Hi lads I'm just putting a new motor togever for my 3dr and I had to have the block decked by 1mm so I'v removed 1mm from the pistons well I'v just come to putting it togever and the pistons are sitting down inside the bore by 1mm spot on is this ok as I fort the last time I put a YB togever they sat above the block any help please

 

It must have been low comp to start with.

 

i built my engine to a completely standard spec and the pistons were above the blocks deck height and at the time i was told this was normal, dont know if having your pistons 1mm lower then the height of the deck will cause you any troubles but will surely give you a really low compression?

 

Do you think it will be ok stu as I'm looking for the same power as the old motor apox .400 bhp . Do you think it could burn the head gadget the piston being 1mm below the to of the block I'm using a multi layer head gadget on this motor with a T34 turbo

 

This is wot is on my mind

 

It's not good practise to stop pistons down the bore but it will be fine. Now yove removed 1mm from the top the bowls in the piston will have lost capacity so make sure you measure the compression ratio and not just guess.

 

Thanks jimbo but this is were I'm going to get unstuck now as I don't no how to work that out :-(

 

Listen to this man's advice! Surely by removing this much from the tops of the pistons the cr will be lowered significantly Jim?

 

You need a burette, cc plate and cc fluid ideally.

Cheap home brew way is with a thin Perspex sheet and a syringe full of diesel.

 

Parafin's better

 

That's right ade, but you loose some with the heigh, gain some because of the bowls, my point wasn't so much where the CR is more so measure it so when the mapping day comes your tuner will have much more confidence

Coley give me the full spec, what pistons they are how much they have had off the top exactly. How much they stop down the bore and combustion chamber cc I can work it out for you quite accurately.

If you can't cc the chamber size then measure the head thickness

It's well worth buying a Burette for checking cc of pistons and chambers

 

Photos / sizes on the way mate give me 5 min

 

the head works out to 138.30mm 2wd and from wot i can see the head gasgit MATT has given me is a 4 layer
can you help me with this info please

 

I'm thinking it might just be best to take the block back and have 1.5mm removed from the top face as I no the lads down there and it only cost £25 to have wire ring groves removed which was 1mm

 

Drop it all over and I will work it out for you Ian.

 

Thanks Martin I should be over day some time thanks again

 

WTF was wrong that you need to remove 1mm ?? That is a HUGE amount ?

And no matter what you remove from the piston, depending on cam choice you may also need to adjust the valve cutout depths as well.

And was the 1mm removed from the piston over the entire crown, or just the outer edges ?

 

Hi mate thanks for ask . Wot it was the block was a wire rung block and as I'm using a 4 layer Wrc head gasgit the wire rings were best off being removed which when this was done the block was 1mm shorter so the pistons had 1mm removed from them on all the faces but I tuck it that the pistons were stander which it turnd out they had been modded in the past so this is we're the problem come from

 

Well today has come out very well at the end I'v been to see my good mate Martin Hadland and he has sent a good part of this Satday working the cc out and coming up with a plan on wot to do next .

A very Big thanks to you Martin for helping me out with this today on your day off thanks very much

 

I found Martin very helpful when I visited him on a Saturday my friend shep
He stopped working on his ferenza on his day off and worked out what offset was needed for his bells/rotors

Big thumbs up Martin from me

 

Glad you've got it sorted, sorry I havnt replied sooner been flat out today but I'd have said anyway that if martin can measure it then do that rather than me roughly working it out

 

Thanks jimbo your a star for your help on this Martin has worked out that if lose .50mm/ 20 fa we should be in the ball park of it working out / going to have the head flashed and wot,s left will be Removed from the block so all being well the motor should be going in the car next weekend

 

Good stuff mate