EJ255 forged internals build. EJ257 pistons hitting head as I manually turn t...
 

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HELP!!!

As per title

Can the EJ257 Pistons be used in a EJ255 Block without any changes to heads or gaskets or anything else?
From What I've read there should be no issue with this... Despite differences in Cylinder Heads.

The Blocks have been Decked (not sure how much was taken off at this stage) do I need to run a thicker gasket to compensate? How do i go about measuring the deck height?

Everything moves freely without the heads on.

Any recommendations?


MY EJ255 Build:

CP Pistons 100mm, 8.2:1
Scat Rods H Beam 79mm stroke 130.5mm length
ARP Head Stud Kit std (260-4701) 11mm
Front and rear crank seals
OEM Complete Master Gasket and seal Kit (WRX/STI 06-07)
Main Bearings
Big End Bearings (Rear Thrust Type)
Oil Pickup Tube
Timing Belt
Main Timing Pulley (Crank)

Machine Shop:
Clean Block (Acid Bath)
Hone and Bore 20 Thou Overbore / Measure Cylinder Bores
Deck the Block (Shave)
Polish Crank / Replace Bearings to suit

Yes, they are the exact same block halves

I've just changed from V25B heads which were on the EJ257 STI to D25 heads that were on the EJ255 WRX without issue.

What rods and pistons do you have?

[QUOTE=dazdavies;834245]Yes, they are the exact same block halves

I've just changed from V25B heads which were on the EJ257 STI to D25 heads that were on the EJ255 WRX without issue.

What rods and pistons do you have?[/QUOTE]

Edited original post to include build info

It sounds like you've had way too much taken off the block halves.

Stock gaskets are 0.7mm I've had blocks skimmed in the past and still been able to use those too. I'm running 1.1mm gaskets now without issue.

Do you know the history of the block i.e has it been decked before?

[QUOTE=dazdavies;834248]It sounds like you've had way too much taken off the block halves.

Stock gaskets are 0.7mm I've had blocks skimmed in the past and still been able to use those too. I'm running 1.1mm gaskets now without issue.

Do you know the history of the block i.e has it been decked before?[/QUOTE]


Hmm I'm running OEM gaskets in it atm so I'm assuming 0.7mm

I Bought the car with 72000km on it back in 2010, it only had basic bolt on mods, the previous owner is a friend of mine and he says that it has not had any engine work done on it in the past...

I'll have to ask the machine shop how much they took off the blocks and go from there I guess...

There's only two possibilities here.
The first is that's the block faces have had too much off them or you're using the wrong parts. I doubt it would be the Pistons because if they were stroker Pistons they'd be too far down not poking out the top.

A good possibility is the rods as some manufacturers do offer them in longer sizes usually one or two mm. If your parts are new I'd be checking part numbers. I'd also measure rod length just to be sure.

EJ255 forged internals build. EJ257 pistons hitting head as I manually turn t...
 

The rods I asked the parts supplier to order were ej25 H-beam rods 79mm stroke, 130.5mm rod length...

2.0L rods and 2.5 are the same length. I know that for absolute certain as I used a set of forged rods from a 2.0l build I did when I Did my first EJ257 conversion.

Measure the rods they should be 130.5mm from the centre of the big end journal to the centre of the little end journal. If they are any longer than that then there's your issue.

[QUOTE=dazdavies;834252]2.0L rods and 2.5 are the same length. I know that for absolute certain as I used a set of forged rods from a 2.0l build I did when I Did my first EJ257 conversion.

Measure the rods they should be 130.5mm from the centre of the big end journal to the centre of the little end journal. If they are any longer than that then there's your issue.[/QUOTE]

Cheers for all the info so far I was pretty certain that the Pistons themselves were not the issue!

I'll have to have a look when I get back from work then, if it's not the rods then the shaved blocks would be the next obvious thing!

Can anyone tell me If you sat Pistons out of an EJ255 WRX motor beside Pistons from a EJ257 STI motor side by side are there any major differences? For example piston length? Any chance of photo proof?

My mate that's helping me do the engine assembly has it firmly stuck in his mind that the ej257 Pistons are longer than the ej255 ones, and that this is why the Pistons are hitting the heads... to the point that he won't help take it apart to check any of the other things mentioned in previous posts in this thread...

I've only been able to find information saying that the difference between Pistons was that the ej257 Pistons had a deeper dome to increase capacity by 50cc. I maybe misunderstanding this part though...