MarkB Posted August 12, 2013 Share Posted August 12, 2013 Hi allI won a couple of 2.5 engines off ebay with the intention of eventually fitting one to my Mk2 GT6. I fancied a 2.5 as I have only owned 2 litre cars. Not sure of the condition of either, one turns over by hand the other feels tight so need I to give both a good soak down the bores with WD before I go any further. Both have some end float but not that excessive. The seller said that both were good running engine's before being stored away for future projects that never happened. One has the MG prefix starting 21 which I think is a late PI and the other MM which has a very short number so believe it is a 2500S. I need to check compression etc. and might have a go at getting them running on the bench. I will probably rebuild one and was wondering if one engine is a better basis for building-up a tuned engine. ThanksMark Quote Link to comment Share on other sites More sharing options...
Gt6s Posted August 12, 2013 Share Posted August 12, 2013 If they are late PI and 2500S then they are both the same spec.Not that there is anything particularly wrong with 2500S or late PI motors for what they are.It is just they have deep chambered heads and poorer cams. You can allways skim the heads and fit better cams. But remember you will need to use shorter push rods.Laurence Quote Link to comment Share on other sites More sharing options...
DJB_Harvey Posted August 12, 2013 Share Posted August 12, 2013 If the MG block starts with 21 it's early 132BHP PI . This won't have the extra ribbing on the nearside of the block .... The other block will have so is a better choice ( in theory ) than the early block . Compression ratio on a 2.5 is governed by the head .. Not the block or pistons . Quote Link to comment Share on other sites More sharing options...
Gt6s Posted August 12, 2013 Share Posted August 12, 2013 DJB_Harvey wrote:If the MG block starts with 21 it's early 132BHP PI ..Dosent follow, I have MG 855 a mate has MG 75 both early 132 bhp engines. Both were fitted with the elusive cross drilled cranksLaurence Quote Link to comment Share on other sites More sharing options...
MarkB Posted August 12, 2013 Author Share Posted August 12, 2013 Looking on the Triumph 2000 -2500 register I think the MM7... is a 2500TC lump not an S, on a 1974-75 car. It lists MG1... 2·5PI Mk2 Oct 1969 – May 1974 and thereafter the prefix is MN so still not sure.Mark Quote Link to comment Share on other sites More sharing options...
CRAJ Posted August 13, 2013 Share Posted August 13, 2013 The only real difference between an early mk2 or later mk2 pi engine is the cam and as Dave says that is an earlier 132bhp engine. The head is slightly different but the compression ratio is still good.The 219016 head fitted to the 2500S/TC engine never featured on a pi engine from the factory and gives a lower compression ratio than a pi engine. It can be skimmed of course.If like me you had a version of each car you would know how much difference there is in the two engines that you have, they are like chalk and chees in standard form.Perhaps an amalgamation of parts from both engines would be the way to go. I believe Andy Thompson uses a late MM block to good effect on his mk1 racer.Colin. Quote Link to comment Share on other sites More sharing options...
andy thompson Posted August 13, 2013 Share Posted August 13, 2013 Early MM block ie <MM20000 is effectively a low compression late PI engine. Same 3 ring cam but 8.5 CR - ran with HS4 - nominally 99bhp but responds well to HS6's Quote Link to comment Share on other sites More sharing options...
Matt George Posted August 13, 2013 Share Posted August 13, 2013 I've got a 2.5 in my car, engine number MM27761HE. Head skimmed down from 3.475" to 3.430" at the advice of Chris Witor. Also got a 308778 PI cam, HS6s, Witor 6-3-1 and full sports exhaust. I can confirm that such a concoction turns out pretty good performance :) Quote Link to comment Share on other sites More sharing options...
esxefi Posted August 14, 2013 Share Posted August 14, 2013 OP if it were me I would strip both engines anyway.Seeing as you have them free standing you could construct a decent unit from either depending on the condition of each unit.what is your intention regards induction,cam choice,any head work and exhaust system and what power are you looking for? Quote Link to comment Share on other sites More sharing options...
MarkB Posted August 14, 2013 Author Share Posted August 14, 2013 esxefi wrote:OP if it were me I would strip both engines anyway.Seeing as you have them free standing you could construct a decent unit from either depending on the condition of each unit.what is your intention regards induction,cam choice,any head work and exhaust system and what power are you looking for?Hi all, thanks for all the replies.I will use an equivalent or close to a PI cam and probably use HS6 carbs. I do have PI throttle bodies but intend on using them to EFI my Vitesse. The head I will have to pay someone to port and skim, just finding the right person at a reasonable price to do it. Exhaust will be 6-3-1, but again trying to find the right one from the right supplier. 150+bhp would be nice. To be honest I am still trying to finish the Vitesse, 7 years in, and I bought these engines now as they were a good price. So realistically I probably wont touch these for a year or so to give me time to finish the Vitesse and get some money together. The GT6 is used most days so will keep that on the road until the vitesse is done.mark Quote Link to comment Share on other sites More sharing options...
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