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worcester19

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I am restoring a Mk2 GT6 and have the original 2.0 Engine which needs a full rebuild.

I have been offered a 2.5 engine (engine number starts with MM) which also needs a full rebuild.

I have always hankered after putting the 2.5 litre engine in the GT6 but I am now not sure if it is really worth it.

Can anybody let me know what the benefits / pitfalls are of upgrading to the bigger engine - basically any opinions would be gratefully received!

Many Thanks

Stephen

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I am in a similar situation to you having owned a Mk2 Gt6 for the past 10 years I have decided to put a 2.5 in its place. It's going to have more torque and overal grunt. I will be going for a PI cam. I suppose a possible negative will be originality for some people if you was to sell it on,  but I believe at least as many would buy it because of the 2.5 being fitted.

Mark

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Depends what you want?

As someone who has repeatedly broken various transmission components I have some experience  

If you want revvy stick to 2 litre, if you want a high speed GT fit a 2500 on carbs with a 3.27.

If you want to keep buying stronger transmissions in a pursuit of reliabilty, fit a 2.5PI.

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I think you need to drive cars that have these engines fitted. The character is quite different.
I would not necessarily see the 2.5 as an upgrade, it is just rather different.

The 3.27 is pretty essential, but is the weakest of the suitable diffs. I broke several in my 2.5 vitesse. I ended up with a 3.63, and that went like a scalded cat up to 5500rpm, I wouldn't go over that. Overdrive absolutely essential.

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I really dont buy into this  3.27 is the weakest diff.

Ive had loadsa 4.11,s 3.89s and 3.63,
not to mentionee 3.45 and 3,7 Stag/salloon diffs

all with same problem, teeth oft Pinnion in the most cases.
a few, {rare } wid a tooth oft CW

In my findings, the later cases, although got bigger gears, bearings, are also a weak link, as
the diff gear area has been cut away so much, there v v little metal left
5 late 3.63s have had cracked carriers
NO craked carriers on the earlier  smaller gear / bearing typs

IF folk gev other diffs as much stick wid a 2.5, then they go bang too.

My self, last diff lasted over 12 years, befor it went bang ont start line,
albeit wit a dumpd clutch at 1700RPMS, and v v stikeee tyres.

My self, would not even consider a 2Lin a GT
2.5  3.27 + J OD 28%  takes some beating
and will almost drive like an auto, pulling OD top frae 700-800 revs easily
and pulling it fastr than a 2L in 3 rd !!

try an cadge a ride in a 2.5 first though,
even a standard 2.5 110 ish hp will go v v weel
a tuned,n will go much better,

My advice, go forit

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Quoted from GT6 M
I really dont buy into this  3.27 is the weakest diff.

Ive had loadsa 4.11,s 3.89s and 3.63,
not to mentionee 3.45 and 3,7 Stag/salloon diffs

all with same problem, teeth oft Pinnion in the most cases.
a few, {rare } wid a tooth oft CW

In my findings, the later cases, although got bigger gears, bearings, are also a weak link, as
the diff gear area has been cut away so much, there v v little metal left
5 late 3.63s have had cracked carriers
NO craked carriers on the earlier  smaller gear / bearing typs

IF folk gev other diffs as much stick wid a 2.5, then they go bang too.

My self, last diff lasted over 12 years, befor it went bang ont start line,
albeit wit a dumpd clutch at 1700RPMS, and v v stikeee tyres.



Marcus, it was my experience. I destroyed 3 3.27 diffs, non lasted more than 2 years. However, the 3.63  did last approx 5 years unscathed, then into my zetec spit, and now in my current one. I think it is partly down to the gearing putting extra pressure on the diff gears (specifically the CWP) To be fair the first 3.27 was "as found", the 2nd came as an unused recon from an abandoned project, the third was rebuilt for me. The 3.63 was also rebuilt by the same person who did the last 3.27. My cars get a hard life......hence the need for a scooby diff.

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I have a 2.5 spitfire with an 1850 gearbox and a 3.63 and I thinks its about right. I don't drive it as hard as Clives Zetec but it is a cracking car to drive. I suppose it depends if you want to rev the nuts of it all the time or if you want a good torque engine that will realy accelerate without have to change gears all the time.

Martin

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I am in the 2.5 with 3.63 and 28% J Type OD Camp. Run with oversize tyres Say 185/70/13 you have 24 mph per 1000 rpm. My 2600 EFI runs this arrangement but 205'50/15 tyres 5800 rpm is shift light on (which is easy to her) is 140 mph.
I also own a 2500 Gt6 and a 2500 Sixfire all cars run on same 3.63 and 28% OD.

Laurence

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Quoted from GT6 M


My self, would not even consider a 2Lin a GT
2.5  3.27 + J OD 28%  takes some beating
and will almost drive like an auto, pulling OD top frae 700-800 revs easily
and pulling it fastr than a 2L in 3 rd !!



This is the combo i have in my Vitesse,whilst i only ran the 2l as standard,i am very happy with the way the 2.5 and saloon box drives.I wouldn`t say i drive slowly either(no no.11 starts though)

I had the 3:27 rebuilt with the stronger(TR7?) carrier.

The engine showed 170bhp on a rolling road and gives good power and loads of torque from low revs.Even on old SU`s.
Steve

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Quoted from worcester19
I am restoring a Mk2 GT6 and have the original 2.0 Engine which needs a full rebuild.

I have been offered a 2.5 engine (engine number starts with MM) which also needs a full rebuild.

I have always hankered after putting the 2.5 litre engine in the GT6 but I am now not sure if it is really worth it.

Can anybody let me know what the benefits / pitfalls are of upgrading to the bigger engine - basically any opinions would be gratefully received!

Many Thanks

Stephen



Put the 2.5 crank in the GT6 engine, keep the hot GT6 cam, bigger 1.75 carbs, big fun and you retain the originality of the matching numbers engine.

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In the saloon, the 2.5 was canted, tilted to the left to clear the bonnet.    So the original engine backplate cannot be used, and you must fit a 2L one - not a problem as the block fixings are all the same.
The inlet manifold  from a saloon 2.5 was made to compensate for this cant, so in an upright installation will droop downwards.    Again, a 2L manifold will do it.

Knocking bumps in the sump to clear the big end throws need not be excessive, but must be localised, leavaing a gap between for the steering rack, which is very close indeed.
A ball peen hammer into the 'frog' in a brick as a suitable anvil does the job nicely.   ('Nice' meaning 'exactly'!)

John

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Quoted from JohnD
In the saloon, the 2.5 was canted, tilted to the left to clear the bonnet.    So the original engine backplate cannot be used, and you must fit a 2L one - not a problem as the block fixings are all the same.
The inlet manifold  from a saloon 2.5 was made to compensate for this cant, so in an upright installation will droop downwards.    Again, a 2L manifold will do it.

Knocking bumps in the sump to clear the big end throws need not be excessive, but must be localised, leavaing a gap between for the steering rack, which is very close indeed.
A ball peen hammer into the 'frog' in a brick as a suitable anvil does the job nicely.   ('Nice' meaning 'exactly'!)

John


Just as well I got an alloy backplate for mine then! Mine's originally a 2500S engine with a PI head. I suppose that's why the sump on mine was canted as well.

I hadn't thought about using the frog of a brick as an anvil. Clever. I just heated mine up with oxy-acetylene and hit it with a hammer then checked for clearance and repeated...

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