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  Topic Review (Newest First)
12-21-2008 08:41 PM
John Strenk
Quote:
Originally Posted by dsfordguy View Post
Could the vacuum leak at the throttle shaft be causing me to have pinging at 8 degrees advanced? Could it also be the cause of it only reaching 3500rpms?

Thanks
Any vacuum leak leans out the mixture making prone to ping. I really don't think it will limit your RPM though. Heck in the good 'ol days I would run a carb up on washers to allow more air in, just need to compensate with bigger jets.
12-21-2008 07:33 PM
hotrod351 you cant always go by the timing, i have had a couple vech. that i ended up setting the timing at tdc, one was a stock 454 chevy, dont know why, it started fine and ran great. any ways id set it to 6 degrees. then it sounds like you need to go through your carb. get a rebuild kit. if you needle and seat are leaking it will cause all kind of problems. and it sounds like its leaking seeing as you said you could screw yoy idle mixture screw all the way in. good rule of thumb, for most carbs, 1 - 1 1/2 turns from bottomed out is a good setting. then you should be able to turn it in 1/2 turn and you should notice it stumble. also im sure you checked your plugs. a easy way to find problems in the ing. or cylinder is to get it running then disconnect each plug wire, one at a time and see how much it affects the engine idle. id loosen them up at the cap before doing this. if you find a wire that you pull and it doesnt make any difference then you know theres the problem, wire, plug or bad cylinder.
12-21-2008 06:55 PM
dsfordguy Could the vacuum leak at the throttle shaft be causing me to have pinging at 8 degrees advanced? Could it also be the cause of it only reaching 3500rpms?

Thanks
12-21-2008 12:40 PM
John Strenk It should kill the motor if it goes in all the way. Usually it indicates the throttle is open to far probably compensating for another problem. Usually a vacuum leak

That sounds right but my book are away for Christmas cleanup.

Sounds like the bore for the throttle shaft is worn out. It can bind the throttle and do other bad stuff.
You can get it fixed if you absolutely need the carb but a new one is easier to find than a place that puts in a new bushing into the base.

Think about switching to a newer manifold and 2 bbl carb maybe Something like a MC2100
12-21-2008 10:15 AM
dsfordguy According to my tach the idle was at about 600 rpms. Shouldn't the motor die if I screw the mixture screw in all the way? It keeps running but you can hear the idle go down a little.

What I did to adjust the metering rod was hold the accelerator pump down and loosen the screw till it lifted off the metal piece it touches then I screwed it to where it was just starting to touch it. Then I tightened it one more turn. Is this correct?

Also when I spray carb cleaner at the outside of the throttle shaft where it goes into the carb it bogs down a little bit. I must have a vaccuum leak there. Does this mean I need a new carb??
12-21-2008 06:08 AM
John Strenk If it leaks around the gasket between the throttle plate and the body it just means that it's not seated and tight for some reason. (Loose screw, dirt, old gasket left over.?

There are a lot of reasons for the fuel level to be too high. Sticking on the side of the bowl, float has fuel in it or soaked with fuel. Top twisted a little, hinge worn out on the float...

Screen should not cause a problem right now but it might let dirt in causing problems.

THe idle mixture is later when your tuning it on the engine. If the idle mixture has no effect you either have a vacuum leak or the idle RPM is to high.

It should have a slight angle to it but not too much. It woul cause it to idle to high.
12-21-2008 12:13 AM
dsfordguy I believe it was air that was leaking around the base plate. But I may still have fuel leaking from the gasket between the throttle body and main body or somewhere near there. Would this mean the fuel bowl is overfilling? My carb did not have a screen with the needle assembly like in the manual neither did the rebuild kit. Could this be a problem also?

I adjusted the screw on the metering rod while holding the accelerator pump like it said in the chilton's manual. Was I supposed to do something with the air fuel mixture screw also? Another question, When the throttle flap is closed all the way does it sit totally horizontal or does it have a slight angle? I think mine had a slight angle.

Also the tach I installed is for a 4,6, or 8 cylinder engine. It has a switch. I made sure I put it on 6 before I installed it.

Thanks
12-20-2008 10:11 PM
John Strenk My 76 with a YF runs with 8*-9* of timing. But I don't know the combustion ratio and other stuff that might make setting it at 3* desirable. It's certainly not the carb that would make it have to be that low.

Did you set the mixture correctly on the YF. Particularly the part where you have to push down on the accelerator pump and adjust the mixture screw. If this is not done correctly you will run to lean and ping and not get very high in the RPM range.

It's all covered in the Haynes manual and did not see what they were trying to do the first time I read it so it's easy to get confused.

Stock Tachs do work with the HEI but did you perhaps put an 8 Cylinder tach in there? That means your actually turning 5250 RPM with a 6cylinder.

The YF can have a leak that looks like it's around the base plate if the level is to high. It will leak out the well for the accelerator pump. Make sure your float is set correctly. Of course a loos base plate will also leak allowing air in and leaning out the mixture causing it to ping and yada yada....
12-20-2008 09:36 PM
dsfordguy I set the timing to 3btdc and I think it is no longer pinging at 55. I still cant seem to get any more than 3500 rpms out of the 258. What else could it be? The chilton's manual says something about some tachometers don't work with hei. Do you think my tach is wrong? Its about 6 months old. According to the tag on the rear axle I think i have the 3.73s still and 31" BFG MTs and when I punch the throttle I shift to 2nd gear at about 25 on the speedo which may be between 25 and 30 because of the 31's. Does this sound right? O ya I think it is the stock 3speed tranny also.

I think i fixed the problem with it seeming like it was flooding. It was leaking around the carb baseplate. Now I can see if I have the choke adjusted right in the morning.

Thanks
12-17-2008 11:23 AM
Mike Romain
Quote:
Originally Posted by dsfordguy View Post
Do I need to advance my timing a little more?
I think I would. You can also fine tune the timing with a vacuum gauge. You advance it until you get the highest manifold vacuum, then you back it off about 1" of vacuum on the gauge. This should be real close to optimal for your engine.

Most of the 2BBL ones run nice at 8 or 9 BTDC, some even higher.

I have noticed my Haynes manual calls for 3 BTDC on a 73 and 74, so maybe you need to go the other way?
12-17-2008 11:02 AM
dsfordguy Do I need to advance my timing a little more?
12-17-2008 07:27 AM
Mike Romain I have the 2BBL carb and intake on my 258 and set my timing to about 9 deg BTDC with 91 octane fuel. Mine will rev to 4400 rpm in 2nd @52 mph.
12-16-2008 05:50 PM
dsfordguy I gapped the plugs to .045 and it still wont rev any higher than 3500 rpms. What else could it be?

When I first start the engine it seems like its running rich cuz there is black smoke and the engine wont idle very well and dies sometimes. It also sputters when i give it gas. It is like this for a while then it stops. Also I have an inline fuel pressure guage installed and when the engine is running I have between 5 and 6 psi but when I turn the engine off the pressure bleeds off. Does this mean the float is sticking? The float wasn't full of fuel when i rebuilt. I checked the float adjustments when i rebuilt the carb and they were good. I also replaced the needle and seat assembly. Could this have anything to do with the metering rod adjustment? What should I do?

Another thing is that I think I may have found what i thought was pinging. I think the cooling fan is contacting the lower radiator hose when under load because when I replaced a power steering hose I moved the radiator up one inch because it was resting on the old power steering line and cracked it from vibrations. What should I do to solve this? The radiator is just about resting on the power steering lines going to the steering box even with it relocated one inch up. Also the fan I have is one of those flex fans.

Thank you for your help.
12-15-2008 07:42 AM
Mike Romain The Haynes CJ manual has very good directions for setting up the carbs. It is also very good for wiring.
12-14-2008 04:59 PM
dsfordguy Thanks for the reply. I will try gapping them to .045 and report back what happens. I will also search the fast idle cam and choke stuff. I would really like to get this thing up and running the way it should.

Thanks
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