Spitfire How does SPitfire accomplish PCV?

[Basil]

How does the Spitfire accomplish positive crank case ventillation? I have a 78 with a 79 motor I got from a salvage yard and rebuilt. But the only crank case ventillation I could find is the line from the rocker cover to the constant depression side of the carb.

But isn't there supposed to be some sort of crank case ventillation from the lower portion of the crank case? If so, where is it or how it it accomplished? I can't find any lines from the lower crank case that look like ventillation lines. (Like on the MGB for example).

Anyone know how or if crank case ventillation is done on the Spitfire?

Basil

 

[martx-5]

I'm not that familiar with the MGB, but most systems vent at the valve cover. I looked at the Moss site, and did see that the breather tube went to the lower part of the engine, but that's unusual. The Spit is venting from the valve cover. There doesn't need to be any more venting.

 

[Darwin]

the only PCV vent on the spit is the valve cover, with vacuum being pulled from the manifold and it appears there is venting to the carbon canister as well. The VB cat is kind of unclear as to how it is all routed.

 

[vagt6]

Although not specifically for a Spitfire, Paul Tegler's website features an in-depth study of crankcase ventilation.

Very interesting: https://teglerizer.com/triumphstuff/emissions/index.htm

I hope it's helpful. /ubbthreads/images/graemlins/yesnod.gif

 

[78Z]

the short answer is "not well"

 

[aeronca65t]

Only the valve cover of the 1500 Spit is vented..the crankcase fumes make their way up through the pushrod openings in the block and into the valve cover.
This is one of the reasons that 1500s tend to "push" a bit of oil out of the dipstick (eventually, I created a threaded dipstick with O-ring to prevent this).

 

[Basil]

[ QUOTE ]
Only the valve cover of the 1500 Spit is vented..the crankcase fumes make their way up through the pushrod openings in the block and into the valve cover.
This is one of the reasons that 1500s tend to "push" a bit of oil out of the dipstick (eventually, I created a threaded dipstick with O-ring to prevent this).

[/ QUOTE ]

My problem isn't that it is pushing oil out the dipstick, but rather it is pushing oil ( a fair amount) out the rear seal (at least I think it is coming from the rear seal). The frustrating thing is, I have twice replaced the rear seal, but it still leaks. I can only think of three possibilities:
1. Too much Crank Case pressure that is not being properly vented (but I'm not getting any dip stick leaks)
2. The rear seal is not sealing well dispite being new (maybe the crank is worn?)
3. The leak is coming from some other location that is not obvious when I had the motor out of the car and rebuilding it.

Basil

 

[aeronca65t]

My car did the same thing (leaked near the rear main seal) until I rigged up my racing PCV system. . You might think that this setup would suck oil from the valve cover, but it doesn't.
The thing to remember is that you can't just vent these engines (as you can with some engines), but you need to have a pretty good vacuum applied to the crankcase all the time. A simple "road draft" tube won't work on these engines (in my experience).
As a trail, you might try hooking a good size hose (about 1/2" ID) to the valve cover and route it into the throat of the carb (you'll have to leave the air filter off for this)...be sure the hose is as deep into the carb as you can get it (without fouling the thottle butterfly). This may create enough suction to keep the crankcase pressure low when running at speed (it won't make much difference at idle speed).

Also, I know you are familar with the little wooden blocks at the rear of the oil pan...I use a pretty liberal amount of RTV sealer when I put them in and I use a fair amount of RTV on the oil pan gasket too. Be sure the pan isn't bent from over-torquing.

By the way, my crank has a slight groove worn in it from the oil seal and it doesn't leak a drop once I got the vacuum system worked out.(and I hardly ever drive it below 5000 RPM).