Weber 34ICH Runs better with Choke Partially on. Help on tuning it?

[kenscs]

I have a 1971 2.25 Petrol engine that, when I bought it was told was converted to Unleaded and compression raised to 8:1. Originally, it ran poorly (it sat in a garage for 10 years and the old fuel had created varnish in all sorts of parts). After trying a few times to get the original Zenith carb to run well with rebuild kits, I bought the Weber 34ICH carb from our hosts here and installed. It now idles like a purring kitten at 700 rpm and once warmed up, comes up to speed relatively fine. However, top end power is pretty poor trying to get up even the smallest hills over 35 or 40 mph. I was assuming this was just the nature of the 2.25 petrol engine and was researching a 200TDI swap, but low and behold, one day recently, I forgot to push the choke in, and I "relatively" zoomed up the local hill I had struggled with. I experimented, and the car definitely runs better and much stronger high end with the choke 75% closed. I checked the Vaccuum advance lines for air leaks, carb base for leaks, etc, but do not see any.

I see anidle adjustment, but I do not see a high speed adjustment on the 34ICH. Does anyone have any suggestions to help? I read some threads related to tuning the engine that suggest the factory timing specs are not advanced enough for current ethanol-mix fuel, but that doesnt seem to answer the air limiting creating more power.

[bugeye88]

I'm not a carb expert, but it sounds like you have either too small of main jets in the carb, Or The other thing I was thinking was clogged jet at the bottom of the float bowel. (which is a common thing with 34 ICH carbs) That clogged jet could still be the culprit even though it sounds like a new install in that there could be crud in the tank and fuel line from sitting so long before this install. Check the screen on the fuel pick up in the tank for crud blocking it. Also check that the line from the tank to the fuel pump and the line from the pump to the carb, are clear. Finally place a fuel filter between the fuel pump and the carb. I also run a low pressure electric pump between the mechanical pump and the carb, with a switch in the dashboard to turn this on and off.

Cheers,
Rob
68 88 Bug Eye 2a

[meatblanket]

In the 34ICH carb the main metering jet is found in the bottom of the float bowl. Remove it and inspect it. Assuming the existing jet is clean, then you might try running a richer jet.

EDIT: Yeah what he said!

[siii8873]

check for an air leak letting extra air into the inlet via any of a number of ways, vacuum lines, intake manifold gasket, carb gaskets, vacuum booster,,,... etc.

[SafeAirOne]

Not to be Captain Obvious, but if you are 'choking' off some intake air to make it run better, then it stands to reason that your fuel/air ratio is not correct. Either you have induction air leaking in from elsewhere or you are supplying too much fuel to the combustion air. The rest is just figuring out which one and how to correct it.

However, being a fan of the dead simple, ever-reliable diesel engine, I tend to agree with you that a 200Tdi is the BEST fix for this conundrum.

[kenscs]

I am making a little progress on this. Replaced fuel filter, tightened down carb, and advanced timing a bit. I still cannot seem to figure out how to "tune" the high end on the Weber. I see idle screw and idle mix, but if I am reading the weber service posts and Aloha Rover's rebuild page, I don't see a "high speed" adjustment screw. I do see a high speed jet where one might have to swap it out. Am I missing something here? I feel like I am.