley PV anyway to be able to fine tune it. Do you have any Autolite main jets on hand? What size?

Your break-in sounds good. What weight oil are you running?

How do the spark plugs look?

The carb has two levers for the accelerator pump; one at the linkage, aka over-reach lever and one at the accelerator, aka pump lever. What holes is the connector rod in at each end?

How much was the head milled on the rebuild? What head gasket did you use? What was your goal CR?

You might want to try using manifold vacuum considering you cam and vacuum signal.

Keep it coming.

Adios, David

 

[cr_bobcat]

She'll idle with both turned out 1.5, but it's above 1k RPM with the idle adjustment screw backed out entirely. So there's a good chance the butterflies aren't closing, but it looked solid before install. Looks like I'll unhook, drain, and recheck all of it this winter.

I mounted it that way because there were enough folks on here commenting that the mix screws towards the fender was backwards and lent towards an even richer run for 3/4 because of how the butterflies open.

I don't have any jets on hand. Is it possible to modify the 2100 to accept Holley jets if they're easier to acquire?

I'll have to go check the acc pump linkage to see how it's set. I know I do get a very healthy shot when I hit the gas....

I used Brad Penn break in oil. The green stuff.

I haven't pulled the plugs yet. I'll try to do that here soon.

Head was milled 0.070" and gave me 48 cc chambers for a 9.5 SCR, if memory serves me correctly. I am using a 0.035" Ford gasket. It measured maybe around 0.040 prior to install. I "think" that I wrote that down somewhere. If not, I have another in the garage. I found them cheap so bought 2.

With having the adapter plate assembled as previously mentioned, I don't have a manifold vac source without tee'ing into the line to the transmission. I do have the parts to do that though because "just in case".

 

[CZLN6]

Howdy Back Bob:

Q- "Is it possible to modify the 2100 to accept Holley jets if they're easier to acquire?"
A- No, not that I know of. But I guess anything is possible with enough money. Autolite jets are available from several sources. But, I'd do an R&R on the carb float, needle and seat and the PV 1st, then new spark plugs and assess from there. If I were guessing on the jets at your locale I'd be thinking a 47f pair.

An afterthought, is your choke wide open?

On seating the butterflies, loosen the screws that fix the butterfly valves to the shaft and then snap them shut using the throttle return spring. Do a couple of snaps, tighten a little and snap shut again then tighten solid. Ideally, when the idle screw is backed out the engine should kill.

Keep us posted on your progress.

Adios, David

 

[B RON CO]

Hi, the vacuum line for the transmission is a good source for your vacuum gauge. Tee it if you are driving or just plug and play in your driveway. Good luck

 

[xctasy]

viewtopic.php?f=1&t=70651&p=554757#p554757

viewtopic.php?f=1&t=73098&p=562120#p562120

http://vb.foureyedpride.com/showthread. ... -Carb-Jets

 

[cr_bobcat]

Thanks xctasy! I think what I'm going to do is pull the carb. I'll check the butterflies first since that's the easiest. I recall checking them prior to installing the carb. Based upon the flow numbers you quoted on FEP, the 50F's should be fine for me. Sounds like more of a PV issue. Most likely, I destroyed the thing on my initial start-up procedure.