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TR6 Engine Improvements


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Hi All

I have a September 1972 US Spec TR6 which I have been restoring for the past year, chassis refurb complete, all running gear replaced, diff and gearbox rebuilt, LHD to LHD complete,  body is waiting to go off to be painted so I'm now at the point of totally dismantling the engine for inspection and rebuild. I want to improve the HP of the engine to about 140 but without spending a ridicules sum of money. I have come across some old threads but at times the topic becomes embroiled with with technical jostling between individuals. So I would like feed back on the following improvements that I am planning

1. Head overhaul, fitting new hardened valve seats, skim head to increase CR to ? please advise, bigger exhaust valves and porting improvements?? please advise.  Any suggested specialists who mare familiar with this work??? I live in East Yorkshire. 

2. Managed to get a pair of second hand SU carbs to replace the Strombergs, these will be refurbished fitting appropriate needles etc.

3. New Cam, fast road cam, any suggested type/supplier

4, SS Sports manifold and exhaust

5. I have read about

6. Distributor improvements? what is required

It would be great if anyone has done similar work to what I'm suggesting and what costs were incurred, my ambition  is just to get performance closer to a UK spec TR6 and will be a reliable and easy drive not a screaming racer.

Regards Paul

 

 

 

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Paul,

Just did this.

1. Newman fast road cam £210 delivered.

2. Rebuilt distributor by Distributor Doctor £250.

3. Rebuilt head with bronze guides and hardened seats. Ported and polished £800.

4. Triple Weber’s £1800 including manifold and linkages.

5. Phoenix extractor manifold and single big bore exhaust. £800 but I picked a second hand one up for £350.

Massive improvement on stock car although I have got new hubs, drive shafts and BMW diff.

165+ BHP. If you can do some of the head work yourself you can save some of the cost.

Happy to answer any questions if you want to PM me.

Colin

 

 

 

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Paul

You mention larger exhaust valves, Triumph fitted the smaller valves on the later engines to improve breathing. I know it sounds daft but the bigger valves I am told, obstructed flow.

I found the Phoenix manifold gave off a lot of heat that caused running issues in traffic and on hot days plus it made changing the starter motor a real pain so I put the original manifold back on, I was surprised to find absolutely no difference in performance.

The difference in performance between SUs and Strombergs is zero, both are good for a road car providing that they are in good condition and set up correctly.

The biggest boost to performance will be having the head skimmed to 9.5 to 1, a good cam like the Newman one that Colin has and a Dizzy Doctor distributor. If you go on the Goodparts website there is a chart that will give you the figures for the skimming work.

George 

 

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Hi, Paul and welcome!

1/ If you can get 99 octane (Shell V-plus or BP Ultimate) then a skim to 10.5 will work.     

4/ Stainless isn't a performance improvement.     A 6-3-1 wil improve power mid-range, more useful than top revs.

5/  Red rotor arm - again no performance improvement but more reliable

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A crank fired ignition system like Megajolt controlled EDIS system would let you really dial in the ignition to achieve maximum brake torque at many rpm/load conditions. So, not only max HP, but max efficiency at other than wide open throttle. The driveability difference is startlingly better for partial load conditions. Amazingly trouble and maintenance free.

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6 hours ago, CK's TR6 said:

Megajolt controlled EDIS system

Does the Megajolt allow transient advance/retard of the ignition? E.g. a change for a specific period of time, triggered by sensor inputs, rather than responding continuously to sensor inputs?

John

Edited by JohnC
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Hi Paul,

You will no doubt receive many different ideas here, but essentially, the items you need to change/improve will be the same.

First of all, there are no short cuts to a successful engine !

1. The later 'ribbed' block is a good starting point.  It is ribbed along the length of the induction side, these are considered stronger.

2. Good quality pistons (unless you only need rings) ? Mahle are a very good quality piston.

3. Get the engine balanced (pistons, rods, flywheel, clutch cover, crank damper, camshaft). Vibration Free in Bicester have a very good reputation.

4. If you're keeping twin carbs, Newman cams do a cam that will work well with them. There are based on a new chill cast blank. Their EN40 steel followers to match are also very good.

5. Gas flowed cylinder head, skimmed for increased CR to match the new cam, with new guides.  You cut have unleaded valve seats fitted at this stage too. Peter Burgess in Derbyshire can take care of the head including valves.

6. 6-3-1 peformance exhaust manifold. Coupled to a 2.25" straight through big bore system.

7. Standard distributor rebuilt will be fine, and contact breaker points will also be sufficient.

 

I estimate the above to provide at least 165bhp.

 

That would be a good start.  If you went for webers, then you could go for a more radical cam, and achieve at least 185bhp easily+

 

Cheers.

 

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6 minutes ago, TRTOM2498PI said:

Get the engine balanced

That's the single most noticeable improvement I've made to my 6. After a rebuild 20 years ago, I still remember the smile the smoothness brought to my face. Not to mention the extra 1000-odd RPM I felt able to use ( didn't dare go close to the red line before!).

11 hours ago, harlequin said:

I found the Phoenix manifold gave off a lot of heat that caused running issues in traffic and on hot days plus it made changing the starter motor a real pain so I put the original manifold back on, I was surprised to find absolutely no difference in performance.

I'm intrigued by that, and not in a skeptical way. That's the next mod on my roadmap, now that I've done the head gas-flowing and CR increase. I'll probably go ahead regardless, but I will do before & after dyno runs. 

John

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Hi Paul,

I restored an ex-US TR6 a couple of years ago. Engine was rebuilt including most of the modifications that you've mentioned, with excellent results. Block chemically dipped, then line bored for cam bearings. All the bottom end rotating parts were balanced, which allows for higher revs without encountering any issues. 218225 cylinder head, new valves, hardened seats, lightly skimmed to give a compression ratio of 10.1:1. Piper Yellow cam, twin SU HS6 (BCH needles) on a long branch inlet manifold. 6-2-1 exhaust manifold and 2.25in Phoenix straight through exhaust system. I know the 6-3-1 manifold is rated more highly, but mine was free, so that went on.

With all of the above, the car goes very well ;) For what was a relatively 'budget' build, I'm delighted. In terms of bang for buck, a well set up pair of SUs with suitable needles are hard to beat. Sure, EFI or Webers will ultimately allow for more power, but the much higher cost put both of those options out of my price range. I also have a 2000 saloon that has been running a tuned 2500TC engine on SUs for the past nine years, again with great results, so I can vouch for that method of fuel delivery over a longer period of time.

Matt

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14 minutes ago, JohnC said:

 

 

I'm intrigued by that, and not in a skeptical way. That's the next mod on my roadmap, now that I've done the head gas-flowing and CR increase. I'll probably go ahead regardless, but I will do before & after dyno runs. 

John

John

It may be that the Phoenix manifold will do somthing for an out and out track car but for what I use the car for, its my daily driver and we do a lot of touring (or will when we can get out) the standard manifold was more suitable, after all Triumph were nobody's mug when it came to building cars.

We often travel with 3 other TR6s all fuel injection and have no issues with keeping up, and as a bonus get about 30 mpg. Probably the best thing to add to an American car is overdrive if it doesn't already have it 

George 

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Chaps,

I believe the factory cast iron TR6 manifold is known to flow quite well anyway. The factory cast iron manifold on the 2000/2500 range, not so much, which is why those models in particular benefit from an aftermarket 6-3-1 version.

Matt

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52 minutes ago, harlequin said:

It may be that the Phoenix manifold will do somthing for an out and out track car but for what I use the car for

That was my experience when swapping back from a TT1200 6:2 manifold. Really good at about 6000RPM! But poor in mid-range. The standard TR6 manifold is much more drivable than that one. But I believe it was developed for top-end power (didn't know that when I bought it) so that makes sense. Horses for courses.

John

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18 hours ago, Paul Drescher said:

Hi All

I have a September 1972 US Spec TR6 which I have been restoring for the past year, chassis refurb complete, all running gear replaced, diff and gearbox rebuilt, LHD to LHD complete,  body is waiting to go off to be painted so I'm now at the point of totally dismantling the engine for inspection and rebuild. I want to improve the HP of the engine to about 140 but without spending a ridicules sum of money. I have come across some old threads but at times the topic becomes embroiled with with technical jostling between individuals. So I would like feed back on the following improvements that I am planning

1. Head overhaul, fitting new hardened valve seats, skim head to increase CR to ? please advise, bigger exhaust valves and porting improvements?? please advise.  Any suggested specialists who mare familiar with this work??? I live in East Yorkshire. 

2. Managed to get a pair of second hand SU carbs to replace the Strombergs, these will be refurbished fitting appropriate needles etc.

3. New Cam, fast road cam, any suggested type/supplier

4, SS Sports manifold and exhaust

5. I have read about

6. Distributor improvements? what is required

It would be great if anyone has done similar work to what I'm suggesting and what costs were incurred, my ambition  is just to get performance closer to a UK spec TR6 and will be a reliable and easy drive not a screaming racer.

Regards Paul

 

 

 

Hi Paul,

There's lots on the forum from the past on this.. But first thing to think about before dolling out the cash is how you drive the car, and what makes you smile? For example, Is it dropping it down a cog or two and whipping it up to redline? or is it the boot of low down torque? or is it actually the throaty raw of the engine? ( I put this one in because my first classic, a spitfire with twin webbers, went through a period of having a really sexy bark on over run. I knew it was a manifold leak, but I left it because it felt good getting the crackeling from the exhaust as I drove it around town :-)

 Obviously you can tune to ultimate power etc but inevitably this comes at a price (money and often drivability) or you can tune for fun... They are not the same thing..

I went through the high reving phase when i had an elan with the lotus twincam. Wonderful when mated to the ford Gearbox..

I now enjoy low down torque and am lazy with the gears. Which is why I went with the supercharger in the TR. I also have an MG midget with a 1.8 K Series engine. This gives you both.. can drive in 5th round town, and howls up to 8K rpm... but not as nice to drive long distances as the TR.

My point (and apologies for meandering) is think carefully about what driving experience you want before commiting.. Ideal drive some examples (I know... not really on at the mo!).

 

Cheers

Tim

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I’m with Tim!

it’s really easy to buy/bolt on inappropriate mods and not achieve the desired result

what is your desired result ?

steve

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3 hours ago, TRTOM2498PI said:

Hi Paul,

You will no doubt receive many different ideas here, but essentially, the items you need to change/improve will be the same.

First of all, there are no short cuts to a successful engine !

1. The later 'ribbed' block is a good starting point.  It is ribbed along the length of the induction side, these are considered stronger.

2. Good quality pistons (unless you only need rings) ? Mahle are a very good quality piston.

3. Get the engine balanced (pistons, rods, flywheel, clutch cover, crank damper, camshaft). Vibration Free in Bicester have a very good reputation.

4. If you're keeping twin carbs, Newman cams do a cam that will work well with them. There are based on a new chill cast blank. Their EN40 steel followers to match are also very good.

5. Gas flowed cylinder head, skimmed for increased CR to match the new cam, with new guides.  You cut have unleaded valve seats fitted at this stage too. Peter Burgess in Derbyshire can take care of the head including valves.

6. 6-3-1 peformance exhaust manifold. Coupled to a 2.25" straight through big bore system.

7. Standard distributor rebuilt will be fine, and contact breaker points will also be sufficient.

 

I estimate the above to provide at least 165bhp.

 

That would be a good start.  If you went for webers, then you could go for a more radical cam, and achieve at least 185bhp easily+

 

Cheers.

 

spot on Tom

especially points 3 and 5 

5 = Pete Burgess is near as well in Derby.  

Roy

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Well, my advice would be to get the car handling properly before increasing any power, ie suspension, brakes, steering and tyres. Cars set up properly in this way will always be a better driving experience than any power increase can produce.
I would then go step by step, starting with the head, valve sizes, porting and compression ratio. After that you start spending more money for often relatively marginal gain in the real world, particularly if you simply drive the car quickly and not flat out or in competition.
A car well sorted in the handling department will beat many a car with more power.
Tin hat on
Ian

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10.25:1 is probably a sensible max CR that will be fine on regular unleaded. As John says you can go higher but you will be looking for super unleaded. 

If you are going North of 10:1 you may need your advance curve modifying to limit low down advance.  Good head work isn’t cheap but can improve efficiency as well as power but the gains in power may not be much unless you use a lively cam.

 

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1 hour ago, cvtrian said:

Well, my advice would be to get the car handling properly before increasing any power, ie suspension, brakes, steering and tyres. Cars set up properly in this way will always be a better driving experience than any power increase can produce.
I would then go step by step, starting with the head, valve sizes, porting and compression ratio. After that you start spending more money for often relatively marginal gain in the real world, particularly if you simply drive the car quickly and not flat out or in competition.
A car well sorted in the handling department will beat many a car with more power.
Tin hat on
Ian

Ian, No need for a tin hat!

Again it comes down to what you want from the car. If you like driving the curves then suspension setup is important... drag racing from the lights, then perhaps not :-) I replaced the chassis on mine to make sure I had a good base but omitted to up-rate the driveline. Result, blown gearbox (spoiling my enjoyment of the RBRR, although we did get her home) and blown UJs (spoiling the 10 Countries run, Again we did get home).. Got to think about the whole package...

Cheers

tim

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If it's any help I was in the same boat regarding a rebuild and decided to go for a more or less std build spec as the car will be no track dog but more of a sedate cruiser able to keep up with modern traffic and hopefully sound good. She will run on her original PI (UK 1969) So I went for the following;

Bottom end; crank regrind, shells, rebore/country pistons/rings, cam bearing (out of spec), new OEM std cam, blue printed oil pump, new damper. The whole bottom end plus fly wheel and clutch cover balanced.

Head; std head, bronze guides, exhaust seats replaced, new valves/springs, hardened rocker shaft and bushed rockers. Distributor rebuilt from DD with electronic ignition.

Exhaust is a nearly new 2 3/4" only decision left is which exhaust manifold. After reading the comments here I'm tempted to keep the cast manifold if it flows as well as people says rather than a tubular design?

I'm getting the impression there are different cast manifolds? Is the early one the one to keep?

Agree with comments around sorting the rest of the car before any increases in power otherwise it will either not end well or will never allow the increase in power to be used effectively.

Cheers

Andy 

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10 hours ago, JohnC said:

Does the Megajolt allow transient advance/retard of the ignition? E.g. a change for a specific period of time, triggered by sensor inputs, rather than responding continuously to sensor inputs?

John

Hello John

                 Yes it will use RPM and and Map sensor and you can alter the map to suit.

Roger

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On 1/31/2021 at 8:04 PM, colin3511 said:

Paul,

Just did this.

1. Newman fast road cam £210 delivered.

2. Rebuilt distributor by Distributor Doctor £250.

3. Rebuilt head with bronze guides and hardened seats. Ported and polished £800.

4. Triple Weber’s £1800 including manifold and linkages.

5. Phoenix extractor manifold and single big bore exhaust. £800 but I picked a second hand one up for £350.

Massive improvement on stock car although I have got new hubs, drive shafts and BMW diff.

165+ BHP. If you can do some of the head work yourself you can save some of the cost.

Happy to answer any questions if you want to PM me.

Colin

 

 

 

Hi Colin

Thanks for the great feed back, I'm planning what you have recommended possibly stick with the SU carbs and maybe change out to Webbers 3 off  at a later date. I've had numerous questions about driving style/need. I believe i want a good noise, some grunt to overtake on a a class road, and fun on my local country lanes but no drag racing.

Did you do any crank/flywheel balancing? who did your head work and what CR did you go for??

Regards Rich

 

 

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On 1/31/2021 at 10:24 PM, harlequin said:

Paul

You mention larger exhaust valves, Triumph fitted the smaller valves on the later engines to improve breathing. I know it sounds daft but the bigger valves I am told, obstructed flow.

I found the Phoenix manifold gave off a lot of heat that caused running issues in traffic and on hot days plus it made changing the starter motor a real pain so I put the original manifold back on, I was surprised to find absolutely no difference in performance.

The difference in performance between SUs and Strombergs is zero, both are good for a road car providing that they are in good condition and set up correctly.

The biggest boost to performance will be having the head skimmed to 9.5 to 1, a good cam like the Newman one that Colin has and a Dizzy Doctor distributor. If you go on the Goodparts website there is a chart that will give you the figures for the skimming work.

George 

 

Hi George

 

Thanks for the reply, had some great feed back, CR 9.5 appears to be suitable for what I require as suggested the cam needs to compliment the head changes, any recommendations for  cylinder head work?

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On 1/31/2021 at 10:30 PM, john.r.davies said:

Hi, Paul and welcome!

1/ If you can get 99 octane (Shell V-plus or BP Ultimate) then a skim to 10.5 will work.     

4/ Stainless isn't a performance improvement.     A 6-3-1 wil improve power mid-range, more useful than top revs.

5/  Red rotor arm - again no performance improvement but more reliable

Hi John

TESCO do a 99 octane much cheaper, our local Rally Drivers fill their cans at the local TESCO'sI take my 370Z their for a monthly fill up. What advantage will CR 10.5 would be compared to 9.5 ? could this compromise any future head gasket leaks that cold require head re-skim?

Rich

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On 2/1/2021 at 10:13 AM, TRTOM2498PI said:

Hi Paul,

You will no doubt receive many different ideas here, but essentially, the items you need to change/improve will be the same.

First of all, there are no short cuts to a successful engine !

1. The later 'ribbed' block is a good starting point.  It is ribbed along the length of the induction side, these are considered stronger.

2. Good quality pistons (unless you only need rings) ? Mahle are a very good quality piston.

3. Get the engine balanced (pistons, rods, flywheel, clutch cover, crank damper, camshaft). Vibration Free in Bicester have a very good reputation.

4. If you're keeping twin carbs, Newman cams do a cam that will work well with them. There are based on a new chill cast blank. Their EN40 steel followers to match are also very good.

5. Gas flowed cylinder head, skimmed for increased CR to match the new cam, with new guides.  You cut have unleaded valve seats fitted at this stage too. Peter Burgess in Derbyshire can take care of the head including valves.

6. 6-3-1 peformance exhaust manifold. Coupled to a 2.25" straight through big bore system.

7. Standard distributor rebuilt will be fine, and contact breaker points will also be sufficient.

 

I estimate the above to provide at least 165bhp.

 

That would be a good start.  If you went for webers, then you could go for a more radical cam, and achieve at least 185bhp easily+

 

Cheers.

 

Great feed back thanks

1.  Ribbed block ? i presume engine block any pictures of what i need to look for?

2. Pistons look in great original condition with a few tiny markings so I'm going to measure and if OK just replace all piston rings

3. Now definitely considering balancing, please excuse my ignorance but how do you balance piston rods and pistons, i understand crank assembly as this could be put in a balance machine as a unit but rods and and pistons how do this work?

4. Removed Cam followers today, look perfect, if i get a new cam do i have to buy the followers to match the cam?

5. 6. 7. Agree 

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