Head Replacement
Posted By : Mark Hellier, 10-Jan-2007, 05:54pm
Yes a 2.5 mk11 head will fit straight on a GT6 mk11, early and late mk111 block - and dependant on which block (i.e. flat or domed top piston) and
which 2.5 head you use (i.e. TR5/6, 2.5 or 2.5s) you will have to have the head skimmed to raise the compression ratio for 2ltr - if you place a std
2.5 head on a flat top GT6 block the compression will be about 8.5:1 and it will produce less power than a 1600cc unit and combined with Webbers will
run like a dog – Also the flat top block uses a non recessed gasket and the domed top uses a recessed gasket (with a square tag at the
back)– please don’t get them mixed up!!!!
With regard to buying a head – the choice is yours – however as in my previous post – as you’ve got triple Webbers you need to match everything up – i.e. cam/head/compression ratio/exhaust etc etc – so a stage 2 head would be normally used for a mild upgrade the road use – using a bank of three Webbers would normally be associated with a race engine and hence you need a short duration high lift cam – the TH6 is one cam down from a full race profile with a power band up to 7500rpm – so using a stage 2 head without a bottom end that is prepared for high revs then firstly the potential for things going bang are bigger and secondly you won’t get the best potential out of the components your are using ( although they may all individually look good on paper) - I hope you see where I’m going – use a decent set of new cam followers as if you don’t the cam will break up – new chilled cast blanks and not re profiled cams is your best option. Again as before I don’t like the cams as every cam I have used has fallen apart and hence I haven’t got a good word to say – facts are facts.
Push rods – you can use std Triumph ones – but again it will depend on what compression ratio you end up with so might need mk1 or early mk 11 push rods.
Pistons loads of choice – std pistons are ok – BL comp department ran all race units on std pistons – you can even use Toyota/Lada/VW
With regard to buying a head – the choice is yours – however as in my previous post – as you’ve got triple Webbers you need to match everything up – i.e. cam/head/compression ratio/exhaust etc etc – so a stage 2 head would be normally used for a mild upgrade the road use – using a bank of three Webbers would normally be associated with a race engine and hence you need a short duration high lift cam – the TH6 is one cam down from a full race profile with a power band up to 7500rpm – so using a stage 2 head without a bottom end that is prepared for high revs then firstly the potential for things going bang are bigger and secondly you won’t get the best potential out of the components your are using ( although they may all individually look good on paper) - I hope you see where I’m going – use a decent set of new cam followers as if you don’t the cam will break up – new chilled cast blanks and not re profiled cams is your best option. Again as before I don’t like the cams as every cam I have used has fallen apart and hence I haven’t got a good word to say – facts are facts.
Push rods – you can use std Triumph ones – but again it will depend on what compression ratio you end up with so might need mk1 or early mk 11 push rods.
Pistons loads of choice – std pistons are ok – BL comp department ran all race units on std pistons – you can even use Toyota/Lada/VW
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Head Replacement
Posted By : John Schuldt, 10-Jan-2007, 09:10pm
thank you for that important info
so i would also need to upgrade my crank (where can i get a crank? anybody know?)
also how many engine parts are interchangeble between a GT6 and a TR6.
TR6 parts are a lot easier to get here in canada.-
Head Replacement
Posted By : Mark Field, 10-Jan-2007, 10:00pm
how do you mean up grade your crank would you wish to change to steel -
Head Replacement
Posted By : Mark Hellier, 10-Jan-2007, 10:12pm
Hi John
Standard crank is ok for road use - the important thing is to get the complete rotating assembly balanced and the conrods end to end balanced and stress relived (it will then rev) use ARP bolts - you can have the crank tuftrided if you can find someone reliable - don‘t go down the route of cross drilling it - the stock flywheel is ok as well but get it lighten and balanced on the crank with the front damper - buy yourself the Kas Kastner Comp manual (available from the Club for about £7) and follow that re engine mods - you can’t go wrong - the mods are race proven and work - unlike other tuning manuals around
Did not appreciate you were out in the Canada - speak to Ted Schumacher at TSI in Ohio http://www.tsimportedautomotive.com he probably wonÂ’t remember me but had good conversations with him - he does all the original BL comp department race profile cams - i.e. S2/S4 profiles - heÂ’ll keep you talking for hours on mods to the GT - perhaps his TSI275-6 cam would suit as its 275 duration with a high lift
Re interchangeability between TR6 and GT6 share the following components hence up to 71 on the GT6 had the flat top block as found in the 150bhp UK cars and post both used the recessed block and similar heads so that the GT6 used domed pistons to up the compression ratio - both have the same std bore size - so the following items are block, rods, head, head studs, (push rods late mk 111) as 2ltr ones are shorter, rocker arm assembly, water pump, oil pump, camshaft ( the CP block has the best cam)- things that are better on the TR’s are the distributor & CP camshaft, camshaft duplex timing wheels and chain so that can be changed as-well - you can even modify the TR export manifold (by cutting it to reduce the angle on the manifold) and fit CD 175‘s or use fuel injection as the heads are the same apart from the depth of combustion chamber and TR‘s have double valve springs - not sure if you’ve considered this one why not drop the TR 2.5 crank and pistons into the GT6 - only mod you have the do is to the sump and make sure you have a deep cylinder head (TR6 or very late GT6) and use the GT6 back plate & flywheel???
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Head Replacement
Posted By : John Schuldt, 11-Jan-2007, 04:26am
i like the idea of putting tr2.5 bottom end into a gt6 block
i really have no sence of these engine or parts but here is what i think:
tr 2.5 crank, gt6 block, domed pistons, 2.5l head with double valve springs and larger valves,
roller rockers, tr distrubuter and duplex timming chain, aluminium flywheel, camshaft from tsi (to match setup),
improved lifters and followers.
anybody agree or disaprove.
thanks-
Head Replacement
Posted By : Leon Guyot, 11-Jan-2007, 07:11am
>>>You wrote:
i like the idea of putting tr2.5 bottom end into a gt6 block
>>>Why exactly?
i really have no sence of these engine or parts but here is what i think:
tr 2.5 crank,
>>>Way too heavy, as is the (32lb) flywheel etc...
gt6 block,
>>>That's OK.
domed pistons,
>>>No, use the flat ones.
2.5l head with double valve springs and larger valves,
>>>No, use the GT6-3 or TR5 head.
roller rockers, tr distrubuter
>>>No, use a Mallory, (the one for the Jaguar XJ6)
and duplex timing chain,
>>>OK
aluminium flywheel,
>>>OK, but the lightened steel one from Canley Classics is more reliable on a road car, and much cheaper.
camshaft from tsi (to match setup),
>>>They are good.
improved lifters and followers.
>>>Do NOT use the tuftrided cam followers from Moss, (complete crap)
instead use the new (correctly heat treated versions from Kingston Sportscars or Chris Witor).
anybody agree or disapprove.
thanks
>>>I suggest that you talk to Tony Lindsey-Dean at Kingston Sportscars before spending money, or Dave Pearson at Canley Classics, or Chris Witor.
Any of the above will be pleased to give you excellent advice.
No disrepect intended, but you need guidance before parting with hard-earned mulla.
Regards
Léon
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Head Replacement
Posted By : Mark Hellier, 11-Jan-2007, 09:07am
Just to confirm
You can't use domed top gt6 pistons on a 2.5 crank - when tuning use only flat top pistons on either 2 or 2.5 cranks. The 2 & 2.5 pistons have different crown to gudgeon pin heights therefore they are not interchangeable
With regard to the weight of the 2.5 crank as apposed to the 2 litre yeah it is lighter but torque is what you need for a road engine the 2.5 will give you this for free – you don’t use the TR flywheel anyway so its only 18 heavier – also there are many reasons why the GT6 doesn’t handle well – remember this is a road car so the additional weight of the crank against drivers fun/enjoyment I consider would outweighs that – anyway why not put a TR crank in ?
No disrespect intended but if you’re that worried about weight then don’t eat anything before you get in your car!! – have you tried keeping up with a new VW golf TDI that produces max torque at 2800 rpm I hope you see my point!!!
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Head Replacement
Posted By : John Davies, 11-Jan-2007, 02:31pm
Absolutely right!
Dome tops were are commonality measure, to allow the 2litre engine to run with a 2.5 litre cylinder head, and acheive the same compression ratio.
Triumph were able to use the same head for both engines, and save money in work, stores etc.
If you run a 2.5 crank, dome tops and a 2 litre head, the compression ratio will be 14 or so!
Do-able, but probably only with ethanol as fuel.
John-
Head Replacement
Posted By : John Schuldt, 11-Jan-2007, 09:01pm
ok i will call some people first then i'll see which way to go.
thanks for all the info
ps: what do u guys consitter a good parts for a road engine. (i like getting to and from work/places fast)-
Head Replacement
Posted By : Mark Hellier, 12-Jan-2007, 10:04am
Hi John
I have got a complete fast road unit up for grabs with all the goodies described in previous posts - the story is I've had all machining/head work done its all still in bubble wrap behind the sofa - it's a 2ltr + 30'' unit with a high compression unleaded head, flowed valves etc, end to end balance, comp spec oil pump/ new bearings, ARP bolts, duplex chain, gaskets, triple inlet manifold with 3no brand new CD's and custom made stub stacks - even had the sump /front/back plate powder coated etc only thing is the cam has a long duration so its not suited to run on a bank of Webbers - but that's easily rectified - either change the cam or the Webbers. I have built a unit as above but running on fuel injection that produced 140 bhp at the wheels (so about 170 @ flywheel) - but as yet haven't run a triple carb unit - so dependant on if you went with Webbers and a different cam or the above setup you should still turn a good 160bhp @ the flywheel - anyway back to the story - having spent all the above money - decided to put a 285bhp Volvo T5 unit with a 5 speed box in my GT6 so the above is now all surplus - let me know if your interested
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Head Replacement
Posted By : Jon Morton, 12-Jan-2007, 10:28am
Show us a pic of your engine bay Mark!!
I would love to see how a volvo engine looks and fits.
Jon-
Head Replacement
Posted By : Mark Hellier, 12-Jan-2007, 01:29pm
Hi Jon
A slight deivation from the original head replacement post - perhaps it should be me who requires the head replacement???
Engine bay - well its more of an engine bulkhead, to aid weight distribution I have moved the entire unit back - removing part of the bulk head - who needs a heater box anyway as the turbo should keep me warm enough!!!
So still very much in development mode at present so excuse everything covered in angle grinding dust and no shiny paint work - picture of engine and box in location on fabricated mounts - chassis will go back to blasters (again) once mounted the Cosworth LSD and the coil overs at the back and removing the leaf spring completely - so back to the drawing board with the rear end as I'm using top and bottom wishbones/coil overs/CV joints and disc's. Body tub undergoing complete rebuild & bare metal respray (once I've finished covering it in angle grinding dust)
Thing is I'm trying to keep the external appearance completely stock apart from alloys - so watch this space!!!!
Head Replacement-
Head Replacement
Posted By : Chris Taylor, 12-Jan-2007, 11:58pm
Still intrigued how you are going to fit the steering rack................-
Head Replacement
Posted By : John Schuldt, 13-Jan-2007, 02:27am
wow thats an insane swap.
ya i am interested in the engine it sounds sweet, how much and how are we gonna arrange shipping to canada thats gonna be interesting.
could you send me a picture of your engine for sale.-
Head Replacement
Posted By : Mark Hellier, 13-Jan-2007, 09:40am
Glad you like the engine swap!!!!
Yeah no problem - I will take some photos today - if you send me a priviate message via the club with your email address in I'll send you some pic's as you can only upload 1 per post on this forum. Also I'll include a price
A brief spec of the unit is below - one thing worth pointing out I was going to run a 5 speed Volvo gearbox on this unit so had a 2.5 flywheel lightened instead of a GT6 one - as this has the spigot bush mounted in the flywheel (which is large than then GT6 one - so you can fit a slightly bigger dia input shaft through) - so the 2.5 weighs just under the standard GT6 one - so could either get a GT6 lighten and balanced on the crank - or go to a lightweight steel one - or even more straight forward would be to fit a 2.5/TR6 gearbox which would mean you can use the 2.5 flywheel 'as is' and get around the main weakness of the GT6 which is the standard gearbox.
Shipping - hhhmmm that will be interesting - I'll do some investigations - as all components are unassembled at present then if you wanted to get your own block bored instead of shipping that then the heaviest part would be the crank and cylinder head so could split the rest up into smaller parcels ?? just a thought but you would need to assemble it your end - which you may rather do anyway
Anyway spec below:-
Block
Acid dipped block and clean oilways
Rebore to +30''
Surfaced block @ zero deck clearance by trial assembly
Bottom End Parts
Dynamically balanced crank with front damper, flywheel and pressure plate
10'' grind on mains and big ends
New Vandervall main and con rod bearings
ARP flywheel bolts
New duplex chain (linkless type)
Lightened flywheel - 2500 saloon with spigot bush to mate 5 speed box
Oil Pump
Competition blue printed oil pump
Con rods and Pistons
Lightend & balanced stress relieved rods
New small end bushes
New pistons
ARP con rod bolts
Cylinder head
CTM unleaded flowed head
New stainless steel stellite face valves - larger inlet/exhaust
New copper bronze alloy guides
Double valve springs - decent one's that don't go soft like most sets available
One piece anodised 'Red' alloy valve caps
Tuftrided rocker shaft
Camshaft
New Chilled cast blank - 40 -80 profile 300 duration - 410 lift
New Followers
Clutch
AP Racing 'Grey' spring cover plate
Powder coating of engine parts
Back plate - alternator/engine mount brackets - timimng cover - water pump housing
Carbs
3no brand new CD175
Tripple inlet manifold - match ported to cylinder head
Custom made stub stacks - as you can only buy ones to fit SU's so had some made
Dizzy
Lucas D25
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