87.5 mm pistons

G

gtir303

New Member
before anyone says anything i done a search and couldnt find much so wanted people thoughts please

thanks

carl
 
A

AJ4

Guest
not really my thing bud, but I think you might need to be a bit more specific.

Are you asking what the best ones to use are, or if 87.5mm makes the liner too weak, or what effect having an oversquare engine is... ?
 
Fast Guy

Fast Guy

Moderators
Staff member
It can be done, as it has been done.
It shouldn't be unsafe, but as I only know of it being done once (I think it might have been on pimps old car?) I can't realy let you know how long it will last or how reliable etc it is.
 
G

gtir303

New Member
thank u any thoughts will do just trying to get my head round things before i make a choice

cheeers again
 
Rishi

Rishi

Still waiting on some shims!
Just remember that the larger the piston the more weight you have... This will affect how high you can rev the engine as there will be more stress on the Pins, Rods, Crank and Bearings although probably not too much more stress...

Now for the sake of £200 fitted i would use thicker liners... Taking too much out the standard block may compromise its reliability... Although it would be fine at lower boost and rpm levels... I know 0.5mm more than the usual 87mm doesn't sound like much but it does make a difference...

Can i ask why you want to use 87.5mm pistons anyway...?


Rishi
 
G

gtir303

New Member
cause i have 2 blocks
1 i got off my nephew but he run it dry of oil and it spun a bearing so that is wrecked the other block has already been bored to 87mm

cheers

carl
 
S

Sirnixalot

Guest
87mm should be the limit if you want to keep the block. 87.5mm will have taken you to th emaximum limit. no more honing or finishing the cylinder walls after that if you crack a piston and score the cylinder, you have to get new liners.

I would only go larger than 87mm if the sleeves were being replaced. Darton offers these sleeves for cheap but its the machining that gets you. Installing liners is a very very very easy job to screw up.

An oversquare motor is more rev happy.

Rishi while i agree that the larger the piston of the same material the more the reciprocating mass. Comparing a 87mm forged piston to an 86mm cast piston, you will find the forged one to be quite a few grams lighter.

All this being said i know that there are at least 4 motors in the US running a 90mm bore, some with a Tomei 91mm (could be 92mm, i dont remember) stroke crank.

Now that my friends is a stroker :shock:
 
Rishi

Rishi

Still waiting on some shims!
Sirnixalot said:
87mm should be the limit if you want to keep the block. 87.5mm will have taken you to th emaximum limit. no more honing or finishing the cylinder walls after that if you crack a piston and score the cylinder, you have to get new liners.

I would only go larger than 87mm if the sleeves were being replaced. Darton offers these sleeves for cheap but its the machining that gets you. Installing liners is a very very very easy job to screw up.

An oversquare motor is more rev happy.

Rishi while i agree that the larger the piston of the same material the more the reciprocating mass. Comparing a 87mm forged piston to an 86mm cast piston, you will find the forged one to be quite a few grams lighter.

All this being said i know that there are at least 4 motors in the US running a 90mm bore, some with a Tomei 91mm (could be 92mm, i dont remember) stroke crank.

Now that my friends is a stroker :shock:
Click to expand...

Crower offer this Kit... 91bore and 91 stroke... :shock:


Rishi
 
A

AJ4

Guest
I had a look at Darton sleeves a while ago, man, they are beautiful. Seems almost a shame to fit them, I'd rather just keep them on my desk and droll over them.

I need to get out more.

P.s, how does 91 x 96 grab you ? :D
 
Rishi

Rishi

Still waiting on some shims!
AJ4 said:
I had a look at Darton sleeves a while ago, man, they are beautiful. Seems almost a shame to fit them, I'd rather just keep them on my desk and droll over them.

I need to get out more.

P.s, how does 91 x 96 grab you ? :D
Click to expand...


91 x 91 is about 2.36L... So what on earth are you trying to build... :shock:

Unless you really meant 91 x 86...? :?


Rishi
 
S

Sirnixalot

Guest
there was a 2.7 SR2*DET being built last time i remember. The had a block spacer and custom sleaves made by golden eagle.

Not sure what became of it. WIll have to check the sr20forum
 
A

AJ4

Guest
upon doing a little research... with a bore pitch of 97mm, its possible to use 93mm bore wet liners, that are 4mm thick ( still thicker than recommended ).

So you could in theory build a square 2.5 litre at 93 x 93.

Or if you stroked it to 96mm, 2.6 litre :D
 
S

Sirnixalot

Guest
you have to keep in mind that a longer stroke crank may require you to notch the block for clearance.

I would rather build an over square motor....less piston speed
 
A

AJ4

Guest
I know, but I have a really low rev limit, so the oversquare / undersquare is not really an issue.

I imagine the block notching is probably the deciding issue. I can't see any reason why 93mm wet liners can't be used, unless it means removing material from the block that is going to seriously affect integrity. I think I'll be making some cardboard liners at the weekend and having a look :D
 
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