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Twin Valve Springs


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Later PI   CP TR6 models were, I believe fitted with single valve springs. CR models were fitted with double springs.( Info from Repair Operation Manual). I have a spare CR head but has single valve springs which I don't know is original fitting ??( Overlap between models from leftovers in the parts bin ?) . I have a 73 CR TR6  on Triple 40 DCOE Webers  with a 285  cam. Anyone have an idea what would best twin or single valve springs for me ?. Jaguar AJ 6 valve springs for a  TR6 have also been discussed in the past. Do these require the inner springs ?

MARK

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7 hours ago, MARK said:

Later PI   CP TR6 models were, I believe fitted with single valve springs. CR models were fitted with double springs.( Info from Repair Operation Manual). I have a spare CR head but has single valve springs which I don't know is original fitting ??( Overlap between models from leftovers in the parts bin ?) . I have a 73 CR TR6  on Triple 40 DCOE Webers  with a 285  cam. Anyone have an idea what would best twin or single valve springs for me ?. Jaguar AJ 6 valve springs for a  TR6 have also been discussed in the past. Do these require the inner springs ?

MARK

Some Tuners are not very keen on double valve springs as they are known to cause excessive wear on the cam lobes. Over the last 25 years there have been plenty of examples of poorly heat treated cams and cams which have had the hardness layer ground off and sold as re-grinds, which have failed in very short service. This does not seem to be the case anymore, after a court case on one of the classic parts suppliers. I have a Newman PH2 cam and  on a SAH head that has got single springs!!!!! What is the valve timing on a 285 cam and who manufactured it? It might be best if you contact them directly for advice.

Bruce.

 

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The point of double valve springs is not to 'improve' the seal at the valve face, but to prevent valve bounce due to resonance.    If the frequency of valve compression approaches the natural frequency of the valve spring, then it will resonate, amplifying the valve movement and bouncing it in its guide, opening and closing inappropriately.

If two springs are in parallel, one inside the other, then their different frequencies are added together to find their combined natural frequency.   Which will be about twice that of a single spring, and way above the rev range of the TR engine.

John

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25 minutes ago, john.r.davies said:

The point of double valve springs is not to 'improve' the seal at the valve face, but to prevent valve bounce due to resonance.    If the frequency of valve compression approaches the natural frequency of the valve spring, then it will resonate, amplifying the valve movement and bouncing it in its guide, opening and closing inappropriately.

If two springs are in parallel, one inside the other, then their different frequencies are added together to find their combined natural frequency.   Which will be about twice that of a single spring, and way above the rev range of the TR engine.

John

Thank you John, I always wondered what the point of a multi-spring setup was and was afraid to ask, now I know.

Robert

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I have TT uprated valve springs in my TR6, which also runs a Newman (hybrid) camshaft, based on a new chillcast blank, and their EN40 steel followers. Installed and driven hard since 2011, without any issues and high revs. (6500 + RPM), based on an accurate Stack tacho. Valve clearances checked bi-annually, and they rarely require any adjustment, maybe 1 tho at the outside, indicating no valve seat recession or issues with cam lobe/followers.  Engine is still nice and quiet.

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Just wondering why Triumph went to single springs for a short time and then back to double on CR model. 

Has anyone actually used Jaguar valve springs on a road car with success and if so, with or without inner spring.? 

What is the current advice for TR6 Fast road car- single or double valve springs?

Thanks for the previous words of wisdom from Tom and Robert on this very good Forum !

MARK  

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I did several tests on single and double springs. Preload and Load @ Full Lift. It is in german, but you understand.

There is a common setting: the spring should be hard enough from preventing fluttering and soft enough not to have any excessive load on the camshaft.

So what do you choose? Good question. In my opinion it depends strongly on the typ of cam (normal, hot).

For my Kent 290° I choose the yellow Uprated springs, but without the inner spring. It has enough load to keep going at 7.000 rpm. However, I very much respect John's theory on this, I would be gladly willing to change to a double spring version. However, I cannot find a combination meeting my load requirements.

VentilfederGelb_.jpg

FederErgebnis1.jpg

FederErgebnis2.jpg

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Jochems TR Thanks for that. Might stick with standard double as 285 cam is slightly less aggressive than your 290 cam ?? I bought a set of the Jaguar AJ6 springs several years years ago and was thinking of using them singly then as they were supposed to be better quality. However this maybe a theory as I dont know if anyone has actually used them on a a road going TR6.

MARK

 

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It is almost common practice to use the "softer" TR5 and TR6-CP springs. I still need to do the measurements on those.

The Jaguar may be good too, but you would have to measure them.

I determined the preload. The spring has an installed height of 35mm. Cam and Rocker give a 11,60 mm Valve Lift. Both values can vary for your installation presenting slightly different load values. In addition, be carefull with rockers exceeding standard ratio. The spring may be pressed and windings touch. I prefer to have 0.8 - 1.0 mm space between windings @ full lift.

Jochem

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5 hours ago, JochemsTR said:

It is almost common practice to use the "softer" TR5 and TR6-CP springs. I still need to do the measurements on those.

The Jaguar may be good too, but you would have to measure them.

I determined the preload. The spring has an installed height of 35mm. Cam and Rocker give a 11,60 mm Valve Lift. Both values can vary for your installation presenting slightly different load values. In addition, be carefull with rockers exceeding standard ratio. The spring may be pressed and windings touch. I prefer to have 0.8 - 1.0 mm space between windings @ full lift.

Jochem

Hi Jochem,

Slightly off topic, what size bore is your 6 ?

 

Cheers.

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33 minutes ago, TRTOM2498PI said:

Thanks.

A few more questions if I may ?

1. VW Polo 1.4 16v pistons (Nural) ?

2. Are you using EFI ?

3. How many revs do you use ?

4. How many miles since built ?

1. Yes. Nüral

2. Yes

3. 7.000

4. none. I am awaiting my own produced Titan Valve caps. Next Step Oil-Pressure check.

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Mark,

I ordered the double valve springs (TR5 spec) from Chris Witor, per recommendations from others on this forum. Also in- and outlet valves, I think they were NOS.

My old springs were 1-2 mm shorter than the WSM dimensions, but spring-rate was ok. I tested the new springs too (I measured/tested every part where I could:rolleyes:), they were a close match to the WSM data.

So well recommended.

Waldi

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19 hours ago, MARK said:

Thanks very much for your words of wisdom Jochems TR !

A final call - anyone ever used the AJ6 Jaguar springs ??

MARK

Hi Mark,

The part number for these Jaguar valve springs is EBC4871.

I have a friend who uses them in a Triumph 2000, with a tuned engine.

 

I can tell you though the TT double valve springs are fine though.

 

Cheers.

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2 hours ago, TRTOM2498PI said:

I can tell you though the TT double valve springs are fine though.

The TT1207 (correct?) are similar to the Kent springs (double) in my diagram. They are about 35% harder as the TR5-TR6CP Springs.

It seems to work, but in my opinion are too hard.

Jochem

Edited by JochemsTR
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On 11/26/2021 at 5:16 PM, JochemsTR said:

The TT1207 (correct?) are similar to the Kent springs (double) in my diagram. They are about 35% harder as the TR5-TR6CP Springs.

It seems to work, but in my opinion are too hard.

Jochem

Hi Jochem,

Yes. TT1207. These were installed when I had the entire engine built in 2011. These were used, in conjuction with a Newman (hybrid) cam, and their steel EN40 B followers. The engine is still nice and quiet, all these years on, despite being driven really hard. It has completed: X4 Round Britain Reliability events- 2000 miles in 48hrs. X5, 10 countries car runs. 10 country run over a 4 day period and circa 2500 miles. Track days, sprints, trips to LeMans, Scotland, Wales, plus many more. Valve clearances are checked bi-annually (car does between 5000-7000 miles a year), and no signs of problems with cam lobes/followers and any valve seat recession for that matter. Oil changed very frequently (Penrite 20/60).  I have a new cam to go in (Newman PH5) with their steel followers, but this time, their 200 poundage valve springs. I am very interested to see how this will work out with my EFI kit, & TLE exhaust manifold, etc. I am not aware of a car with this set-up (Triumph 6 cyl).

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