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P38 4.6 Engine repair - what to do next?


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Hi all,

I have a p38 4.6 with engine problems.

First some history. I bought this cheap with no MOT multiple electrical woes and a clacking engine (yes I'm mad).

Took it for an MOT and it failed on a couple of ball joints, rear pads too low and emissions miles off - over 2000 HC and high CO.

Fitted new ball joints and pads. Sorted the electrical problems. Then had a look at the emissions.

The left hand Lambda sensor wires were mashed over where they entered the sensor (more bodgery/ham fistedness which seems to be common theme with this car).

Replaced lambda sensor and took it for a re-test. Passed everything except emissions, which were better but still way off around 1500 HC. Maybe not surprising considering the clacking engine!

So time to get into serious investigation.

Did a compression test (cold so not ideal).

Left bank
1 179
3 110
5 132
7 129

Right bank
2 171
4 176
6 173
8 179
Right bank looks OK assuming 170ish is OK? But left bank obviously has problems.

So starting with the obvious problem the clacking sounded like a typical worn out camshaft lobe, so I pulled the plenum and took off the rocker covers. Exhaust on number 7 had shed loads of slack, all the rest seemed fine.

So pulled the inlet manifold to look at the cam. The exhaust lobe on 7 looked fine and the lift on it was the same as a coupe of the other exhaust lobes, so not the cam.

Next pulled the rockers and found a poorly rocker. I think that will account for the clacking. As its exhaust I don't think it would account for low compression (inlet might but not exhaust?)

Rocker.thumb.jpg.02f67fc4e038f448f1f4272142fac393.jpg

 

Next was to remove the LH cylinder head, I say remove "remove head" - see 

With the head finally off this is what I found.

 

Block.thumb.jpg.85b24afc00d4582ae1bcbca996a06254.jpg

Head.thumb.jpg.5ad0f81d559b1838a8d2244fa25b2f1f.jpg

1645012723_GasketBottom.thumb.jpg.1d49f7a0ec28ec4f49e7cfd7fbae37fd.jpg

217986012_GastketTop.thumb.jpg.2a52efafa1d047c5bbf349a91225edd2.jpg

 

Number 3 definitely is not right, in the picture it looks a bit steam cleaned but actually it has an oil film on it. The plug on this was also a bit sooty compared to the rest.

5 and 7 don't look too bad.

Bores look OK can't feel any wear ridge on 3 ,5, and 7 and only very slight on 1 using thumb nail (very scientific).

Looking at the top of the head gasket there is slight discolouration between the cylinders, don't know if that means anything?

So thoughts and suggestions please.

Thanks

Mike

 

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16 minutes ago, Peaklander said:

Doesn’t an exhaust valve need to seal just as well as the inlet for good compression?

Definitely.

Not sure what that rocker picture is showing though. Is that dished or buildup of some sort?

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Posted (edited)

It wasn't the sealing of the exhaust valve I was thinking of. The rocker has a significant dish in the end causing massive slack in the valve train hence the engine making a "clacking" noise. My train of thought was that significantly reduced valve opening on an inlet would restrict air intake and reduce compression pressure but reduced opening exhaust valve, which this rocker is on, would not.

Since then I have put the head combustion chambers up on the bench and filled them with petrol. Cylinders 3 and 7 leaked away in about 5 minutes into the inlet ports so leaky inlet valves. 1 and 5 took significantly longer 15 mins and still not empty with no leakage visible in the ports so may have been evaporation rather than leakage, its warm today. Not sure if that's sufficient to account for the lack of compression on 3 and 7?

At this point were it not for the oil in number 3 I would be tempted to re-seat the valves put a new head gasket and rocker in and give it try.

But the oil in 3 concerns me. There are no oil ways near by so where is coming from? Only thing I can think of is piston rings, but would be happy to hear of another explanation.

So a bit unsure on how to proceed now.

By the way in the head gasket pictures number 1 is on the right.

Thanks

Mike

Edited by MikeAK
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Not sure about oil consumption. Car was dropped off at my house and I have only driven about a mile each way to MOT garage.

No noticeable smoke from exhaust though.

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I always found it easier with the V8's to put in a second hand engine. Unless there are historical issues you want to preserve the engine route is a lot less hastle and with a know running engine you will be good to go in no time. 

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I agree a second hand engine is the fastest and often the cheapeast solution to keep a car on the road. But you do run the risk of facing similar problems before long.

And there is a huge amount of satisfaction to be gained from rebuilding an engine yourself (and the V8 is an easy one) and then hearing it come to live and enjoying the renewed performance. 😉 

Filip

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Hi all,

Been away from this for a few days. Had another quick look today, cleaned up the head and checked it for warping. Can't get a 0.05mm feeler between head and a straight edge anywhere so I think head is sufficiently straight?

Put a 50/50 mix of petrol/ATF in the bores and that hadn't run away, or even dropped after best part of an hour so I think the rings are OK?

Given the inlet valves are on 3 and 7 are leaking and I think I can see evidence on a leak (or the beginnings of one) on the gasket between 3 and 5 I think I will re-seat the valves and replace the broken rocker and re-fit the head. That will only cost a head gasket, bolts and rocker so not to bad if it doesn't work. With the head and rockers back on I'll spin it over and do a compression test again before building the rest back up.

If at that point it has brought the pressures on 3,5, and 7 back up to the 170ish PSI of the rest, I'll put it all back together and give it a go. If not I'll have a think about replace or rebuild.

Agreed second hand engine is quickest/easiest but have been down that road before (not in a Landrover) and ended up repairing the replacement 9 or so months down the road. Having rebuilt a few engines in the past, including RV8, I find it quite a therapeutic way to spend a few evenings in the garage. Also as Escape says a lot of satisfaction when it starts as well.

Mike 

 

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5 hours ago, MikeAK said:

Agreed second hand engine is quickest/easiest but have been down that road before (not in a Landrover) and ended up repairing the replacement 9 or so months down the road. 

 

Yep...………………………………………………...

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17 hours ago, MikeAK said:

 

Agreed second hand engine is quickest/easiest but have been down that road before (not in a Landrover) and ended up repairing the replacement 9 or so months down the road. 

 

by putting in a replacement engine it gives yoú the opportunity to use the car and troubleshoot problems with it while also having the benefit of therapy sessions in the workshop rebuilding the engine. best of both worlds.

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Its always handy to have a spare engine ( or 7 ) for many reasons 😄

As has been said, Rover V8 is simple and relatively inexpensive provided you dont go silly with trying to get extra oomph

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I put the head back on this last night and did a compression test.

5 and 7 are now up at 172 and 175 same as the rest but 3 is still a bit low at 150.

A bit of oil down 3 and that was also mid 170s, so worn/stuck rings?

But it's a distinct improvement on what it was, so I think I will put all back together and see if It will go through an MOT. If so at least I can use it and look for a second hand engine to rebuild properly. If it still fails I will put the car somewhere more convenient and and rebuild the current engine.

Mike

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1 hour ago, MikeAK said:

I put the head back on this last night and did a compression test.

5 and 7 are now up at 172 and 175 same as the rest but 3 is still a bit low at 150.

A bit of oil down 3 and that was also mid 170s, so worn/stuck rings?

But it's a distinct improvement on what it was, so I think I will put all back together and see if It will go through an MOT. If so at least I can use it and look for a second hand engine to rebuild properly. If it still fails I will put the car somewhere more convenient and and rebuild the current engine.

Mike

It could be stuck rings, chuck a slug of ATF into the bore with the piston at BDC or close to it, so you can get enough to cover the piston and leave it for a few days to soak in nicely, that should free the rings up for you.

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  • 3 weeks later...

Finally got some time on this again yesterday.

All back together and and running a lot better but still not right. Now the very loud clacking from the rocker has gone I can hear other rumbles etc. Also still struggling to pass MOT on emissions, although vastly better HC still to high and slight visible blue smoke when revved for fast idle test.

So as I've decided this is a keeper, I'm going to pull the engine out and do a proper re-build.

So a few more questions!

Will the manifolds clear the bulkhead if the engine is removed with all the front ancillaries removed but the radiator still in place? I ask because it looks like it might be a bit tight and the right hand manifold looks a pig to get off in the car.

Anyone got suggestions for a better camshaft? FridgeFreezer has already recommended a "Stump Puller" which I will be looking at. I want something that is still drive-able for road use, green lane etc. 

I am looking using ARP head studs in the rebuild, what are peoples experience of these? As they are more "traditional" rather "stretch" bolts I assume they will need to be re-torqued after a period of running?

Unfortunately none of this will happen for a few weeks as my garage floor is being screeded next weekend, then I want to paint it before putting everything back in.

Thanks

Mike 

 

Edited by MikeAK
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Ok radiator out and flushed it is then.

Thanks for the cam recommendation, are you using standard lifters? From linked website "Can be used with standard OE lifters however, for better performance consider Rhoads Bleed Down Anti-Pump lifters"

Will be using ARP studs, if they don't require re-torquing how do they maintain clamping force as the head gasket "settles"? I thought stretch bolts did this by acting as a spring or more traditional studs/bolts had to be re-torqued after a few hundred miles?

Thanks

Mike

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Standard lifters I think.

Pretty sure the head gasket doesn't have that much give, at least not the modern ones. As I understand it, yielding head bolts are used because they yield at a very predictable torque, not because they're springy.

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We've always run those cams with standard lifters, with good results. I do have a set of Rhoads lifters in a newly built engine, but that car is still far from finished.

As Elbekko says, the gasket doesn't give that much. And all bolts/studs will stretch to some degree, to take up both settling and temperature effects.

Filip

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Right looks like I will probably go with the cam Elbekko suggested with standard lifters.

Yes L19MUD it would have been much easier 😉. At the time it wasn't very convenient to take the engine out so I was going for a quick fix, which almost but not quite worked.

Now I've got the opportunity to remove the engine in some ways I'm quite pleased it didn't work so now I can do a proper job!

Unfortunately it's on hold for a few weeks as my garage floor is being screeded tomorrow so I'll have to give that time to cure before running an engine crane etc. over it.

Mike 

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