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Fitting a 2500s engine & j type box


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Hello to everybody on this forum. I am new here altrough i have owned the gt6 mk2 for 9 years now. I did much work when i first got it to complete its restoration after 20 years of the road. I have now finished a major house project and i finally have some time for the old 6. Currently runs well on a vitesse 2l engine with cd150s.
    But would prefer it if it outpreformed the alfa diesel idrive daily! I have a 2500s engine and J type overdrive in the garage. I have heard that the cam is crap in the 2500s. Is this true? Can i use the one from the vitesse lump would this be better? Or is it best to buy anothr cam if so what one and from where. Also other than the prop what issues will there be fitting the box. Thanks Rich

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The 2500S cam is not as bad as many say, my vitesse was fitted with that combo for 8 years, went VERY well. However, the std GT6/vitesse MK2 cam is better and a bit more sporty. Use that with the vitesse distributer. Or even TR5 cam or one of the "fast road" jobbies. The std vitesse/gt6 one is nice as an all rounder IMHO. I changed mine to a fast road cam and regretted it.
The engine fits no problem, need to saw off the engine mounts or swap front plate, swap the sump and make some dents to clear the longer stroke crank.
Carbs, you need to either get the std 2500s manifold machined or cut welded etc to clear the bonnet, or use the GT6 inlet. Thats easier. Need dolly sprint short dashpot carbs (and needles)
That is the easy part. The gearbox is MUCH trickier. I used the vitesse/GT6 flywheel and starter. This meant I had to have the flywheel machined to accept the spigot bush for the big gearbox. There was much messing with clutch slave cylinders, and it never was right. In retrospect, it needed a longer bearing carrier made to get the geometry right. The gearbox is good and strong, but first gear is very low, really needs dolly spring gearset fitting. It also requires quite a lot of fiddling. To be honest I would use the GT6 box, it will last if treated with a little respect, better gearing, easier etc etc. OR go type 9, but thats another story!
Clive

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Agree with clifty... Just slapping a 2500 engine in to replace your 2 litre definitely will not result in a faster car. I used to have a GT6 mk3 with a mk2 engine and and I had a mate with a mk3 with a 2500 saloon engine. Both were on 150CDs

His was no quicker - and believe me we tested them  8) Both had exactly the same top speeds and neither of us could really get away from each other.

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Oh dear.
I LIKE the 2500 engines, good for high torque lazy driving (not slow either!)
I am sure the 2500 is quicker than a similar spec 2000, ie std. After all they have more power, a lot more torque and so on.
Its the gearbox I wouldn't swap.

As for handling, the difference in weight is pretty small.....getting tyre pressures wrong will make a much bigger difference!

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Hi just been in loft and found two sets of CD150s and a set of CD175s. I know i have (somewhere) a manifold for a gt6 i have modified to suit these carbs. Sorry to sound stupid but the engine and box were from the same car so whats the problem with flywheel set up on the 2500 engine? Does the J type box give better motorway crusing than the gt6 box as its loud atm on the motorway . So really a 2500 engine with gt6 cam cd175s with the current s/s exhaust wont make it go faster? I hoped it would but if theres no significant benifit i wont bother! If i was going to put a sierra box in the car it would have to be a cossie one with the engine to mate, But then it wouldnt be a six. Thanks for replys Rich

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You CAN use the 2500 flywheel, but it is very heavy. The clutch arm on the saloon hangs down where the GT6 chassis is. You need to either turn it upside down and bend it, or get a dolly sprint version. Plus the dolly sprint slave cylinder mount. It is the physical size of the box which represents the fitting challenges, chassis may need a bit if a trim, speedo cable is difficult, need to weld different mounting plate and so on.
The J type is very similar to the GT6 d type in terms of gearing, most are 25%, some j types 28%, but little real difference.

The car will undoubtidly be quicker, but more importantly it is the way the power delivery comes in. I found 2000cc car lethargic compared to my 2.5 under nearly all driving conditions.

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Agree with Clive here, except you may find the Vitesse/GT6 distributor gives too much advance on a 2.5 causing it to pink and maybe run on too. If so fit the guts from the 2.5 dizzy into the GT6 body to retain the cable driven tacho.

A 2.5 on 150CDs is probably a tad strangled which may explain the similar performance to a std 2.0. (106bhp for 2.5 to 104bhp for 2.0 I think) SU HS6s would be better with, as Clive says, Dolly Sprint dashpots to clear the bonnet.

Glen.

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Hi
I live in the midlands and have just fitted a 2500pi to a type9 box with hs6 carbs.  You can come and have a look if you want.  Be careful with type 9 it don't fit as some will lead you to belive.  My brother has tr6 box in his your welcome to look at that too.

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I have used the GT6 flywheel and clutch pressure plate .  You also need to remove the water pipe outlet from the 2500 cylinder head and use gt6 blanking plug, i have also used gt6 alternator mount inc adjuster arm, sump (modified) engine front and back plates, engine mounts, water pump housing and crank pulley. all of which i have found to be slightly different.  I have also removed the shims from behind the rubber engine mounts in order to lower the engine.  

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Fitted a 2500s to mine.  Got the whole lot balaced and the GT6 flywheel lightnened.  Used Dolly hs6 carbs and needles.  Used my existing front and back plates and already had a type 9 gearbox installed.  Also used the TR5 camshaft I had in the GT6 engine.

Goes well and seems to be getting better all the time.  I am continusly managing to improve timimg with the Megajolt and am fairly happy with the carb setup now.

To Do:
* Sports Manifold
* Work on GT6 inlet manifold
* Flowed head
* Unleaded conversion

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705 wrote:
I'm rebuilding a 2.5 pi engineto be fitted with carbs for my GT6 mk3. The man from Carlow Engineering suggested fitting a Vitesse flywheel, he said they were lighter. I don't know if anyone has both and can compare them to see it there is that much difference?


I have both at home, unfortunatley I couldn't lift the saloon one to see if it weighed more as it was too f**king heavy.

:-)

Colin

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So deos anybody want a j tpye overdrive box, If not it will go on ebay this weekend. Just looked at the cd175s (cant remember where they came from and i am only 30) and they are only about 20mm higher thean the cd150s most of that being the dashpot. Will that foul the bonnet? I Would rather not spend out on parts if i can use the bits i have and i dont really see strombergs are much different to Su carbs (i await correction!)
Probably a crazy idea but i  have a Eaton m62 supercharger which if i remember rightly will be about right for a 2.5l engine. It has a v belt pully so i could machine another one and bolt it to the end of the crank. I work as an engineer in the dairy industry so fabrication of pipework wouldnnt be an issue. What sort of boost could i run without forged pistons etc etc. Dont mind putting a thicker gasket to reduce compression and would consider going down the fuel injection route or perhaps 3 dellorto 45s as from memory i think they can take up to a bar of pressure.

Assuming the supercharging idea is a non starter what sort of improvement in power would i get from a 2500 engine running on cd175s with gt6 cam over the current set up. Is it worth the work or shall i just keep caning the 2l. Thanks again guys

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I have fitted stromberg cd175's to my 2.5 gt6,it run's really well seems to rev nice and freely might be due to the pi cam.I have not driven 2l gt6 so I guess I have nothing to compare it with.I don't think it will need any more power,it seems over powered to me, a little bit of an animal ??)

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I can quote some figures from "retrocar" mag that did a rolling road shootout 5 years ago. My vitesse (2.5, mild road cam, twin 1 3/4 carbs)113bhp@5000rpm, 175Nm torque from approx 2000rpm, pretty flat.
A std GT6 but with sports manifold/exhaust 91bhp@6100rpm, approx 100/105Nm torque but at higher rpm.
These results all seem lowish, but comparable as all the same RR, day, operator etc.

If you look at 3000rpm, the 2000 had 30bhp/95nm, the 2.5 50bhp/110nm. Substantial!

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Jason wrote:
PI had the heaviest flywheel of all  :( It's not just a case of swapping one for t'other though.


Hi Jason
"It's not just a case of swapping one for t'other though" Why not?  I didn't have any problems fittting my GT6 flywheel to the PI crank. Am i missing something??

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cliftyhanger wrote:
The flywheel from a GT6/vitesse will bolt on most 2.5 cranks, but will need the matching starter motor. No problem if you then use the Gt6/vitesse box/clutch mechanism.


Well I was using a 2.5 pre-engaged on a GT6 flywheel (don't have to worry about the chamfer with a pre-engaged).

Then I went Nippon Denso!

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Forgot to mention I put a Nippon Denso on after we (mainly Gilly) had to push start the damn thing the whole way to Italy and back!

Amazingly she didn't leave me and on Saturday we get married!  ::)

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  • 1 month later...

not sure about the engine, as though I've fitted the 2500S engine to my mk1, I've used a Kent cam and webers so it's not really a 2500S engine any more, is it. Also, it's not on the road yet so not sure exactly how it'll drive.

That said, I had it rocommended to me to fit a stronger gearset, so I've used a Dolly 1850 gearset in a Vit casing. It was replacing a non-OD box and I wanted OD, so as the 1850 used a J-Type, I fitted a J-Type onto the back of the Vit casing. The bolt holes line up okay, though the flanges are a little askew. Though it doesn't LOOK like the J-Type was made for the VIT casing, it does fit, and I'm assured will be a much stronger combination.

It is also suited to a 3.63 diff, as opposed to my original 3.89, so as I got a stronger 3.63 diff I shouldn't need to change the speedo drive.

hope this helps,

Guy

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Well the GT6 is back on the road now for the first time in two years. Sold the J type overdrive on ebay for 210 pounds. I am in the market for a TR5 or PI cam if anybody knows of one for sale email me on rharrison751@hotmail.com. Once i have a decent cam for the 2.5s i will fit it on cd175s and see how it goes. Feels good to be back in the six but 100 bhp seems a bit slow. Guess i am after a bit of an animal like Kristian says his is. Various rattles here and there but seems to run ok about to try its biggest journey in about 4 years a mere 50 miles. Fingers crossed it wont let me down again!

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