Pistons for TR6

[michaeljf]

Hello, somewhere on the forum there was a mention of a VW piston to fit a TR6. It was a 1.4 Polo in 76.5 with a .5mm over-size .I would like a bit more information if possible.Regards,Michael.

[Melmac]

I have read about the VW pistons but also the Mazda pistons. They seem to be easier to convert. I have a mechanic who do the more advanced jobs on my engine. He's about 80 years old now and very experienced in (re)building engines. Many of the drivers in the historic racing series here in Sweden goes to this man for advice and maintenance of their engines (which he built in the first place).

He recommended the Mazda +0.50 mm pistons when I commissioned him to build my engine. So we choosed them and they have worked fine so far.

However, if i remember it right, there are some VW parts involved in the build and it is the tubular push rods.

[michaeljf]

Hello Melmac, The VW pistons seem like a fair bit of work and are expensive here in Australia. So which are the Mazda pistons (part no.? or model ) and an idea of the modifications, please.Thank you.Regards,Michael. 

[Melmac]

On 6/2/2019 at 2:55 PM, michaeljf said:

Hello Melmac, The VW pistons seem like a fair bit of work and are expensive here in Australia. So which are the Mazda pistons (part no.? or model ) and an idea of the modifications, please.Thank you.Regards,Michael. 

Im pretty sure it's from the Mazda's E3 family. I took a picture of the box to have as reference if I should need more of them. Here you can read more about it > https://en.wikipedia.org/wiki/Mazda_E_engine

[michaeljf]

Hello Melmac, Thank you for that,I will look them up.Any ideas about the mods to these pistons? Regards,Michael.

[Melmac]

1 hour ago, michaeljf said:

Hello Melmac, Thank you for that,I will look them up.Any ideas about the mods to these pistons? Regards,Michael.

The end cap you see in the picture has to be made (12), other than that I don't know.

[michaeljf]

Hello Melmac, Thank you for that I will follow that up and hopefully have a good result. Regards,Michael.

[michaeljf]

Hello, Just a quick note to say I have progressed a little; Block is bored and I have Mazda 323 1981-'90 E3 77.5mm pistons (still have to connect pistons and rods) head gasket is being made.Will have to start a post? and report the whole build.Regards,Michael.

[michaeljf]

Hello, Here a couple of pictures.  Have to machine top of piston to suit compression, piston machined to suit std. floating gudgeon pins, new head gasket to suit 77.5 mm pistons. Regards,Michael. Will now start a thread to keep it all together as I put it all together!

[Triumph-V8]

On 5/29/2019 at 3:48 PM, michaeljf said:

Hello, somewhere on the forum there was a mention of a VW piston to fit a TR6. It was a 1.4 Polo in 76.5 with a .5mm over-size .I would like a bit more information if possible.Regards,Michael.

Piston is the BBY type,

Small end must be modified to accept the smaller gudgeon pin from VW.

Also rod it too wide so piston must be milled 2mm on each side or rod

must be milled smaller (not recommended)

 

Works nice with the MaxspeedingRods.

All in all I have 5 friends driving that.

 

If you want it perfect you may want to make new small end off centric to get a longer rod working length

and remove a bit from the top of the piston.

If the block is recessed you have to mill the 0,7mm off to get a clean surface.

 

Thats it! Go on and build a nice engine!

 

Should you want to go further I have a set of MAZDA pistons in 77.75 and one in 78mm to sell.

[Triumph-V8]

 

Original rod with off centric small end, right TR6 piston, left MAZDA piston.

[JohnD]

I've never seen before such a detailed description of the parts needed to ramp up the capacity of the 2.5L Triumph engine!   Thnak you!

But isn't it far from the whole story?    Over boring by only 60thou (1.5mm) risks such a thin wall between the paired cylinders, or the water jacket that sleeving is necessary.    Over boring to take + 3mm pistons will surely make sleeving essential for all the bores?     Having come across the first for a lesser bore out, what have you found for the greater?

Melmac, you have done this - did you need to offset the bores?

JOhn

Edited June 1, 2020 by JohnD

[toofast2race]

Most blocks will take 77mm bore without issues - after that its pot luck although you can look at the underside of the block and get an idea of how central the bores are to the casting

 

[michaeljf]

Hello, my version is at the thread "One step foward two steps back" Regards,Michael.

[TRier]

On 6/1/2020 at 9:28 AM, Triumph-V8 said:

 

Original rod with off centric small end, right TR6 piston, left MAZDA piston.

Hi Andreas, very interesting modification. What material did you use for the small end bushing? I imagine its phosphor bronze but if it is what grade? 

 

Niall