Cracked Blocks

Aragorn · Post by **Aragorn** » Thu Dec 31, 2009 12:31 pm

I'm looking for some info on the common cracked block issue and the remedies for it.

I've done some reading and it seems the issue is caused by "shift" in the waterjacket at casting time, causing one or more of the walls to become thin. The block eventually cracks (sometimes helped along by overheating) and coolant begins to get in behind the liner. Eventually enough coolant gets behind the liner and it pushes thru into the cylinder itself. The liner then becomes loose and has a tendancy to drop making the problem worse.

The oft mentioned solution is to replace the block with one that has top hat liners fitted.

I cant work out how the top hats themselves would stop the block cracking. The walls of the block arent going to be any different, so surely they can crack just the same on a top hat block? My only guess is that because the new liner is clamped between the block and the cylinder head due to the top hat, they "seal" better, so if/when the new block cracks, it doesnt actually make its way into the cylinder itself.

If that assumption is correct, then it means it should be possible to have the top hats fitted to an already cracked block, rather than having to shell out for a completely new block?

Has anyone done this? Any success stories with fitting top hats to cracked blocks instead of completely replacing it?

Cheers
Kev

ged · Post by **ged** » Thu Dec 31, 2009 2:40 pm

Hi Aragon,
Yes I've had this problem with a 4.6. V8D re-linered it for me. Rather than spending ages typing an explanation I've added a link for you to read. If you give them a call they are very helpful.

Follow the menu on the left:- Technical-Liners & also Services-Reliner

Hopefully this will answer all your questions.

http://www.v8developments.co.uk/

Regards Ged.

kiwicar · Post by **kiwicar** » Thu Dec 31, 2009 3:14 pm

Hi
Yes you are correct on what happens, the solution, and the ability therefor to use a cracked block. The top hat liners effectivly convert the block to to a wet liner block with the head gasket sealing to the wider flange at the top of the liner. It doesn't stop the block cracking again, but it no longer matters as the combustion gasses can't get past the headgasket seal and into the block, if you look at the pictures in the thread about the 4.02" bore conversion then you will see that that work is just an extream version of what is going on in a top hat liner conversion.
Best regards
Mike

Aragorn · Post by **Aragorn** » Fri Jan 01, 2010 9:08 pm

Excellent that all makes good sense.

I notice that v8developments charge £850 for the job, including a new cam and things.

Is that the "going rate"?

Anyone know how much the liners themselves are?

Be interesting to find out how much cheaper it would be if i had the work done locally by an engine builder, than going to a Rover V8 Specialist...

Cheers.

ChrisJC · Post by **ChrisJC** » Fri Jan 01, 2010 9:48 pm

V8 dev are charging a fair price IMO, at least, you'll do well to get it significantly cheaper.

The actual work is done by Chesman Motorsport, who charge about the same.
The liners can be purchased from
http://www.westwoodtrading.co.uk/
however, then you need to tool up for the machining work.
Turner Engineering charge about £1200 for the same job, however, they use o-rings at the bottom of the liner whereas the others just use a smudge of sealant.

Chris.

Aragorn · Post by **Aragorn** » Sat Jan 02, 2010 11:04 am

Turner charge 1250, but that appears to be a whole new block, rather than just relinering an existing block.

Cheers for the links. At least i can start looking for Range Rovers now with an idea of what these repairs will cost!

topcatcustom · Post by **topcatcustom** » Sat Jan 02, 2010 7:14 pm

Aragorn wrote:Turner charge 1250, but that appears to be a whole new block, rather than just relinering an existing block.

Cheers for the links. At least i can start looking for Range Rovers now with an idea of what these repairs will cost!

Dont forget if you have a seasoned block top hat linered (may as well make sure it is X-bolted first) you will have a pretty bullet proof engine whereas a new block could have the exact same problem after some use or an overheat!

Aragorn · Post by **Aragorn** » Sat Jan 02, 2010 7:47 pm

Sure that was always the intention, i just meant that for £1250 turners supply you with a replacement block, that has had the liner repair done, rather than performing the repair on the existing block.

Looking again though, i see its "service exchange" so in effect its the same, as you'd need to send your old block to them.

The V8 dev offering is a better deal it would seem.

Cheers

SuperV8 · Post by **SuperV8** » Sun Jan 03, 2010 2:10 pm

I had the same issue.

Had my 4.6 pressure tested and turned out three liners were leaking. I had Chesman engineering top hat liner it. Very nice work, and yes loads of V8 Dev't blocks waiting for the same job.

v8alligator · Post by **v8alligator** » Sun Jan 03, 2010 7:22 pm

Owslburry Crankshafts have done 5 blocks for me over the last few years and have not had any problems. It was around the £1k mark with the VAT.

cant fault there workmanship or quick turnaround.

www.ocservice.co.uk

Bryan

kiwicar · Post by **kiwicar** » Sun Jan 03, 2010 7:35 pm

Golly are Owslebury crankshafts still going!

they used to do Mini blocks and cranks for me 25 to 30 years ago, they used to do a good job at a good price. They relinered a mini block to take 74mm pistons fo me, did alot of extra work on it to save the block when it was found the Oil gallery core was a mile on off where it should have been (top quality BL castings for you

) and didn't charge me anymore for it than the original quote.
Sorry not a very up to date recomendation

but just if they are still going and as they are based in the middle of darkest Owslebury/ Baybridge they must still be pretty good beacuse they do not get passing trade!
Best regards
Mike

v8alligator · Post by **v8alligator** » Thu Jan 07, 2010 9:16 pm

Owslburry Crankshafts are in winchester now. I cant fault any of there workmanship and they do all our engine work.