Oil baffles and modern piston's

[John Mason]

Hi all following on from the thread by Rubyman and his question about fitting oil baffles or not. It got my small brain thinking. I have run my Ruby for the past 10 years without oil baffles and this seems to have no ill effect. Do other forum member think it maybe down to the newer modern type of piston that has the second oil scraper ring at the bottom of the piston below the gudgen pin. Thus removing more oil from the bores.
I await your replies from people with greater knowledge on auto engines particulary Austin Sevem engines.


John Mason

[GK5268]

I am still running in my re-built engine without the baffles, so still burning oil and too soon to say as yet. I am using a straight oil currently, will be changing to a 20/50 detergent oil at the next oil change.

[Bob Culver]

This raises the question of typical oil consumption. When broached a few years ago I recall Ruairidh was about the only person who reported a very low consumption. My car with original wide rings used very little; my father considered it due for new rings at 1 pint in 800 miles. I took it over very worn but still not with excessive oil use, but a Cord ring fitted under the top ring as spacer as per a Cord pamphlet proved hopeless and it then used gallons.  I fitted narrow ring pistons in another block worn moderately but barrel shaped (not initially noticed from usual top and bottom measurement) Again used a lot of oil. So was rebored with 4 ring pistons, ci oil rings, expanders behind the top oil ring but still used 1 pint per 300 miles on long main road trips. With baffles.
Just what is achieved with/without baffles? They must have considerable effect to justify the complication. The situation for racing is different; consumption matters little.
3 or 4 piece steel oil rings would presumably help. I dunno if now used but  Seven experts used to reckon these sapped too much “power”

[Ian Williams]

Consumption as opposed to oil leaks are difficult to seperate, I can only say that my largely oil tight cars are not fitted with baffles and use virtually no oil. Mind you I also do bother to record usage in finite detail, provided I have clean combustion I cease to worry about it.

[Chris KC]

In my case oil consumption is mostly about leakage. It is by no means a constant - I used a frightening amount up the A1 to Newcastle, then next to nothing in a couple of thousand miles of subsequent gentle touring. I don't have the original Seven baffles but I do have a spacer plate under the block which restricts splash somewhat.

[Robert Leigh]

In my case oil consumption is mostly about leakage. It is by no means a constant - I used a frightening amount up the A1 to Newcastle, then next to nothing in a couple of thousand miles of subsequent gentle touring. I don't have the original Seven baffles but I do have a spacer plate under the block which restricts splash somewhat.

What is the purpose of the spacer plate? Perhaps you are using non-Austin rods and/or pistons, otherwise it will reduce compression ratio, or have I misunderstood?
Robert Leigh

[Steve Jones]

I gave up using oil baffles maybe 25 years ago or so. Since then I've used 4 ring traditional pistons, 3 ring traditional sports pistons, modern low expansion pistons, modern low expansion 3 ring sports pistons, good pistons and, in one case, some very poor pistons and none of the engines has ever burned oil. The odd one has leaked a small amount but that too can be sorted with careful assembly or re-assembly.

The secret to not burning oil is to have the block re-bored to the exact specification of the piston manufacturer (they know better than your machine man whatever he might say) and, most importantly, very careful running in. Starting a newly built engine and standing back watching it tick over happily thinking how well you've done is the perfect recipe for glazing the bores after which it will always burn oil. I don't understand the concept of '....it's newly built so it's still burning a bit of oil'. They don't, not if done and run in properly.

Steve

[Ruairidh Dunford]

My experience is very similar, the two engines that used a pint every 2000 miles were run in over month-long trips of around 3000 and 5000 miles each. Great fun too!

[Robert Foreman]

Spot on Steve,
block boring to the correct size is must and the correct running in process making the car work to bed the rings in is most important.
My reproduction Ulster returns 800 miles to the pint and like all my cars I give it the stick!

[Chris KC]

In my case oil consumption is mostly about leakage. It is by no means a constant - I used a frightening amount up the A1 to Newcastle, then next to nothing in a couple of thousand miles of subsequent gentle touring. I don't have the original Seven baffles but I do have a spacer plate under the block which restricts splash somewhat.

What is the purpose of the spacer plate? Perhaps you are using non-Austin rods and/or pistons, otherwise it will reduce compression ratio, or have I misunderstood?
Robert Leigh

Good guess Robert - it has a Reliant crank and rods, which are I think 1/8" longer than Austin ones. Hence 3 main bearings & pressure oil feed to big ends and C/M.