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V8-250 Saloon: Overrun Blues

classiclife
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V8-250 Saloon: Overrun Blues

Post by classiclife »

Hello,

I have studied the archive section in relation to the various threads concerning blue smoke being emitted, but I'd like to confirm my understanding is correct.

My 1968 saloon has just under 49K documented miles recoded. The car was laid up for quite a number of years before being restored structually, with some attention to the mechanical side (not engine) all before my ownership.

Have noted that a very small puff of blue smoke is emitted quite often after overrun with the accelerator then applied - the usual test for such. I have to say it's not much at all really, but I have noticed it.

It seems that some of these engines are prone to such, with the finger pointing to the requirement of valve seals or that the guides may have wear - depending on mileage accrued.

The car runs perfectly without any concerning engine noise and the oil pressure is as it should be when cold / running / hot idle - albeit the hot idle can get very low after a long run.

Very recent quality oil change and Flexolite oil filter adaptor fitted.

Also noted, I do get a small amout of oil in the spark plug tubes and again I am aware that this is not uncommon.

Taking all the above in to consideration is this a case of live with it enjoy the car and deal with guides and valve seals when such a time occurrs to necessitate taking the heads off ??

Or is this a case of something I need to look at sooner rather than later ??

Sorry for the ramble, but thought I'd try to cover as many pertinent points as possible in one go.

Observations welcome and thank you in advance.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Sydsmith
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Re: V8-250 Saloon: Overrun Blues

Post by Sydsmith »

Hi Richard.

It would be a rare V8 either SP 250, V8 or V8 250 that did not smoke to some extent on the over-run.

My SP smokes quite badly on the over-run when hot or cold. My V8 250, which has a Russ Carpenter engine of 5,000 miles vintage, which is as sweet as a nut, but it smokes when hot on the over-run.

Oil in the plug tubes has been discussed at length on this and the old forum, live with it or try one of the solutions often suggested here. My SP engine has the problem but the V8 250 is dry, so Russ Carpenter has the solution.

As a matter of interest, my SP engine had leaky rocker covers which leaked oil onto the exhaust and into the centre valley, I used the Wilf Stevens solution of fitting 3 mm "O" ring material super glued into the groves round the underside of the rocker covers. My rocker covers are now 100% dry. You may or may not however have the grooves. Syd

classiclife
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Re: V8-250 Saloon: Overrun Blues

Post by classiclife »

Hello Syd,

Many thanks for your reply and you certainly know how to appease a concern !!

That's probably what I was looking / hoping to hear - so I am glad I asked.

Yes, I have read the threads on leaky tubes and that is something I will look in to later this year; it's only a tiny amount but would be better with no trace of it.

Thanks again.

All the best.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

connort
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Re: V8-250 Saloon: Overrun Blues

Post by connort »

Hello Richard

Firstly, I'd say that, providing the blue puffs aren't 'fogging out' following motorists carry on enjoying your motoring. Before we restored our engine we used to use our oil puffs to deter 'bumper huggers' !! We've had our 1967 saloon for thirty years and drove it many miles and years producing the minor 'overrun blues' (good song title there).

Eventually, we decided at 75k miles to overhaul the engine (my son Russell being a motor engineer at the village garage). Imagine our shock when we found the oil control rings (all 8 pistons) flush with the piston surfaces and seized in their slots !! We invested in a 0.010" rebore/pistons and crank balance that was, in hindsight, probably an overkill. Years on, we feel that a new set of piston rings and our head work of new valve stems /seals and new stainless exhaust valves would have been good enough and saved a bunch of time/money. While we were about it we polished imperfections out of the head ports and the inlet manifold.

We initially ran the restored engine on Texaco 15/40 and it only produced a momentary 'wisp of blue' at cold start from the n/s exhaust (making us wish we'd changed the inlet valves that we'd passed OK). We've now moved to Gulf 20/50 for better 'hot' pressure and will give Dynolite 20/60 a go at the next oil change.

Very likely you can get away with rings and valve/valve stem upgrading when the time comes.

Best regards ...
Trevor & Russell Connors

classiclife
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Re: V8-250 Saloon: Overrun Blues

Post by classiclife »

Hello Trevor & Russell,

Many thanks for the info and I like what I've read.

Your account puts the situation in to perspective and I think one has to be pragmatic about such situations; couple that with what Syd has mentioned already, really does give a decent overall picture.

I have not written the words for the song yet, just doing the notes on the piano :o !!

Best wishes.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

connort
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Re: V8-250 Saloon: Overrun Blues

Post by connort »

Hello Richard

I forgot to comment on the oil in the plug tubes issue but Syd has it dead to rights ... i.e. it's not easy to keep it out.
Before we restored our engine there was oil in all the tubes and some were probably 6mm - 8mm deep in oil (plugs always came out nice and easy !!). In the restoration we fitted new copper washers but it wasn't totally successful and something like 3 tubes still leaked. We had to have the engine out a second time due to an oil pressure problem and (we're experts at engine & gearbox removals/replacements) this time we used one of the modern sealants on the tube threads (can't remember if we junked the copper washers). I think my son used one of the Sikaflex sealants they use in the garage trade and now we have totally dry tubes.

Regards ...
Trevor

Pinto
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Re: V8-250 Saloon: Overrun Blues

Post by Pinto »

Hi all,
what an interesting thread as my 64 Saloon has all the above issues, lots of blue smoke on start up, not quite excessive oil consumption and rear crankshaft
seal leak. The car shows 92,000 miles but I doubt this to be correct as I have the original owners manual, the engine is the original according to the data plate. According to the information that came with the car I don't think it has had a re ring job done. My attitude is to keep driving the car on club outings and car displays and just enjoy the experience of owning a classic car.
Regards,
David B. Australia.

PatrickDixon
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Re: V8-250 Saloon: Overrun Blues

Post by PatrickDixon »

I used Hylomar universal blue on the threads and new copper washers on my plug tubes and they seem dry now. Biggest pita was getting the tubes out; I bought a second hand oil filler in the end and used the nut from that and the one from the oil filler tube my car to lock on the threads on the tubes.

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Re: V8-250 Saloon: Overrun Blues

Post by John-B »

PatrickDixon wrote: Sat Jan 19, 2019 2:17 pm I used Hylomar universal blue on the threads and new copper washers on my plug tubes and they seem dry now. Biggest pita was getting the tubes out; I bought a second hand oil filler in the end and used the nut from that and the one from the oil filler tube my car to lock on the threads on the tubes.
Laurence Jones had a lot of special plug tube spanners made. I've got one and it works a treat. It has a very large opening with a small cut out to get across the plug lead. Or contact Barry Thorne. (See back of DM for both contact details).
The plug tubes can get bent very easily if you use force that isn't equally distributed around the rim.

tjt77
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Re: V8-250 Saloon: Overrun Blues

Post by tjt77 »

Oil smoke on overrun is almost always due to wear in valve guides.. the current guides supplied have provision for modern stem seals that will eliminate the problem if fitted with new valves to assure correct tolerances.. oil smoke under load and on initial start up is commonly an issue with piston rings..early cars had a one piece cast iron oil control ring that is ineffective..
Id recommend you do a compression test to get a better idea of engine condition.. variation of more than 20 lbs between cylinders and figured below 120 psi will and you engine requires attention. Being '68 your car should have the multi piece oil ring which works well IF everything is clean around the ring groove and drain holes in piston. when cars sit for extended periods often these drain holes become choked and the oil cannot drain via it normal route through the piston.. and hence finds it way upward to the combustion chamber and gets burned as part of the combustion process..
the best cure is an intermediate engine overhaul :- remove and rebuild both heads using modern guides and seals.. remove all pistons and clean out all the ring grooves, whilst at it, drop the intermediate main bearing caps and check condition of those bearings.. at stated mileage, given the car had sat for some time its likely due for overhaul to be 'right' .. the saving grace is a light freshen up,with head overhaul, bearings and rings will probably do the trick and bring it within proper specs. .. BTW.. you can use rings for a BMC 1622cc engine which uses same bore size (3.0") and ring width.. these are often found inexpensively via ebay.. the old 'cords' band really work well as regards oil control and they last well too.. some will state that the 'cords' rings cause excess bore wear..that is total hogwash..they are however designed to compensate for up to .005" of bore wear and light wear in ring grooves.. the old 'Hepolite apex' rings are also designed for worn bores..but are not as effective as cords and produce more friction initially.

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