One carb not drawing-what's up?

[jonalley]

Thanks for the input. I swapped out plugs on 1&2 plus wires with some spares I had and still no results. The draw does come up to match the other carbs on a throttle blip.
If you remember an old post I made I was frightened of cylinder wash in this new build but having the draw jump would suggest the two cylinders are o.k. wouldn't it. I'm trying to count out cylinder wash but will do a compression test to check.
I'm trying to get to the syncing stage but have the very low number draw on the front carb to adjust against. Should I try to bring the otherer three down to that number??
Swapping carbs around is another step. I was trying to not take my linkages apart. Thanks, jon

[dallas_]

Can you post a picture of your linkage setup?
Let's see how you are making the adjustments for your airflow.

[jonalley]

Well I think we found the problem. I have 160-180 pounds in cylinders 3-8 and 65 in 1&2. I say not good. O.k., so I'm grabbing at straws here but since this is a new build do you think those rings might finally seat or am I looking at tearing the whole thing apart. Anyone got a really good epoxy??? Jon

[zrayr]

Originally Posted by jonalley

"..........I'm trying to get to the syncing stage but have the very low number draw on the front carb to adjust against. Should I try to bring the others three down to that number??......."

reading on I see you have a compression issue, but for healthy engines it doesn't take much adjustment to bring up the vacuum readings. A quarter screw turn can be the difference between zero and "all balanced".

Z.

[Gaz64]

Originally Posted by jonalley

I'm trying to get to the syncing stage but have the very low number draw on the front carb to adjust against. Should I try to bring the other three down to that number?
Thanks, jon

Jon,

You should be able to raise or lower the airflow of any of the carbs independent of the other 3.

If you can do this with one of the other carbs and not with the "NO. 1" carb, then your 65 psi in the two cylinders is still your main problem.

[jonalley]

Just reporting back in. I realized that the compression tests were not done with WOT. Redoing those produced good numbers. From everyone's comments I also realized ( and correct me if I'm wrong) that a totally closed throttle plate is not acceptable- slightly open is in order and I moved the linkage adjustment to set that in place. I have had a measure of backfiring too and noticed that two of the carbs show a somewhat wet area at the gasket from the carb to the manifold. I think there is leaking. I am going to pull the carbs off and use some gasket compound on those intersections. I'll report back in as soon as I get a chance to do the work. Thanks for all your support. Jon

[Eljaro]

I would take the valve cover off and look a the valves and the rockers. If the leakdown test is ok but the compression is low you may have those valves not set right.
When you check compression you should have the carbs throttle plates wide open, otherwise you will not draw enough air into the cylinders.
You can also be having a bad seated intake gasket and the engine is drawing air through there.
You could also have you linkage not set right. Check that all carbs have the idle position set by the linkage and not by the individual stop on each carb.

[Eljaro]

I missed a few posts and see that the mismatch on the compression was effectively the not WOT position of the carbs.
If you have fuel around the base it is because the fuel dumped into the throats is not drawn into the cylinders because of the missing vacuum and stay on the throtle plates dripping down slowly and wetting the base gasket.

The manifold intake gaskets,especially the ones from felpro with the print-o-seal bead move when you tighten them down, and often slip out of place allowing air to be drawn from there. There might be no gasket now between cyl 1 and 2 and both cylinders may be drawing air from each others intake runner.