Rover 4.6 main bearing caps, very tight?

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n1tr0_9
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Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

Dear all, I recently picked up a 4.6 block and was looking to rebuild it, so started stripping it down.

I don’t think it has been too well looked after. All the big end bearings were just about past it and looks like it has got hot.

Started removing main caps but found them very difficult to get out. 1,2 and 5 came out with some wiggling. 3 came out but put up a real fight. After it was out I found the bearing had picked up and smeared. Not good. Strangely the crank journals so far have some minor scoring but nothing really nasty.

Number 4 I can just about wiggle with considerable effort but refuses to come out.

Does anyone have any tips?

And is their reluctance to come out evidence that the block has distorted in some way or are they always like this?

I’ve only ever taken apart Sd1 2 bolt main cap v8’s.

Thanks



n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

Finally got the last one out. Wiggles it until I could get some string under it, then suspended it off an engine crane by the string and continued to wiggle it. I think the block is fooked.

minorv8
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Re: Rover 4.6 main bearing caps, very tight?

Post by minorv8 »

Yes they do need some wiggling.

n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

This is what i had to resort to!!!

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sidecar
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Re: Rover 4.6 main bearing caps, very tight?

Post by sidecar »

How easy was it to turn the crank? That will be a good indication of the state of the block, even more so when you put new mains in it, if the crank is easy to turn then in my humble it will be OK.

n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

It was actually pretty easy, even with the ruined bearings. I know the crank will need a regrind so I think I’ll take it to an engine rebuilders and get them to have a look.

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Re: Rover 4.6 main bearing caps, very tight?

Post by russell_ram »

Caps are supposed to be interference fit into the block. It's like that to stop fretting failure particularly on cap 4 - common failure on 4.2 engines. In contrast to your analysis of 'I think the block is fooked' - it's not, it would be if they were loose though !
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n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

russell_ram wrote:
Tue May 01, 2018 8:11 am
Caps are supposed to be interference fit into the block. It's like that to stop fretting failure particularly on cap 4 - common failure on 4.2 engines. In contrast to your analysis of 'I think the block is fooked' - it's not, it would be if they were loose though !
Phew good to know. Tried refitting one again. As soon as you start tapping it in, it acts like a cheese grater and chews off the side of the block!

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Re: Rover 4.6 main bearing caps, very tight?

Post by sidecar »

Put the caps in the freezer few a few hours before fitting them.

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Re: Rover 4.6 main bearing caps, very tight?

Post by DEVONMAN »

When the caps are fully in place you should be able to slide a 2-4 thou feeler gauge between the cap and the block just in the zone where the cross bolts go though without the cross bolt in place. This is ONLY on the starter side of the engine. On the other side of the engine there should be no gap and both sides should be snug in the block at the top --- (Top meaning top of cap with the engine the correct way up). This only applies to cross bolted 4.6 / 4.0 blocks.
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n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

sidecar wrote:
Tue May 01, 2018 7:50 pm
Put the caps in the freezer few a few hours before fitting them.
Good tip, thanks.

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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

DEVONMAN wrote:
Wed May 02, 2018 5:06 am
When the caps are fully in place you should be able to slide a 2-4 thou feeler gauge between the cap and the block just in the zone where the cross bolts go though without the cross bolt in place. This is ONLY on the starter side of the engine. On the other side of the engine there should be no gap and both sides should be snug in the block at the top --- (Top meaning top of cap with the engine the correct way up). This only applies to cross bolted 4.6 / 4.0 blocks.
Cool, thanks for the info. I’ll leave the block in the sun (if we ever get any), caps in freezer, go for a trial fit and have a measure. Just hope I can get them out again!

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Re: Rover 4.6 main bearing caps, very tight?

Post by stevieturbo »

It all sounds very tight ?

IMO, have the block checked for straightness down the main crank bore, as I had one that although when I pulled the used engine apart the crank spun freely....when I assembled with new parts it would not.

Turned out the block was twisted.
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n1tr0_9
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Re: Rover 4.6 main bearing caps, very tight?

Post by n1tr0_9 »

Ahh crap. I hope that’s not the case. I called a local v8 specialist yesterday. I’m going to drop it off for inspection. He said that it doesn’t sound good but will check it over.

If it is warped he said it can be repaired by line boring or similar and gave me recommendations of a company in Dartford that might be able to help.

It will then be a decision based on what’s cheaper, line bore it or source a better 4.6 engine.

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Re: Rover 4.6 main bearing caps, very tight?

Post by stevieturbo »

In my case, the block also had a burst liner...no doubt it had been cooked at some stage which led to the twisting.

As to whether line boring would remedy it, depends how bad it is. Without adding material somewhere....you can only line bore something a very small amount because no matter what you are still removing material
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