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Post by clifford on Aug 31, 2023 10:23:04 GMT
After so much work on my 998 A+ auto, I finally got around to trying to get it running nicely. Couldn't get it to idle. Checked and double checked timing and carb settings but it needed choke to run at all, but nowhere near idle. After much trial and error I found that it only seems happy if I pull the breather pipe off the carb and plug the port. This port has a 1/4" hole directly into the carb on the manifold side. It's simply sucking too much air in when the throttle is closed.  In the absence of a proper PCV valve, I believe BMC opted for the cheaper solution of a restrictor in this port, part number 12G3436. Of course, this part is no longer available so what are my options? It appears the restrictor has something like a 1/8" hole in it so would be easy enough to make, but after asking on other mini forums, many people don't have one fitted. Anyone got any any thoughts or knowledge in this area? |
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Post by jockduck on Aug 31, 2023 11:10:55 GMT
I guess it depends on the year of the engine, BMC/Leyland used a number of different engine breather arrangments, my 1968 mini has a pcv valve the same as used on the cooper S, MG B, around thing about 4" in diameter. the system sucks from one of the tappet covers through the pcv and into the inlet manifold, works fine, I did have a manual Mini which had the breather hose feed into the carburetor damper valve, did not work well I re-arranged it into the carb inlet elbow.
Jock
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Post by 6886auto on Sept 1, 2023 13:09:23 GMT
Does the butterfly have any holes in it and does it close properly. If the butterfly is closed I don't think that port should have much of an effect.
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Post by clifford on Sept 1, 2023 15:57:16 GMT
I guess it depends on the year of the engine, BMC/Leyland used a number of different engine breather arrangments, my 1968 mini has a pcv valve the same as used on the cooper S, MG B, around thing about 4" in diameter. the system sucks from one of the tappet covers through the pcv and into the inlet manifold, works fine, I did have a manual Mini which had the breather hose feed into the carburetor damper valve, did not work well I re-arranged it into the carb inlet elbow. Jock First going to try a new filler cap and breather hose, could well be too much air getting in that way. Next I shall try a few different sized restrictors and maybe an in-line PCV valve just to see what the different effects are. Failing that I shall feed it into the air filter, which is how nearly every other car I've had deals with it. |
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Post by clifford on Sept 2, 2023 21:55:06 GMT
Does the butterfly have any holes in it and does it close properly. If the butterfly is closed I don't think that port should have much of an effect. The port is 'downstream' of the throttle, between butterfly and manifold, so the port has maximum vacuum when butterfly is closed. I'm getting upwards of 15"Hg! Also, anything entering here is sucked straight into the engine but wont be drawing any fuel, thus significantly weakening the mixture. PLEASE IGNORE THIS POST, IT'S ABSOLUTE RUBBISH ! DON'T KNOW WHAT I'M TALKING ABOUT! GOING TO SLEEP ON THIS AND START ALL OVER TOMORROW. |
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Post by 6886auto on Sept 2, 2023 22:07:28 GMT
With the oil filler cap is the mesh still in place inside it. I have had them fall apart before, maybe yours is like that.
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Post by clifford on Sept 2, 2023 22:18:04 GMT
With the oil filler cap is the mesh still in place inside it. I have had them fall apart before, maybe yours is like that. Just been out to check by torchlight. Seem's I've been talking total nonsense! Need to start from scratch and fully take on board what's really going on here. |
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