Return to Website

Welcome to the Austin Seven Friends web site and forum

To get a quick overview of all the messages click on

" Switch to Threaded style "

Forum: Welcome Austin seven Friends
Start a New Topic 
   Board|Threaded
Author
Comment
smoking engine

i have a 36 ruby ive replaced the piston rings plus 60s, valve guides,valves, cleaned out the engine fitted new oil baffles and top hat filters that were missing i have 85lbs compression on all four cylinders cleaned out all the oil ways but still smokes like it runs on coal, oil on top of pistons any suggestions as i am thinking of fitting reliant regal engine if i cant solve the problem many thanks dave

Location: northants

Email  
Re: smoking engine

David,
Did you glaze bust the bores to allow the new rings to bed in? Also if the bores have a step at the top, the new top compression ring which will be thicker than the old worn down one you are replacing will be catching on the step. You could at one time buy a stepped compression ring to avoid this possibility. I have when fitting new rings in old bores removed this step with a scraper. I glaze bust the bores with 400 grade wet and dry paper and scrupulously clean the bore out afterwards. Don't forget to make sure you set each ring gap at 0.006 to 0.008" at the least worn part of the bore. Do this by pushing the new ring down the bore towards the bottom using an old piston and checking with a feeler gauge. The old piston keeps the ring at right angles to the bore.
Dave.

Location: Sheffield

Email  
Re: smoking engine

hi david yes i have honed the bores and made sure the rings and pistons are fitted correctly with the right gap the oil on top of the pistons has not receaded and the bores are smooth with no lip there are no visable signs of marks or scoring so i cant see how its sucking up oil from the sump with it not being a pressurised system by the way all the breathers have also been thoughly cleaned i will also say that doug woodrows book has been absolutly bloody useless many thanks dave

Location: northants

Email  
Re: smoking engine

Quote: David Loveridge
....i will also say that doug woodrows book has been absolutly bloody useless many thanks dave


I got my first Seven when I was 14. I'm 65 now and, whilst there has been significant gaps in between, I've had a lot of involvement with the things over the years. I know them pretty well but I don't, and will never, know it all. Nobody ever does. In addition, I'm now starting to forget some of the things I once knew!!

I still refer to Doug Woodrow's Red Book regularly and, given your comment, can only assume that you've got a very different edition to the one I've had for years. Either that or you're looking to blame it for your own failings. One thing it's not is 'bloody useless'.

Steve

PS: The correct spelling of absolutly is absolutely

Location: North Yorkshire

Email  
Re: smoking engine

I am afraid I have to concur with Steve's comments, yes if being pedantic you can pick fault with Woodrow as you can with most books, but overall it is an excellent publication. It is not intended to be a Haynes manual and assumes that you a basic understanding of the workings of a motor car to start with. Think yourself lucky to have Woodrow today, most of us didn't when we started!

Location: NZ

Email  
Re: smoking engine

That makes three of us.

Re: smoking engine

Does it need more running in? 85 compression isn't much, I have 120 on a second hand engine with low comp head.
How worn were the pistons and bores when you started work on them?

Location: On a hill in Wiltshire

Email  
Re: smoking engine

I've recently been involved with the re-building of an Austin 7 engine and the first thing I did was get hold of a copy of Doug Woodrow's book, following advice here.
I'd never been involved with 7s before and found it invaluable along with help from the folk here.

I'm now involved with a very smoky bull-nosed Morris. The tail pipe looks like it's a 2-stroke. Have to do some research on that.

Email  
Re: smoking engine

I would think 85 psi per cylinder in a Ruby engine properly assembled with good fit pistons, new rings and honed bores is low - should be nearer 100 psi.

Try working on an Austin Seven using only Pitmans 'Book of the Austin Seven and Eight'.

Cheers, Tony.

Location: Melbourne. Victoria, Australia.

Email  
Re: smoking engine

As others have mentioned Woodrow assumes a general knowledge of car practice. It is now very hard to find any book which will guide the newcomer from scratch. Mechanics and busy amateurs build up over years of observation (and blunders, many of which mechanics never learn about). Older manuals used to give reassembly tolerances but these were quite stringent and applied to more conventional engines. Modern tolerances when given are almost nil.

Various sources reckon honing unnecessary with plain iron rings and I never did on other cars, but with modern oils and low use probably good practice with Sevens. Scrubbing with detergent and water after is recommended.

In my limited experience, for main road running it is difficult to reduce oil use to very low figures with the current narrow rings, even with 2 single piece oil rings There are various ways of tweaking but not to counter your situation.

As with other makes the reason for wide variation in consumption is often hard to determine. But with Sevens at least the oil feed is relatively consistent.

Is there some gross defect with the oil jets? Is the wrong dipstick in use and the sump too full? Just what was state of bores in taper and piston fit? Bores are sometimes barrel shaped which escapes notice. Do all bores oil up? Some/many c.i rings can be distorted if opened too far, or twisted. Were the rings truly +60 or something bigger gapped down? All rings influence oil use. If block was lowered over pistons, were rings broken? Broken top rings can often be seen with a strong light and fine scriber. Are you using rings sensitive to which way up? Or multi section oil rings which can be assembled wrong? Is a piston riding on a ring? Were the pistons finished wrong with no oil relief? Rings must have definite minimum clearance in grooves. Is the gauze filter panel fitted? Etc

The crew handle is a good test device for compression bounce.

Location: Auckland, NZ

Email  
Re: smoking engine

Test

Location: Sheffield

Email  
Re: smoking engine

If you have double checked the quality of the bores and the rings and you have low compression pressure and high oil usage I would check the valve timing. If it way out you could get a vacuum in the combustion chamber and be sucking up the oil

Location: Fremantle, Australia

Email  
Re: smoking engine

David,
What is the history of the engine? Was it very smokey before, do the pistons have very large ring groove width allowing the rings to pump oil through?
Dave.

Location: Sheffield

Email