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P38 4.6 Engine repair - what to do next?


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I tend to err on the more "particular" end of the scale, but my logic is:

 

  • If they are stretch bolts and you re-use them, you might get issues.
  • If they are not stretch bolts but you buy new, they won't cause issues (just cost).

 

There is only risk one way on this. Besides, I'm sure shiny new bolts add 1hp each.

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58 minutes ago, ThreePointFive said:

If they are not stretch bolts but you buy new, they won't cause issues (just cost).

I would tend to agree, but having had some stretch bolts for a Toyota engine (from a reputable supplier, just not Toyota) be the most likely cause of a subsequent head gasket failure, I would say there is risk there, both ways.

The parts shoved into these vehicles originally are almost entirely better than you can get on the aftermarket, in my opinion....

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I used new big end bolts, £3.60 each so £58 ish for 16. Not cheap but cheaper than having a used one let go.

 

All back together now apart from tappets pushrods and rockers. Will finish tomorrow then I just need some decent weather to refit it.

I also used ARP suds and nuts for the heads, way better than the stretch bolts.

Mike

 

20201218_194530.jpg

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Nice, I found it really satisfying to build the engine back up. Almost a shame to hide it in the guts of the car. 

Just realised we're talking about the conrod cap bolts (clearly wasn't paying attention). I didn't replace mine as I am sure on the phone Turners said they didn't need to be and saw no mention of it in the manual.

Looks like I might be pulling my engine, then.

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James It will be getting new cats when it all goes back together.

Delayed again, life keeps getting in the way! Engine nearly ready to go back in now, put on the rockers on today and checked the tappet preload. It was around 70 to 85 thou across all the valves. Interweb suggests 20 to 60 thou is the range to go for, so I have ordered a shim kit. Depending what I can achieve with the shims is it better to go towards 20 or towards 60 if I can't get mid range?

But why does it matter? Tappets have a range of about 100 thou (4mm) so as long as say 10 thou is allowed at each end for a bit of headroom that gives a range 10 to 90 thou. So the tappet would not be loose or binding and would pump up to take out the slack unless I am misunderstanding, comments from a grown up would be appreciated.

Some advice says that at preloads above 60 thou the tappets can excessively pump up and hold the valves open at high (>5000rpm). However this engine is in a Range Rover not a race car, so again does it matter?

Thanks

Mike

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  • 3 weeks later...

After being delayed yet again by the weather (I'm too old for lying in the snow under a car!) but the engine is back in now just the ancillaries to fit.

So if the weather co-operates it should be running tomorrow/Saturday.

I'm trying to remember the cam bedding in procedure, there's nothing in rave. I seem to remember something like vary between 2000-2500rpm for 20 minutes.

Does that sound right?

Thanks

Mike

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46 minutes ago, elbekko said:

Keep steady somewhere around 2000rpm for 20 minutes.

That's what the instructions from Kent Cams and Piper say, seems to work for us. But it can be unnerving revving a newly built engine like that, while watching for leaks etc. I always feel more comfortable when there's 2 of us.

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It's been horrible doing the run-in on mine, stopping every minute for one problem or another so my 20 minutes is in minute blocks, reckon I've already ruined the cam.

I believe the Kent booklet said 2500-3000 RPM, but will be different depending on what you gone for.

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Worst we had was a blocked cat that actually caught fire after about 15mins. My first rebuild in a P38 too... Luckily I had friends watching everything while I was behind the wheel. After about 10mins he could light a cigarette on the glowing cat (and gave it to me, all good fun and games), then he put the fire extinguisher closer by and when that needed to be used we decided to abandon the run-in... The cam still did fine for many miles. 😉

 

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6 hours ago, ThreePointFive said:

It's been horrible doing the run-in on mine, stopping every minute for one problem or another so my 20 minutes is in minute blocks, reckon I've already ruined the cam.

I believe the Kent booklet said 2500-3000 RPM, but will be different depending on what you gone for.

From what I've read, as long as you don't allow the engine to idle, stopping/starting shouldn't matter much.

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Thanks all, having done some more reading it seems anything between 2000 and 3000rpm for 20 mins should be OK. It's not allowing it to idle that is the critical thing.

I am using this oil from Smith and Allan. Although it doesn't say on the website I emailed them and it has a ZDDP content of 1300ppm and is ideal for older flat tappet engines. I also used high zddp assembly paste on the cam and followers.

Snowing again today so delayed again Grrrr.

thanks

Mike

 

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At last! Got it running today.

Started straight away. Took me by surprise, I was expecting a bit of cranking.

Ran it at 2000rpm for 5 mins with the wife looking for any major leaks, then switched it off and had a proper look round for leaks. Fortunately there were none.

Then ran it again at 2000rpm for another 15 mins to finish off bedding the cam in.

Very happy with it, it's much smoother than before and the idle is much more stable.

Must be the longest engine rebuild ever! Started looking at it in August, although didn't pull the engine out till November. I blame painting the garage floor, lockdown and the weather!

Booked in for MOT on Wednesday, so fingers crossed.

Thanks to every one for advice and encouragement.

Mike

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Took it for MOT this morning

It Passed

CO 0.4%

HC 32ppm

A world away from where it was before rebuild (high CO and 1500ppm HC).

Of course being a Land Rover it wouldn't let me off that easily so it started leaking from the heater O rings on the way back! I knew it had a slight leak sometime time in the past because of staining on the carpet, but it's leaking properly now.

So that's the next job, not too bad as I had to get to the heater anyway to change a faulty blend motor.

Wonder what it will be after that...

Thanks again

Mike

 

 

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Wonder what it will be after that...

I wrote my list down on a roll of wallpaper I had lying around so I didn't run out of space 😄 It must feel great to have it back on the road again , well done .

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