Now wouldnt this be an easy way of installing my Rosten rods

I assume this isnt possible, but what if I could

- Take gearbox off
- remove clutch/crank
- lower pistons down so that the rings are still in the bores but I can remove the rods
- fit my rosten rods (having measured centre to centre distances to ensure they match orignal items so that head gasket is still the correct thickness)
- push pistons back up from below
- re assemble everything with new main bolts etc.

My stock pistons are surely good for 250bhp/500Nm (AFN with 19.5:1 compression)

The benefits in this are that:

- my head is properly installed already with PD150 head bolts, and not leaking at almost 200bhp, so assembled nicely
- the head was off 30k miles ago and bores looked great still, so keeping piston rings would be fine in the bores I'm sure. HEad is already ported and been skimmed before.
- massive cost and effort saving as i dont need new head gasket, head skim, hone bores, new rings, etc etc

The rods are simply swapped from below and then allow huge power.

Is this impossible? To confirm, the pistons arent dropped out completely, just low enough to get onto the main pins to change the rods, whilst keeping rings in the bores so as not to need a ring compressor

I have a spare block thats stripped so can actually try this!

Now shoot me down!

i don't think you can get the pistons low enough to get the pins out, even if you remove the oil squirters.... MAYBE if you turned the pistons 90* you could squeak the pins out just enough to slip the rods in ... interesting idea though
on second thought i think it's completely impossible because the main crank webbing won't allow that much downward travel of the piston skirt

Boooo!
Many thanks

Dude I have a piston ring compressor you can borrow, also surely the rods are safe at your level of power? 283hp on stock rods for a while now
Btw cheers for dropping off the rs4 arb

No need to change the rings or hone, or even skim the head if its all working at the mo. If you pull the head you don't need to take the 'box off or crank out either. Far, far easier to do it from the top, and if you follow the proper sequence you won't warp the head taking it off.

Pull the head and sump, pop the pistons out of the top, swap the rods, new bearings, and stick 'em back in. A piston ring compressor is less than a tenner on ebay

jimbote said:

i don't think you can get the pistons low enough to get the pins out, even if you remove the oil squirters.... MAYBE if you turned the pistons 90* you could squeak the pins out just enough to slip the rods in ... interesting idea though
on second thought i think it's completely impossible because the main crank webbing won't allow that much downward travel of the piston skirt

Click to expand...

^^This . There is simply no room to lower the pistons down not to mention trying to get those wrist pin clips in would be an absolute nightmare.

On top of it all, you should always check the piston deck heights afterwards.

Just a bad idea all the way around.

Many thanks all!

Numbnuts - you have a PD so ARL rods which are much beefier than my AFN. I didnt realise you had the PD mk2??? Would have been great to have seen it!
I do have access to a ring compressor, but many thanks.

Just thought it might be a nice way of a) saving cost and b) not touching what I'd call the 'sensitive' head gasket (and having to cut down more ARL bolts.....)

But yes maybe the head wont need skimming?

As mentioned in my original post, Id be measuring the rod lengths for protrusion so i'd have taken this into account.

Its not that bad an idea!

The bottom line is, are my AFN pistons good for 250bhp?
Car has done 207k miles now....but no smoke/oil usage so I assume rings can last for 500k miles if all is well?
I just dont want to get the ring bedding in process wrong etc and end up taking a step backwards! Seems a shame to change whats running well.

I have brand new ARL 79.5mm pistons and brand new BHW 81mm pistons - but thinking I may not need either really....but I guess with head off I can measure bores and see if 79.5mm ARL pistons/new rings will work with just a hone as itd be good to drop the compression to 18.5:1. Honing on the car can be done properly? Saves removing the block! But then thats box off to get crank out - or is there no 'swarf' from honing so crank can stay in?

Im just looking for the quickest way to do the job properly - limited spare time these days!

Many thanks

Easier to just pull the head and oil pan.

It sounds like to get me running at ~230bhp I'll just keep my current pistons/rings
The 2.0ltr upgrade can wait - its a shame to have too much too soon anyway!