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Weber Question?

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jcatnite

jcatnite

Jedi Knight
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Hello everyone. Sorry it's been a while since I last posted. I hope this finds everyone well. I do have a question though. I've been running a DGEV in my 76 1500 Midget for a while now. I thought I was pretty happy. Just bought a recurved 45D from Jeff with a pertronix in it. As I was installing it, I noticed #1 and #4 plugs were pretty and white while #2 and #3 were black and sooty? Seems like the center cylinders are running rich. Anyone have any ideas on this? I was baffled by the whole thing.
Thanks,
JC
 
Been thinking about this a little and thought I would toss these two suggestions to see what you guys might think.
1. Manifold leak on the two outer runners of the manifold? I'll check tonight when I get home.
2. Something hinky going on with the idle circuit and maybe I'm riding the idle screw too much, slightly uncovering the primary circuit?

Two guesses that could be way off. But when I figure it out I'll share. There are a lot of 1500's on the road with webers instead of Strombergs these days.
JC
 
My car has this problem to a lesser degree with a stock manifold and carb (sort of). I will be watching this thread with interest. In my case, I am pretty sure it is not a manifold gasket as I have a box of them and change them out every time I remove the manifold (which is a lot).

I had always chalked it up to insanely poor manifold design. But you are not running a stock manifold... right?
 
Hello JC,

I find it hard to believe that either end of the manifold is leaking, and affecting cylinders 1 and 4.

What are the compression figures like?

The other factor would be manifold design?

Alec
 
I didn't check the compression when I was swapping the plugs out. I was kind of on a tight time table. I plan to do a leakdown test this weekend to make sure there isn't something going on with the rings or the valves. The engine has around 3.5k on it since the rebuild. It is strong(relative to before the rebuild). As a side note, I did swap the plug wires between 3 and 4 to make sure that it wasn't a plug wire problem. As unlikely as that might be...
JC
 
Just as an update to this thread for future reference...
No vacuum leaks on either #1 or #4 at the intake manifold. That seemed like a long shot to me anyway. Those were the only two that I felt good about when I put the intake on...lol.
I pulled the plugs today after about 100 miles of driving. #3 seemed clean and crisp on the electrode but there was evidence of soot down inside the plug cabity while #4 seemed a bit dingy on the electrode with evidence of less soot down in the cavity..
I don't know for sure. I'm waiting on my fuel pressure regulator to get here. Turns out my pump is pushing 4 psi of fuel pressure and that is right at the top of the band for DGV's. If I find more, I'll post.
JC
 
On my DGV 2.5 PSI seems to work the best On a nother note.
It semms to be very sensitive to float level. I ran mine as spec. but ran it to the same issue as yours. I found that adjust loat height just a little less than spec. and it works great.
Mine is setup on a Pierce manifold. Dont expect it to run well until its warmed up these manifolds are so long it seems to take forever to warmup.
I'm in the process of trying some things to deal with the smooth as a mirrior welded on plate directly under the carb.
why perice choose to do this is a mystery to me. it has to be making a puddle.Plan is to rough it up. disturb flow across it.
 
Thanks for the input. I'll check into the float level as well. The area under the carb on the cannon manifold is corrugated. I guess that is to break things up a bit. I was wondering about smoothing that out a bit but it doesn't look like casting flash. It is an obvious engineering design.
JC
 
Thanks for the link the grooves in the picture are cut at an unexpected direction. I would have that that that they would have followed the dirction of flow... at the least chevrons and been a lot smaller in height Hmm More info will need to be gathered.
 
I still have the rough "and I mean rough" idle till the car is warm. After that she is pretty stable. My fuel regulator will be here Monday. I'll try lowering the float height a couple of mm then as well.
Thanks for the input.
JC
 
Bumping an old thread with recent update. I measured the fuel pressure and it was right at 4psi. The weber documentation that came with the carb recommended 2.5 to 3psi. I finally got the holley fuel regulator installed and set the pressure to 2.5. The idle smoothed out significantly. Before it would idle great for a while then kind of rough out and drop a hundred rpm or so. I'm thinking the float bowl was overflowing a bit. Hopefully this helps the rich/lean issue with the intake as well since an overflowing float would be atomizing through the mixture screw. Now if the tapered roller bearings come in I can enjoy this 70 degree weather...argghh.
JC
 
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