Hey guys,

About 2 months ago I was fixing a rather big exhaust leak where the 2 pipes go to one, So after looking at the exhaust flange (the nuts were so rusted on we couldn't get them off) we had to remove the entire carby manifold setup etc. After doing that and replacing all the parts (gaskets etc etc) it was running really well for about a week or two. Then it started to only run when the choke was half or fully open. So, first, we tweaked the idle screws abit with no luck. Then we started looking into the hoses, after replacing all the important hoses with new ones it was still happening. Finally we found the problem by running a carby rebuild kit in it and it fixed the choke problem. but a new one arose. It's got a vacuum leak but we don't know where. We took both the manifolds back off and found the old new gasket was faulty and had a leak on the bottom. So after replacing it and making sure it's air tight it's still got the problem. Any ideas?

 

 

Cheers.

What car is it in? if its in a ke30, brake booster could have developed a crack or have a look at your PC valve,

 

cheers!

Yeah it's a ke30, I've checked the brake booster (holding thumb over vacuum inlet) and doesn't seem to make a difference. Checked the PC valve and nothing. I was spraying Carby Cleaner all around the possible leaks and found when I spray it at the base of the carby it runs well. So I'm pretty sure the leak is at the gasket where it bolts to the manifold just above the PCV hose inlet. Seems like this is notorious for these carbies. Time for a Weber setup I think ;)

strange, i don't even have a gasket there and i have no issues.

Have you got a photo of that area you could post?? please?

I simply have a big rubber block thing with a metal plate sticking out of it, which encompasses the manifold vacuum port and the PCV hose connection. My carby is bolted straight through that to the manifold, no gasket.

Speaking of which, what is this thing called? Thermal Spacer??

I think its plastic moulded around a metal plate.

Edited February 19, 20179 yr by rebuilder86

That's exactly what i've got. At the start it had a really bad leak between the carby and plastic plate thingy, put the gasket in and seemed to help a little. The mechanic said I shouldn't need a gasket there either. the plastic may have a scoring or something. I'll put some gasket goo sealant stuff on it and see how she goes

We used to a thin smear of gasket goo on both sides of that plate (or plates with the twins) to eliminate any small leaks

so the secret places ive found vacuum leaks are inside the carby!! which take air from within the normal airflow so you can't test for them.

1. hot idle compensator rubber valve under the little plate with 3 screws on the side of the carb (stuck open or simply leaking)

2. 2ND barrel butterfly valve

3. Power valve piston air bleed port due to worn power piston or walls

4. gasket between the bottom plate and main carby body leaking into the manifold area.

5. PCV valve itself, it may shake and appear corret based on the standard tetsing procedures, but i managed to only solve my biggest idling issue by creating a plastic seat inside my dissmantle-able PCV valve, which gives a near perfect seal under high vacuum idle conditions. The standard PCV valve does not. This is especially useful (required) if running a 3K carb on a bored out 3k block, or a 4K block.

 

And if you're really unlucky you will have what i had, where the intake valve guides and seals have been destroyed at the same time from use of a synthetic oil in this ʞ©$ɟing engine. This will be evident pretty soon with blue smoke out the exhaust. HOW IS THIS POSSIBLE YOU ASK?

Synthetic oil does 2 bad things for this engine,

1. looses pressure to the top of the engine dramatically, and

2. warps the valve stem seals.

those two things cause 2 severe issues,

1. no oil pressure at top end means hot as top end and also a lateral force applied to the valves by the rocker arms, du e to shit lubrication, which causes valve shafts to expand and damage the guides

the ability for synthetic oil to move more freely ( do not tell me it doesn't you are wrong) for a given viscosity compared to mineral oil, makes it loose pressure in the journals of stock engines. These engines have relatively loose bearing journals from factory.

2. synthetic oil will warp valve stem seals if they are allowed to be expanded lateraly from the above issue

Edited February 20, 20179 yr by rebuilder86

I don't think it's inside the carby, seems to be the plastic plate thingy. I'll have a look later and see what I can find

so the secret places ive found vacuum leaks are inside the carby!! which take air from within the normal airflow so you can't test for them.

1. hot idle compensator rubber valve under the little plate with 3 screws on the side of the carb (stuck open or simply leaking)

2. 2ND barrel butterfly valve

3. Power valve piston air bleed port due to worn power piston or walls

4. gasket between the bottom plate and main carby body leaking into the manifold area.

5. PCV valve itself, it may shake and appear corret based on the standard tetsing procedures, but i managed to only solve my biggest idling issue by creating a plastic seat inside my dissmantle-able PCV valve, which gives a near perfect seal under high vacuum idle conditions. The standard PCV valve does not. This is especially useful (required) if running a 3K carb on a bored out 3k block, or a 4K block.

 

And if you're really unlucky you will have what i had, where the intake valve guides and seals have been destroyed at the same time from use of a synthetic oil in this ʞ©$ɟing engine. This will be evident pretty soon with blue smoke out the exhaust. HOW IS THIS POSSIBLE YOU ASK?

Synthetic oil does 2 bad things for this engine,

1. looses pressure to the top of the engine dramatically, and

2. warps the valve stem seals.

those two things cause 2 severe issues,

1. no oil pressure at top end means hot as top end and also a lateral force applied to the valves by the rocker arms, du e to shit lubrication, which causes valve shafts to expand and damage the guides

the ability for synthetic oil to move more freely ( do not tell me it doesn't you are wrong) for a given viscosity compared to mineral oil, makes it loose pressure in the journals of stock engines. These engines have relatively loose bearing journals from factory.

2. synthetic oil will warp valve stem seals if they are allowed to be expanded lateraly from the above issue

 

Agreed!

well i hope so for your sake, coz its a KENT to take apart the carby and fix all those issues, essentially if u can't solve this problem from outside, just buy a cheap replacement 3k carby on ebay. China has them for like 100 bucks now! seriously.

Hahah yeah hope so. Thanks for the info!

So I put some gasket goo on the plate and still nothing, I can completely cover the air intake hole on the filter and runs without a single hiccup (revs quite high though) Getting so done with this lmao

what air intake hole on the filter?? you have a hole in your air filter??

super high flow air filter??

The stock air box I mean that hole haha, but yeah I dunno I'm so done