2.5litre engine in a GT6

[Rubce]

Hi All

I am considering purchasing a spare engine for our GT6 as a project to work on next year. Seeing as our cars are getting rarer etc I am would like to obtain a spare engine now whilst they are stil available.

I am thinking of buying a 2.5litre. Are there any modifications required to enable a 2.5 to fit into a mark 3 GT6. Have any of you guys done it?

Regards

Bruce

[Clive]

All very simple. The engines are almost identical.
Only things are you have to use a gt6 sump. But that requires denting to clear the extra throw of the 2.5 crank, all very simple.
Second part is the carbs.  Needs hs6 carbs with the short ( dolly sprint) tops. In fact the sprint needles are about correct the OK. These need fitting to a gt6 inlet manifold. Not too tricky at all.

Other things to consider are the diff ratio. Ideally 3.27 but rather weak. I ended up with 3.63 in my 2.5 vitesse as I kept breaking 3.27's. Overdrive obviously a must.

[Richard B]

Dave P. reckons that the weak 3.27's are all gone and any rebuilt 3.27's will have the stronger carrier.

Personally I reckon a 2.5 in a GT6 needs injection, not carbs  ;D ;D ;D

[Tim Bancroft]

Can of worms this one!

I'm in the revvy 2000cc camp.

I can see the attraction of a 2500 engine in a GT6, the torque etc. But with such a light little car, I think the 2000cc engine suits, suitably breathed on and cheaply modified. Lightened and balanced bottom end, Flowed head, HS6s, extractor manifold etc etc.

Of course, why bother when you can get that power from a well put together 2500 engine!!!???

Roy Lacey and Tim Ward have 2500cc GT6s and mighty fine cars they are. However, I rather the 2000cc engine, these six cylinder engines howl after 5K and I rather the sound of a 2000cc, sounds more manic.

[mpbarrett]

cliftyhanger wrote:

All very simple. The engines are almost identical.
Only things are you have to use a gt6 sump. But that requires denting to clear the extra throw of the 2.5 crank, all very simple.
Second part is the carbs.  Needs hs6 carbs with the short ( dolly sprint) tops. In fact the sprint needles are about correct the OK. These need fitting to a gt6 inlet manifold. Not too tricky at all.

Other things to consider are the diff ratio. Ideally 3.27 but rather weak. I ended up with 3.63 in my 2.5 vitesse as I kept breaking 3.27's. Overdrive obviously a must.

My 2.5L OD GT6 (mk3) had a 3.89 originally and got very very noisy, changed to a secondhand 3.63 and it broke, brought  a new reconditioned 3.63 and that broke after 2 years.... not sure what to do next.
I think the torque from a 2.5L is at the limit of the diffs or I have been unlucky? Or maybe you accept that the diff is a consumable and after every second oil change you should change the diff :)


cheers
mike
mike

[Gt6s]

mpbarrett wrote:

My 2.5L OD GT6 (mk3) had a 3.89 originally and got very very noisy, changed to a secondhand 3.63 and it broke, brought  a new reconditioned 3.63 and that broke after 2 years.... not sure what to do next.
I think the torque from a 2.5L is at the limit of the diffs or I have been unlucky? Or maybe you accept that the diff is a consumable and after every second oil change you should change the diff :)


cheers
mike
mike

Fit a Quaife to a 3.63 unit.
I have just bought another one for my old 2.5 carb car. Allready have one in the EFI motor it has had dogs abuse.
Tip. Do not buy one off evilbay go direct to Quaife.

Laurence

[Spitfire2500]

Gt6s wrote:

Fit a Quaife to a 3.63 unit.

The 3.63 diff in our Spit 2.5 (it's really a 2.7!) was built with a Quaife LSD eleven years ago now and it's been troublefree so far - and it gets a fair amount of abuse... ??) ;D

[MrSpeedy]

timbancroft61 wrote:

Can of worms this one!

I'm in the revvy 2000cc camp.

I can see the attraction of a 2500 engine in a GT6, the torque etc. But with such a light little car, I think the 2000cc engine suits, suitably breathed on and cheaply modified. Lightened and balanced bottom end, Flowed head, HS6s, extractor manifold etc etc.

Of course, why bother when you can get that power from a well put together 2500 engine!!!???

Roy Lacey and Tim Ward have 2500cc GT6s and mighty fine cars they are. However, I rather the 2000cc engine, these six cylinder engines howl after 5K and I rather the sound of a 2000cc, sounds more manic.

Pretty much my train of thought when building a replacement engine for my Vitesse.

Yes it would have been 'easy' to gain an extra 25ish BHP by doing nothing more than swapping engines, but I wanted to get the same power gain from te same displacement. (and make it an absolute bitch to drive in traffic! lol)

[mpbarrett]

Gt6s wrote:

Fit a Quaife to a 3.63 unit.
I have just bought another one for my old 2.5 carb car. Allready have one in the EFI motor it has had dogs abuse.
Tip. Do not buy one off evilbay go direct to Quaife.

Laurence

that changes the diff cogs but do you keep the same pinion and crown wheel? It will be interesting to see whats broken in mine when I get it back.

regards
mike

[Gt6s]

mpbarrett wrote:

that changes the diff cogs but do you keep the same pinion and crown wheel? It will be interesting to see whats broken in mine when I get it back.

regards
mike

It will be the differential unit it'self. I recently had similar discussion with Tim Curry on a US forum. He had blown up a 3.63 with a Quaife. Turned out his had blown the crown wheel and pinion Quaife was undamaged. CWP most probably blew because he was putting 240 horses through it, Honda S2000 motor.
As previously said the one in my 2600 EFI car has had dogs abuse. Autotests, track work and doing donuts in the yard at work. that was untill the boss walked out of the cloud of tyre smoke and said "Laurence would you please stop doing that"  Quote cleaned up.

Laurence