Crankcase breathers for a Sprite
Turbo Mini Forums

I've used the search button honest, but...

My e-bay Metro Turbo set-up is being levered onto my 1968 Sprite. It has the in line 1275 as standard.

At present it has the factory breather setup, a canister/seperator thingy on the timing chain cover that goes to a Y-splitter and then to each of the HS2 carbs. There's also some breathing going on via the vented rocker cover cap.

The snag I can see on the horizon is with regard to the lack of a proper rear crank seal. Motors of this age only have a scroll type groove, that "winds" oil back into the crankcase. Crankcase vacuum is reckoned to assist keeping the oil in the motor.

So my question for the panel is; 'Where do I feed the existing breather, and do I need to add more, say from the rocker box or the dizzy aperture?' (I have just built and tested the MegajoltLJ) Or do I need to add a rear main oil seal? If so which one, I've heard mixed reports about those from Peter May.

As a supllementary query, the whole manifold and turbo assembly strikes me as very heavy. Is it held on only by the head/manifold studs, or are there support brackets that I should 'win' from ebay?

Sorry for the essay first real post. Thanks for your help

Ta, Mark

have a search for Tadge44's build; he is running an inline set up and may be able to shed some light on your issues

I might save you some time here.

The "evacusump" (see the Vizard yellow bible) idea did not work for me and I have abandoned it - the parts are available if anyone else wants to try it.
I have breathers from the timing cover, the distributor hole (I have Megajolt)
and the rocker box to a catch tank, which was supposed to be evacuated from the evacusump system but is now open to atmosphere via a filter. That doesn,t work either.

The Metro turbo used a three way valve (the red valve) which was supposed to use manifold depression when available and shut off when boost came on. I did not think that worked either !

Like you, I have had mixed reports of the Peter May seal arrangement and Steve 1275, who runs a lot more boost than I on his drag race Midget also gave up on it. He might have some ideas, but the last I heard he does the same as I - mop up the oil underneath from time to time.I park the A35 on a piece of the curtain side material from a lorry which makes it easier to clean up.

I have a glimmer of hope to offer. On my next build, for the van, I am going to try something that I first heard of from Glyn Byrns in the US, who drag raced a Midget turbo.

Basically, he filled up the gap between the crank and the rear main cap (and the "horseshoe") with something like JB Weld and then very carefully cleaned it all up to leave minimal clearance for the scroll to work. This. combined with the biggest breathers you can fit, might reduce the oil loss, but, with a turbo you are always going to have some blow by into the crankcase (at least at the levels of boost that provide fun) and this is the real problem.

Please keep us posted on how you get on.

Yes the turbo assembly is heavy and no, I dont think anyone has had problems with the manifold studs giving way.

Thanks Tadge, Rob.
So its lots of breathers vented to atmosphere via a catch tank and filter. Possibly fettle the rear main carrier. Kitty litter for the driveway and no further waxoyl duties.
Mark

David covers all the points.The key is a tight rear main bearing clearance and a scroll/cap in good condition.Mine takes a beating and I renew the bearings every 2 years- the rear main is well worn in this time.

'Where does the engine go?'