2.5 crank

[TimW]

So while looking on Chris Witors site yesterday for thrust washers and gaskets I found that he sells H-Beam con-rods and makes the claim that they will allow a 2.5 to rev to 7100rpm.  I spoke to Chris and he confirmed this but I was always under the impression that the 2.5 crank isn't strong enough to rev that high.

Comments please :)

[Richard B]

339 wrote:

they will allow a 2.5 to rev to 7100rpm...

Comments please :)

You just need one of those very nice billet cranks as well. Only £2500  ;)

[Nick Jones]

I was under the impression that the 2.5 crank has a torsional resonance issue somewhere in the upper 6ks which means a very short fatigue life is used over that point.  May be controllable using a decent torsional damper (that factory one isn't sufficient) but these are also pretty pricey to do properly.

If you need much more than 6k on your 2.5 one could argue that you've tuned it wrong  :P

If you really need (want) more grunt then how about a super/turbo charger  ;)  but better have a spare engine or two (I have a spare 2.5 engine needing rebuild that needs a good home)

Nick

[TimW]

"If you need much more than 6k on your 2.5 one could argue that you've tuned it wrong"

Who said anything about "need"?????  My setup goes very well indeed as some found out on the RBRR.  I just thought that if the engine has to come apart for new thrust washers then why not try and get more revs 8) 8) 8) 8) 8) 8) 8) 8)

[GT6boy]

Nick_Jones wrote:

I was under the impression that the 2.5 crank has a torsional resonance issue somewhere in the upper 6ks which means a very short fatigue life is used over that point. Nick

Sorry Roy!  :B ;)

[Royboy66]

GT6boy wrote:

Sorry Roy!  :B ;)

:'( :'(

[Nick Jones]

339 wrote:

"If you need much more than 6k on your 2.5 one could argue that you've tuned it wrong"

Who said anything about "need"?????  My setup goes very well indeed as some found out on the RBRR.  I just thought that if the engine has to come apart for new thrust washers then why not try and get more revs 8) 8) 8) 8) 8) 8) 8) 8)

Hence the "want" in brackets  :P  

I understand it's fairly nippy already  ;).  Given that you've got plenty of grunt, perhaps you just need taller 1st and second gears - they are available for the T9 and cheaper than billet cranks!

Are your thrust washers definitely dead?

Nick

[Gt6s]

339 wrote:

"If you need much more than 6k on your 2.5 one could argue that you've tuned it wrong"

Who said anything about "need"?????  

Yeah who mentioned  "need" exactly.

I run to seven on modded stock rods and balanced crank. because my cams powerband is four to seven. Okay soft cut limiter is set at six eight, hard cut at seven. The build of the engine allways was to run this high rpm.
A rev limiter is a must !

Kastner found that the 2.5 crank came into a state of uncontrolable harmonic imbalance at seven two.

I have not encountered a problem.

[Gt6s]

Gt6s wrote:

I run to seven on modded stock rods and balanced crank. because my cams powerband is four to seven.

I should add to that, even though the cams powerband is four to seven. Due to the engine management she has smooth idle, lots of low down grunt and completly tractable. But she really starts to pull hard after four.
Not bad for a competition cammed engine on 46mm direct to head throttle bodies considering it is "tuned wrong".

[TimW]

Nick_Jones wrote:

Hence the "want" in brackets  :P  

I understand it's fairly nippy already  ;).  Given that you've got plenty of grunt, perhaps you just need taller 1st and second gears - they are available for the T9 and cheaper than billet cranks!

Are your thrust washers definitely dead?

Nick

I'm starting the strip down tomorrow but when you put your foot on the clutch the front pulley moves away from the front cover by about 1mm so i'm assuming they are on the way out.
I don't want to mess with the gearing because it's so well suited to my driving style.  Takes alot of folk by surprise I can tell you!!!  I would however like a taller 5th gear for more comfortable high speed cruising.  I think the engine would easily pull a 6 speed but haven't got the £5 grand to spend on one!! ??) ??) ??)

[thescrapman]

It is possible to produce a 2.9:1 diff for a Triumph.

Involves fitting a ford internals into a Triumph casing.

That would give you a nice long-legged cruiser.

Cheers

Colin

[GT6 M]

Seems Tim is finding oot what Ive been on aboot for yonks.
a GT with a tuned 2.5 will pull 30mphin top nee bother.

rgarding thrusts Tim, I hope that they were put in the right way round first time,!!!!
I pulled one to bits years ago, and the thrusts were back to front.



M

[TimW]

thescrapman wrote:

It is possible to produce a 2.9:1 diff for a Triumph.

Involves fitting a ford internals into a Triumph casing.

That would give you a nice long-legged cruiser.

Cheers

Colin

That would make the difference i would be looking for!  Do you have any further info?

[TimW]

796 wrote:

Seems Tim is finding oot what Ive been on aboot for yonks.
a GT with a tuned 2.5 will pull 30mphin top nee bother.

rgarding thrusts Tim, I hope that they were put in the right way round first time,!!!!
I pulled one to bits years ago, and the thrusts were back to front.



M

I didn't build the bottom end but I know the original thrusts were used.  I should know more by Sunday next week.

[Greeks]

796 wrote:

Seems Tim is finding oot what Ive been on aboot for yonks.
a GT with a tuned 2.5 will pull 30mphin top nee bother.

M

Doesn't really need to be tuned that well does it?

I can pull in top from 1k and i only have a cam skim and lightened flywheel ... And SUs. Runs into the 6k zone ok too. And that's in a bus.

[thescrapman]

339 wrote:

That would make the difference i would be looking for!  Do you have any further info?

MikeyB might be able to remember, it was a guy Dave Davies nr Southend that did it.

Cheers

Colin

[mikeyb]

hmmn, I remember Dave extolling the virtues of 3.27's, don't remember the Ford version though.  

Dave was a nice guy, always with an entertaining story to tell - but I was never sure how many of them ought to have been taken with a pinch of salt    :-/

I seem to recall Dave was running a 2L - a good cruiser but a tad lethargic up hills and away from traffic lights.

Of course it could just be my defective memory, not getting any younger you know!

[Nick Moore]

I'm watching Tim's (engine) stripdown with interest. Has anyone here modified their thrust washers? I've read articles which mention pinning them with dowels or screws, and yet most experts say that sort of thing isn't necessary. I've seen the result of a 2.5 droppng a thrust washer, so it does happen.

[GT6 M]

If n ew thrust going in,and if crank back s ok,
then I would put diff sized thrusts in,
say tou need tow at 20thou, then put a 5 thou int frunt, and a 15 thou int back,
its the back that gets the stick frae,t clutch.

now some folk may say that the actuall bronze stuff is the same thickness, true it is,
BUT the thrust is thicker over all, so has less chance of actually dropping oot.
if it ever does want to..

the one i pulled to bits was well worn away, both thrust and crank, but it did not drop oot.
they must need to be well worn to drop oot.

wee tip, dont sit wid foot ont clutch for yonks.

M

[thescrapman]

MikeyB wrote:

hmmn, I remember Dave extolling the virtues of 3.27's, don't remember the Ford version though.  

Dave was a nice guy, always with an entertaining story to tell - but I was never sure how many of them ought to have been taken with a pinch of salt    :-/

I seem to recall Dave was running a 2L - a good cruiser but a tad lethargic up hills and away from traffic lights.

Of course it could just be my defective memory, not getting any younger you know!

You got any contact detals for him??

Other option of course is an overdrive.

Is it the Volvo ones that are a separate unit?

Have and input and an output flange?

Cheers

Colin

[GT6 M]

Col, it was the land rovers, they had a separate stand alone yan.
I looked into this, putting it onto diff end, so having 2 od,s
as I got one in the shed, actually got it to doo same thing onto the auto PI
i got of Dad, but it would no go on easy.
this set up would have given 33 mph x 1000 rpms.

would fit, BUTT, needed some work on chassis body area, so did nae carry on.
but any one already chopping the car aboot,  then its a go go.
M

[mikeyb]

thescrapman wrote:

You got any contact detals for him??

No, lost touch when he did a Lord Lucan some 10 years ago.  He is still around though, was at the Club Triumph Eastern Quiz night we attended.  I still have a few CTE contacts, can make enquiries.  Some on this forum too I believe!

thescrapman wrote:

Is it the Volvo ones that are a separate unit?

Have and input and an output flange?

similar on ebay recently 190730540325

[thescrapman]

MikeyB wrote:

similar on ebay recently 190730540325

Thats the idea, but that one is a monster. Very cheap though for an A-type, and a 28% one.

The Land Rovers have Fairey Overdrives, big buggers as well.

The J-type version is much more compact that I have seen.

Must be Volvo or Transit van, something like that.

Cheers

Colin

[thescrapman]

http://www.odspares.com/phdi/p1.nsf/supppages/odspares?opendocument&part=4

Cheers

Colin

[mikeyb]

Dave's contact details emailed to you!

The Volvo 240 I stripped had an o/d fitted similar to Triumphs - ie. pushed onto a splined mainshaft