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Does my V8 need a rebuild?

Ben Jordan

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Some of you might remember that a while ago i was winging about snapping a spark plug off in number 2 cylinder. Anyway today i have got my arse outside and started to get the head off. Sometime ago i remember somebody telling me that if it were all black and gunky underneath the valley gasket the engine would need rebuilding. So as i have been taking the engine apart today i have been taking some photos to show you all and get your opinion on if it needs some work or not?






If there are any other photos you need or closer ones just let me know.

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Sometime ago i remember somebody telling me that if it were all black and gunky underneath the valley gasket the engine would need rebuilding.

Not much wrong there! You know when it is knackered as there are big black "cornflakes" in there. Yours is one of the cleanest I have seen.


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That looks fairly clean.

I would have a closer look at the camshaft though if I was you, especially the lobes for no.7 and no.8 cylinders as they tend to wear first.


Here is a pic of the No. 7 and 8 cylinders. Can't see much of them. What am i looking for when checking for wear? The lobes seem to wearing on the outside.


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Clean so thats good....

Pull a couple of the tappets out and check the bottom of them for dimples or tracks which would indicate they have not been rotating. Also check the wear patterns on the cam.

You could probably rotate the engine and measure the distance each tappet assembly rises/falls to give you an idea of the amount of lift left for each lobe. Not the most accurate of solutions but when I replaced the cam on the 4.2, there were two lobes which were almost round like a journal :huh: and that method would have highlighted them as caput.

Personally, if it was me, I'd pop a cam and tappets in as a minimum. Then probably a new timing chain. :)

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If you are lucky, the tappets should just pull out. If they resist, it is because there is a rag of metal on the bottom (unlikely) then you need to push them out the bottom after you've got the cam out.

Changing the cam with engine in is ok. I did one of mine with the engine in. It got a bit fiddly because of the air con condensor but I wiggled it up and snuck the cam in ok. :)

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If the engine has more than 70K on it and the history of oil changes is unknown then as a minimum I would change the cam, lifters (Tappets), & timing chain / gears. ;)

Big problem with this engine is marginal oiling to the top end ….. especially at the back of the engine, so wear in this area is not at all uncommon. I have pulled cams on perfectly running engines to find them extremely worn. Because the hydraulic tappets (lifters) auto adjust for wear, they can hide a phenomenal amount of top end wear. It’s difficult to see in the pictures but you might also consider changing the rockers & rockers arms.

If the mileage is as above then also consider changing the oil pump gears to restore the health of the oil pump. Be aware that changing the oil pressure relief valve plunger can cause it to stick due to scoring in the bore ……… careful use of a polishing mop with a dremmel can fix this problem.

After doing the above, change the oil every 3K to ensure longevity.


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Not much wrong there! You know when it is knackered as there are big black "cornflakes" in there. Yours is one of the cleanest I have seen.

I hate to be a killjoy, but that's pretty much how mine looked when I had to do the head gaskets at about the same mileage - I stuck it back together and a few thousand miles later the timing gear disintegrated...

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I changed my cam at 125k miles and it was toast so at 142k.... :(

I didn't want to be the profit of doom and mention the rockers and shafts but it does makse sense. Neither did I want to quote the "Geoff" case because I was being sensitive. :ph34r:

Really, if you get the exhaust manifolds undone without too much problems, leave the engine in.

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If its a 3.5, fit a 3.9 cam for a bit of extra oomph. If its a 3.9, fit a 3.9 cam. :D

Fit a Duplex timing chain.

Tappets / Rockers / Shafts - use OEM.

Check the heads for flatness, potentially skim.

Check the tappet clearances / preload (as per RPi site) and buy shim kit just in case.

You can get the kit from RPi (www.v8engines.com) or Real Steel.

Enjoy... :)

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top end overhaul is easily done with engine in place.

check Craddocks and Paddocks for engine spares; if you want the rockers to be the original alloy type (el cheapo aftermartket ones are steel), then you need to get them from rimmer bros; how do I know? I bought up the last ones! :rolleyes:

also the the cam gear; I'd avoid the nylon tooth ones.

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Looking at your pictures gives the following observations ……..

1) From the head pictures it appears if gasket sealing compound has been used on the head gaskets.

Were the gaskets tin or composite ?. The use of sealant in this area is a very big no no and could have been done as a cheap fix. Ideally the heads should be skimmed before replacing ……. The trick is to just take enough off so that they are perfectly flat. That job is usually about £30 per pair and needs to be done by a very competent machine shop as there are no right angles (perpendicular faces) to set it up with.

Can you post a picture of the head gaskets ……….. face up …… as this will give an indication of any blowing into the valley …… yet another common problem and the source of all the carbon build up in the valley area.

2) It looks as if the head bolts on the inner and outer rows have been either thread locked or sealed with blue hylomar.

Again this is incorrect and smells of ‘grease monkey’ and I suspect has been done to avoid the usual corrosion problems …………. Ideally, at reassembly these bolt holes in the block should be carefully cleaned and then finally cleared with an air line. The bolt threads should then be lightly oiled. A good mix for these HT steel bolts into the alloy block is a 60/40 mix of EP90 & paraffin…… EP 90 to protect and paraffin is an alloy lubricant.

What it is difficult to quantify is,

1) How long ago were the heads off & for what reason ?

2) What other work was done at the time ?

I would think that these questions are difficult to answer, but further examination may give you more clues as to the health of the engine. If its all genuine ……. at 142K then under normal circumstances the engine is near the end of its useful life & could be restored to good health by a full rebuild.

What was the oil pressure like ? …………….. It should be 28 to 30 psi @2500 with the oil at normal running temp (80C) …….. and at tickover it should be 18 to 20 psi. Low oil pressure generally indicates the need for rebuild due to wear in the oil pump, big end shells, & main bearing shells.

Whilst you have the heads off the following measurements can easily be taken.

1) Check the bores for ovality (internal micrometer required)………… the bores always wear more on the thrust side so therefore end up slightly oval. Ovality of less than 1 thou can be ignored. 1 to 3 thou can be taken up by glazebusting and a new set of rings …… over 3 thou requires a rebore. For the ovality check, if you don’t have an internal mic, then take a length of 3mm welding rod and using a warding file carefully file the ends until it is a perfect fit in the bore. Rotate it through 90 degrees and measure any difference in fit with some good quality feelers.

2) Check the general condition of the bores ……….. how large is bore step at the top (the bit of the bore above TDC) …..ideally this should be measured but can also be felt using your finger or thumb nail. Also look at the bore walls for any scoring…… often an early indication of ring problems. Equally bores still showing signs of cross hatch honing marks could be considered as in very good condition.

3) To check the general condition of the cam without further stripping, measure the lift (using a dial gauge) of no1 inlet and no 8 inlet and compare the difference …… if there is any difference then the cam is showing the classic designs of being very tired. The wear will be very apparent on no 8.

4) Try to pull out one of the lifters (preferrably cylinders 7 or 8) and see if the bottom is pitted. This may or may not be possible………. If they have not been rotating correctly then the leading edge of the lifter will have a slight burr on it, or, if the lifter is original there will be a carbon build up on the lower body ……. Both of these factors will stop it being pulled out from the top. Do not under any circumstances try and force it out as this will cause bad score marks on the lifter bores.

5) Check the play of the rocker arms on the shaft ..... there should be none ........ the arm should be a perfect sliding fit on the shaft. Again the rockers wear oval due to the thrust side being at the bottom of the rocker.

How far you go depends upon what you are looking for in the longer term. You can fully rebuild a 3.5 /3.9 yourself for about £800 including all the machining of the rebore, crank grinding and head skimming. Without too much expense its fairly easy to get just shy of 200 ponies with the EFI variant of the above. Half decent cam together with careful gas flowing / skimming of the heads, HC (9.75) pistons and decent exhaust headers.

HTH :)


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It's a 3.9.

Ian, I will get some photos of the head gasket although it has been rained on now.

So does everybody recommend OE parts and not some performance or higher-grade bits?

Depends on what you replace.


GENUINE Gaskets all around etc

Later rubber rover gaskets

Black LR Goo glue for sump - no gasket

COMPOSITE Head Gaskets (Genuine) NOT tin **** ones

Steel Timing gear and chain (Non Genuine).

20/50 duckhams classic oil

Cam and followers, branded or genuine, Piper do good ones, stay with grunt low down, do NOT fit one with "fast Road" etc.

Use NGK Plus not champion, BP6ES, and NOT the silly multipronged things

Just some thoughts


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