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Sebastian
Sebastian

Posted: Sat Dec 31, 2011 10:36pm

Post Subject: Low oil flow 1500 bmc diesel

I have Totaly rebuilt my 1500 bmc. My oil pressure is fine, but I don't seem to get much flow to the head. The rocker shaft stays full as it runs, and it drips oil from all the rockers, but not very quickly...... I seem to remember more oil flow? The valves don't seem to get splattered / splashed....... there is oil flow ..... But...... All the oil ways are clear....... How much oil should there be? I can run the engine at idle and the oil doesn't overspill the edges of the head..... Are the valves mist fed or splash? Please help!

Tony-B
Tony-B

Posted: Sun Jan 01, 2012 8:37am

Post Subject: Low oil flow 1500 bmc diesel

Some things to check. Did you use jointing compound on the cylinder head gasket, if you did it may well have oozed out and partially blocked the small oil hole in the head/block. Is the rocket shaft correctly aligned within the rocker posts with the posts in the correct order because this could block the oil drillings. Are the rocker bushes worn, allowing oil to drip from them rather than pass down the rocker itself and into the pushrod cup. If any machining was done on the engine parts did you give the oil galleries a good clean and flush through. Would you be a mechanic with little experience of OHV engines? Modern overhead cam engines throw oil all over the place if you run them without the cover on but OHV engines are normally far better behaved with little oil being splashed about at lower revs so there may well be nothing wrong. I suspect the valve stems are lubricated by mist produced when the engine is revving a bit and remember we use stem oil seals to minimise the oil that gets between the stems and guides. Tony Brooks

Sebastian
Sebastian

Posted: Sun Jan 01, 2012 1:36pm

Post Subject: Low oil flow 1500 bmc diesel

Only gasket seal used was on the core plugs - so thats water section, no the rocker is lined up, the hole is clear, if i remove the locating screw oil flows - but doesnt 'jet out' all pushrod cups are full of oil, the bronze bearings in the rockers are fine. Heres why i thought i had a problem - after rebuild i ran the engine - all fine, (remember i oiled the valve stems when refitting) then, after the oil had burnt off inside the engine i noticed she 'popped' a little and there was white smoke (unburnt diesel) i reset tappet gap, and injector pump timing, and tried again - same, then, noticing there was little oil on the valve springs i poured a little around the base of each valve spring and ran engine - totaly clear exhaust, no popping noise, this suggests that a valve was hanging open a bit. I will say tho i havent had to oil them again and all seems fine, but im just not sure. I have had the engine down to block and crank, (decoke a perfect engine with a few oil leaks)oil pressure had dropped off slightly, but the problem was a leaking front seal on injector pump - easy fix - so oil was very thin. - hence oil pressure loss (very little oil pressure loss - 40 at anything over 1200 rpm, 10 at very low idle, was 14, now back to 14.

Tony-B
Tony-B

Posted: Sun Jan 01, 2012 3:13pm

Post Subject: Low oil flow 1500 bmc diesel

I suggest that you consult the manual about oil pressure. There is one on the Calcutt Boats website. Although I always say 40psi is fine for an older engine I think the BMC figure is closer to 60psi. I always used a graphite running in compound on the valve stem like Grafogen (may be ph instead of f) so would not have suffered any sticky valves. I think you need to rev the engines a bit to throw the oil around in the rocker cover. Tony Brooks

Sebastian
Sebastian

Posted: Sun Jan 01, 2012 4:39pm

Post Subject: Low oil flow 1500 bmc diesel

my lowest oil pressure reading is at hot idle, 1 bar, 1500 rpm hot is 3.5 bar. i notice, to my suprise, that the calcutta boats manual shows the rockers cross drilled both ways - to the pushrod and valve i dont have this - is mine an older version?

Low oil flow 1500 bmc diesel
Tony-B
Tony-B

Posted: Sun Jan 01, 2012 6:27pm

Post Subject: Low oil flow 1500 bmc diesel

I do not recall having seen any BMC B series (petrol or diesel) with a drilling to the valve end of the rockers but I think some had a small drilling to the top, above the shaft. There have been many variants of the 1.5, vans engines, tractors, refrigeration or compressor engines apart from marine units so anything is possible and it could have been a modification made after the Indians/Turks got hold of the manufacturing rights. Tony Brooks

Sebastian
Sebastian

Posted: Sun Jan 01, 2012 9:28pm

Post Subject: Low oil flow 1500 bmc diesel

any idea who sells big end shells for these? and also, are the new / modern shells as good as the original type? i hear the whitemetal is poor these days.....

Tony-B
Tony-B

Posted: Mon Jan 02, 2012 7:51am

Post Subject: Low oil flow 1500 bmc diesel

Calcutt Boats, ASAP Supplies, Thornycroft/AMC and if you know the dimensions a local engine machinists. White metal? Been reticular tin, lead indium or some such alloy for at least 50 years. The alloy is chosen to suit the application but that is not to say some Indian sourced spares do not use substandard materials, which is why sourcing from well know companies may be your bets policy. Tony Brooks

Zoot_T
Zoot_T

Posted: Tue Oct 21, 2014 2:15pm

Post Subject: Low oil flow 1500 bmc diesel

The op mentions "core plugs" I have a leak from a core plug behind the alternator (no 65 on page a4 of the available service manual pdf) How do you repair a core plug leak? does it need replacing? If so how?- or can you temporarily use some sort sealant to stop the drip until a proper service by a proper mechanic - if so what's a good product for a temp repair? Thanks

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