Austin 10/4 1933

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Jasper
Posts: 65
Joined: Wed Jul 21, 2021 9:30 am
Location: Hailsham East Sussex

Austin 10/4 1933

Post by Jasper » Thu Jan 27, 2022 11:53 am

Hi
I have a problem with my 10/4. It was running fine on our last trip out and then started making strange noises!. She will not start. There is spark and fuel but on checking the bores there is only about 1 inch of movement on the pistons. Am I right in thinking timing chain and or crankshaft??

Kind regards

david_ralph
Posts: 9
Joined: Wed Nov 20, 2019 4:04 pm

Re: Austin 10/4 1933

Post by david_ralph » Thu Jan 27, 2022 12:55 pm

The timing chain connects to the camshaft and operates the valves. If the timing chain has broken the crankshaft would still turn with the pistons going up and down as usual. Turn the engine over with the starting handle to try and feel what is happening. You say the pistons are only moving about an inch. Is that all four pistons doing that?

Jasper
Posts: 65
Joined: Wed Jul 21, 2021 9:30 am
Location: Hailsham East Sussex

Re: Austin 10/4 1933

Post by Jasper » Thu Jan 27, 2022 1:00 pm

Hi

Yes, I am sure they all go a short distance
Regards

david_ralph
Posts: 9
Joined: Wed Nov 20, 2019 4:04 pm

Re: Austin 10/4 1933

Post by david_ralph » Thu Jan 27, 2022 8:24 pm

If the crank isn't broken then there cannot be any change in how far the pistons move up and down. That is fixed by the throws on the crank. If the crankshaft was broken then, depending on where the break is, some pistons will move the correct amount but others may not move at all. All the pistons only moving about an inch isn't possible.

Rod
Posts: 100
Joined: Sun Nov 24, 2019 9:44 am
Location: New Zealand

Re: Austin 10/4 1933

Post by Rod » Thu Jan 27, 2022 10:16 pm

Something weird here! I’ve edited my post after reading some of the others
You say you have spark, if you’re checking this by rotating the crankshaft and the crankshaft turns 360+ degrees then the timing chain must be intact otherwise no distributor cam rotation and no spark because the camshaft isn’t turning to drive the distributor.
As others have said with a broken crankshaft a couple of pistons at least will move full stroke. Typically they break (on most cars) adjacent to the rear main bearing. I have seen cranks break outboard of the front main bearing but as the crank pulley falls off when this happens it’s obvious.
If all 4 pistons aren’t going full stroke which should be 3.5 inches according to my references, (and you are getting full crankshaft rotation over at least 360 deg) we would need to consider unlikely events like simultaneous big end bearing caps loosening off the con rods, simultaneous piston failure etc.

Edit after a cup of coffee: without meaning to sound unfriendly/ hostile: how are you estimating how far the pistons are going? Is the head off or are you getting a sideways look through the spark plug hole across the top deck of the block. I’m assuming here that A10s that early have the stepped ‘Ricardo’ combustion chamber with the spark plug adjacent to the valves.

Jasper
Posts: 65
Joined: Wed Jul 21, 2021 9:30 am
Location: Hailsham East Sussex

Re: Austin 10/4 1933

Post by Jasper » Fri Jan 28, 2022 7:44 am

Many thanks for your kind help...we will investigate on Monday and take the head off first

Kind regards

Rod
Posts: 100
Joined: Sun Nov 24, 2019 9:44 am
Location: New Zealand

Re: Austin 10/4 1933

Post by Rod » Mon Jan 31, 2022 1:23 am

Seriously..............if you're getting full rotation of the crankshaft you implied when you say you are getting spark and fuel I would leave cylinder head removal until last. If you're trying to assess piston movement imho it would be better to drop the oil pan and have a look from underneath-less chance of opening a can of worms with head studs etc- and removal can wait until you find out if something inside the engine has acually broken.
As I said, if the crankshaft rotates freely at least two turns, and the distributor rotates as well (which you haven't confirmed is/isn't happening) its unlikely that the timing chain has broken, excess play perhaps but not broken. I can't visualize a feasible situation when ALL four pistons wouldn't go full stroke when the engine is rotated. I can however visualize several scenarios where you will get a locked crankshaft, either locked solid or only capable of a partial rotation.

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