Good morning,
Apart from the obvious injectiony bits, are parts from a 2000mk2 likely to be the same as the 2.5 PI mk2? They look it.
Thank you,
Simon
Compatibility between 2000Mk 2 & the 2.5 PI
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simon.williams
- Senior Member

- Posts: 176
- Joined: Mon Jan 20, 2025 11:30 am
Compatibility between 2000Mk 2 & the 2.5 PI
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
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johnfrancis898
- Groupie

- Posts: 85
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- Location: Berkshire
Re: Compatibility between 2000Mk 2 & the 2.5 PI
Hi Simon
There are quite a few differences between the two. The main block and head are unique to each model and variation. The main block on the 2.5 is a different size, slightly taller to accommodate the extra 500cc. Many of the smaller items such as fixing brackets are the same. The parts book is a good indication as you can cross reference part numbers.
Rgds
John
There are quite a few differences between the two. The main block and head are unique to each model and variation. The main block on the 2.5 is a different size, slightly taller to accommodate the extra 500cc. Many of the smaller items such as fixing brackets are the same. The parts book is a good indication as you can cross reference part numbers.
Rgds
John
Member no. 7941.
2500TC Mk 2 saloon 1976 od/PAS BRG
2500TC Mk 2 saloon 1976 od/PAS BRG
Re: Compatibility between 2000Mk 2 & the 2.5 PI
The interior trim is largely the same, except for the dash pieces/ clocks (although the wiring is in the dash loom as with other models for the rev counter etc, although the early rubber plugs and late hard plastic connectors are not interchangeable)
The PI has the additional body trim pieces - black trim piece on the rear light panel, vinyl on the C pillars, and black grill, and obviously the wheel trims.
The PI has a 3.45 diff (manual and auto), whereas the 2000 is either 3.7 or 4.1.
The PI had 185 13 tyres whereas the 2000 had 175 13
The PI gearbox was supposedly different from the 2000 (both A type and J type), but I've known people fit 2000 gearboxes to a 2.5/2500 without issues.
The PI had a blue 11 blade (I think 11?) fan whereas the 2000 had the 7 blade yellow fan
There were minor differences in the wiring loom, but if converting 2000 to 2.5PI or ice versa, or manual to auto, then the original loom can be utilised - the majority of the wiring was present in the 2000 for the PI (feed for the pump in the boot, and the inertia switch etc).
The fuel tank was different too as were the fuel
lines.
There are probably other minor differences which I've not mentioned, but that's generally about it I think!
The PI has the additional body trim pieces - black trim piece on the rear light panel, vinyl on the C pillars, and black grill, and obviously the wheel trims.
The PI has a 3.45 diff (manual and auto), whereas the 2000 is either 3.7 or 4.1.
The PI had 185 13 tyres whereas the 2000 had 175 13
The PI gearbox was supposedly different from the 2000 (both A type and J type), but I've known people fit 2000 gearboxes to a 2.5/2500 without issues.
The PI had a blue 11 blade (I think 11?) fan whereas the 2000 had the 7 blade yellow fan
There were minor differences in the wiring loom, but if converting 2000 to 2.5PI or ice versa, or manual to auto, then the original loom can be utilised - the majority of the wiring was present in the 2000 for the PI (feed for the pump in the boot, and the inertia switch etc).
The fuel tank was different too as were the fuel
lines.
There are probably other minor differences which I've not mentioned, but that's generally about it I think!
Register Member no. 1596
1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red
1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red
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simon.williams
- Senior Member

- Posts: 176
- Joined: Mon Jan 20, 2025 11:30 am
Re: Compatibility between 2000Mk 2 & the 2.5 PI
Thank you for all this detail.
1973 Carmine red 2500PI (work in progress)
1975 Mk 2 Stag (white)
1975 Mk 2 Stag (white)
- triumphman
- Site Admin

- Posts: 61
- Joined: Fri Sep 16, 2005 10:05 pm
- Location: United Kingdom
Re: Compatibility between 2000Mk 2 & the 2.5 PI
I think the 2000 and 2500 cylinder blocks are the same. The extra 500cc is gained by having a longer stroke, and the 2.5 sump may be different to cope with the longer crank throw. Early 2000 and 2.5 cylinder heads were different, but later models used the same cylinder head (218225) and the 2000 had domed pistons in order to increase the compression ratio. That didn't do the performance any favours, though.
Re: Compatibility between 2000Mk 2 & the 2.5 PI
The sumps are indeed different - the 2000 sump is part no. 308570, and the 2.5PI / 2500 sump is 307834.
Register Member no. 1596
1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red
1967 Mk1 2000 in Gunmetal Grey
1969 Mk1 2000 in Royal Blue
1970 Mk2 2000 in Valencia Blue
1972 Mk2 2.5 PI in Triumph White
1973 Mk2 2.5 PI in Sienna Brown
1976 Mk2 2500S in Carmine Red