Offy 3 X 1 Running very poorly

[mustang652]

Have spent the past two days trying to get the car running properly and I'm about ready to shoot it and put it out of my misery. Today was spent with a friend who is a retired mechanic. Several years ago he had built and owned a 200 CID Mustang with the Offy system. Even he could not positivly pinpoint the problems.

At idle it sounds great and has excellent throttle response. I've got initial timing at 14 degrees BTDC, plugs gap now at 45 (had them at 35 until a couple of hours ago, after the regap to 45 it did improve the running a little)
I do have the Dizzy II out of an 81 Zepher, but it has not been recuved (Next month's project}. Under load, it bogs down and sounding like it is missing on at least one cylinder, and not much power. I've checked and I have fire to all cylinders, and it sounds the same on two different set of plugs, and plugs are black in color. An application of carb cleaning spray on the end of the throttle plate rod indicates I do have a bit of a vac leak on at least two of the three carbs. My friend thinks this is the majority of the problem. In asking for help and advise, I also ask, can there be somthing wrong with the distributor or the control box? I had what seemed like a simular problem even before I put the OPffy adaptor on the head. While I was testing out the carbs I rebuilt, I ended up with what sounded like a miss, new plugs at the time helped but did not cure the problem, assumed the problem was with the old head. I'd like to try to get it running well enough by Friday to take it to an MCA show. Even thought it's in the early stages of rough sanding and looks like crap, I really wanted to show it as one of the alternative that can be done with an I6.

I have run out of idea and would appreciate any help.

 

[powerband]

The problem as you alluded to could very well be one of the carbs. three carbs = three times the likelyhood of problems. I can only suggest trying each carb individually by making block off plates for the outboards and running each carb individually in the center position for testing. It's a pain but if you do this you can eliminate them individually as a problem or confirm.

I made block off plates simply by tracing a carb flange gasket on a piece of flat aluminum and drilling bolt holes.

My moth balled 250 has three Holley 1904's and for initial startup and testing, I blocked the outboards and ran a "known good" 350 CFM 7448 2bbl in the center (w/adapter). I tried the Holleys recently individually and found ONE ran good, one ran bad and one wouldn't run wort a crap., Now I'm back to the 2bbl and trying to get the Holleys working individually before attempting all three.

Powerband.

 

[mustang652]

I made block off plates simply by tracing a carb flange gasket on a piece of flat aluminum and drilling bolt holes.

Powerband.
[[/img]

Thanks, the block off plates sounds like a place to start.

 

[powerband]

I made block off plates simply by tracing a carb flange gasket on a piece of flat aluminum and drilling bolt holes.

Powerband.
[[/img]

Thanks, the block off plates sounds like a place to start.

Of course you could leave the blockoff plates in place for a while if you find one good running center carb as I've heard some have done ...

Powerband

 

[gtm1086]

Set up and tuning can be a real challenge.

Have you installed a vacuum gauge to see if you do have a leak? Getting the offy to seal against the log can be an adventure.

When it comes to setting up the carbs. Shut the mixture screw completely down for your outer carbs. Do all of the idle adjustments with just the center carb. Think of your set up as a three barrel carb. Center is your primary the outers are your secondary.

You will find that there is a lot of trail and error on getting everything set up. But once they are dialed in they seem to stay put

 

[addo]

The "throttle spindle vacuum leak" can be a red herring. Unless it's a sealed bushing of some type (ball race most common) all leak slightly. You just unconsciously factor it in while tuning. Rebush only if the throttle plate is binding in the bore, or the spindle flopping about.

I'd suggest the bog is overfuelling. Also, was the cam dialled in for this motor, and is TDC verified? A vacuum gauge will help in tuning, and you might also look into the Colortune kit.

Many British cars ran successfully with triple carbs. The XKE is one of them. Don't give up, just pace yourself so that knowledge and good outcomes are locked in.

 

[mustang652]

Sorry guys, response in a tad long with several questions, but right now I'm at a standstill.

Set up and tuning can be a real challenge.

Have you installed a vacuum gauge to see if you do have a leak? Getting the offy to seal against the log can be an adventure.

When it comes to setting up the carbs. Shut the mixture screw completely down for your outer carbs...

You will find that there is a lot of trail and error on getting everything set up. But once they are dialed in they seem to stay put

You're right on about the hard to get them to seal. I'm hoping thats not the problem and why I kept working with the JB Weld until I got what appeared to be good seats built for the o rings If it turns out to be that, it means that I will pull the head again. With the large flange on the clifford exhaust and its almost impossible to get to bottom bolt between # 5 and 6. and the bolt down from the bottom (early model) adapter, I found it easiest to install head, headers and Offy adapter as a single perassembeled piece. I've done it three times this way already due to a couple of screwup on my part and the realization that I could not get to the bottom bolts on the adapter. No I don't have a vacuum guage installed at present. but can't one be purchased as a shop tool, I'll get one. How would I use it to determine a leak. Also, on the mixture screws, do you mean turn them all the way in, and does this make it richer or leaner and would blocking off the outboards help in the process.

The "throttle spindle vacuum leak" can be a red herring... You just unconsciously factor it in while tuning. Rebush only if the throttle plate is binding in the bore, or the spindle flopping about.

I'd suggest the bog is overfuelling. Also, was the cam dialled in for this motor, and is TDC verified? A vacuum gauge will help in tuning, and you might also look into the Colortune kit....

Addo, I would have thought that there would be some inheirant minor leaks on the shaft as the Autolites were not an overly sophisticated or well engineered carbs. That amoung other reasons has kept Pony Carbs in business. No binding or what I would consider excessive play on the shaft or plate in my opinion. The answer on "dialed in" is no. The mechanic/friend that has been helping/advising me here locally, installed the cam himself and set it a "0" I ask if I needed to accuire the tools for this process and he indicated that he didn't need to do that unless I was wanting the cam set up at other than "0". The instructions that came with the cam seemed to agree with that statement so I did not push the issue. Apparently that was how he had set his up a number of years ago. I think I have varified TDC. Set me straight if I am incorrect in this proceedure. I set the pointer at TDC, verified that the rotor was on #1 and piston at top of block when cam was installed and again last night checking the piston by pulling #1 plug. Piston was just below the plug opening so I'm hoping that I did that correctly. If it is overfueling, How do I correct that with the Autolite 1100's. Is it possibly the metering jets. I have 60's on the outboard and a 68 on the center. What is the Colortune kit, and what would I be looking at price wise and learning curve wise to get and use one.

Just as a side note, I've a retired aquaintance here that got so frustrated with learning to work on his Mustang , he has enrolled in the local community college and is taking the mechanics program including the welding courses.

Thanks guys, all the help and advice I can get is appreciated.

 

[mustang6]

I can't tell where you are drawing your vaccuum advance from in your avatar, but it looks like you are running three SCV carbs and your signature says you have a DS2 distibutor. So you are having a vaccuum advance mismatch just like anyone running a single carb would, unless you are usig manifold vaccuum, which is in itself more problematic because you will have less manifold vaccuum than someone running a single carb....

Ideally your center 1100 would be a non-SCV type and your vaccuum advance would be coming from it.

 

[mustang652]

...looks like you are running three SCV carbs and your signature says you have a DS2 distibutor... So you are having a vaccuum advance mismatch just like anyone running a single carb would, unless you are usig manifold vaccuum, which is in itself more problematic because you will have less manifold vaccuum than someone running a single carb....

Ideally your center 1100 would be a non-SCV type and your vaccuum advance would be coming from it.

I've got the SCV blocked off , or at least I think I do. I teflon tapped the holes in the threads on the back side of the screw in valveand have put brass plugs in the vac lin inlet holes. The brass fittings comming off the intake log just below the center carb is what I used to create a manifold to split the vac to the distributor, PCV and the vac modulator for the C4 automatic. What year(s) would I look for to get an non SCV 1100 carb.

 

[gtm1086]

You can pick up a vacuum gauge at just about any parts or tool supply house. Hook it into the log. You should see a steady needle wih around 12 to 18 " of vacuum. If the reading is low or the needle is bouncing around you have a leak.

Turning the idle mixture screws all the way in pretty much shuts off the fuel or leans it out. I ended up with the center carb out around 1 1/2 to 2 turns and the outter carbs open maybe 1/2 turn. Hoever what works for one may not work for everyone.

 

[mustang652]

...Turning the idle mixture screws all the way in pretty much shuts off the fuel or leans it out. I ended up with the center carb out around 1 1/2 to 2 turns and the outter carbs open maybe 1/2 turn. Hoever what works for one may not work for everyone.

Thanks, for that info, I think I've been starting with much to rich a setting. Do you remember what size jets you used. I'm currently using a 68 in the center and 60's on the outboards.

I did get a vac guage yesterday morning and posted the results on another thread (http://fordsix.com/forum/viewtopic.php?p=272285#272285), but the short of the story is that I had 2 1/2 to 3 " on cranking and 12 on the running with an idle of 1100. Pulled the carbs off and could see part of an o ring protruding into the insite of the adapter.

Think I'm going to pull it and start from scratch.

 

[Anonymous]

Ahh, sucked an O-ring.

When I set up mine, I spent a day smoothing and reshaping the log all around where the O-rings seat. I'd press a layer of modeling clay over the area, bolt up the intake (w/gasket) on the center carb boss, remove the intake and check the resluting clay thickness to make certain that I'd be getting a uniform squeeze on the O-rings. A little brush-on gasket adhesive on the O-rings, bolt it all up, and it's been leak-free for over ten years. There's been a couple times I was certain that it was leaking, tore it apart and reassembeled, only to (eventually) find the fault was elsewhere.

 

[mustang652]

Ahh, sucked an O-ring.

When I set up mine, I spent a day smoothing and reshaping the log all around where the O-rings seat. I'd press a layer of modeling clay over the area, bolt up the intake (w/gasket) on the center carb boss, remove the intake and check the resluting clay thickness to make certain that I'd be getting a uniform squeeze on the O-rings.

Modeling Clay? Does it actually harden and adhere to the log and the clay become a "permanent " part of the log like using the JB Weld or the steel epoxy putty. Where would I purchase it. As I have got to replace the O rings you wouldn't happen to know what the actual size I need to attempt to order.

 

[wallaka]

I think he's talking about using the modeling clay to guage the thickness and evenness of the mating surfaces.

 

[gtm1086]

here's what worked for me on sealing the offy and the log.

I got some gray marine tex. and placed it around the openings on the log. Then with the o rings installed on the offy I bolted everything together and let it sit over night.

I can't tell you much about high speed jetting the old holley carbs i used I couldn't get much in the way of jets. I also disabled the the acellerator pump on the back carb. With three of them squirting gas it made for a pretty good bog.

 

[mustang652]

Would appear that I 'm dead in the water for a few days. One of the two o-rings whas damaged beyond use. I finally got a phone number and made contact with Offenhauser and was able to order 4 of them. $7.00 with shipping. Will take 10 to 14 days at best as they do not have online services and do not take credit cards, so I have to wait for them to get my check before they will ship. MustangSix gave me the location of another place, so I will try them tomorrow and see if I can get the correct size. Thanks again to everyone for the help over the past few days.

 

[Jett's_Pony]

Hi
On my daughters car we have a later head (D7) so we have a different manifold adapter for the 3 carbs. I am not sure exactly how the one you have attatches to the intake log. The rubber O rings should be available from any auto parts store. Make sure that they fit properly in the groove in the manifold. The ones that came with the Offy kit had shrunk and were slightly undersized. We did not use any sealant with the O rings, just made sure that they were well compressed when the manifold was tightened down. We have not had any problems

The center carb is off a 1966 240ci truck motor so it has a larger venturi and throttle bore. We had to change the throttle shaft to make the linkage work properly. The outer carbs are off a 1964 170ci truck. They bolted on fine. All three carbs have a 56 main jet and it is still a bit rich. Runs well and does not foul the plugs, the plugs are just a bit darker than they should be. No problems with any pinging and gets better gas mileage than it did stock if Jessica keeps her foot off the loud pedal.

We disabled the load o matic by putting a spring on the valve as we screwed it in making it not operational. The vacuum for the distributor is pulled off the port on the carb just like when it was stock. We are running the stock 1967 Califonia distributor with a pertronix. 1967 200ci California cars did not have the load o matic and had a smaller carb.

We tried the common manifold for all the vacuum lines like you describe and the car ran like crap. We just ran the vacuum for the transmission to the intake manifold. We ran the distributor vacuum to the stock port on the carb, (be sure to disable the load o matic valve as all it does is change the source of the vacuum to the distrubutor port).

Get a carb sync tool that sits on top of the carbs and will show you exactly how much air is being drawn through each carb at idle. We set up the three to pull exactly the same and it idled pretty well. Idled a bit better when the center carb is drawing just a bit more. You should be able to get the sync tool from a shop specializing in older foreign car parts. Also great for synching the four carbs on an old Corsa Corvairs.

I think your biggest problem is the common vacuum source.

You can see pictures of Jessica's Mustang in an earlier post about the miracle air cleaners.

Hope this helps

Greg and Jessica

 

[Mercury Mike]

Load-o-matic valve = Spark Control Valve...?

 

[wallaka]

Yes.

 

[mustang652]

... All three carbs have a 56 main jet and it is still a bit rich. Runs well and does not foul the plugs, the plugs are just a bit darker than they should be...

...disabled the load o matic by putting a spring on the valve as we screwed it in making it not operational. The vacuum for the distributor is pulled off the port on the carb just like when it was stock... We tried the common manifold for all the vacuum lines like you describe and the car ran like crap... Get a carb sync tool that sits on top of the carbs... Hope this helps

Greg and Jessica

Thanks, the whole posting helps. The older style adapter, part #5205 looks more like a long box and the area that mates with the log is an arch with a groove for the o rings and the best description is, a very lousy fit. The front and back of each opening on mine leaves + or - an 1/8 inch gap to be filled or built up. I thought mine was running way to rich, plugs were very black. Just took a break from this response and ordered the smaller jets from a guy on ebay. I did have a serious question on one of the o rings, not to small, but one look a little streached and slightly out of round like it had been through a dry fit and got pinched. I had to glue it into the grove. Oh well, I knew I was buying the last one they had in stock, and when I got it it was obvious that some parts had been robbed and and some that had been replaced with incorrect size parts. Locally I have tried to find the o rings at AutoZone, Quest, & NAPA but without scuess. Even tried ACE Hardware with no luck. Have some on order from Offy and am hoping for the best. What kind of spring did you use on the SCV to make it non-operatiional. Since I have got to make up some JBWeld to again puild up the intake again, would a few drops of that on the fromt to puld the intake hole work as well. I'll revamp the vac manifold and leave it for the PCV valve and the auto tranny. I'll start looking around for a Carb sync later today and see what I can come up with. Have been contemplating using Quick Steel epoxy putty instead of the JBWeld and seeing if I can apply it thick enough enough to create an impression of the o ring from the groove as part of the build up. I did go back and find the pictures you mentioned.