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Sptifire 6 Son Of Frankenstein


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Hi folks,

so I have what appears to be...

Mk3 spitfire tub

Mk1 GT6 chassis with rotoflex conversion

2500TC (MM) block

lord knows what head

the PO claimed it had a hot road cam but that could mean anything from a Kent to a cheese toasty

 

The good:

it starts, stops, corners, rides nicely

the gearbox is excellent

the OD works (as long as the oils topped up)

its pretty from a respectable distance

rust free

I fitted all the dials and switches. Totally overkill. love it.

 

the bad:

it likes oil more than I like lager. Since I'm doing dry January I chucked in some Wynns stop smoke so it can too.

based on Nick's experience I just bought a cheepo borescope so see how expensive that's going to get

The rear rotoflex conversion is a bit of a botch. I have improved it with some new bolts/sleeves/poly bushes but I'd like to do it properly with CVs and possibly a coilover solution. In fairness it looks ugly but handles well.

 

 
the ugly:
the electrics. Some people just shouldn't go near wiring. Oil pressure light didn't work, or the temp gauge. or the hazards. 
The indicator dash lamp would flash at random and there was no ignition key....just a toggle hanging behind the dash and a doorbell for a starter!

The paint job up close

And the massive gaps between the doors and the sills

Badly knackered hammeron wire wheels. After one adapter sheered through 3 studs I got some minatours.

 

But its so pretty and puts a grin on every time I drive it.

 

got a few pics of stuff I've done which Ill post at some point...might be of use to someone.

 

cheers

Rich

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Rich,

 A GT6 head would have chambers for 2 litres.  Put it on a 2500 block and the compression rockets, to more than 14:1, it would pink like a carnation, and not last long.

The incompatibility arises from fitting the intake manifold from a 2 or 2.5 L Saloon, as the engine there was canted to the right to make for a lower bonnet line.    The manifold was built to mount the carbs horizontally, so if fitted to a vertical GT6 engine, the carbs point upwards, not really enough to make much difference to fuelling, if they didn't foul the GT6 bonnet.

So as yours looks undented, I deduce that the manifold is for a GT6.

 

Show a picture, we'll tell you for sure.

John

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Hi,

the people from Coventry don't make life easy (I should know I married one ;-)

 

The head is stamped 219016 which {according to my brain in the cloud} is from a late 2500. Pretty sure its a gt6 manifold as it is vertical.

 

No pinking that Ive noticed

 

heres a picture...any info most welcome.

 

Also any recommendations for tweaks as it will have to come apart at some point to sort the oil issue??

 

cheers

RIch 

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219016 is the 2500S head and, according to some (Chris Witor for one) gives the best flow of any of the Triumph heads in standard form.  It is also the thickest of all (bar the low compression export engines) and thus gives a low compression ratio (8.5:1 IIRC) in standard form.

 

Even with a standard cam it benefits from a good skim and if you truly have a "hot" cam, the need for a higher basic compression ratio becomes greater.  Would be interesting to know what cam you have, but if you get a reasonably steady idle at < 900rpm it probably isn't all that hot.

 

As a point of interest, it would be possible to have a late GT6 Mk3 head on a 2500 because at that point Triumph were using domed pistons in the 2L engines so as to have as many common parts as possible.  Doesn't make a great deal of difference - most of the heads are based on the same basic casting.

 

That is a GT6 inlet manifold with a pair of SU HS6 carbs knife & forked on it with a pair of slightly dodgy looking adaptor plates.  Looks like the linkage has been adapted from a 4 cylinder one.......

 

Probably plenty more horses to be had with some fairly mild sorting - but it is worth keeping in mind that well sorted 2.5 will make fairly short work of the transmission (all of it!) if used to it's potential.

 

Wynns is good stuff.  Kept my 2.5 PI use down to manageable proportions for a short while and it kept my Vitesse engine alive for about 10 years.

 

10 CR 2009 - 3000 miles door to door, no Wynns, used about 5.5 litres of oil.  I promised to rebuild it before the next one, but took 6 years to do it.....

10 CR 2011 - 2600 miles door to door (but about 20 Alpine passes in full attack mode), with Wynns, used < 1 litre.

10 CR 2013 - 2600 miles door to door, with Wynns, used about 2.5 litres.

10 CR 2015 - 2700 miles door to door, new engine, used no oil.

 

Can give scary oil pressure (high!) when cold though.

 

Agree that the H bracket will improve the driving experience - dash and bulkhead are much less floppy with it fitted.

 

Looks like a decent, usable car with plenty of potential.

 

Nick

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does anyone know the difference in combustion chamber volumn between GT6 mk2 and TR6 of the same vintage?

 

I found this reguarding TR6 cyl. heads http://www.goodparts.com/tech_docs/TR6_Compression_Ratio.html

 

 the GT6 MK2 head 3.30 inches. The TR6 PI head is 3.4" with flat top pistons and the head is used in the GT6  Mk3 w/dome pistons http://www.chriswitor.com/cw_technical/head_applications_chart.pdf

 

Will a 3.3" head on a 2.5L bottom end produce 10:1 static comression ratio? What will the effective compression ratio be with cams of increased duration.http://members.uia.net/pkelley2/DynamicCR.html

Edited by motov8id
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Thank you, Nick, "As a point of interest, it would be possible to have a late GT6 Mk3 head on a 2500 because at that point Triumph were using domed pistons in the 2L engines so as to have as many common parts as possible."

Spot on, and I completely forgot that.  But it wouldn't work with a 2.5 crank (how bitsa can you get?)

 

And motov8id, the difference between the 2 and 2.5 L chambers is the same as the volume of the dome on late GT6s.   Memory tells me that is about 9mls, but memory ain't wot it useta be - see above.

 

As to skimming, it's a mistake to ever rely on someone else saying, take  certain height off the head or the volume of the dome was such and such.   Always MEASURE the volume by buretting the chambers.      You will probably want to flow them as well, and buretting ensures equality of volume across the block after that work.   Aim for no more than +/- 0.5mls.

 

John

Edited by JohnD
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Hi,

it did come with an H bracket...just not bolted to anything!

Should the bottom feet bolt to the metal floor or the plastic tunnel (I only ask before I start ripping up the carpet)?

 

So the gearbox looks like a GT6. Clutch slave is above the starter and accessed from the engine bay. Syncro on first. Reverse is push down, left and up.

88306468/v3038 casting behind the bell. Cant face ripping the tunnel out just to get to the stamping at this point

 

I cant get it to idle smoothly under 1000. Might have another go this arvo since its chucking it down and I now have a colourtune to play with. I reckon I need to do a proper service on the carbs...it does look botched, one was leaking when I got it (PO reckoned problem was heatsoak) and lord knows what needles in what state are in there.

 

Nick...what engine oil and plugs did you use for best results with the Wynns? I'm currently on Halfords classic and BP6ES.

 

cheers

RIch

 

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 H bracket bolts to the dash frame at the top and down through the tunnel and floor into captive nuts in the chassis - it is a structural item.  Lining everything up can be a challenge.

 

Sounds like you do have a standard gearbox.  No bad thing apart from the strength/life issues.

 

I was mostly using Comma 20/50 (cheap!) with the Wynns.  Plugs...... triple electrode Bosch, something like WR7DTC. Those are resistive due to the engine management and I'm not sure the straight W7DTC are available anymore.

 

I wouldn't really quarrel with your BP6ES (you can get triple electrode versions of these too - BP6ET).  If you find that these foul you could go down a heat range to 5s.

 

Good luck with the colour tune........ I like the principle but never had much luck with them.  With a possible big cam, lots of oil burning and suspect carbs........  :wallbash:

 

Nick

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Evening all,

 

can I assume if my BAE needles have a massive flat all the way down one side they are scrap? i.e. they are no longer round in cross section.

 

reckon Ill refurb carbs before I even bother with the colourtune!

 

cheers

RIch

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Basically yes.  But before replacing like with like, bear in mind that it may have been done on purpose though (amazingly enough) in an attempt to increase fuelling to "suit" the engine. This because when you have an engine which is a non-standard combination of bits (some parts themselves "tuning" parts) it is not at all obvious what needles to choose as a starting point.

 

Always a smart move to renew the jets at the same time.

 

 

There is a reasonable amount of information about on what needles to use with which combinations...... but the unknown here is the cam.

 

This is one (big) reason why I like Megasquirt injection and wideband O2 sensors!

 

Nick

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well I suppose if its a bit under powered its less lightly to eat the gearbox. 

Ill bite the proverbial and rebuild with BAG needles, plain butterflies and new everything else.

Might treat the manifold to a mild port (2 & 5 etc).

 

reckon its better to loose the adapters and try to modify the manifold to take the HS6 directly or is there a benefit to a longer leg as it were (like old school 2 stroke spacer blocks)

 

OR maybe I should have a fiddle with that old TZR125 ;-)

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Re inlet manifold to HS6's, I have tried all 3 methods.

The best  (possibly) was plugging the existing stud holes in the manifold with threaded ali and threadlock, filing flat and re-drilling/tapping the inlet. The easiest is to elongate the carb mounting holes.

Both times I opened the manifold out crudely using a cone drill as a rotary rasp, took 10 mins to do.

 

As to needles, I used BDQ on my std 2500s engine fitted with k+n's in an airbox, massively smooth and torquey. And it may have been BAG on the TR6 engine fitted with a piper cam. More power but never as smooth. Still when you keep breaking diffs you tend to be a bit more careful anyway. (I used a big saloon box, so that was never an issue)

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bores look OK...a few light scrore marks but all shiny.

 

valves look a bit crunchy apart from C6 where they look cooked. Which explains the low compression on that one.

 

and I suspect the culprit for the oil is C2. oil tide marks in the bore...so stuck or knackered oil rings. Maybe the former since the bore's not chewed up.

 

compressions, cold.

c1: 127
c2: 140
c3: 129
c4: 130
c5: 127
c6: 72
 
so looks like the head will have to come off. 
Anyone know a good head engineers in the South East?
 
cheers
RIch
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Near Lewes.

I did try a place up near Maresfield for a dyno tune-up.

As far as I can tell they charged me north of 200 quid to thrash the nuts off it, screw up the timing and mangle the vacuum advance hose.

Afterwards it wouldn't start cold until I re-did the mixture

And they claim to be classic specialists!

 

 

So on balance for the sake of a courier Id send the head anywhere that gets a personal recommendation but nearer is better. 

cheers

RIch

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a bit far from you but I have used Thurston engineering in Ongar,essex a few times,they do a lot of classic and racing stuff and they have a dyno.

I saw ant anstead was in there on an episode of 'for the love of cars' so that is as good an endorsement as any.

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There are relatively few RR operators who know what to do with SUs. ie selecting correct needles rather than tinkering with the mix at one point and hoping for a workable compromise.

 

Peter Baldwin has a decent rep but not very handy for Lewes (nr Cambridge). http://www.wilshers-garage.com/rolling-road

Steve Harris (Cranbourne chase) http://www.bjautobits.co.uk/harris-motorsport.htm

Tipton Garage (between Sidmouth and Honiton) are the ones I use - but I'm using a laptop.  Steve knows his SUs though.

 

None very convenient for you though - sorry.

 

Nick

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  • 3 weeks later...

Was the tuners CCK? I know somebody who took their spit 6 there and was happy with the results. 2.5 mk1 PI engine on SU's

 

There was a good chap (Gerald Dale) near hastings, but my car was the last one on his rollers before he had to move (and no more RR)

 

Personally I like the 2.5 engine, but it is all a matter of taste!

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If you've got the skills to fit it, go for B. The Busso V6 Alfa engine is a fantastic engine, musical, flexible, powerful and charismatic.

 

I've had Triumphs all my driving life, but IMHO the Alfa V6 is in another class to the Triumph lump.

 

Not sure what you'd do for a gearbox though, unless you want to go the whole hog and fit a 75 transaxle...

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