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PostPosted: Wed Oct 12, 2011 4:42 pm 
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Just thought I'd have a quick check on valve clearances while changing the oil pump. Inlets are fine, but exhaust clearances range from 3 thou, most at 6-8 thou and a couple at 12 thou. Spec is 11 - 15 thou.

I have no idea what the clearances were before the LPG so may be a red herring.

This engine has done about 60K miles on LPG now. A few shims every 60K miles (probably do every cam belt change) is a small price to pay for cheap motoring I think.

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PostPosted: Fri Oct 21, 2011 11:40 pm 
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well you will get valve seat regression on just about any engine running LPG im affraid.

I did some research and development work in this area before the resession hit in 2008.

Running engines on cng and lpg systems and carrying out an extensive program of measurements at regular intervals.

from memory, the first 100 hrs wasnt to bad and little or no real wear but as wear set in it progressed more rapidly with ever 50 to 100 hrs.

if i remember correctly the test ran for some 600 hrs but the last 200 i was re shimming every inspection and was soon beyond the thinnest shim.
i ended up having to measure the actual clearance and have the difference machined from the shim to give the correct clearance.

The test unit was an i4 ford/mazda engine.

i have also seen the results in the field, a factory fitted system on a 1.8 focus which was ok as the test but soon got to the point where it was being reshimmed at every 12.5k service until the head was scrapped when shim sizes ran out.

i havent run on the road myself with lpg so couldnt comment on cost/savings.

in my mind i cant help wondering if i was running as joe public.....

system purchase and additives and system service (ie £100 micro filters) reshimming and eventual head replacement if it would break even in cost vs savings.

well when i was testing fuel was still under a £ now maybe there is economy in it.

if you can do it all yourself (corgi registered to fit it) and have a supply of shims and spare heads yep it certainly could be.....

good luck with that Nibbles

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PostPosted: Sat Oct 22, 2011 5:33 pm 
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Was the Ford unit modified for LPG?

Iirc when they offered dual fuel cars, certainly with volvo, the seats were hardened for the higher temps. The 3SGTE should take it better than a Zetec etc with the head already designed for turbo EGTs?

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PostPosted: Sat Oct 22, 2011 9:37 pm 
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Seems strange the wear rate accelerating, I'd expect the opposite as contact area will increase as the seat wears back. Sounds more like a thin surface hardening wearing through.

As above, the consensus I've heard is that turbo engines are more able to cope with LPG as they have hardened seats as standard.

I'll be keeping a closer eye on it from now on.

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PostPosted: Fri Oct 28, 2011 12:49 am 
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Engines were supplied by ford at various spec known only to ford R & D. A set of test instructions along with measurement and service requirements were also supplied.

Ford as did everyone else paniced and pulled the plug on its R & D at the start of the credit crunch as they all run way over budget so to secure a higher budget for the following year.

_________________
1990 JDM ST185 Grey.
ST205 head gasket.
ARP head bolts.
ST205 Koyo Rad. (almost)
Front mount intercooler.
Colder plugs.
3" decat pipe.
4 Branch manifold.
Nitrous Oxide Steroids for Cars!


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