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John Culham

TR250 Cylinder swap

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I have a Stanpart inlet manifold from a Triumph 2500TC that I would like to fit to my TR250 1968 ( eng No CC/7078-E ) cylinder head,

but ports do not line up as US spec, cylinder from which models of Triumph will fit my block ?

Will this Cylinder Head fit :- 3.475" 219016. 2500, 2500TC, 2.5‘S’ complete with valves and springs Used Superior flow characteristics to earlier heads ?

 

Also would it be possible to fit a TR5 PI cam to my engine ?

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Hi John,

 

All TR6 heads will fit the '250 block, and so will all TR5/6 camshafts. I believe the inlet manifold from the 2500TC is not perpendicular to the head and will tilt the carbs upward ( this is to allow the 2500TC engine to be installed diagonally vs. upright ). I suggest using the later carb TR6 inlet manifold if keeping the Stromberg or SU carb option; its ports should line up with the 2500TC head.

 

I have the TR5 cam and wide port head on my driver '250.

 

Cheers,

Tom

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Tom

 

MY inlet manifold is perpendicular to the head, so must be from a TR6, good news.

 

Just need to find a head if the 2500TC head will not fit the TR250 block

 

Regards

John

 

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It appears that the exhaust valves on the 2500tc head are 30.3mm in dia and the TR250 and TR5 exhaust valves are 32mm in dia as shown on Chris Witor dator sheet , so I will have to keep locking.



Regards


John


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I wouldn't worry too much about exhaust valve size, the 30.3 were used on all the late TR6 and GT6 heads without problems, its inlet valve size that is important. There was a trend in the 70's to increase Exhaust valve sizes until is was discovered that it made virtually no difference.

 

Decent rim flowed 30.3 valves will handle more that you can throw them with twin carbs.

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The small valves can quickly be swapped to the bigger ones

and at that job also the outlet can be modified a bit with a grinder.

 

The outlet mostly has a bad undercut 4mm under the

valve seat where the casting cores did not fully meet.

 

So no need to refuse the head. I would look for the distance

of inlets. The smaller distance heads do not accept PI manifolds

and need the other carb manifold that in my opinion is not as good

as the later one....

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Hi John

 

I have the S head with TC manifold on my 250 works fine the S head is better gas flowed than the standard still run the Strombergs also.

 

Mark.

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Hi john,

 

Yes stamped 219016 I had it machined for unleaded not sure if it was ok as standard.

 

Mark.

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The 2500 TC head & manifold assy is a direct fitment to the TR250 block as stated above.

BUT

I think you will need to get the push rods as well as I think TR250 are a different length and construction to the 2500TC

Manifold tappings on the TC manifold are probably different too. Check the water routing and servo tappings.

 

What will you do about the distributor, as the TR250 has an advance and retard vacuum unit system.?

 

The 307689 TR5 cam is a PI cam and may make your engine run like a bag of poo with carbs. Think about the 311399 late TR6 cam which was used on all 2500 / TR6 after 1974 beit carb or PI.

http://www.moss-europe.co.uk/internal-engine-585005.html

 

You can always go sporty cam and have to get the thing tuned with replacement needles etc.

 

Those who know more will be along in a moment.

 

Cheers

Peter W

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Peter/John

 

It was a few years ago I fitted the S head and seem to remember I reused the push rods as they were the same (wait to be proved wrong!?) I blanked off the retard unit as it really is only needed on tick over and for the emissions. I removed all the emission control gear from mine and fitted mixture adjustable Stromberg's rather than the sealed originals which are identifiable by a red label on the cover.

 

Mark.

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Hi

 

The push rods are the same length for both the 2500TC and TR250 as shown on the attached http://www.chriswitor.co.uk/cw_technical/head_applications_chart.pdf

 

Also have a 2500TC inlet manifold which I will be fitted with SU carbs ( jet replaced to suit cam ), also a 123 distributor.

 

It appears from the data sheet that the head can be skimmed by 0.075" then the push rods will have to be changed.

 

Regards and many thanks for your comments

 

John

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Guest ntc

Hi

 

The push rods are the same length for both the 2500TC and TR250 as shown on the attached http://www.chriswitor.co.uk/cw_technical/head_applications_chart.pdf

 

Also have a 2500TC inlet manifold which I will be fitted with SU carbs ( jet replaced to suit cam ), also a 123 distributor.

 

It appears from the data sheet that the head can be skimmed by 0.075" then the push rods will have to be changed.

 

Regards and many thanks for your comments

 

John

John

It is to far,63 thou off a std head is as far as you should go for road use and the std pushrods will fit.

Edited by ntc

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If you are using carbs can suggest you use Cam Stanpart 308778 which was used on the Mk1 2500PI, GT6 Mk2 and Vitesse Mk2. It's generally considered the best ST cam when using carbs on the 1.6, 2.0 and 2.5 Litre engines. I have used it on a number of 6 cylinder engines over many years. The last was a 2.5 Litre which also had a skimmed S head (cr 9:1), HS6 carbs and Vitesse Mk2 dizzy. Around 130 bhp with smooth power from 1000 rpm, no rough tick over. Used in a Gitfire.

 

Regards,

Dave

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