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2.5 P.I. Cold Start and Engine Number.


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Hello, and Seasons Greetings to all.

I have a Triumph Stag with a 2.5 P.I. Engine.

I hope not a silly question but,
Cold start no problem but I do not like to have a choke on for any longer than possible.
Can I assume that choke on, drive as soon as possible, choke off as soon as possible is O.K.
Always worried leaving Choke on for to long, excessive fuel washing oil from cylinders.

I have searched but cannot find. I would like to know what Triumph and what year the Engine came from, it's number is,

MG21730 H EBW

Any information would be gratefully received.

Many thanks,  Don Kennedy.


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MG is a MK II Saloon/Estate engine at a guess circa 1972. If it is un-molested it will be a 132bhp engine, power slightly down on a Stag 145bhp and it wont rev as well as the 3litre V8.

You can take the bhp up a bit with some (not too) excessive work. You might want to consider a 3.45 PI diff, if it has not already been fitted with the engine?

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Yep, PI's have twin choke cables similar to the Stag - the one cable goes direct to the metering unit enrichment lever, the other to a fast idle cam on the throttle linkages.  

I've got a late cable on an early PI so the second cable does not connect to the fast idle cam.  Full chole to start cold, push in half way immediately, keep car running on acc pedal then push choke in fully asap works fine for me.  I usually warm up the car for a minute on the acc pedal (no choke) before driving off.  

my 72 car had engine no 58741, so I think yours would originate nearer to 70/71.  BW denotes that it was orginally an auto btw!

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Many thanks to all for your time replying. Very interesting.

Looks like if I need to get normal service parts ( Oil filters etc ) from my local motor factors I will advise them that the engine is from an early 1970s 2.5 P.I. Can I assume that all 2.5 P.I. Engines from the early 1970s are the same ?.

You know what the "Young Lads" are like in some of the motor factors although there is one in Plymouth who are Very good. I realise that more "special" parts will have to ordered from the dealers/suppliers of Triumph parts.

The use of the choke is what I expected, I understand the P.I. system, I just like to "turn off" the choke as soon as possible and keep the revs down until the engine warm.

Once again many thanks,  Don Kennedy.

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Don does it have a Spin on oil filter conversion? They are very common on 6-pots. If so then the normal 2000/2.5 oil filter will not fit.

If the is a pressed steel container over the filter it is OE, if there is a an aluminium castingbetween the filter and the block it has a conversion.

The conversion filters are easy to get, Unipart GFE30 is a good version. PI air filter maybe a bit had to source from a motor factors.

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