4.2 crank.

Technical advice Q&A

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lee-type
Posts: 60
Joined: Mon Jun 18, 2018 5:43 pm
Great Britain

#1 4.2 crank.

Post by lee-type » Tue Jul 10, 2018 8:07 am

Good morning.

Can 4.2 cranks and engine blocks be interchanged?

For example a rearly crank fitted in a later block?

Cheers Lee
S1 OTS

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christopher storey
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#2 Re: 4.2 crank.

Post by christopher storey » Tue Jul 10, 2018 9:46 am

Yes. All 4.2 cranks are interchangeable ; however , blocks are more complex : there can be differences in front cover, water pump, oil filter housing etc, so keep your old ones if you are doing a swap, and if you mix a later longer head with an earlier block , or vice versa ,( this is undesirable but not impossible ) it will be necessary to blank off the extra water passages . Others who have done this may add to this list

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Topic author
lee-type
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Joined: Mon Jun 18, 2018 5:43 pm
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#3 Re: 4.2 crank.

Post by lee-type » Tue Jul 10, 2018 10:09 am

Cheers Chris

I know what your saying about using a newer block with a old head witch is what im doing but engines are going for silly money! I have lots of engine parts as i have two 4.2 engines that are cracked inbetween the bores so now one is a wine rack! Lol
S1 OTS

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christopher storey
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#4 Re: 4.2 crank.

Post by christopher storey » Tue Jul 10, 2018 6:49 pm

Cracking between the bores is very,very common with 4.2s and interestingly appears to be becoming more common in 3.8 and even 3.4s now. I really would not let it put you off using an otherwise reasonable block unless the cracks were catastrophic, which they rarely seem to be. There are two methods of repair . The first, and probably cheaper way , which I have used is to drill and tap each crack and then fill it with a nickel screw left slightly proud and and sealed with JB weld, the whole surface then being faced down until the head of the screw is eliminated . The better way which involves more engineering is to bore the block and use top hat liners which eliminate the cracks completely and also have the advantage that the block can be returned to standard size

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abowie
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#5 Re: 4.2 crank.

Post by abowie » Wed Jul 11, 2018 12:26 am

christopher storey wrote:
Tue Jul 10, 2018 6:49 pm
The better way which involves more engineering is to bore the block and use top hat liners which eliminate the cracks completely and also have the advantage that the block can be returned to standard size
We do this routinely on all 4.2 block rebuilds.

It doesn't add a huge amount in terms of the overall cost of an engine rebuild, and gives you a reliable block back to standard bore.
Andrew.
881824, 1E21538. 889457..oops
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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