Cylinder Liners

[Motorsport Mickey]

Just had a couple of confused PMs and I should make it clear that where I say

6 hours ago, Motorsport Mickey said:

For maximum power the engine piston to cylinder clearance on Pistons of this size can be set at 5 thou ( forged Pistons) or 4 thou for cast

This means these increased piston to liner cylinder wall clearances reduce the effects of piston drag and the power losses from it, maximising the power from the engine.

These clearances are more than the standard workshop manual figures which reflect matched new components without any wear or beneficial clearances (reduced drag) in them. In the instance quoted above Nigel was commenting he'd felt his engine "was tired" intimating it had lost power, if when measured the piston and cylinder clearances are as quoted above, these will allow maximum power to be developed from the engine when fitted with replacement piston rings.

Because the clearances between piston and cylinder liner bore are increased from standard it does mean that there is less life left in the engine overall (it's running at part worn dimensions) but we are all aware of the saying "it's not the remaining breaths in life that count but the life that takes your breath away". 

Mick Richards

[Nigel C]

great info, thanks Mickey. I'm going down the replacement/rebuild route as I'm still running this engine whilst trying to sort the other one out.

I've got a steel crank ( being reground), rods and forged pistons, lighten flywheel, dipped block already stacked up waiting and looking at which cam to use (any advice would be most helpful!) as it should rev to 6,500. I've also got an ali head that looks to have been well worked (valves/ports etc) and I've had that decked and tested and all looks good.......just not to sure weather to really go for it or not....would it be reliable enough?...would the whole thing be reliable enough!

[BlueTR3A-5EKT]

31 minutes ago, Nigel C said:

great info, thanks Mickey. I'm going down the replacement/rebuild route as I'm still running this engine whilst trying to sort the other one out.

I've got a steel crank ( being reground), rods and forged pistons, lighten flywheel, dipped block already stacked up waiting and looking at which cam to use (any advice would be most helpful!) as it should rev to 6,500. I've also got an ali head that looks to have been well worked (valves/ports etc) and I've had that decked and tested and all looks good.......just not to sure weather to really go for it or not....would it be reliable enough?...would the whole thing be reliable enough!

You could go the whole hog and have your Pistons Keronite coated.

https://www.highpowermedia.com/articles/1390/keronite-coatings/

 

Peter W

[Motorsport Mickey]

4 hours ago, Nigel C said:

I've got a steel crank ( being reground), rods and forged pistons, lighten flywheel, dipped block already stacked up waiting and looking at which cam to use (any advice would be most helpful!) as it should rev to 6,500. I've also got an ali head that looks to have been well worked (valves/ports etc) and I've had that decked and tested and all looks good.......just not to sure weather to really go for it or not....would it be reliable enough?...would the whole thing be reliable enough!

Depends what you want to do with it !

 

1. I ran a standard Triumph crank lightened and with the webs machined reground to -60 (yep, minus 60) thou big ends (Massey Fergueson tractor) so we could offset the crank grind and get a longer stroke, with -10 thou mains, and used 6500 max revs all season. Standard prepared conrods shotpeened, Omega 89 mm pistons with
2. If you want more info drop me a PM and we will go through the specs.

So unless you have a stiffer test in mind as long as you build the engine well... yes it should be reliable.

Mick Richards