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Compression problem
#1
Our car is in getting a major service at a specialist, and he's discovered one cylinder that is significantly lower on compression than the rest - I'm not sure on the figures, but it's enough for him to be concerned. Is there anything these engines tend to suffer from? Do they burn valves?

I'm thinking, from best to worst, it could be a) head gasket, b) damaged valve, c) damaged valve seat, d) sticking piston rings, e) damaged piston rings, or f) damaged bore.
Med Venlig Hilsen
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#2
The only one I've ever had/known with that problem was the original engine ( turbo-charged) in Frenchy. Its still in roof of my garage awaiting further investigation.
Chris Parnham in Derby  chrisparnham@live.co.uk 
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#3
As per the other post, Personally if it were me I would try getting the injectors done and see if it runs better as they are 'toast'. Is the engine oil getting full of fuel? It's one of those things you 'could' chase forever and spend large £ or the engine will run on for 100k miles without any problems. It was running reasonably well before as well.
Chris
Membership Secretary DOC UK
2018's DeLorean event: http://deloreans.co.uk/forum/showthread.php?tid=5715
VIN#15768 Ex VIN#4584 1972 Bond Bug.
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#4
Had a long and depressing chat with the guy tonight - he's a Volvo Master Tech, so has been around these engines forever. It would appear no 5 cylinder has only 35psi, and none of the cylinders survived the leakdown test - all lost their pressure in under a minute. He didn't think it was rings, more likely something up with the valves. The engine or box needs to come out to do the crank nose seal, he's suggesting pull the engine and do a tear down.

I'm tempted to source a good used engine, might be easier in the long run. Or go mad and get a twin turbo crate engine. Sadly I don't have £8k...
Med Venlig Hilsen
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#5
mmm, not good news, I would be surprised if it's the pistons as I wrote above. The heads can be done in situ but if there are other things to do then probably easier to pull it out. Good used engines are getting harder to come by as well now. Probably best just to strip the heads off and see whats wrong to start with.
Chris
Membership Secretary DOC UK
2018's DeLorean event: http://deloreans.co.uk/forum/showthread.php?tid=5715
VIN#15768 Ex VIN#4584 1972 Bond Bug.
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#6
Well he's pulled the head off 4 5 6 and bench tested the head - valves are leaking badly. Pistons and liners are looking serviceable. Heads are getting stripped down and assessed later in the week.

I'm wondering if the ineffective injectors have caused very lean running, which in turn has burned the exhaust valves? If they need replaced, are there any Volvo alternatives in the UK that might work out cheaper?
Med Venlig Hilsen
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#7
Quote:I'm wondering if the ineffective injectors have caused very lean running, which in turn has burned the exhaust valves?
that seems a reasonable assumption to me as well. I did not think it would be a liner/piston problem. Not sure if there really are any other cheaper valves you could use, best to just bight the bullet and do it right the once!
Chris
Membership Secretary DOC UK
2018's DeLorean event: http://deloreans.co.uk/forum/showthread.php?tid=5715
VIN#15768 Ex VIN#4584 1972 Bond Bug.
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#8
Does anyone have a rough feel for the expected garage bill for replacing a pair of cylinder heads on one of these? We have the first installment received and it makes for eye watering reading...
Med Venlig Hilsen
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#9
Doive Wrote:Does anyone have a rough feel for the expected garage bill for replacing a pair of cylinder heads on one of these? We have the first installment received and it makes for eye watering reading...

I sold a pair of fully refurbished heads with re ground valves and new stem seals for £210 (I have another set waiting to be done) + gasket set ~£50 so that gives you an idea of the hardware cost.

It's the labour that can clock up fast I would emagine a competent mechanic with all the right tools on hand would have it done within a day?

James
www.classicdelorean.com
Colchester - Essex - UK
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#10
We have just this afternoon been given their guesstimate to completion... I had to sit down for a while. I thought he had made a typo.

£3,500.... Shock

That's to remove both heads, strip, rebuild and replace on the car, and reinstate all ancillaries - injectors, fuel distributor, water pump, etc. Given that the car is in bits, I don't see many options as an alternative.

I've had heads rebuilt before on more humdrum machinery, and they didn't cost £1,750.

Anyone think this figure seems reasonable, or are we getting tucked up?

I really wish we had parked the car in the barn until the winter and forgot about it, until I had time to fix it myself.
Med Venlig Hilsen
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#11
All I can say is I would normally do work like this myself.

But a couple of years ago I had a valve problem an a V6 Petrol VW Toureg …(caused by using LPG.) We bought a couple of s/nand heads for £500 and had them fitted by a local specialist…it's a heck of a job on one of these, because the engine is basically in back to front. He charged me £1200 for the work, which I thought was very fair.
Chris Parnham in Derby  chrisparnham@live.co.uk 
RHD Auto MGJ 126Y (AXI 1699)
Outlander PHEV 4X4
MG ZS EV....Full Electric SUV.
TR7 Convertible 

DOC Club Historian 
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#12
At that price you would be better sourcing a decent condition PRV and just getting the garage to swap it in!
VIN 4494, Grey interior, 5 speed, October 1981
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#13
Long story short - bent inlet valve on cylinder 5. Looks like someone timed up the nearside bank incorrectly, and valve must have gently contacted piston before they noticed and retimed it correctly. As a result the valve wasn't properly sealing onto it's seat, nor were the inlets on 4 and 6, but these were rectified by lots of lapping. Bent valve was replaced. After all this work, the engine is as sweet as a nut, pulls well, and sounds magnificent.
Med Venlig Hilsen
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#14
An unusual fault that…glad it all sorted. Smile
Chris Parnham in Derby  chrisparnham@live.co.uk 
RHD Auto MGJ 126Y (AXI 1699)
Outlander PHEV 4X4
MG ZS EV....Full Electric SUV.
TR7 Convertible 

DOC Club Historian 
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#15
phew, bet that cost less then £3500!

i had 2 new fully rebuilt heads from PRV guru Darren Bowker (Renault 30 expert)
back in 2003, he charged me £70 each for them back then including P&P, and I knew
I was getting a bargain!
Claire Wright  - Club Treasurer
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