In the shed this weekend.

[Lebro]

+1 for Trispark, got it on my Daytona (1968)

Bob

[PriceLes]

That Tri-Spark digital ignition was for a dual point Moto Guzzi  distributor (Tonti) I have a 1973 Moto Guzzi Eldorado which has a single point distributor and even with a new trigger mounting plate it was was to big to fit inside that distributor so I machined that new body that had a 8 mm bigger inner diameter which allowed the unit to fit (with the new mounting plate) A 3.6 kg bar ended up weighing under 300 grams after machining, a cap was retained so it looked stockish. I will machine a new distributor for the TR4A to suit the Patton Machine ECU controlled distributor internals as per the TBI kit.

Edited April 6 by PriceLes

[BlueTR3A-5EKT]

Tight cam followers.

Resolved by polish with scotch brite and stoning the burr around the oil drain hole.

Now a nice slip fit.

Here is one after stoning but before polishing.   All 8 needed the same treatment to get the desired smooth fit.

[BlueTR3A-5EKT]

On 4/3/2026 at 10:46 PM, PriceLes said:

I know a machine shop who love jobs like that as they say they earn more money from the scrap/swarf than the finished job.

Nice outcome of a well thought through solution.

[Drewmotty]

1 hour ago, BlueTR3A-5EKT said:

I know a machine shop who love jobs like that as they say they earn more money from the scrap/swarf than the finished job.

Very true. I know a machine shop which used to machine free issued bronze oil slinger castings for Lister FOC just to sell the considerable swarf. 
A colleague of mine quoted a price he thought couldn’t be beaten and was amazed when he didn’t get the contract. 

[Chilliman]

1 hour ago, BlueTR3A-5EKT said:

Tight cam followers.

Resolved by polish with scotch brite and stoning the burr around the oil drain hole.

Now a nice slip fit.

Exactly what I do with new followers to get a nice rotating fit 

[Ian Vincent]

I polished mine by making an expanding mandrel out of a long bolt and a rubber cork and then fitting them in my bench drill, running them at a slow speed and polishing them with 1200 W & D.

Rgds Ian

 

[Hamish]

1 hour ago, Chilliman said:

Exactly what I do with new followers to get a nice rotating fit 

Great to catch up with you at Shelsley. Interesting weather and track conditions.
hows the car ?

[Chilliman]

10 hours ago, Hamish said:

Great to catch up with you at Shelsley. Interesting weather and track conditions.
hows the car ?

Compression test - pretty even across the board at 200. Leak down test showed an issue with the seating of No. 3 inlet valve. So head off which showed all the pots & head were very wet with oil, no scoring to cylinders, & no apparent cracks. I've dropped that head into the machine shop to skim a bit more off for me & re-seat the valves, I'll then zip it back together with some stronger valve springs & add stem seals this time. Hopefully that will sort the oil problem. Still haven't explored the heating issue yet.

Good to see you the weekend, brave man to drive down in those conditions.😁

[Lebro]

Why do you want stronger valve springs ? They will put more pressure on the cam & followers. Only advantage would be to allow higher revs before valve bounce.
When I re-built my engine, using the Newmans PH1 cam I removed the third exhaust spring from my (previously) standard TR3A set up.
Revs to 6000 no problem, (don't do that very often !), & I would not go any higher anyway.

Bob

Edited April 14 by Lebro

[Chilliman]

I'm revving beyond 6000 Bob & the current springs are (in my opinion) too soft - they are a standard TR4A set but I can easily open the valves with thumb pressure.

[stuart]

2 hours ago, Chilliman said:

I'm revving beyond 6000 Bob & the current springs are (in my opinion) too soft - they are a standard TR4A set but I can easily open the valves with thumb pressure.

I killed a set of valve springs (Like you John I could compress them with my fingers) on my 4a a long time ago when up in Lincolnshire with Neil and we were exploring limits of handling on the Lincolnshire wolds, went to see Darryl at Racetorations and he supplied me with a set of progressive uprated springs and they are really good and have lasted very well since so maybe have a word with him.

Stuart.

[Hamish]

5 hours ago, Chilliman said:

Compression test - pretty even across the board at 200. Leak down test showed an issue with the seating of No. 3 inlet valve. So head off which showed all the pots & head were very wet with oil, no scoring to cylinders, & no apparent cracks. I've dropped that head into the machine shop to skim a bit more off for me & re-seat the valves, I'll then zip it back together with some stronger valve springs & add stem seals this time. Hopefully that will sort the oil problem. Still haven't explored the heating issue yet.

Good to see you the weekend, brave man to drive down in those conditions.😁

🤞

 

[john.r.davies]

I bought a 'prepared' six cylinder engine from the brother of the deceased, so no information.      It had never been run, but shortly after I used it, it started throwing push rods.    The poor man had fitted extra-strong valve springs, so strong that the camshaft eroded the bare bearings in the block and had bowed!   Stronger springs may not be the answer.

But I believe that some TR4s do not have double valve springs?     If yours does not, then this is a much better way of preventing valve float at high revs.   With one spring inside the other, they are 'in parallel' and their constants should be added  to derive their spring constant.   This means that their natural frequency, at which they would oscillate and float is much higher, putting that above the rev range of the engine.

John

 

[RogerH]

A few years back I needed a replacement head in a hurry so I bought a new Moss head.

This came with up rated valve springs.  The original cam was murdered in very short time.
So I then bought a Newman PH1 and fitted the original standard springs from the broken head - all is well.

Roger

[Chilliman]

On 4/13/2026 at 8:13 PM, Hamish said:

hows the car ?

Skimmed head & re-cut valve seats, new springs & stem seals (Landrover 🫢) has sorted the oil clouds from the exhaust. Changed the coolant system to fully pressurised & added a bleed valve on the back of the head which appears to have sorted the coolant dumping issue.

It never ceases to amaze me how even small sometimes innocuous changes can have a significant impact somewhere else, but I guess that's what I enjoy about playing with these old tractor engines.

[Hamish]

23 minutes ago, Chilliman said:

Skimmed head & re-cut valve seats, new springs & stem seals (Landrover 🫢) has sorted the oil clouds from the exhaust. Changed the coolant system to fully pressurised & added a bleed valve on the back of the head which appears to have sorted the coolant dumping issue.

It never ceases to amaze me how even small sometimes innocuous changes can have a significant impact somewhere else, but I guess that's what I enjoy about playing with these old tractor engines.

Glad you got it sorted. 
I only just round to washing mine after Shelsley the drive there and back got it a bit mucky 

[BlueTR3A-5EKT]

My box of slip gauges slipped off the bench……

I think I have found them all….

Now to sit down and sort them into their respective compartments 

[Hamish]

2 hours ago, BlueTR3A-5EKT said:

My box of slip gauges slipped off the bench……

I think I have found them all….

Now to sit down and sort them into their respective compartments 

Doh !!!!

[PriceLes]

Another 20 days of work completed and the weekend tomorrow. I had cobbled up a reed valve crankcase breather oil separator for the Moto Guzzi so only fair the TR gets something also, fully machined of course.

[NigelC]

wow!

[BlueTR3A-5EKT]

A delightful project.

[PriceLes]

My sliding drum arrived at Overdrive Repair Services a few days ago so hopefully it will be relined and on its way back to Australia asap.

Edited May 7 by PriceLes

[BlueTR3A-5EKT]

Using a linked timing chain to set the cam timing sped up the on off on off move link, turn gear malkarky.

Just unloop the chain from the cam sprocket and do the adjustment.

Ended up with the cam advanced by 3° measured on the crank, so half that on the cam.  Measurement 107° instead of 110°, alternative placed the cam at 112 after TDC). We like advanced as the chain will stretch and retard the cam in service.   The equal at TDC is within 0.002” lift.

[Bfg]

23 hours ago, BlueTR3A-5EKT said:

Using a linked timing chain to set the cam timing sped up the on off on off move link, turn gear malkarky.

Just unloop the chain from the cam sprocket and do the adjustment.

Ended up with the cam advanced by 3° measured on the crank, so half that on the cam.  Measurement 107° instead of 110°, alternative placed the cam at 112 after TDC). We like advanced as the chain will stretch and retard the cam in service.   The equal at TDC is within 0.002” lift.

I was talking with a specialist Jaguar engine, gearbox and diff rebuilder last week, about my wanting to replace the upper timing chain on my XK 3.8 (standard camshaft) engine. And that I've heard that it is do-able without removing the cylinder head  ..when one uses a new split-linked chain.  To which he emphasised his distrust of the split link chains and that, in his 50 years of experience, these chains will go on for hundreds of thousands of miles without issue. 

My own experience of duplex chains is very limited, from my days riding Norton motorcycles.. to which he replied that these are not motorcycle engines.  The 750 & 850 Commando's primary drive was duplex, but I don't recall my ever having seen a split-link one.  Possibly it was simply not necessary because their sprockets are easy enough (engine in frame) to remove anyway. 

I note that well known Jaguar parts suppliers ; David Manners and SNG Barratt,  sell split-link timing chains for these engine. The latter say theirs are made by Iwis, Germany. I see also that Reynolds chains similarly offer Duplex chains in this size with split links, so clearly they seem to think it's okay for some applications.  There are contributors on the Jag-Lovers forum who have fitted split link chains, but then ask why does someone want to replace their timing chain.? 

Why change the timing chain on my car ?  Well firstly because it was running very loose, and I have no way of knowing whether part of that was because of excessive stretch or poor adjustment.  The tappets are x2 greater than they should be  (new shims on order to correct these).  Even if the engine had been prepared for racing.. they're still excessive  ... so I don't really trust what has been done before. 

   

^ the sprocket teeth do not appear to be hooked, and still have some meat at their tips (I don't know how fat they should be), but the chain rollers are well polished from use, which suggests - the chain was not replaced a thousand miles ago when the engine was rebuilt (according to file invoices).    I did noted sideways slack in this chain, but then also recognise that some sideways slack is necessary for the sprockets to be pushed forward off the camshafts.  

What are your thoughts Gents ?   Am I just over-thinking the issue and this chain is likely to be good for another 60,000 miles (of normal road use) or would I be prudent to replace the chain, even though that necessitates the use of a split link.? 

Thanks for your thoughts,

Pete