venting my 1275

Post by **peeweethepinstriper** » Sun Oct 04, 2009 8:07 pm

I recently aquired a Minor with a Frogeye 1275 engine in it.. It was done years ago and only has ventilation on the top of the valve cover (rocker box?) what additional venting can be done to the engine to help stop the oil leakage? thank in advance

Post by **mike.perry** » Sun Oct 04, 2009 8:23 pm

Haven't we seen this engine before recently? It was identified as a 1275, not the original 948 Frogeye engine.
Can anyone find the original thread?

Post by **bmcecosse** » Sun Oct 04, 2009 8:28 pm

Should also have a vent on the timing case cover.
http://www.minispares.com/Product.aspx? ... %20BREATHE...

Something like this - although that one is for the 'tensioner' set-up, it can be used without. Other Co's will sell the normal cover with vent. But if you can braze - just make your own!

Post by **peeweethepinstriper** » Sun Oct 04, 2009 8:36 pm

Oops! Yes 1275 ...it's just the previous owner said it came from a Bugeye Sprite. http://www.morrisminoroc.co.uk/index.ph ... ic&t=27794

Post by **bmcecosse** » Sun Oct 04, 2009 8:39 pm

Well - it came from a Sprite - but not an original engine from a Frog(Bug)eye !

Post by **ssnjimb** » Sun Oct 04, 2009 8:44 pm

definitly not an original

Post by **mike.perry** » Sun Oct 04, 2009 11:20 pm

Found it. General Discussion, Sept. 10th
I commented on the fact that the 1275 engine normally has a crankcase breather on the front of the timing chain cover. This should be piped into the carburettes to draw the air out of the sump and reduce the air pressure in the sump and so prevent oil leaks from the back of the engine. That's the theory, I wish it would work on mine!

Post by **bmcecosse** » Sun Oct 04, 2009 11:53 pm

Yes - it was discussed at length at that time !

Post by **peeweethepinstriper** » Mon Oct 05, 2009 1:11 am

bmcecosse wrote:Yes - it was discussed at length at that time !

I am not sure that the breather pipe on the side of the rocker box cover would work correctly on a 1275 engine. The crankcase ventilation needs to be drawn directly from the sump, normally from a breather pipe on the timing chain cover. Still, if the engine does not drip oil at the back then the system works. ................ So this was at length?

Post by **DirtyShirt** » Mon Oct 05, 2009 1:39 am

bmcecosse wrote:Should also have a vent on the timing case cover.
http://www.minispares.com/Product.aspx? ... %20BREATHE...

This is a cover for a single timing chain. All the 1275's I've redone had dual chains.

Post by **RogerRust** » Mon Oct 05, 2009 7:54 am

This is of course an American spec engine. There are different systems for breathers ovber there. But it looks to me as if the previous owner who fitted the engine discovered that the breather on the timing chain cover fouled the fan so has moved the arrangement to the rocker cover. The problem is that air is drawn in at the vented cap on the tappet cover and straight out through the breather.

If the engine has a plate where the mechanical pump could be fitted you can put a small K&N there to give some air flow through the crank case.

Post by **bmcecosse** » Mon Oct 05, 2009 9:00 am

The timing cover I showed from Minispares is also suitable for duplex. There is no other specific 'duplex' cover. However - it is just an example I plucked from the 'net to show the idea - there are many other suppliers! Yes - if the fuel pump is not fitted that hole can be used for a breather - but I suggest NOT a 'K&N' thing which will just fill the engine bay with carcinogenic fume (which will come into the cab) - but DO connect it to the inlet system for good negative crankcase pressure - which eliminates leaks (and smells).

Post by **mike.perry** » Mon Oct 05, 2009 12:33 pm

The problem with the fanblades fouling the timing case breather pipe can be solved by inserting spacer washers on the bolts between the fan blades and the pulley. With the correct size washers there should just be clearance between the breather and the rad. It may be necessary to file a flat on one side of the washers so that they all fit around the water pump boss

Post by **bmcecosse** » Mon Oct 05, 2009 3:25 pm

Or just bend the fan blades forward slightly!

Post by **mike.perry** » Tue Oct 06, 2009 9:00 pm

Just looking at the photo of your carbs, I would suggest swapping the front and rear float chamber lids over then you can run the fuel pipe from the pump to the rear carb then on to the front carb and you would not have fuel pipes dangling around the air filters.

Post by **peeweethepinstriper** » Wed Oct 07, 2009 2:34 pm

thanks guys! Those were the answers I was looking for.. Now I will look for that plate and make the mods.. Thanks again!

Post by **mike.perry** » Thu Oct 08, 2009 8:07 pm

Crankcase ventillation using a breather control valve. (no provision on carbs)<br>

<br>Float chamber lids swapped front to rear

Post by **bmcecosse** » Thu Oct 08, 2009 10:50 pm

Straight into the manifold - I assume the 'valve' unit contains a restrictor - but this IS the best way to do it - just limit the flow with a 1/8" dia hole !

Post by **mike.perry** » Thu Oct 08, 2009 11:16 pm

The valve contains a diaphram and spring and a small hole. It does need the occasional clean to remove the crud. When I find my Y piece connector I am going to plumb in the rocker box vent to see if I can reduce the black oil stains on my concrete drive.
On the other hand it could have the opposite effect by drawing air out of the rocker box and not out of the sump.