What to do with this TV175 engine?

[Warkton Tornado No.1]

If you assess the port timings you have, it’s likely you can easily tolerate an increase in transfer & exhaust ports, which is one benefit of deleting the head gasket. If any gasket is likely to weep, it will be the head gasket IME. Personally, I’ve not used them on any engine for the best part of 50 years.

Metal base gaskets are extremely reliable & have the advantage of being re-useable & serve as a brilliant means of matching the barrel & case transfers…..

[Storkfoot]

These were done in a bit of a rush so will need rechecking.

With 2mm packer:

Exhaust 153
Transfers 118
Inlet 144

With 3mm (2mm packer and a couple of 0.5mm paper gaskets):

Exhaust 159
Transfers 124
Inlet 140

To my limited knowledge eye, the 3mm packer option seems to offer a very rideable engine but lacking power because of the relatively low exhaust timing. I knew that would be the case when I made the conscious decision to not have the barrel tuned.

Thoughts please?

[Warkton Tornado No.1]

The 175 S III engine is quite a rarity by comparison with the other capacities, but in my experience very smooth.

I have only ever tuned one & that was already fitted with an Indian alloy finned barrel. I would never do one again unless there was a ton of money upfront to cover the time involved. However, it turned out extremely well.The poor quality, mismatched transfers & chilled - extremely hard - cast iron ports required many hours of work & almost dictated the extent of tune just to get things tidy.

I realise that none of that helps you, but if I can track down my notes of port timings, I will let you know. The tune was not wild but the exhaust was some aftermarket un-named expansion chamber that worked well.

[Storkfoot]

The 175 S III engine is quite a rarity by comparison with the other capacities, but in my experience very smooth.

I have only ever tuned one & that was already fitted with an Indian alloy finned barrel. I would never do one again unless there was a ton of money upfront to cover the time involved. However, it turned out extremely well.The poor quality, mismatched transfers & chilled - extremely hard - cast iron ports required many hours of work & almost dictated the extent of tune just to get things tidy.

I realise that none of that helps you, but if I can track down my notes of port timings, I will let you know. The tune was not wild but the exhaust was some aftermarket un-named expansion chamber that worked well.

Thanks again for the reply. I think I am just going through a phase where I crave reliability and the chance of being able to easily strip a top end on the road, if needed. Cast iron barrels, Piston port, Japanese piston with a gudgeon pin that slides in easily, not tuned to the max, that sort of thing.

I checked the timings and, other than getting an inlet timing of 141, as opposed to 140, they were the same. On that basis, I have ordered a 3mm packer.

I had another look at the layshaft. The pitting isn’t too bad and I am sure in years gone by, I’d have just stick it back in. But, there is a ridge where first gear sits. You can see it in this photo and you can catch your nail on it.



Let’s see if I can set up one of the new layshafts when they come back from the machine shop. If not, I may well just put this one back in. The threads and splines are spot on.

[Storkfoot]

The exhaust studs have had timeserts fitted. The thread of the timeserts starts about 2mm below the flange surface. For this reason, I think, the exhaust studs are engaging with the cylinder studs.



My thoughts are to take about 1mm off the studs which I will then loctite in place. I don’t want to take any more off the studs. I want to make sure that all the remaining threads are used.

Does this seem the correct way to address this issue?

[Fast n Furious]

Because the Timesert is recessed like you say, then yes, it is likley that a standard length exhaust stud will make contact with the cylinder spiggot, which must be avoided. Shortening the stud is your only practical option.
Good luck finding a threadlocker product. I've never found one that works on exhaust studs. The temperature in this region of the engine is just too high.

[Storkfoot]

Because the Timesert is recessed like you say, then yes, it is likley that a standard length exhaust stud will make contact with the cylinder spiggot, which must be avoided. Shortening the stud is your only practical option.
Good luck finding a threadlocker product. I've never found one that works on exhaust studs. The temperature in this region of the engine is just too high.

Thanks for that. I shall shorten the exhaust studs by the minimum I can get away with. Hopefully, once I have done that, the stud will feel more like an interference fit in the barrel.

The highest temperature resistant Loctite I have is 270, which I use on cylinder heads. I’ll clean the thread path as best I can and keep my fingers crossed that the 270 will stop the studs vibrating out of the cylinder.

[Warkton Tornado No.1]

Regarding studs for any position on a Lambretta, I’ve got in the habit of always assessing what will be best within my available stock & fit accordingly. Probably all of them are rolled threads as per OEM.

In general, the exhaust studs I fit will stay in place with Loctite Studlock though I will fit studs that have the best length of plain shank appropriate for the exhaust flange & solid copper gasket. I would never use any other type & if solid copper has not been available - on the odd occasion - bathroom silicon has provided a good seal on it’s own.

The exhaust studs I fit are double nutted to drive in hard to the shank. The nuts are usually M6 10 mm AF Hexagonal long nuts (Toolstation/Screwfix) tapped through to M7 & cross drilled to be lock-wired to each other.

I found my notes for the alloy finned 175 engine that I built seven years ago. The Indian cylinders really are a dog’s dinner & only suitable for people with an awful lot of time to kill. Anyhow, after weeks of work, the result was extremely good for a 175. It was also smooth which was likely due to the 116 mm rod. For the record, I got the bore clearance to 0.003” with the new piston which may have been a Gor(?) with an (eventuallly!) ring gap of 0.015”. Inlet was 151°, Transfers 127° & Exhaust 167°.

Somehow, that machine went far better than it had any right to without drama & I understand would embarrass quite a few ‘tuned’ large block engines. Allegedly

[Storkfoot]

Regarding studs for any position on a Lambretta, I’ve got in the habit of always assessing what will be best within my available stock & fit accordingly. Probably all of them are rolled threads as per OEM.

In general, the exhaust studs I fit will stay in place with Loctite Studlock though I will fit studs that have the best length of plain shank appropriate for the exhaust flange & solid copper gasket. I would never use any other type & if solid copper has not been available - on the odd occasion - bathroom silicon has provided a good seal on it’s own.

The exhaust studs I fit are double nutted to drive in hard to the shank. The nuts are usually M6 10 mm AF Hexagonal long nuts (Toolstation/Screwfix) tapped through to M7 & cross drilled to be lock-wired to each other.

I found my notes for the alloy finned 175 engine that I built seven years ago. The Indian cylinders really are a dog’s dinner & only suitable for people with an awful lot of time to kill. Anyhow, after weeks of work, the result was extremely good for a 175. It was also smooth which was likely due to the 116 mm rod. For the record, I got the bore clearance to 0.003” with the new piston which may have been a Gor(?) with an (eventuallly!) ring gap of 0.015”. Inlet was 151°, Transfers 127° & Exhaust 167°.

Somehow, that machine went far better than it had any right to without drama & I understand would embarrass quite a few ‘tuned’ large block engines. Allegedly

Can you anneal the solid copper exhaust gaskets with a blow torch?

The exhaust studs. I had to shave a couple of millimetres off each one but they do now lock hard in when double nutted. I have used the green Loctite 270 too.

[Storkfoot]

Surflex 4 plate clutch fitted. The 81 link IWIS chain, which should have fitted the 48/15 set up, didn’t. So I had to go to an 82 link with a pull down tensioner.

The air leak test. Well, it kept pressure for 25 minutes and, try as I may, I could not locate any potential leak.

[Adam_Winstone]

Looking good.

[Warkton Tornado No.1]

Can you anneal the solid copper exhaust gaskets with a blow torch?

Yes, though against our instincts associated with steel, copper should be heated then quenched immediately to soften back to a ’normal’ state. Copper work hardens over a period of time with the engine heat cycles.

Whilst a solid copper gasket is ideal for the exhaust flange, IMO copper - or any other material such as aluminium alloy - should not be used in the sealing of head to barrel unless there exists some means of annular retention. Inevitably, head gasket materials being of a softer metal, composite or possibly even nitrile, will soften over time & become even more likely to leak. Modification to the OEM conventional head to barrel interface by spigotting works extremely well & in such a scenario, a ring gasket could be added to fiddle the squish/port timings as required because the concentric rebate will retain it.

[Storkfoot]

I may give a copper gasket another go then

If the blow torch doesn’t heat it sufficiently, I may need to wait until my mother in law nods off so I can use her gas cooker