Hot Rods !!!Please Help Me With My Stumbly 283!!!

I have searched and found a lot of info and tried most of the fixes but my little 283 still has a stumble at low speed cruising. I try to just drive fast but I can't always .

Here's the skinny- Engine is a swap meet 283. It is stock as far as I know. I have not opened it up. I am running 3 2G's progressively on an Edelbrock intake. The end carbs are the real deal, not just doctored-up center carbs.

The engine idles well ( a little "poppy" out of the exhaust at times ) and wide open throttle is good. It runs down the highway at 85mph (allegedly) with no problem. My problem is that is wants to hesitate at initial throttle tip -in. I've screwed with the timing to no avail. I got a new set of jets from one of the carb gurus here on the HAMB. I also got a new re-curved dizzy from Bubba's. Still the same issue.

I tried a different carb that I had. Still the same issue.

I tried a different coil. Still has the same issue.

So, at this point, I have removed and blocked off the two end carbs. I put the first center carb back on after I went through it again and opened up the air bleed tubes a couple thou (as per something I read here.)

Still has the same issue!

I don't what what the timing is set at. I've been setting it with a vacuum gauge. It reads about 18-20 inches.

I know the engine is worn. All of mine are, but they don't have this issue. I have not done a compression check. I may do that tonight.

Oh, the exhaust is 2 into 1 Fentons to 2" straight pipes with motorcycle baffles installed.

I am sure there is something I am forgetting.

Help...


Here's a video

 

Does the dizzy have vacuum advance, and is it working?

 

Yessir. New (reworked) dizzy from GMC Bubba. It does it with and without the vac connected.

 

Have you checked for accelerator pump function? I'm not familiar with those carbs, but I assume it has one.

 

Accelerator pump works on both carbs that I tried. I should say I changed the dizzy out because I was running the '55 style Delco. The new one is the '57 style that Bubba swears by.

 

Are you sure the other carb you tried didn't have the same problem? 2GC carbs had accel pump issues, and usually have two pump balls depending upon which one you have and whether it has a rubber cup or leather cup. Does it have a number tag so you could get a rebuild kit? Sounds like your timing is fairly close, according to the vacuum gauge.

 

cactus, setting the timing to the maximun reading on the vacuum gauge will generally leave you too far advanced, just slightly. Back off or retard the timing 2-4 degrees. Unless Bubba told you otherwise, are you hooked to full manifold vacuum? Are you setting your mixture screws using the vacuum gauge? Also you want to check the center carb baseplate for play within the shaft and baseplate. TR

 

Dbljay, do you mean this ball? What kind of problems?



It came out of here...


Is there suppose to be one in here as well?





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I am backing it off a bit. I have tried advanced and retarded and can only get the flat spot to move around if that makes sense. I haven't had much noticeable change with the mixing screws. Much different that the EBU carbs I'm used to working with on my old 239 Y.


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Why don't you know ?
If you can afford a triple carb intake, you can afford a timing light.

Quit screwing around.

Set the initial timing correctly, with a light.
Check the Dwell, with a meter.
Then check the total timing, and vacuum advance.

 

I had it set as per the '55-'57 chevy manual I have is what I should have said, sorry . I have since been screwing with the full sweep trying to see if it made any appreciable difference.

Oh, and Bubba set the dwell. I have the tools, just lack the knowledge!

 

I forgot, the vac source for the dizzy is off the carb as original.

 

OK...
Changed the carb, same problem
changed the distributor (dizzy in Australia) same problem
change timing, problem moves to different RPM.
Set the timing mark to 0 (zero)
Pull off the distributor cap.
Rotate the engine until the rotor starts moving.
Mark the balancer (chalk)
back and forth until you just see the rotor move in each direction.
(Woops, a 265 does not have a balancer bolt, you may have to use the water pump)
If it is more than 10 degrees (estimate it from the degree marks) your
timing chain may be worn and causing the timing to change too much when accelerating creating a stumble.

 

The stuttering I heard doesn't sound like timing or a carb issue. If the timing were off it would either ping or bogg, not stutter....it would be a smooth stutter, not an erratic one. If the carb had an issue it would bogg, starve or flood. I personally think it's a spark issue. Are your wires new? Do any of them have nicks that are leaving the wire core exposed to arcing? Do you have a hot/power lead laying across one of them, or even too close to one of them? Are your plugs new? Could one be fouled? What about your coil? Is it possible that your hot lead to the coil is loose? Maybe your ground is loose and the coil is arcing out? Maybe the coil is just bad. This is too intermittent to be a carb or dizzy...IMO.

 

I will try this. Thanks.

Two new coils. Plug wires are new. Spark plugs have a few miles on them. I have only driven the truck a handful of time since getting it roadworthy in April. I have been cleaning the plugs in between tests. I do have another set I could throw in it. All connections, wire, everything is brand new.

I ran it in the dark last night looking for any arcing. I also sprayed carb cleaner around carb base/s , throttle shafts, intake bolts, etc.

I am stumped (easily accomplished, ha!) but tried all the stuff I could find before starting my plea thread.

 

Set the total timing. I cursed and damned and was ready to torch my truck because it ran like shit for about a year until I finally set the total timing. Even though I had set the initial, the new distributor must have been setup differently because the total timing was 10 degrees retarded. Runs strong, now.

 

Oh the Ironey of this thread..... I also have a 283 that runs good but has a stumble. I got to the point of doing a compression check, and all my cylinders have 120 except the #1 which has 0.... the big goose egg.

Check your compression! and I hope you have better luck!

 

Have you tried changing the accelerator pump timing? You can usually change this by bending the linkage a small amount. In your case it sounds like the pump shot is either not enough or coming in at the wrong time. Both can be changed by the linkage.

 

Trying all this stuff guys. Thank you.
Timing chain seems good, about 5 deg backlash.

 

Hard to diagnose over the internet, but I think I agree with Buzznut, sounds more like ignition breakdown to me than fuel.

 

when I was running 2GC's on everything I owned, I got real good getting them to work good.

The first step was always to shorten the power valve spring. cutting off 3 coils is what I remember doing. This helps the tip in stumble by opening the power valve sooner. And doesn't affect the idle or cruise or WOT operation.

And it's been awhile but I'm sure there should be a ball in the accel pump well. it's the inlet check valve.

 

This comes apart?




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No, the part in the cover that pushes on that has a long spring around it. snip off 3 coils.

 

Ha! Ok sorry. Pretty, but dumb. I think you're right about the ball as well. There appears to be a place for it to rest ( like a slot) at the bottom of the cavity. I know there was not one in there when I first rebuilt the carb.

I'm not gonna be able to sleep tonight...

 

all someone needed to do is turn the carb over one time with the lid off and the ball is gone. I done it too.

 

When you get a carb kit there will be two balls for the accel pump, a large and small...the small one goes in the inlet opening under the pump and the bigger one under the "T" and spring (outlet). Put that ball in there first before you cut the spring for the power valve. You can adjust the length or timing of the pump shot with the rod on the outside of the carb, set it to factory spec to start with. Hope that helps!

 

Thanks DJ52. The ball is back in. Still trying to get stuff back together to try it out. What is a good baseline start for the mix screws? Back 'em out 2 turns?

 

Two turns wouldn't be bad...turn them in slowly until you just start to get a rough idle, then back out 1/2 to a full turn, as long as the idle stays smooth. Should be good to go.

 

Had the same issue with a 327 years ago it turns out the cam was going flat..

 

X2 (in a 350)