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P38 4.6 V8 Top End Rebuild


Fatboy

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Hi all,

My 1996 P38 has been chuffing a bit and got a bit lumpy.. Theres oil in more places than there is usually and a bit of muck in the rockers so as its done 100k miles, I felt in was time to replace the head gaskets and cam shaft.

I'm in the process of stripping it down at the moment and didn't realise there were so many electrical plugs! Anyway, I'm going to clean the rockers out to get rid of as much muck as possible but I was wondering what the best thing to do with the loom / plugs.

I've got brake cleaner, WD, Duck Oil etc etc. Should I blast the connectors with cleaner, dry them with compressed air then apply duck oil before connecting them back together or are they best left as they are?

Opinions gratefully received ! :)

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Depending on how bad the engine is you may need to allow the lifters to drop into the sump and recover them by taking the sump off. Often at 100K + the lifters will have a carbon ring on the lower edge which will damage the lifter bores if forced upwards……….

whilst you are in there try and blow the lifter oil galleries clear with an airline and some plastic tube………… ;)

You can also probably lay a safe bet that the rockers and shafts are both worn out ……….

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Thanks for the tips with vaseline - hadn't thought of that.

I am replacing the timing chain, lifters, rockers & shafts as well. Heads have been pressure tested, skimmed and valve guides replaced so I'll need to shim the pedestals too.

Sump is off to clean it out although there wasn't any sludge. All but one lifter came "up", I'll prod the last one down later.

I've taken the baffles off the rocker covers to clean the breathers out and get the muck off them, all going okay so far. :)

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In your original post you mentioned 'chuffing' - did you mean sluttering on idle out the exhaust? I take it your heads are o.k. for use after skimming. What were the valve seats like?

Reason for asking is mines got 170,000 miles and will not run clean on idle or low revs.

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In your original post you mentioned 'chuffing' - did you mean sluttering on idle out the exhaust? I take it your heads are o.k. for use after skimming. What were the valve seats like?

Reason for asking is mines got 170,000 miles and will not run clean on idle or low revs.

Has it ever had a new cam and timing chain ? …………. They usually break at between at over 150K because they just cant stretch anymore ……………I would guess that the cam is worm and the valve timing is way out due to the chain.

Occasionally if there is enough slack the chain rides a tooth and the plastic timing gear breaks up ...............

Either way, damage is severe ………….

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Steve,

The chuffing was coming from the front, possibly from the exhaust gasket at the bottom of the manifold where it joins the pipe. Idle is low and a bit uneven but thats typical of them apparently.

I optimistically hoped to get the engine stripped today but have failed - The front cover has been tricky with one bolt sheared off (N/S, above the water passage). I had a narrow gap but it just wouldn't budge so I cut the bolt with a hacksaw blade and will get the stump out tomorrow (drill or weld a nut on it).

My timing chain is very slack!

The lifters are all dished on the bottom so I guess they've been rotating happily. A couple are quite concave so it is indeed about time they were replaced.

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The front cover has been tricky with one bolt sheared off (N/S, above the water passage). I had a narrow gap but it just wouldn't budge so I cut the bolt with a hacksaw blade and will get the stump out tomorrow (drill or weld a nut on it).

Weld quite a large nut on the end and weld through the end of the nut to build up a plug to get as much heat as possible into the bolt ......... this will free it off.........

My timing chain is very slack!

This has the effect of retarding the valve timing. The net result is loss of low/ mid range torque, but an increase in the torque at high revs. It tends to make the engine very lazy. Retarding the cam at idle also allows for better emissions (VVT engines).

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N/S head off, slight marking between the front two cylinders and the head bolt that suggests its been leaking somewhat. One of the new exhaust gaskets I put on a couple of weeks ago has been leaking too - that might have been the chuffing..

I've spent most of this morning trying to get the exhaust manifold off the O/S.. The tin heat sheild was a royal PITA, ended up using a wrecking saw from below to get one of the little bolts - It had corroded smaller than an 8mm Irwin but was not willing to give up without a fight.

No matter which sockets I try, I can't get to the furthest back manifold bolt and get a ratchet on it so now its off with the steering linkage :blink: to provide a bit more space..

The joy!

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Time for a couple of photos:

NSBlock-1.jpg

N/S Head between the front two cylinders.

NSHeadGasket.jpg

Corresponding marks on the head gasket. Note there are similar stains between 4&6.

OSCylHead.jpg

O/S Head. Looks to me like No.3 was leaking to atmosphere.

OSHeadGasket.jpg

Again, the corresponding gasket.

TimingChain.jpg

One worn timing chain... :P

3RearOSWaterPassage.jpg

Interesting - This may have contributed to its slight loss of water - although the carpet is also damp with antifreeze so the "O" rings on the heater are next on the list... :rolleyes:

5NewNSExGasket.jpg

Looks like I did a poor job of fitting the exhaust gasket a couple of weeks ago..

Current State of Play:

Heads are both off, timing cover is off, new crank seal is fitted (2mins but I wanted to do somthing positive today).

By removing the steering linkages from the column to the steering box, I got enough room to get the exhaust manifold off. The tin shield bolt eventually gave way to the wrecking saw..

Sheared bolt on the block is still in place at the timing cover end - I decided to see if I could shift the air con rad & oil coolers enough to get the cam out - Sheared a fitting off the autobox oil cooler in the process - spendid!

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  • 2 weeks later...

Ian,

Sorry I didn't post a valley photo... it turned out fuzzy! The heads and valley were dark but no lumps or flakes.

Oil cooler arrived yesterday so that was fitted, radiator refitted and fluids replaced before I went through 20mins of panic as I sat at 2000 to 2400rpm to bed in the new cam. Had to shut it down once to top up the water but didn't idle it so should be fine.

Since then, I've done 200 gentle miles over to Aviemore and back - engine is much smoother! CHUFFED :D

Tonight, I'll be realligning the steering wheel, adjusting the throttle cable and checking bushes and props to try and find the vibration.

Many many thanks for the help and encouragement. Hopefully thats it sorted!

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