Piston query (Update 17/8/08)

[Ad Mayo]

Do bluetop pistons fit in redtop engines, reason I ask is one of mine has a hole in it and I have found some on ebay in america cheap that are from a bluetop.

If anyone has any spare pistons they don't want that would be great.

Regards Adam

[crazybrightman]

i could be wrong but even if the pistons are the same design and fit the bore ok at some point the 4age went from 18mm big ends to 20mm big ends so the pistons wouldn't fit the conrods. how ever this may not effect the mk1?

[MartG]

at some point the 4age went from 18mm big ends to 20mm big ends so the pistons wouldn't fit the conrods. how ever this may not effect the mk1?

I think that change came in with the smallport head engines, midway through the AE92 lifetime, so didn't affect the MR2. However I'd recommend checking part numbers to make sure.

[Ad Mayo]

I'm taking the piston out tonight so will check numbers.

[crazylegs]

early mk1a had the smaller end. it was changed on the mk1b but the date is a bit vague

[Ad Mayo]

I have the chance of getting a piston from another member, it is no.2 piston and I need no.3, will this work or will I need the exact piston again.

[Speedy]

There aren't any differences between each piston - 2 will be the same as 3, the same as 1 the same as 4.

[Ad Mayo]

Fantastic, cheers buddy

[jimi]

Make sure you get the gudgeon pin with it, the piston and the pin are a matched pair !
Jimi

[crazybrightman]

whats wrong with the old piston exactly anyhow? they dont usualy fail unless there is a cause, plus they usual damage the cylinder wall or head when they go pop. so best to make sure theres no other damage and a piston is all thats needed to get it running ok again.

[LimeyMk1]

There aren't any differences between each piston - 2 will be the same as 3, the same as 1 the same as 4.

Other than their weight. The numbers stamped on their faces denote slight variations in weight. It amazes me how well balanced the stock 4AGE was, during manufacture they had 4 different weights of piston to choose from to fine tune the bottom end balance.

[Ad Mayo]

My piston has blown a hole up the side of it, there isn't any visible scoring to the bore and it seems to feel ok.

[jon_st205]

Chris is correct - when replacing a piston you need to make sure it's the same marking on the crown. In addition to the weight I believe the letter also makes a difference (bore-ring gap matching?).

Goes without saying if you're doing a quick & dirty fix like this you'll need to do the bore with some sort of honing tool.

To be honest I would just re-engine.

Jon

[Ad Mayo]

My mate is going to rehone it if it needs it, engine is now in bits the piston is out and waiting for new one can't afford new engine at mo.

If there are any problems after rebuild it will be getting broken.

[crazybrightman]

seems an odd plan you could get an engine for £50 £100 at most and just bolt it in. its surely going to cost you more for the piston, gaskets, seals, head bolts etc and may end going wrong again.