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1500 Crankcase Ventilation

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jcatnite

jcatnite

Jedi Knight
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Has anyone made any modifications to their crankcase ventilation system on a 1500 Midget? My 76 had the air pump and rail removed and the holes plugged by the PO. A while back I thought that I had a problem with the charcoal canister and bypassed it by routing the hose from the top of the valve cover straight to the connection on the right side of the carburetor. I think I'm burning a great deal more oil now and am wondering if it isn't sucking the oil straight out of the valve cover. Just wondering what other people had done in this situation.
Thanks,
JC
 
I did the same thing to my 1980 1500 a few years ago when I installed a Weber downdraft. Ran the valve cover vent to the bottom of the K&N filter. I have an electric fuel pump in the "boot" and replaced the mechanical pump w/ a cover plate. Installed a vent in this plate and routed the hose to a catch tank. Seems to work well and stopped blowing oil out the dipstick tube.
 
I tried several cures on my racer. Venting out of the valve cover to a 3' hose resulted in too much crankcase pressure (and it started pushing oil out of the rear seal).
Then I ran it between the carb and air filter (via a spacer plate made from PVC) and now it seems to have about the right amount of suction to prevent any oil weepage from the engine. I added a catch can mostly for race rules. There is no other vents to the crankcase.
Note: My car has an electric fuel pump so I also tried using a vented fuel pump blanking plate but that was big flop.
carb-vent-1500.jpg
 
Nial, I may try your solution this weekend. I'm running the stock ZS and air filter setup right now. I too have an electric fuel pump and had considered trying something on that blanking plate. Guess, I'll utilize your testing and not put myself through that. The car didn't smoke at all before I "improved" it but now it looks like a mosquito fogger when I romp on it...though I don't "romp" on it very much...lol.
Thanks,
JC
 
Well, I decided to put it back like it was last night. I had broken the "tee" so I fashioned one out of things I had laying around the garage. It seemed to bump the idle up a bit (only maybe 150rpm) but it didn't smoke this morning. I know I was sucking too hard on the valve cover since when I pulled the hose off oil dripped out of it...lol. Anyway, may just try this setup for a while.
JC
 
Now that I have reincorporated the charcoal canister into my crankcase vent line I think I'm pushing oil out the dipstick. I guess the addition of that small amount of air that the extra line lets in is causing too much pressure in the line. On the other hand I'm not sucking a quart of oil a week through the vent line either. I wanted to ask a question, with the valve cover vent line removed and the engine running, how much pressure should I get out of the valve cover cap if I remove it. It seems to me that there is more than should be there, (worn engine) and if I'm playing around with this vent system should I be shooting for an almost neutral condition at the valve cover cap...playing with different size restrictions and possibly different conections. I'm not sure this post will make sense to anyone but here it goes...
JC
 
Yeah, I was going to play around with different orfices in the hose from the valve cover to the carb, but the regular hose (with no restricting orfice) worked out fine for me. With the engine running, my engine generates a moderate amount of pressure at the valve-cover "exhaust"....but no real smoke. Maybe just a bit of oil fumes. My engine is rebuilt on a regular basis, but it is also run much harder than most 1500s.
One thought: be sure the hose comes out of the valve cover and goes "up" as high as possible (against the bonnet). This may keep liquid oil from migrating to the carb (because it will have to go uphill).
Whatever you do, you need to have a slight suction to the valve cover so that the crankcase is under a slight vacuum, but somehow keep from sucking oil.
It's interesting to note that you are pushing a bit of oil from the dipstick. That's pretty common. Probably because the engine is pretty long stoke. Mine was doing that a little when I autocrossed it, but it became much worse when I began racing regularly. Eventually, I threaded the dipstick hole. Now, I run the car with a bolt threaded (and safety wired) into the dipstick hole. I remove the bolt (and use the normal dipstick) when I need to check the oil.
I enjoy working on my car, but frankly, I think the Triumph/BL 1500 engine is one of the crappiest engines ever put in a sports car.
The upside is that it keeps me busy and out of trouble. /ubbthreads/images/graemlins/tongue.gif
 
I agree that the engine does have its peculiarities. This is my first experience with anything that isn't an American V8 so I'm learning as I go. My engine is in need of a rebuild but when I did a leakdown test there wasn't as much coming from the valve cover as I expected and only 1 cylinder has a burned valve so I thought I might get another season out of it if I treated it right. I'm afraid the little soldier is wore out and I think I'm getting more blowby than I would like to admit. Still, I will tinker with the ventilation hoses till I find the balance I need till I get a chance to freshen it up a bit. Thrust washers and rod bearings this weekend...another bandaid...lol
JC
 
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