Another Crankcase breather thread

[Stagdad]

Seeing some posts on venting the crankcase got me thinking that i should understand what is going on with the original system so that when i swap over to efi i can better deal with the venting .I already have an idea of how i will do it but it may not work.I have therefore made a quick way of measuring the vacuum after reading that Chris had tested the vacuum of his system but not sure how he did this,it will be easy to swap from engine to engine and if nothing else will allow quick comparisons.Maybe if an engine has more blowby the vacuum will be less given the same carb set up so it may also be a useful test for the health of an engine.Anywho i'll start playing with it once this rain stops.Cheers Steve
IMG_2998.jpg

[jleyton]

Looks interesting Steve, I'll be interested to see your findings - although if you're unsheathed positive terminal moves much more than a gnat's whisker you may not have too much left to look at

Cheers

Julian

[Stagdad]

Good Point well made Julian, the gap is a bit bigger than appears but a pair of terminal covers just ordered.

Cheers Steve

[GDPR]

Steve - like the fitment but I don't think you'll get a vacuum high enough to move the gauge - I use a gas fitters manometer to check crankcase pressure, it is much more sensitive and will also show a positive pressure if you have it on the same display should you have blowby...

I use a mityvac conical adaptor into the dipstick tube as a tapping, which also eliminates air leaks from that seal when checking the true pressure...

If you end up with a manometer, do remember to put a clamp on the sensing tube and open very slowly just in case it should suck the water in

Russ

[Stagdad]

Excellent idea Russ and I have an LPG u gauge which is a lot longer so will be less chance of sucking water,and why didn't I think of using the dipstick tube .
cheers Steve

[GDPR]

Just trying to help with your research - been using the manometer to check shagged engines since I was 16... a long time ago....

[Stagdad]

Russ so whats a ball park figure of vacuum (mm of fluid moved in the manometer) for an idleing stag engine in good shape with stroms?I'm really quite keen to see how the different setups contrast.

Cheers Steve

[GDPR]

Hi Steve

Average reading at idle I've found using my kit is between 7 and 10 millibar or 3 - 4 inches of water.

I just tested mine, and filmed it for youtube, and it increases in a fairly linear fashion to 28mb at 5000rpm at light throttle - if it ever uploads from my phone I'll send you the link...

Incidentally, mine was 8 millibar at 750 in N

[Stagdad]

Thanks Russ ,look forward to seeing that.

[Stagdad]

Hi Russ ,did you video get uploaded in the end?
Cheers Steve

[GDPR]

Just emailed you a link...

[Stagdad]

Thanks Russ,could you PM it, cant see it in my inbox.
Cheers Steve

[GDPR]

Done

[Stagdad]

Thanks Russ,got it .will check mine soon.

Cheers Steve