Some days ago I noticed that two engines that I have let buildt got different piston to wall clearances on all four cylinders. The 3rd cylinder gots the biggest clearance, two and one are a little smaller and cylinder four has the smallest clearance.
The block is an Darton-MID-sleeved b16 with 84mm bore size and JE pistons.
Of course it seems to make sense to give cyl. 3 a little more clearance becuse it is the hottest one.
What are your experiences? Or do you mostly set all cylinders to the same clearances?

I regard it as an interesting topic.

 

To keep the engine in balance, all the clearances should be as close to identical as possible.

 

Yes that how I usually buildt my engines. But after I noticed the differences in the two blocks that I have let buildt I started to think about this topic.

As we all know the average temperatures in the 3rd cylinder are a little higher.
So doesn´t the 3rd piston expand a little more than the others? That would mean that all the clearances where the same when the engine(or better all pistons) reached theire operating temperatures.

What´s your oppinion?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondaapi &raquo;</TD></TR><TR><TD CLASS="quote">Yes that how I usually buildt my engines. But after I noticed the differences in the two blocks that I have let buildt I started to think about this topic.

As we all know the average temperatures in the 3rd cylinder are a little higher.
So doesn´t the 3rd piston expand a little more than the others? That would mean that all the clearances where the same when the engine(or better all pistons) reached theire operating temperatures.

What´s your oppinion?
</TD></TR></TABLE>

I agree that #3 probably gets hotter, but if anything maybe run a bigger end gap on your rings...I'd still keep the piston to wall clearance the same as the other 3. Personally I ran pretty loose ring gaps on my setup, but I made all 4 ring sets the same.

 

no more ideas?

 

What kind of measurements are we talking here?

 

Most shops bore all the cylinders to the same size, otherwise it can look like they can't hold tolerances properly. Kind of an ego thing.

 

Are you saying its not important for the cylinder bores to be consistent Earl?

 

@earl

I´m definetly sure that the company can hold the desired tolerances.
The interesting thing is that both blocks they have buildt got exactly the same differences in piston-to-wall-clearance. So it seams that this are desired differences.

What do you thinks about this?

 

For us, we will only use pistons that measure identical. Never a problem with the CP's.

 

Not sure what your shop is doing but we set clearances at .003" for allmotor and .0035" for turbo builds.

 

sell your current pistons. have it bored one over. buy pistons for your new bore. /thread.

 

To what degree are they different?

If cylinder 1 was at .0035 and three was at .0037 and this was done on purpose by your builder then trust your builder and run the block like that.

Personally I wouldn't build it like that but I don't see anything wrong with running it as is if the difference isn't much.

 

Measure the piston skirts. Real machine shops will hone to each piston. I've measured many different brand pistons and i've seen different sizes boxed together. Trust me, you have the best machine work done to your blocks

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">Not sure what your shop is doing but we set clearances at .003" for allmotor and .0035" for turbo builds.</TD></TR></TABLE>How does five tenths make a difference...better yet...how are you able to machine to five tenths on a cylinder. I don't think the new Ck-21 can even machine to five tenths of a thousandths.

 

Are you serious? Most good machinist can hold one ten thousandth (.0001")
I don't think that kind of precision is necessary on every 400whp street build but it is nice to have.
Personally, I would never use a set of pistons that did not mic to within .0001-.0002" of each other. CP and JE always hold that tolerance. We want all out bores the same size and all out cylinders the same size. This just seems to me to be the proper way to blueprint an engine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">Are you serious? Most good machinist can hold one ten thousandth (.0001")
I don't think that kind of precision is necessary on every 400whp street build but it is nice to have.
Personally, I would never use a set of pistons that did not mic to within .0001-.0002" of each other. CP and JE always hold that tolerance. We want all out bores the same size and all out cylinders the same size. This just seems to me to be the proper way to blueprint an engine. </TD></TR></TABLE>

I'm glad I went to Earl

 

I agree with Earl. And for the final machining anyways, the pistons should be double checked and measured no matter which piston company to make sure they are all the same size. But yes, same tolerances for each cylinder.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93LSivic &raquo;</TD></TR><TR><TD CLASS="quote">Measure the piston skirts. Real machine shops will hone to each piston. I've measured many different brand pistons and i've seen different sizes boxed together. </TD></TR></TABLE>

Yup, no matter which brand. Can't assume they are all perfect.

 

pistosn are not going to all me exactly. if you have one that's lets say 81.5mm exactly and then the next int he same batch is 81.5mm +.001

do you think you can bore all the cyclinders out the exact same and still stay in specs?

any good shop i have ever used marks each piston to each cyclinder bore. so each cyclinder is held to the proepr tollerances of pistont hat goes to that cyclinder. This may be the reason theya re different sizes. your pistons may be diffrent sizes and they are compensating and ensuring you have exact specs per piston to cyclinder.

this si jsut a guess since that's how the shops i use do it, but that may be wrong. the best thing you can do is ask the machine shop why it's like that and see what they say.