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Building a high compression piston

7K views 18 replies 6 participants last post by  sunfowerggs 
#1 ·
I don't know if anyone has ever thought of this but I'm tearing down a 1.6L miata right now that happens to have flat top pistons if I'm not mistaken. Now I'll eventually be down to a bare block and I was wondering if anyone has thought about welding a rectangular piece of aluminum on top of the piston in order to raise the compression ratio? Melting point of aluminum is 1220 degrees and a normal combustion engine creates temps around 1000 degrees. I'd use play-doh to check clearances before I even started and the 1.6L miata motor is a non interference motor. Also i'll be cleaning the welds so there's no high spots anywhere. I was thinking about the air that'll be trapped between the plate and the piston itself but not sure if that would do too much. Also I know to do tack welds so I don't overheat and warp the piston or rings.
 
#2 ·
First off, pistons are cast or forged. This means they are made from a single solid material and any finishing work done on them is to remove excess material.

Welding anything on to the top of the piston, especially something that would trap air between itself and the top of the piston is bound to fail. Also, most pistons are not aluminum and welding 2 different materials together is never recommended.

If you are handy with a welder, you might want to read up on welding in quench pads in the head.
 
#6 ·
Yes but I can't find any exact info on what epoxy they used... when I figure that out i'm doing it
 
#7 ·
http://www.alvinproducts.com/Products/Products.asp?id=2#Durability

I'm doing it... muahaha I'll document everything as I go along and let everyone know how long it takes to blow the motor... if it does blow... also to put on a 2.5cc piece of aluminum which will increase the compression from 9.4:1 to 10:1 will need a 21lbs adhesion strength to handle the 1450g's the piston sees during the change in direction at 7,000rpm... JB weld has a 3,963 lbs strength +/- a couple pounds
 
#9 ·
I know that's why i'll be using that 1000degree epoxy. i'll have to use a 2part epoxy like jbweld in the middle of the piston then run a bead of the 1000degree stuff on the outside to protect the jb weld
 
#11 ·
I've had problems with adhesion before but I realized it was my own lack of prep work that caused the problem. Not saying that's what you did just throwing that out there
 
#16 ·
Well it took awhile to get the new gaskets. Once I got them I started the port and polish job on the head/intakemanifold/tb/exhaust I completed the intake side but the exhaust side still needs work. I checked all of the clearances already and everything looks fine thus far. I'm doing everything I can to this with as little out of pocket as possible. I'm already saving up for the build of the 302 that'll eventually replace this and obviously it's not my dd so not worried about the motor blowing. If it was a 1.8 that everyone wants to swap in the miata then I certainly wouldn't be risking it like this lol.

If anyone wants to read more about this:
http://forum.miata.net/vb/showthread.php?t=308510
 
#18 ·
I will be following this post and the one over at miata forums too. i can't wait to see how this comes out!! Best of luck to you, and I think its awesome that you are actually doing something and hopefully seeing some results.
 
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