Crank Pressure TR7

[Matt306]

Hoping someone may have a bright idea here.

 

I converted my TR7 to run on Fuel Injection this meant replacing the manifold new plenum and a throttle body. The old crank breather was router to the carbs, I have now routed it to before the butterfly on the throttle body, helpfully there is an inlet there for it. 

I have removed the fuel pump and blocked it off. The rest of the engine is pretty standard apart from the fuel delivery of course. 

Now the car like to lose as much of its oil as possible through the rocker cover spray it out.  Breather hose is clear so I cant understand why the pressure would force its way out of the cam cover gasket (its silicone btw) as opposed to taking the easier breather route.  I can blow through the rocker breather in to the cam cover so I don't think that's blocked.

Any ideas?

Cheers Matt

[Nick Jones]

Not familiar with the TR7 breather, but presumably it was routed to the atmospheric side of the carbs without any pcv? That being so, what you have replaced it with is pretty much like for like.

It is interesting though…. I had a similar issue a couple of weeks ago after swapping my tried and tested plenum manifold with ITBs.  The breather system lost its pcv and got routed to the airbox via a catch pot.  

First drive revealed that I was back to square one on the mapping ….. and it was blowing oil out of all sorts of places.  I thought it might be the loss of the pcv (Smiths flying saucer), though I ran it for years with a simple pipe to the air filter without problems before I fitted the Smiths thing.

Anyhow, after messing with firmware I now have ITB mode and have the mapping back to something like. Happily, if surprisingly, now the mapping is about there, it’s stopped blowing oil, even though I’ve not changed the breather at all…..

So check your mapping. Ignition timing especially I would think….

Nick

[RobPearce]

47 minutes ago, Nick Jones said:

Not familiar with the TR7 breather, but presumably it was routed to the atmospheric side of the carbs without any pcv?

I'd expect it to be the later default breather type, where it's routed to the CD chambers of the carbs, so not the same as atmosphere at all - more like what a PCV gives, in fact.

However, blowing lots of oil from gaskets isn't normal even without any depression on the breather. The mapping is worth looking at.

[Beans]

On a TR7, fitted with SU's, the cam cover breather's connect directly behind the throttle disc.
I can imagine there's a fair amount of negative pressure there when the engine is running.

With the original FI set up the cam cover breather connects first to a small breather box, from where it is split to the throttle body and an emissions canister (not much pictures on the 'net)

[Matt306]

Bit more investigation with a can of brake cleaner.  I took the cam cover off and filled the space behind the breather with brake cleaner, none was coming out of the breather.  This section appears to be covered by a plate and wire mesh underneath. After sever squirts and a soak some started coming out. So I imagine my original assessment of not being blocked may have been incorrect. 

That EFI build is a bit different to mine as I chose some more modern equivalents, plus I thought with the Brake master on a different side it would foul the factory plenum , even if i could get one. My set up doesnt use the cold start injector and a TPS with throttle body.