Rocker arm ratio

[John L]

Would anybody know the rocker ration for a CP PI engine,  arms 109023/24.  Some say 1.5:1,  others say less

I replaced mine a while ago from Rimmers, ones without the bushes and a new shaft, but notice now 3 of them open the valve much more that the others.

I checked the originals I took off, I keep all my parts, and the dimension is less than the smaller one below. so different ratio again

I have measured from the shaft to the outer side of the ball, and there is quite a difference, so the rocker ratio or lift of the valve will be different.

I have asked Moss if they have any drawings to see what I have, but they dont have any, Rimmers say they will ask their supplier, but nothing yet.

Does anybody have an original set that could compare the dimension with please?

Comparing the 12 on the shaft the valve contact part is very much the same, but the balls on the 3 are much further out from the shaft diameter, and the these 3 have 1/2" spanner nuts, the other 9 have 12mm spanner nuts.  Never thought they would be different so just changed straight over.  Another parts issue.  Does the club have any records of dimension of parts.   I think they have used a common part with Spitfire perhaps?  How can the likes of Moss supply/order parts without a drawing to check too??  Has anybody else noted this?

The 12 here came in the same packet,  will take this up with Rimmers who supplied them.

John

 

[boxofbits]

Hi John

I don’t have dimensions of an original rocker, but clearly a mixed bag of parts.

I’m not that surprised as Rimmers often manage to fxxx up, or their parts are rubbish. I would be tempted to return the whole lot and buy from Moss or a dedicated TR supplier like TR shop and reference their parts. TR shop will likely have second hand ones that they might measure for you to ensure you get the right part. HPN!

Kevin
 

 

 

[PodOne]

Hi John

Have to agree with Kevin regarding Rimmers QA its sketchy at best for almost everything. I would reject them and send them back.

Bought everything I needed from Chris Whittor when it came to engine parts.

Andy

[John L]

Bit difficult to send back as have been used, It was only when I have been checking may cam that I noticed the difference, if you order that part you would have expected to have got the same items, I wouldnt have checked, so want the dimentions to get ether 9 or 3 to make up the set.

John

[paul bond]

I came across this issue some time ago. Not only is the ratio different, but the offset (front to back) is not as the original Standard Triumph originals.This came to my attention on reassembling the rockers with  when the pushrods were then fouling the head casting tunnels. As a temp measure I machined small spacers for the rocker shaft to move the rockers, however the valve stems then contacted the very edge of the rocker pad.

I fed back to (Rimmer if I recall).but their stock was all the same. I obtained other samples (copies) from other suppliers which were obviously from the same manufacturer and identical. I finally obtained a set of original boxed ST rockers which I was told were the last ones available. Even then a couple of these were beyond use with rust.

With the original rockers the problem was solved. You may need to live with these patten parts unless you can find a set of original ST items.

Hope this helps.

Paul B

 

 

[Kenrow]

This seems to be a problem going around the parts suppliers:

Rocker Arms

[RogerH]

Hi Ken,

I don;t know it you noticed but John (above) started the thread you posted.

One would think that is the correct spare was no longer available then the supplier would inform the customer of the difference for the available item.

 

Roger

[astontr6]

27 minutes ago, RogerH said:

Hi Ken,

I don;t know it you noticed but John (above) started the thread you posted.

One would think that is the correct spare was no longer available then the supplier would inform the customer of the difference for the available item.

 

Roger

In my ownership of my TR6, I do not know how many times I have crossed this sort of path where pattern parts are not the same as originals. I still say this is all down to the likes of Rimmer/Moss not having the Technical know how and Goods Inward Inspection. As far as them not having an engineering drawing that is rocket science to them as they do not yet know how to procure machined parts even if they have been in business for over 50 years. They need a good kicking from the Register on this subject.

Bruce.

[BRINDUS44]

Hi John,

If it helps here is the dimension on a NOS BL rocker arm supplied by Chris Witor a few years ago. 
Regards

Ian

[John L]

Thanks Ian,  Is your gauge on the thread or on the outside of the ball, mine with .720" on the outside of the ball give .703" on the thread.  I would just love to know what the dimensions should be, so that NOS one must be very close.  One other, question does yours have a lube hole in the top of the shaft?  I understand that they all have a hole now, but the original CP's didn't.  Is that the only one you have?  I'm looking for 6 left and 6 right.

John

[BRINDUS44]

Hi John, 

outside of ball with inner jaw square to shaft drilling.  From what I’ve seen on various engines I’ve pulled apart , early 2.5pi, TR5, TR250 have single oil drilling adjacent to adjuster, later cars, but I can’t say from when , extra drilling on top of rocker. The one in the picture has the single drilling and I’m afraid I only have the one. I’ve also seen big variations in rocker pad position over the valve tip with the modern repro rockers and clash of pushrods to head casting as mentioned earlier. 
Ian

[Kenrow]

John, I have a rocker setup from a 70’s TR 6 sitting in a box for the last 35+ years. Let me know if you need any measurements. It does have a lube hole on every individual rocker arm.

[saffrontr]

John,

I believe that all TR engines had the lube hole on the rockers, it was the saloon engines that didn't originally have them.

Derek

[astontr6]

On 1/1/2023 at 5:13 PM, John L said:

Bit difficult to send back as have been used, It was only when I have been checking may cam that I noticed the difference, if you order that part you would have expected to have got the same items, I wouldnt have checked, so want the dimentions to get ether 9 or 3 to make up the set.

John

Hi John.

I think that if you go on the Revington site and speak to them. You will see that they have OEM rockers they are not cheap but they are the correct part? Also I hope that you have run this saga past Roger H. who looks into the QA aspect.

Bruce.

[Kenrow]

John, here are some measurements. Measurements are from the rocker inside hole face to the center of the adjusting ball:

TR 6 (US). These have single oil hole per rocker:

Right: 

1) 0.721 2) 0.721 3) 0.720 4) 0.720 5) 0.720 6) 0.718

Left:

1) 0.718 2) 0.711 3) 0.718 4) 0.714 5) 0.718 6) 0.718

 

 

Edited January 3, 2023 by Kenrow
added info

[Kenrow]

Below are numbers from a brand-new Moss Bushed Rocker Set with Matched Shaft. These have two oil holes per rocker:

Right: 

1) 0.715 2) 0.715 3) 0.715 4) 0.714 5) 0.715 6) 0.712

Left:

1) 0.718 2) 0.711 3) 0.718 4) 0.714 5) 0.718 6) 0.718

 

 

 

 

[John L]

Thanks Ken,  That is really very interesting,  looking at you photos second from the end, upside down arms, it seems you have 4 rockers that are much longer on the valve end!  Have these been fitted yet to an engine yet?

I'm hoping to get some info from Rimmers supplier, but I wont be holding my breath!

Thank you again for your trouble.  I need to go to Moss and measure theirs over the counter, no use ordering them on their site unseen.

John

[PodOne]

2 hours ago, John L said:

Thanks Ken,  That is really very interesting,  looking at you photos second from the end, upside down arms, it seems you have 4 rockers that are much longer on the valve end!  Have these been fitted yet to an engine yet?

 

Looking at the pic there can't be two that are the same size!

Maybe the original BL offerings were no better and allowed a wide range of tolerances?

[Kenrow]

They have not been installed (fingers crossed in the next few weeks). In the previous photo it looks like it is an optical illusion due to the balls not being leveled at the time of the picture. I did level them out for the all the measurements.

As for the rockers, all are in a range of 25 thou of each other in total length (2.540" to 2.565"). The original set is a little more consistent in length (2.560"), but the new are what I would call within tolerance.

Edited January 4, 2023 by Kenrow
left out word

[John L]

Thanks Ken, your measurements are a great help!

John

[Kenrow]

Good luck. if you need anything else just holler...