Rebore + new pistons

[crankedup]

Looks like I am going to have to bite the bullit and have major engine work carried out on my little Austin 7 (1931). It has its original engine and I want to retain this, so may have to have it resleeved.

Not sure of best way forward, drive it to my local garage who I respect and trust for them to strip engine and send block away OR send the whole car to specialist and let them do the lot.

Comments and advise gratefully recieved.

[Daston]

I would say specialist as they will have an idea of the little details that will save them time and you money

[99hjhm]

I agree... Long term, a better option.

[wildoliver]

It's a great pity your not nearer Yorkshire I could have helped you out with this and saved possibly a lot of money for you, I restore classic cars and my neighbour restores Austin sevens! He will know the best source of parts.

That said will you need new pistons? Maybe just new rings and use the original pistons.

[crankedup]

Thank you, other owners of 7's have suggested that an complete stripdown and replacement of everything is very worthwhile, but at 3000 pounds + I cannot do that. My nearest A7 specialist seems to be Kent, which is still an hike away. If new rings solve the problem for a few years I'm more than happy with that. Who is your A7 Neighbour?

[the_stoat]

crankedup said:

Thank you, other owners of 7's have suggested that an complete stripdown and replacement of everything is very worthwhile, but at 3000 pounds + I cannot do that.

I would take such comments with a pinch of salt. Until the engine is stripped and the various components measured you cannot be clear on what is required. Have you also considered doing it yourself as if you ignore the measuring equipment engine rebuilds require quiet a basic set of tools. Any good machine shop will be able to do the measuring and let you know what is required.

[crankedup]

the_stoat said:

crankedup said:

Thank you, other owners of 7's have suggested that an complete stripdown and replacement of everything is very worthwhile, but at 3000 pounds + I cannot do that.

I would take such comments with a pinch of salt. Until the engine is stripped and the various components measured you cannot be clear on what is required. Have you also considered doing it yourself as if you ignore the measuring equipment engine rebuilds require quiet a basic set of tools. Any good machine shop will be able to do the measuring and let you know what is required.

Having never ventured into rebuilds before I am very short on confidence for this. However, 7'ners have advised me of an good workshop manual and say the 7 is an simple little engine, so I am tempted to have a go. Reckon if I do I will start end of this Summer.

[wildoliver]

What's actually wrong with your engine? There must be something prompting the rebuild?

[crankedup]

wildoliver said:

What's actually wrong with your engine? There must be something prompting the rebuild?

I overheated badly the engine last year and since then things have steadly got worse. The engine starts fine but if I leave it ticking over for a few minutes and then drive off clouds of blue smoke cover the road! The longer the engine ticks over the worse the oil burn off is. Last year leaving an car show with stop start Qing for half an hour, when I got onto the A140 my car fairly obliterated the carrigeway with oil smoke for a good half mile! Top speed is down from about 50mph to around 37 now (well its an Austin 7) and general lack of go really. I have been advised on the A7 site that an rebore/pistons/rings and so on is possibly needed now.

[wildoliver]

Till you split the engine you won't know really.

If I can help let me know.

[99hjhm]

£3k for a 7 engine... Who's that, Harrods???

[rev-erend]

I think you should do a compression test first .. that will help identify the problem. A leak down test is even better but only garages have those (generally).

[theshrew]

Any good local garage will be able to do the repair mate. Would think parts would be your biggest problem.

You can look at this 2 ways.

Take the chance while the engine is out or stripped down to give it a good going over pretty much end up with a new engine

or

As someone said get a compression test done then work from there see whats wrong. If you have overheated it its prob picked up on a cylinder or something along those lines.

Anyway if you find someplace that does a re bore can you let me no my Mrs could do with one lol

[crankedup]

Thanks guys for all the replies. I have done an compression test earlier and found that all four cylinders are within an reasonable tolerance showing 83-85lb. I was advised that this is accepted as reasonable compression. I do have a good source for any parts I need and I have been recommended a machine shop if a rebore is required. Just seems a bit strange that the compression is OK pointing to a rebore is perhaps not required?

[Pumaracing]

I don't know exactly what the compression ratio of your specific engine is although a quick search on Google says about 6:1 for that year of car. If so I'd estimate that 95 to 100 psi would be a decent figure for cranking pressure although there's no direct relationship between CR and cranking pressure because it's affected by cam timing, cam duration and heat build up during cranking. There's a detailed article on this on my website.

http://www.pumaracing.co.uk/

80ish psi sounds low. It should never be less than CR x atmospheric pressure (14.7 psi) with road duration cams even at very low CRs and for modern engines with CRs in the 9 to 11 range it's usually about 19 to 20 x CR due to thermal considerations. (as a gas is compressed its temperature rises so it expands to produce a higher final pressure than the simple calculation "initial pressure x CR" would indicate)

Try a compression test with a squirt of oil in the bores however the smoke symptoms mean it's going to have to come apart anyway so you might as well just have everything measured properly then. If I wasn't in 'retirement' I'd offer to rebuild it for you. I'm quite fond of these historic engines, but other matters are more pressing at the moment.

I'd steer clear of anyone who says it's going to cost £3k though. £2k sounds a lot more realistic.

Dave Baker
Puma Race Engines

[crankedup]

Thanks for that Dave, yes the engine is going to have to come apart for sure, but I am determined that the 'big bits' remain as they are all original and I have all matching numbers. The '7' is an 'Swallow' saloon. Most of you will know that this is the forerunner to Jaguar, so for me its important to keep things as original as is possible. Thanks for all the advise and comments, most helpful.

[dirty boy]

Pumaracing said:

If I wasn't in 'retirement' I'd offer to rebuild it for you. I'm quite fond of these historic engines, but other matters are more pressing at the moment

I'd steer clear of anyone who says it's going to cost £3k though. £2k sounds a lot more realistic.

Dave Baker
Puma Race Engines

Dave,

Any clue as to what you're up to? I've always had your website 'bookmarked' as a VERY useful reference quide (you never did get any pictures up )

Are you writing a book or something?

PS I think my old man is still considering 'tapping you up' but things on the job front aren't too secure at the moment, so he's holding back before parting with a five figure sum.

[Pumaracing]

I'm having a couple of years (three maybe) off while I do up the house, sell it, move, clear up some other loose ends and maybe start up again later in a new workshop. However if I make enough to live on by trading shares I might not ever do engine work again. It's a damn sight easier sitting at a pc watching share prices than grafting over a porting bench or lugging engines around. I was doing just fine on the stockmarket until everything crashed in October (I made about 8 grand profit just in July and August alone) and then it all went to hell in a handbasket. Over the next few months 8 grand up turned into 20 grand down. Still, it'll come good in the end once the recession is over.

Ain't it just the way that the very time I decide to stop work and try and live by share trading we hit the biggest recession for 70 years? Ho hum.

I'll never get rid of the workshop equipment though even if it's only to do engines and heads for my own cars. I'd hate to be back in the position of having to trust someone else to get things right after 20 years of seeing what crap most of the trade put out. I suspect in time, even if I'm mainly living by share trading, I'll enjoy the occasional job for other people but I'll pick them very carefully. If I've learned anything it's that if you take on all and sundry you end up bogged down in jobs people aren't prepared to pay properly for.

If I look back over the work I've done in the last 20 years the jobs I've enjoyed most have been historic engines like the Daimler Dart 2.5 V8 engine I rebuilt for a barrister 12 years ago, a very rare Lancia Gamma boxer engine for Earl somebody or other and I suppose some of the championship winners which are always satisfying. I'd quite like to have some part to play in keeping venerable engines like the Austin 7 one in this thread going properly so I might move from mainly race to historic rebuilds. Who knows though - tomorrow is another day.

[tr7v8]

I wouldn't have thought a 7 lump would be 3K although if it's not been machined (if it can) for shells then white metal bearings are big money. Looking at the spares prices here the costs seem very low!
http://www.sevenworkshop.com/

[crankedup]

Thanks for link, yes the A7 spares are very inexpensive and readily available. Like everything though, its the labour cost which is going to be the big money. Ho Hum, time to save up.