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Greg55_99
Greg Williams

(98 posts)

Registered:
11/01/2007 07:12PM

Main British Car:


Are cracked blocks safe for reuse?
Posted by: Greg55_99
Date: July 10, 2019 08:04AM

I've seen conflicting into on this and I'd like to get a reading. If a block is leaking behind a liner, is it OK for reuse? I see the Top Hat Turner/Darton sleeves have an o-ring on the bottom to prevent coolant from getting into the crankcase. In theory, the top hat stops coolant from getting in through the top. RPI says "No Way" to any block that's cracked. Any thoughts on this? Is there some definitive tech on this (other than "get a 300").



Edited 1 time(s). Last edit at 07/10/2019 09:34AM by Greg55_99.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1074 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: ex-tyke
Date: July 11, 2019 11:15AM

Don't know why anyone would want use a known cracked block. Thermal cycles will surely make it a ticking timebomb that might leave you stranded.
Do the right thing and replace with a good one.


Greg55_99
Greg Williams

(98 posts)

Registered:
11/01/2007 07:12PM

Main British Car:


Re: Are cracked blocks safe for reuse?
Posted by: Greg55_99
Date: July 11, 2019 12:09PM

If you swing by a boneyard and pick up a Rover V8 block, how do you know it's not cracked?


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1074 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: ex-tyke
Date: July 11, 2019 03:06PM

A machine shop would have to use a commercially available 2-part dye penetrant to locate cracks.
The other possibility, depending on the crack location, would be to perform a pressure test.



Edited 1 time(s). Last edit at 07/11/2019 03:14PM by ex-tyke.


minorv8
Jukka Harkola

(161 posts)

Registered:
04/08/2009 06:50AM

Main British Car:
Morris Minor Rover V8

Re: Are cracked blocks safe for reuse?
Posted by: minorv8
Date: July 12, 2019 01:41AM

To do the dye penetrant test properly you need to remove the liners. Sure, you can put the dye in the water galleys but it needs a lot of dye and it will be a nightmare to wash away after testing.

Apparently the pressure test should be done on warm/hot block. Having said that, I made a set of flanges to block the water ways and put 40 psi of air. It has now sat for 2 weeks and there is still pressure inside. How reliable ? Who knows, the block is at ambient temp.


Greg55_99
Greg Williams

(98 posts)

Registered:
11/01/2007 07:12PM

Main British Car:


Re: Are cracked blocks safe for reuse?
Posted by: Greg55_99
Date: July 13, 2019 11:43AM

I get what all of you are saying, but it comes down to my basic question. If you pick up a used block (and they all are now), is it worth sleeving and will it be safe afterwards? There doesn't seem to be much point in picking up a 4.0 or 4.6 if they ALL have a propensity to crack and eventually grenade. It also seems the only "safe" blocks are the Buick 215 or Rover 3.5 blocks.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5799 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: BlownMGB-V8
Date: July 14, 2019 11:06AM

I like the 300 iron block. No liner problem, no pulled threads.

Jim



mstemp
Mike Stemp
Calgary, Canada
(197 posts)

Registered:
11/25/2009 07:18AM

Main British Car:
1980 MGB Rover 4.6L

Re: Are cracked blocks safe for reuse?
Posted by: mstemp
Date: July 14, 2019 11:36AM

Jim,

They just are not available in the number that the Rover is for most of us.
Also I feel this block topic is like the Porsche intermediate shaft bearing. Lots of talk but not really all that common in reality. Hope I am not wrong as that is what I have in mine, 4.6L. If it ever fails, I will sleeve it. If block ends up with a crack I will have it welded and sleeved. Man built, man can fix it. U.K. sources offer re sleeved blocks for 2200 GBP, not all that expensive compared to a new LS4 etc.



Edited 1 time(s). Last edit at 07/14/2019 10:30PM by mstemp.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5799 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: BlownMGB-V8
Date: July 14, 2019 09:42PM

To each their own Mike. IIRC Buick sold something like 3/4 million 300s so they really aren't all that scarce even today. I realize a few Rover based engines have been built to over 300hp but the block really isn't all that strong. I always had reliability issues with it and I know a lot of other people have too. The iron block otoh has been shown capable of power levels of 1000hp and while I'll never build an engine to that level it's nice to know it is a solid foundation on which to build.

I suspect that was at least part of the appeal of the early SBC. It was a heavy engine, but the block held up very well. The 300, being a high nickel block also happens to be a high mileage engine because it wears more slowly. That in combination with the light weight makes it pretty ideal for an MGB.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3708 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: MGBV8
Date: July 17, 2019 12:20PM

I would think that anyone reusing a Rover V8 with a crack behind the liner would have the crack welded before installing new liners.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5799 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: BlownMGB-V8
Date: July 19, 2019 09:53AM

Might not be that simple. Welding will distort the casting and it will have to be bored oversized which could complicate things even further. I wonder if a good sealant might not work?

Jim


MGBV8
Carl Floyd
Kingsport, TN
(3708 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: MGBV8
Date: July 19, 2019 11:00AM

Have to bore it to size anyway for the liner.


Greg55_99
Greg Williams

(98 posts)

Registered:
11/01/2007 07:12PM

Main British Car:


Re: Are cracked blocks safe for reuse?
Posted by: Greg55_99
Date: July 19, 2019 02:02PM

OK, here's another wrinkle. Do the late 3.9l blocks with thick but undrilled mains and caps crack just as the 4.0/4.6L blocks?


MGBV8
Carl Floyd
Kingsport, TN
(3708 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Are cracked blocks safe for reuse?
Posted by: MGBV8
Date: July 19, 2019 02:06PM

Any Rover V8 with the 3.7" bore is susceptible to a crack and/or liner slippage. That said, I mostly have only heard about the late blocks cracking.


waterbucket
Philip Waterman
England
(77 posts)

Registered:
07/30/2011 01:08PM

Main British Car:
1978 MGB GT

Re: Are cracked blocks safe for reuse?
Posted by: waterbucket
Date: July 20, 2019 01:48AM

I have always understood that the 3.9/4.0 engines were not that badly affected by cylinder bore cracking whether pre or post cross bolted cranks. The longer stroke 4.6 crank put greater stress on the block aggravating the problem, to overcome this the blocks were ultra sound tested in the factory for wall thickness and colour marked for thin, medium and thick walled bores. 4.6 engines got all the thick walled blocks and some mediums, 4.0 engines got thin and mediums. On that basis the later 4.6 blocks should be better than the earliest ones.
Another factor was in the P38 Range Rover the top hose was the highest part of the cooling system with no air bleed, this led to air locks and overheating. The discovery did not suffer the same problems.
A company in the UK known as Wild Cat Engineering specialises in putting top hat liners in these engines and producing high output engines. The company has recently been sold and is now known as;
[www.automotivecomp.com]
other companies doing the same,
[www.v8developments.co.uk]
[www.johnealesroverv8.co.uk]

I have no affiliation to them but when owned by Ian Richardson were renown for overcoming cracked blocks with top hat liners, no welding was involved, do a google search on "Rover V8 top hat liners" their prices do not look bad either.



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