150bhp engine in a GT6 mk3

[Rubce]

Hi All

I have the opportunity to fit a 2.5 litre engine complete with a TR6 camshaft into our GT6. My question is, will the diff, propshaft and driveshafts cope with the increase in power?

The car is a late Mark 3 with swing spring rear suspension.

Regards

Bruce

[Clive]

All a bit marginal, so will depend on how it is driven.
My biggest concern would be a 3.27 diff. While it gives the best ratio, it is weak. I settled on a 3.63 in my vitesse (swing spring, shafts were no issue, just the 3.27 diffs) but Icheated and used a saloon gearbox.
However, I know of 2x2.5 gitfires, one has triple webers etc, and neither have killed any mechanical parts, but then again neither driver has a heavy right foot

[Nick Jones]

Don't go drag-racing.....

Nick

[Martins Stag]

I ran a 2.5 in my Spitfire 1500 for many years. If you upgrade the brakes and suspension and treat it with some respect your should be ok. As previous comments don't go drag racing or drifting in it though...

Martin

[Tim Bancroft]

My GT6 with a 2000cc engine developed reasonable power, obviously not as much torque as a 2.5, no problem with a GT6 gearbox with 1850 internals, CV shafts and 3.63:1 diff. Autsoloing did not help the gearbox as high revs and 1st gear driving did put a strain onto the unit.

Roy Lacey's mk1 has a 2.5 with GT6 box and 3.63:1 diff, no issues. I do not know how he drives.

Dave Langrick's 2.5pi Spittie with saloon box and 3.63:1 seems to be bulletproof.

[glang]

Hi John, can ask what commission youre getting on this sale?

[glang]

I dont think a disclaimer would hold up in this case and I cant see how your post helps the OP......

[Guppy916]

Okay 2.5 fully lightened and balanced, if it moves it has been lightened & balanced, gearbox fully uprated, overdrive unit up'ed by 20%, diff reconed, prop shortened and balanced, the gearbox, o/d & diff all done by TLD, it all runs as sweet as a nut ! I need to do a few more miles then its off to a rolling road to finish setting up the 40's, the head is flowed and chambers / ports balanced through out,

[Rubce]

Hi Gully

Which cam have you fitted into the engine?

Regards

Bruce

[Rubce]

Hi All

So several have people 2.5 engines fitted but I am also interested in whether they have the 132 or 150 bhp camshaft fitted.

With regards to gearboxes, what work is involved in fitting an ex Stag/Saloon  gearbox with J type overdrive?

Thanks for all the replies to date

Regards

Bruce

[Guppy916]

Sorry I believe I have a cam that is slightly hotter than fast road, I'm hoping for slightly more than 150bhp and J Type o/d, cam details for the tech guys amongst us
          TIMING°                    DUR°           V/Lift          V/Clearance        F/Lift °        LATDC     
     OPEN                CLOSE          290                                          110          
INLET     35     BTDC     75     ABDC        0.445             0.016                              0.107     
                                                       11.30     mm      0.40mm                       2.7mm
EXHAUST     75     BBDC     35     ATDC  290      0.443        0.018       110                     0.105     
                                                                11.25     mm     0.45     mm                            2.65mm
there's more only i can't fit it in

[Clive]

It isn't as simple as what cam, and IIRC the 150bhp was a bit of a fudge anyway.
My 2.5 had a piper cam fitted. It "only" made 115bhp or so, but was "beaten" or a rolling road shootout by a jigasaw 2.5 engine with triple strombergs, ported head, fast road cam and all the other goodies. By 3BHP, and had a little less torque than mine. Think the RR was out of calibration as all results that day were a bit on the low side.

The 2.5 is all about torque, So a longer diff and slightly more relaxed driving style are called for.

Saloon box, but with sprint first gear is best bet. Went in OK into my vitesse, a few nibbles off the chassis edges, and I welded a mounting bracket in place. Needs a sprint slave cylinder and cross shaft, and a longer bearing carrier. Plus a fiddle with spigot bearing. Gearstick came out in same place as std gearbox.

Tiggr did theconversion in a GT6 a few years ago, there was a thread on it. Have a search, I am off to the pub now!

[Steve P]

I have a Vitesse but could offer some of my experiences with running gear...

Engine spec is 2.5 (PI Originally) with ported and flowed head,Jag valve springs,only running 2 x HS6`s but with worked on manifold.TR5 cam,fully balanced,blueprinted oil pump etc.Compression 10:1 ,Mike the pipe 6-3-1 into custom made single box system by Simpson race exhausts.

I went for the Saloon box with J type OD which as Clive said went in fairly easily.I have a 3:27 diff with a different carrier(TR7?).I did away with the cable speedo and went electronic along with the rev counter.

The car made 172bhp on a rolling road after running in and it is a joy to drive with tons of low down grunt and great acceleration with a top speed i haven`t come near to as its scary in convertible Vitesse.
The only part of the running gear i managed to break was a driveshaft but mine were MK 1,i have now gone the Nick Jones CV route.

Steve

[JohnD]

SofS had a 2.5L engine for ages, until I grenaded it.
Still trialling a 2L at present.

I use GT6 gearboxes, never damaged one, save once when it was my own miss-change that did the damage.
I run either a Quiafe ATB diff, or one of GT's LSDs, both 3.68, but either of these just replace the sun and planet gears.  The crown & pinion are Triumph products.  No problems
It's the half shafts that go, and it's a design fault, an abrupt change of radius at the hub, which is a stress concentrator.   Wheels fall off.

So now I run the usual upgrade, LoBro joints inboard, Metro half shafts, CV joints outboard, and in my case MGF hubs, uprights and disc brakes.    Twice as many bearings as Triumph, no design faults (that I know of)
And fabricated wishbones - see pics.    Mk.1s lasted nearly ten years but eventually broke - see 'field repair'!   Which wasn't a disaster, but a rather entertaining drive, when the car would steer itself around right handers.
Mk.2s more robust and strengthened by cross brace above.

John

[Gt6s]

My EFI car runs a 2600 with a pretty wild "sprint" cam, comes on at 4 runs to 7. The box is 2500 S with competition 28% J type OD. Diff nor saloon box have ever given issues. Having said that diff is 3.63 with Quaife. I gave up on stock components many years ago. 3.27 diffs IN PARTICULAR ! Driven without mercy.

Laurence

[cruza]

My Mk3 has a genuine TR5 injected engine that has been rebuilt with higher compression etc so is over 150hp. It also however has the TR5 o/d gearbox and the Subaru diff conversion so the drivetrain is pretty bulletproof.

[BiTurbo228]

Seem to remember fitting my saloon 'box the first time round was pretty simple. Needed to make up a new mount for it, but went pretty smoothly.

Try shifting the engine back 3" though and you need to hack out quite a sizeable bit of your chassis. Does let you (sort of) fit a TR6 exhaust manifold though. Mine still fouls on the suspension bolt so need to sort something out for that...

Glad to hear it should be fairly solid though