Missing a beat

[Garth]

Hi Chaps and Chapesses

Sorry to be boring but this is really doing my head in.

RRC 3.9 efi Duel fuel, Tartini gas convertion (draw through with Lambda sensor)

Has a missfire mainly noticable on tick over.

Work done so far:-
New plugs BP6ES set to .9
Changed plug leads for Second hand (but quite new) 8mm High Power Silicone
Different dizzy cap (again second hand spare)
Cleaned and re terminated coil LT
Compression test (LH bank 155-165 RH 145-155)
Different (spare) ECU

After doing all this the missfire is worse on LPG (its like a fluff on petrol and a miss on LPG) so leading me to HT electrics

Looked at in dark tonight and there was tracking from coil lead so re routed (no tracking but no better)

Also noticed tracking coming from either - end of plug cap or base of Spark plug on 2 cylinders but not every cycle
Anyone see this before whats causing it?

 :(  :(  :(  :(  :(  :(

[gtomo2]

Got the same thing on my disco running lpg. Close your plug gap to .8. and clean the contacts in the dissy then run for a bit and re check the dissy i found that the dissy on mine was warped and was missing the rear pin out you will be able to see which one is missing if its the dissy as it will still be clean and the rest will have a black mark on them were the spark jumps from the rotor arm to the dissy pin. i fitted a new dissy and it still did it found the brand new dissy had warped as well. Best to use lucas dissy cap not a copy. if the dissy is ok check your ht leads are not touching or crossing as that can do it as well.

[Range Rover Blues]

Don't fit hong-kong-fuey ingnition parts like rotor or cap, LPG takes a lot of igniting hence the closer gap, say 27 thou rather than 30 thou.

[Henry Webster]

I went through some of this earlier on the year on a petrol only set up.  The only point I would make is don't rely on SH parts to make a diagnosis.

I went right round the houses several times and then in the end threw another NEW set of leads at it and it runs fine!

[Garth]

Well we now have NEW NGK BP6ES plugs at 0.8
NEW Lumenition 8mm Silicon Blue plug leads
New Lucas Coil
New Lucas Dizzy Cap
New Lucas rotor Arm

The misfire on tickover is worse and now missing midrange under load on PLG and petrol so what ever it is is getting worse

[Garth]

Dyslexia rule KO :oops:  :oops:  :oops:

[Range Rover Blues]

Ok, silly things time, did you check the routing of your new plug leads as per the diagram in the manual, it shouldn't be a problem with good leads but tracking between leads can cause problems on a V8.

When did you last change the oil and did you use good stuff, there was a post recently by Eyore to the effect that cheap oils froth inside the hydraulic lifters and cause an intermittant misfire.  On that theme so can a badly worn cam.

Inlet manifold leak
Badly worn dizzy
faulty coil
leaky injector

So what colour were the plugs that came out?

[MuddyMike]

How many miles has the engine done on the current cam shaft?

Mike

[Garth]

Plug leads routed as per manual
Oil :- Millers Magnol and new
Plugs :- light brown
Sprayed WD 40 around all inlets - plenim etc.  OK
Dont know how many miles engine has done (its a different one to original)

[MuddyMike]

If a Rover V8 has had regular changes with decent quality oil the camshaft will last up to 100,000 but no more. If however the oil has not been changed regularly or poor quality oil has been used it wont make 50,000 without serious wear. The lobes simply wear away with those on the rearmost cams going first. Have a good look inside the rocker covers removing one if necessary. Is there a lot of black tar like deposit? If so this is a sure sign of poor oil change routine and a good guide to the cam being worn. The hydraulic lifters both mask the effects and contribute to the early wear by keeping in constant contact with the cam. Replacement of the cam shaft and lifters is not a massive job, nor are the parts that expensive. Its a good idea to replace the timing chain and sprockets and fit an oil pump overhaul kit whilst you are in there. Take a look at http://www.v8engines.com/engine-4.htm#worncams it gives useful information on cam wear and lot more.

Mike

[MuddyMike]

Just noticed you are from Chester Le Street Garth. I am up you way on Sunday for  NERO club trial at Middridge.

Mike

[Garth]

Sounds like LH rocker cover is comeing off, as when pulling leads off when running there is very little difference on no. 8 plug (back of the engine) and the RH head has been off (before I got it).

Trying my Dads Dizzy in this afternoon

Regarding trial depends what under the rocker cover :!:

[Range Rover Blues]

Did you do a comp test?

[Garth]

Yes
Compression test (LH bank 155-165 RH 145-155)

[Range Rover Blues]

RH being the head you're about to take off.  Any chance No. * is the one at 145?

Anyone else think they sound a bit low :?

[Garth]

N0 8 is on the LH side (looking from front)
I presume whoever did RH head put a composite head gasket on hence the difference in compression

[Range Rover Blues]

So the head with better compresion is running the worst :?

I think you shold take both heads off then if you go that far, get them skimmed and refit with composite gaskets.  I'd expect a minimum of 165 PSi though and up to 185/190 on a good 'un.  Mine does over 200 but I now it's been tweeked.

[Garth]

Well took heads off this weekend and passengers side was NG leaking between 1 and 2 and 1 and waterway.
Has been off before not to long ago buy the looks of it. Had composite 10 bolt gasket fitted to a 14 bolt block and head.  Minor pitting on head between no 1 and waterway.

Drivers side head and block was OK with a 14 Bolt tin gasket (could be original but no signs of witness mark on head if it has been changed its been done properly, new lock tabs on exhuast etc)

So heads are off ready to be skimmed and here is where advice is needed.
As it many years since I have done this sort of thing.  Do I decoke the heads/ports with wire brush and drill (they are not that bad) or do engine company's now have a magic solution they can dip heads in to clean them up.

Also do I lap valves in before or after getting the heads skimmed.

Composite or tin gaskets. Why?

10 or 14 bolt? again why.

Acording to manuals should have 14 bolt tin gaskets.

The piston tops look OK no major carbon deposites, so will leave well alone, but what lateral movement is accepable.

Yours in anticipation Garth

[Range Rover Blues]

Strip the heads and have them skimmed, as one has been done already you may need to have the other skimmed more to 'catch up'.

There is a witness mark on the front of the RH head (back of LH head) to judge how much has already been skimmed.

Composite gaskets are 1.2mm once fitted, alloy ones are 0.5mm.  Get the heads skimmed by around 0.7mm and fit the composites, they are far more reliable.

The outer 4 bolts can actually distort the head and cause gasket failure, dealers were advised to refit heads with the later 10 bolt gasket.  You can also buy a 14 bolt composite so I'd say go for that but tighten the 4 outer bolts to the absolute minimum torque, so they are hardly doing anything.  One of them holds the alternator bracket after all.

You should be using a thread lubricant/sealer rather than copper slip on the head bolts.

Once skimmed you need to clean all the swarf from the heads, that's the time to clean everything up.

WD40 will desolve all the carbon deposits nicely with no scratching, use a kitched scourer (not wire wool, the green plastic thingy) and seal the edges of the pistons with grease before starting, do both the pistons and the heads the same way.

Lap the valves in, rude not to.  You should all but get rid of the small round black marks on the valve/seat mating faces when you lap them in.  Any sign of deeper pitting then replace the valve, look particulary at the exhaust as these are the ones that go.

Put new valve springs in and renew all the stem seals.

I spent a little time fetling the cast surface of the inlet too, don't go mad unless you are measuring the gas flow but getting rid of any big ridges is a good idea.

As for the tolerable slap on the pistons I can only refer you to the relavent manual, but if the following advice helps....

Was it making a piston slapping noise before you stripped it? if not I'd say if it's not bust don't fix it.

If it was slapping a little, look for signs of scoring in one cylinder or a ridge indicating a possible broken top ring.

Does it use a lot of oil too.

A new bottom end (short engine) will set you back £1700, is it really this bad?

Did you ever do a compression test?

Chances are the bottom end will be ok, expect it to be unless you see evidence to the contrary.

Take you time and keep things clean.

[Garth]

Thats a prity comprehensive reply THANKS

Yes to matching heads had planned to do that

Still can not find whitness marks but have found original dimensions for thickness of heads so will bring verners home tommorrow to check

Yes to outer head bolts (read somewhere 30 for outer 2 and 20 for inner 2)  

Leaving piston tops alone as they are not bad

Lapping valves in as a matter of course (as you say rude not to) leaving original springs in as never had problem with valve bounce etc. and dont rev over 4K if I can help it.

Bores are as smooth as, oil use acceptable, compression tested posted earlier.
Just wondering as I have memories of Mini days doing heads up and knocking bottom ends out a month later

[Range Rover Blues]

I know what you mean about knocking the bottom end out but as posted above be someone else, it's the top end of the V8 that suffers and whilst the big ends could be going through the lining I'd not touch it unless you have to, disturb the big ends and the rings might catch the wear lip and shatter.  Bores would be nice to still see the honing but if not scratched then unless you are stripping it down just ignore it.


Back to the witness mark, on the front of the driver's side head there is a small square block facing forewards with a hole in it, it's less than an inch square and roughly in the middle of the front face, almost insignificant.

HGowever if you know how thick the heads should be I think you'll be interested to see which areas of the heads have had the most skimmed, as the heads tend to bend and go concave some combustion chambers get skimmed more than others :shock:

[Garth]

Measured heads before went for skimming and niether had been skimmed which was a big surprise as surfaces looked totally different.

Both measured 23.9 at thin side and 63.5 at thick side which is correct for original as new heads non suffix B engine. Definately no witness mark.

As there is only machined faces on 4 corners I cannot measure accross heads.

The engine has been changed at some point going off engine number I thought for an older engine.  But looking at manufacturing date marks the heads were manufactured November/December 1993.

Checked pistons and bores they look fine.

[Range Rover Blues]

All sound ok then.  Check for flatness with a steel rule and feeler guages, you may find the heads are now concave.  Skimming will also get rid of any pitting in the surface around the water jackets.  Is the top face of the block ok too?

[Garth]

The one with the NG gasket has slight damage going from the edge of the liner towards (but not to) the waterway tried to sand out with flat block but too deep but you can only just feel it with finger nail.  Currently looking on net to see if there is anything that will fill it before I put head back on.  Not unduelly concerned about it though.

[Range Rover Blues]

Leave it, fit composite gaskets, don't worry.

[Garth]

FINISHED :D  :D  :D  :D

Put all back together turned over with no plugs in till oil light went out.
Put plugs in and started straight away.  Tried to set timing but was a tooth out so sorted that and took for a couple of runs and seams and sounds  OK.  
Stinks though :!:

[Garth]

P.S.

Thanks for all the help and advice

[Range Rover Blues]

FINISHED :D  :D  :D  :D

Put all back together turned over with no plugs in till oil light went out.
Put plugs in and started straight away.  Tried to set timing but was a tooth out so sorted that and took for a couple of runs and seams and sounds  OK.  
Stinks though :!:

Ah, smug mode on, you must be feeling pleased with yourself :D

Well done mate, daunting task first time out isn't it?

If you can try a comp test on it now it's running.  Don't worry about the stink, it will and for some reason Ali engines stink worse but even just the grease from your hands will burn off, let alone any WD40 from stripping it or machine oil from the skim, plus of course the new gaskets.

Glad it went ok though, you're now an expert (not everyone bothers to skim the heads you know).

[Garth]

Not going to bother with the compression test.  Its running on 8  :D

Doing the heads was not a problem (as said before done many Mini ones)
its all the ancillary items (injectors, power steering pump Air con conpressor etc) and the fact that all these were add on items so bolts are in the most inaccessable places.

Just hope the therory of "do a job properly do it once" works.

[Range Rover Blues]

:D