Difference between F and G grade Sprint pistons?

[sydney.wedgehead]

Can someone explain the difference between F and G grade Sprint pistons?

I have a Sprint engine with pistons that are stamped with G on the crowns. Two of these pistons are damaged. Number 1 has broken under the top compression ring and has pre detonation damage on the crown. Number 2 just has pre detonation damage on the crown. Number 3 and 4 pistons seem undamaged and suitable for re-use.

I've been looking for some second-hand pistons as I just want to repair this engine without spending a lot of money. I've been offered some F grade pistons but am unsure if I can use these to replace the damaged pistons.

I'd appreciate some advice.

[Jon Tilson]

I'd reuse the best of the spare F grades and try to balance them with the rods weight wise.

But I'm a known cheapskate...

More important is: Is your bore damaged?

This is showing the dangers of BL's decision to weaken Sprint needles in the later cars and how its compounded
with modern fuels.



Jonners

[MIG Wielder]

With my anorak firmly zipped up the difference in " F " and " G " grade pistons is in terms of diameter, and is about 1.5 thou. So not a lot.
The actual differences are in the Sprint workshop manual.
But after a reasonable mileage these differences will be lost in general piston / ring / bore wear.
Tony.

[dursley92]

Like Tony says after a fair bit of running it shouldn't make much difference anyway. I would be more concerned to find four that all weigh more or less the same.