2500 TC has the wrong head ?

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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tadge44
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Re: 2500 TC has the wrong head ?

#21 Post by tadge44 » Mon Jul 08, 2019 7:24 am

I may have the opportunity to buy an engine from a 2500PI automatic.

Will I be able to use the flywheel and manifolds from my present engine which is a late 2000 ?

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Re: 2500 TC has the wrong head ?

#22 Post by tadge44 » Mon Jul 08, 2019 7:29 am

And the distributor of course !

I won,t be trying to use the PI equipment, just the twin HS6,s

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Re: 2500 TC has the wrong head ?

#23 Post by Alec » Mon Jul 08, 2019 2:37 pm

Hello Tadge44,

Yes to the flywheel and manifolds.
The distributor is another matter, P.I. and carburettor engines have different curves and as putting carburettors on a P.I. engine makes it non standard so some trial and error may be necessary to get the best from the engine.


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Re: 2500 TC has the wrong head ?

#24 Post by tadge44 » Tue Jul 09, 2019 4:32 pm

Thankyou Alec.

I am considering Megajolt ignition if I ever get this done.

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Re: 2500 TC has the wrong head ?

#25 Post by johnnydog » Tue Jul 09, 2019 5:32 pm

Is this PI engine a 125 or 132bhp?
Chris Witor recommends certain needles for HS6 carbs on a standard 132bhp PI engine - BPZ (from memory). You may have contact him for his recommendation of needles with the later 125 bhp engine.
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Re: 2500 TC has the wrong head ?

#26 Post by tadge44 » Wed Jul 10, 2019 6:42 am

Thanks again. Will be rebuilding the engine for installation next winter,hopefully.

Looking for a complete rocker assembly and some pushrods so will post this request elsewhere.

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Re: 2500 TC has the wrong head ?

#27 Post by tadge44 » Mon Aug 19, 2019 4:52 pm

Moving on.
jonnydog is supplying all the parts that I need. What a very nice and helpful person Top man !

The block is now bare and degreased awaiting the above parts as well as new rings bearings etc.

The bores and all the journals are all well within tolerance as are the cams and followers so it looks as if I am lucky with this one.

However the thrust washers look odd. One is worn away enough to lose the oil grooves and the bearing metal is coming off the backing. The other looks absolutely fine.

Whilst they will be replaced I need to work out what size will work Do they have a nominal value for thickness as standard ?

Given the state of the one mentioned above it was hardly surprising that I had 15 thou end float !

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Re: 2500 TC has the wrong head ?

#28 Post by Clifford Pope » Mon Aug 19, 2019 5:10 pm

The thrust comes from the rather strong clutch release springs, so the wear is mainly on the bearing taking that thrust.
The design is deficient in having only a semicircular thrust washer, rather than 360 degrees froma washers in the block and the cap.
There is someone in America who sells much better quality washers - I can't now recall what exactly is so special about them.

Mine had been fitted with an adjustable external thrust ball-race on the front of the crankshaft. I've never seen any mention of this idea, but it seems a good one.
I have to use an electric fan of course.

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Re: 2500 TC has the wrong head ?

#29 Post by tadge44 » Mon Aug 19, 2019 5:18 pm

I do understand the function of crankshaft thrust washers.
I hesitate, as a newbie on this board, to contradict anyone but my engine most definitely had two thrust washers covering 360 degrees and I am puzzled why one is very badly worn but not the other.

Perhaps someone just managed to feed one new one in there at some stage just before the engine was removed ?

Anyone please have a value for the thickness of a standard thrust washer please ?

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Re: 2500 TC has the wrong head ?

#30 Post by Alec » Tue Aug 20, 2019 5:58 am

Hello Cliff,

the design is the same as the Jaguar XK engine, and that does not have a thrust washer problem. Nor is the design deficient as a full circle thrust puts load on the cap which is designed for vertical rather than horizontal load. People don't say there is a problem with the big ends or mains when thay are worn , so why is a worn thrust bearing a design defect?

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