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MG Midget and Sprite Technical - Block breathing

Chaps,

Back in the garage over the weekend and not doing rear end work..

Engine is coming on nicely but I am not sure if I have gone too far..

You know on the front of the block there is a hole and a corrisponding hole in the front plate to allow oil to go into the timing cover?

Well, as I no longer have a timing cover, just a billet plate which has oil seals for the crank and cam I welded up the front plate hole and used a bit of gasket paper to cover the block hole..

Given that there will be a cover with oil seals covering the two sticky out bits and there is no provision for breathing I dont think its too much of an issue - I have emailed the guys who designed the conversion to see what their thought are but in the interim..

Breathing-wise I have a breather stuck on the old fuel pump location to let the block vent so that should cover off most of the issues I think...


Toby Anscombe

..and the 2nd photo showing the modified front plate


Toby Anscombe

..and finally the new timing cover; no breathing provided..




Toby Anscombe

Toby is the new ovoidish shaped plate going to block off the original pair of drain off holes in the front main bearing cap?

has it an oil seal built in?

I wonder whether there will be a potential draining out onto the rubber belts from that vicinity

I am sure that blocking off the cover opening is OK, as you say there isnt any need if there isnt a flow.

And have you added an oil seal at the back end? (I cannot remember, cos I'm getting old...)
Bill

Toby,

Are you the first person using this conversion on an in-line engine?

Read page 25 ....

I'd have thought you'd be more than Ok with the crankcase breather on the side of the block. If it were my engine I'd still want a breather of some sort from the cam cover (easy enough to sort).

Daniel
Daniel Thirteen-Twelve

No, the two holes next to the crank are still there, presumably to let any excess drain back, as per original design.

The ovalish plate has oil seals for the cam and crank (or should that be oil pump and crank?)

I decided not to go for a rear main seal; given that it was line bored to the crank and someone mentioned in a book somewhere that the RMS is not really recommended for high revving engines I thought I would give it a miss.

I wish that I could make it next weekend to talk to Chris and Peter but I shall be in France for a friend of mines birthday..if you go can you enquire on my behalf?

While you are here, given that I will be running 3bar fuel lines do jubilee clips really work to seal?
Toby Anscombe

Daniel - there is not enough meat in the new timing cover to fit one...

I have a billet bit of alloy to block off the dizzy hole so might use that as additional venting...
Toby Anscombe

Toby,
i read this interest as i have a cam belt set up to fit next time the engines out & am concerned with venting past the rubber belt.
Brad
Brad (Sprite IV 1380)

Brad,

I fitted a cam belt conversion years ago when I built a 1420cc and it had no breather. Never had any problems, the engine was breathing out of the fuel pump port and the rocker cover via 1" breathers into a catch tank. The fuel pump port had an oil separator fitted.
David Billington

I'd have thought just the block breather (was fuel pump aperture) would suffice + a top end breather from the cam cover. I wouldn't mind seeing a photo of the cam cover again. Since I have a friendly local aluminum welder if it were me doing the conversion I'd drill and they'd weld a threaded weld bung (£5+£5)on the top and then run a 90 degree fitting off that with a length of hose on the end. However, if the metal is thick enough it's possible to drill and tap for a male/male fitting which is what I've always done on my engine's rocker covers. Of course it takes a while to drill the hole when your drill's chuck isn't big enough and you have to work the bit by hand (without gloves too!). You could also use this breather to double up for oil filling but I think you should fit a Monza cap to do the job properly (I know, more expense).

Jubilee clips simply hold the hose against the barb of the fitting or flange.

I think 3 BAR is a lot for a barb and a hose clip but if the barb is a really good one (sharp) then you might get away with it. However, for the cost of a proper fitting even if used with crimped fittings I wouldn't risk it, well not for long anyway.
Daniel Thirteen-Twelve

Barbs - see, thats what I thought! Low Pressure from tank to pump is fine but after the pump I want to have aeroquip fittings; the one downside is the existing fuel rail has barbs for the inlet and outlet...I know that my welding is not up to fuel+pressure...

I have already planned on a 1" combined oil return/Breather from the head coming back to the box on the fuel pump - 2 more additional returns from the cam cover and a single K&N filter to vent.

For a regular A Series what Daniel says; rocker (avoiding the posts!) and the fuel pump venting to a catch tank, if you want one then a return to the sump...

As mentioned, the new cover sits almost flush so no chance to add in a vent aperture..

It'll be fine!


Toby Anscombe

that threw me til I got over my wrongwayupitis
----------------------------

purty innit

The Sayab has jubbly clips on the fuel rail

but I don't trust them even after all this time


I'd rather see proper fixtures and fittings for fuel fittings
Bill

It's about time you swept that blooming floor Toby

and mopped up some of those multi-spillages

he he

I guess that if someone wrote a book they'd remind the "dear reader" that the scroll bearing works by keeping the inside pressure lower than ambient wouldn't they?

Then they'd remind him not to vent freely to atmosphere willynilly so there would be no tendency for oil to push out of the nearest weak spot it can find... maybe a scroll bearing under pressure...

Thus no doubt by now you have decided how you are going to keep the internal "low" via a source of lower atmospheric pressure induced from the inducing system

So

How are you going to manage the crankcase pressure with the throttle bodies in situ?

I meant to ask this before, or have I asked and forgotten the answer?

I forget

If the fuel rail is designed for the hose clips I wouldnt waste time having extra work done there. Just get the Aeroquip fittings where they will do the most good

I'm fairly sure that 3BAR is ok on hose clips but be ready to "maintain" the hoses them selves, the hose on Lara to her HIF is about 8 years old-ish

I have just had to replace a length of it because of longitudinal cracks and splits which have been failing to hold fuel pressure in service.

worth a thought I hope
Bill

Morrosso evacusump system works for me, it's in Vizzards bible. Think it may be discontinued now though, buts its easy enough to make your own.
Brad (Sprite IV 1380)

cheers Brad

does that work whilst using power I wonder or is it "free" like the intake vacuum?

I'd best get out my copy of the good ol' Viz to have a look

When the PMOS eventually does give up I might like to give it a go
Bill

Bill, you are so sexist, the 'reader' might be a her.

My experience is that a properly vented to atmosphere engine doesn't shove oil past the rear scroll or anywhere else.

Are you an advocate of fitting in-line non return valves to all the breather hoses that would feed into a catch tank?
Daniel Thirteen-Twelve

If my reader "as might be a she" will only read works of detectivey fiction I may have erred, sadly I confess.

I am not a devotee of any especial method but after reading of various attempts to stop the leaks in here and with an accceptance that my Peter May may be reaching an end to its first life after a few years of 6k or more operation I am embarking on an evangelical journey. Maybe more in hope than expectation, but so far nowt seems to have worked perfectly in service for all the protagonists

I even considered adapting the Rivergate method of applying the new seal without the posh PM carrier, just adding RTV to the backplate to glue the seal in place.

maybe machining a carrier plate instead of the bracketry

seemed to work on Gary's Nissan box adapter it took me ages to split that from the backplate adapter


so to sum up

I'm jiggered if I know!

cue the "fit a K series" cries

Bill

This thread was discussed between 26/11/2008 and 27/11/2008

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