Michael-carb issue-I think

[RobG]

Ok, I've attached a couple of photos of the throttle shaft and bracket off of the carb you sent and also off of my old carb. As you can see there is an extension of some type on my old throttle body, it looks factory. I have a problem with the new carb not returning to idle and it looks like it is trying to come up and go past center which the linkage won't let it do. Should I just swap throttle bodies on the carbs? The old shaft with the extension has about .001 to .002 wear on it. Is this an issue. I'm still having trouble getting the engine to run right, it still bucks and pops in third gear and just doesn't feel right. I've disconnected the pcv as suggested but haven't had a chance to run it yet, probably this weekend. Any more ideas would be helpful.

Thanks
rob

 

[Michael Mayben]

The part added to the throttle lever on your factory carb is "not" original. That is something that's been added in the past.

The carb I sent you is original. In fact, one of the nicest carbs I've had in some years. But it's certainly something I can now share with others when I have 'em also.

If you think the carb needs that throttle body with the extra lever, then install it. But for a carb with a standard throttle lever and all oem systems are a go, then the one I sent you is correct.

 

[RobertC]

A couple observations...

I do not know what the rubber hose in the first pic is for, but it looks like it is interfering with the action of the throttle.

I would route it in a way so that it does not go by the throttle linkage - around the other side of the carb?.

Do not know what the "wire" is for -- hand throttle?

Second, I would disconnect the accelerator linkage from the throttle butterfly.

Rotate the throttle butterfly thru fully closed / fully open -- to get an idea of the range of operation.

Reattach the linkage -- have someone get in the vehicle and press the pedal -- to the floor / limit.

I bet there is not the same range of operation.

I would guess you have a po installed accelerator linkage and that is why some po braised the extension to the other throttle linkage.

Have not followed this thread that much, but

have you checked the fuel pressure of your fuel pump?

And, checked / replaced the fuel lines -- wear, pinched hose, pinholes?

 

[RobG]

Robert, I had a lot disconnected when I took the photos. The hose is a vacuum hose, I just had it shoved out of the way for the photo. The cable is the manual choke cable, once again disconnected. I probably do have a problem with the linkage, I'll work on it some this weekend. My big problem is that I have no power in third gear, will hardly go up a hill and pops and bucks when driving. Timing is right, this is the third carb, it's one of michael's so I know it's right. When I work on it this weekend I've got the pcv and wiper vacuum disconnected to see what the result of that is. It's really driving me crazy. The engine is rebuilt, I know it's right. It's got to be something small that I have missed.

Rob

 

[RobertC]

Hmmm,

did you do what Robert kenney suggested in his post(s) in your 1904 air filter / cast iron intake -

from post #21

"the intermittent bouncing vacuum reading to me indicates a sticky valve. Make sure the fuel is fresh and clean. Even the remnants of old fuel and varnish can exasturbate (abc?) the valve sticking issue. Even if you have verified that you have a good valve train oiling condition"

who did the valve job? (assuming one was done) were new guides installed?

As far as "popping" going up a hill -- might you be lugging the engine? 3rd gear = 3 speed in your 800? Imo IH engines do not really like to run below 2000 rpm. So, if you are pulling a "steep" hill at 20 mph in high gear, you might get the "reaction" you describe... But, so would a sticking valve, I assume.

But, with a bouncing needle (vacuum gauge), you cannot rule out the engine as a source of your problem...

 

[Robert Kenney]

Rob,
I'm catching up on your issues. Here is what I understand or think I understand.

1) carb rebuilt by mayben.
2) engine rebuilt.
3) hei ignition.
4) bouncing vacuum needle while at idle.
5) engine runs well in 1-2 but in 3rd it pops out of the carb and bucks around
6) you have an intermittent tick/tap at idle.

Humor me and tell me if I have it right/wrong then I will give you my thoughts on your deal.

 

[RobertC]

Re accelerator linkage

I saw your carb pictures in a previous thread...

The rod from the pivot to the carb is bent...

I checked Robert kenney's pictures of his 80 (I know not a 800.)and the rod is straight.

I assume the rod should be straight -- do not know if yours is original and bent or someone replaced it with a longer rod and bent it to fit.

 

[RobG]

Robert and Robert, you are right on everything except the noise at idle. It's a steady and fairly loud valve noise, like a lifter, it's got all new lifters but May still be a problem. As far as the bent accelerator rod, we bent it trying to get the carb to idle down. It should be straight.

Rob

 

[Robert Kenney]

In that case I don't believe your problem is carburetor related.

Was the hei system new? I assume it is a true GM coil in cap hei like a d.u.I..

You say valve noise like only one valve or many ticking?

 

[RobG]

It is a brand new dui distributor and the engine starts in no time at all. I think I have two seperate problems, one with the engine performance and the other is valve related. I'm planning on working on it this weekend. I have the pcv disconnected along with the wipers to see if that makes a difference.

Rob

 

[RobG]

Just got back from a test drive, did ok till it got up to operating temp then started bucking and popping again. I checked the vacuum and it's all over the map! The pcv and wipers are disconnected. I'll check for vacuum leaks in the morning and see where the timing is. I'm beginning to think I May have a sticking valve since it runs ok when cold.

Rob

 

[RobG]

I'm also going to check hot and cold compression in the morning. I'm really thinking I have a valve problem.

Rob

 

[Robert Kenney]

I'm also going to check hot and cold compression in the morning. I'm really thinking I have a valve problem.

Rob

That is where I was going. Sounds like a textbook intake valve sticking issue. See if they installed full stem seals.
I would go through the full lube verification routine. If the rocker assembly is properly oiling I suspect bad fuel sticking the intake valves.

 

[RobG]

Ok, we pulled the head today and you can see what I have. It looks to me like #1 cylinder has some oil issues with it getting past the valves. The rocker assembly oils fine. I didn't see a blown head gasket and the spark plugs also show some fouling on the #1 and 2 plugs even though #2 combustion chamber looks ok to me. I checked compression and the range was 135 to 150 with #1 being the highest. Vacuum was still all over the map. It's going back to the shop tomorrow to see what they can find.

Rob

 

[Michael Mayben]

I'd pull the entire rocker assembly down to the last component and look carefully at every "wear point" on each rocker arm inner circle and the corresponding wear point on the rocker shaft.

This could have been easily done with the engine running on a "half" valve cover to determine what is causing the #1 cylinder to go away when fully up to temp.

 

[RobG]

Will do michael, nothing is going unchecked when I put it back together this time. It's a new rocker assembly with boat type rockers, the shaft is supposed to be new but I'll check it. I have run the engine with the valve cover off and the oiling is good. I should know tomorrow what they find in the head.

Rob