MGB & GT Forum

Wonderful day! 90 degrees here, but not as hot on the golf course!

Here's the set up: 1980 MGB, 1800 low compression motor with 1972 dual SUs installed.

Basil Adams side plate, into a oil catch can (cheap EBay) with a breather filter on top.

Compression is 1- 140 psi; 2-4 is 135 psi. I'm getting substantial blow-by out of the breather on the catch can, and out of the oil filler on top of the valve cover. About 2 quarts over 135 miles!

Any ideas? Thanks. bh

Was it doing this before you put the side plate on?

You do not have any oil trap, which was in the original front tappet cover. It was the box filled with a type wire wool that caught the liquid oil droplets and only allowed the vapours to pass through. You need to put in line, before the catch can, some sort of oil trap as per original. I did this, a canister filled with stainless steel wool. The canister is made from plumbing pieces easily available from your local hardware store.

This will help to prevent the excessive oil blow by you are experiencing. This is of course assuming you did not have the blow by prior to installing Basil's one piece tappet cover.

BTW, the oil catch can at this point is probably redundant as I do not get any oil in it, but I installed it before thinking about the original set up with the oil trap. The hose goes from the catch can to the back of the carb filter plate so that there is a little bit of vacuum draw on the tappet vent. I too have Basil's one piece cover installed but I vent it from the rear



Edited 1 time(s). Last edit at 2015-07-29 02:30 PM by lewk.

Chris - put the dual SUs on at the same time as Basils side plate. No blow-by prior to that. I buggered up the original side plate.

Keith - I understand your post. Got it the first time I posted this issue, and tried to modify the oil can. My reason for reposting is that I am also getting blow by out of the valve cover, but that may be just a need for a new cap. I could not find anything like you have at Lowes or Home Depot. Maybe I'm looking in the wrong place? I may just get another sealed catch can and stuff steel wool in it, then send to a breather. Thoughts? Thanks for your patience. bh

The idea of a catch can filled with steel wool might work. If I remember correctly there might even be a catch can made like this. Do some looking on eBay.

Brian,
I have a homemade side plate and vented it to my carbs sans catch can or steel wool. I felt certain I would have an oil consumption problem, but so far no increase. Do your new SUs have the vents built into them or do you have your tappet cover to catch can connected to the intake manifold? If it's connected to the intake manifold you may have too much flow which would increase oil consumption and a restrictor would be a good idea. The normal restrictor is located on the valve cover and attaches to your carbon canister. You may also have a vented valve cover cap that's allowing too much air to flow.
Rut

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1960 Bugeye,1275, 5 speed
1970 MGB, Pale Primrose
1967 Triumph TR4a
1966 Triumph TR4a
When I went to school, they asked me what I wanted to be when I grew up. I wrote down 'happy'. They told me I didn't understand the assignment, and I told them they didn't understand life. John Lennon

That was going to be the next question; what style of SUs? This is the routing that I used on a pair of late SUs. This car used no oil and had a vented filler cap. If there was a way to incorporate the steel wool trap on the back side (internal) of the side plate, that would be unobtrusive. Early Sprite/Midgets had a can of sorts that came off of their side covers.

I had that too. It was a broken oil ring.

No steel wool is going to stop blow by. It may catch a little aerosol but that much oil is being pushed out of the engine by exhaust gasses or being sucked out of the engine by a vacuum source. Make sure there is no vacuum source anywhere n your vent plumbing. If you're absolutely sure there is no vacuum line plumbed into the catch tank or either vent line, a leakdown test is in order. I know compression looks good but exhaust gasses are getting into the sump. Another test: take the vent line from the valve cover and run it into a coke can. Take the vent line from the side cover and run it into another coke can. Do not use your catch can. See if either can catches oil. If both do (after some initial drainage), time to pull the head. If neither continuously pumps oil, check the plumbing to that catch can - you've got a vacuum source plumbed in. If only one of the two, call me for further diagnosis (this is a very remote possibility.) Basil 707.762.0974 basiladams@yahoo.com

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Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

Not trying to suggest that an oil trap will prevent blow by. Just saying that incorporating some kind of oil trap, as per originally designed, will help stop some liquid oil and allow the passage of vapours. I agree that if excessive oil blow by is occurring it is too much vacuum pressure or a ring job required.

Brian has some plumbing issues to sort. Basil presents a good troubleshoot and this should be done promptly. Pumping 2qts in 135 miles is excessive for sure.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

I had a head gasket leak from cyl 2 into one of the pushrod channels. The side cover was blowing like a steam locomotive. Blow by is usually rings, but I got lucky.

Let us know what you find out! I for one am really curious.

sorry to take so long to update with findings, but life got in the way, including a British car show on Saturday, and other issues.

As for Basil's suggestion, we only got oil coming out of the side plate in very little droplets, but enough to eventually make a mess. Nothing out of the valve cover line. Ideas?

We finally did a leak down test today, and here are the numbers:

1: 38%
2: 40%
3: 34%
4: 34%

I really appreciate everybody's input! I was even looking for ideas at the car show. We are going on a trip with British car owners, but I'll be able to see email, and will respond when I can. Any ideas will be addressed, and I'll respond more when I return. thanks. brian

Those are some very poor leak-down results. Did you determine if the leak was in the intake, exhaust or into the crankcase? Numbers that low would typically indicate the need for a complete rebuild and valve job.

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jeff@advanceddistributors.com