the truth about d16's and pm3's

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garagemonkey

Junior Member
Hello all, this is my first post on any site and I thought I would start with you guys.

I have read lots of stuff in these forums saying that the pm3s will not work in a d16 becuase they stick out of the hole, however no one ever tried it....until now. I had a spare d15b2 and a d16a6 bottom end and alot of time so I said wtf lets see. The d15 was trash and the d16 had no head, dissassembly began on the d15 and I pulled and cleaned any parts I wanted as extra, mainly the pistons. Then I pulled the rods and pistons from the d16. Next was the pita part...swapping pistons and rods. I cut a slice along the wrist pin journals of the junk rods (d15), to ease tension and gently pushed out the pins. Then I took one of those junk wrist pins and shaved the diameter down so that when I used it to press out the d16 pins, it would not be stuck in the rod. Since the d16 pistons were junk, I just placed them in a vise with wood on one side and the junk pin on the other, and pressed the pin out to the edge of the piston. Then I stacked two of the d15 rods with slits cut into them on that side so that the wrist pin would have somewhere to slide into, and with a little muscle and patience, my pm3's were out and my d16 rods were free. On a side note, the pm6's appeared unscathed but who knows. To press the d16 wrist pins back onto the d16 rods with the pm3's, I put the pins in the freezer for twenty minutes and heated the rod ends with a propane torch for a few minutes. After that I quickly lined up the piston and rod, and pushed the pins in by hand like butter-- if you are carefull you can get them to just the right endplay, you need to be quick before the pins start to heat up once removed from the freezer. I kept good record of which rings came from where and put the original d16 rings on the pm3's. I installed them into the a6 block in the same holes they originally came from to keep the bearings in check, and at TDC they do stick out about .5 to 1 mm-- not sure had no measuring devices. I only had the used stock head gasket (.048) so I put it on and put the head on and set timing. I did not torque the head all the way down since I was going to remove it again, but it was pretty tight. Then I just turned it over by hand and I didn't notice any clearance problems with the pistons and valves. So if all was done correctly, this set up should work, I plan on using a slightly larger .078 Cometic headgasket just to be sure clearance is'nt an issue. Im not sure of the compression ratio becuase I'm having trouble with the numbers, I put in all the corresponding info, plus .078 for head gasket thickness, and -0.7 is what I came up with for piston to deck height, and it comes out to negative 11.504:1? Now the only problem i have is how to test this setup seeing how i no longer have a honda. Hopefully one of my friends will need an engine soon and I'll let you know how it goes.

If anyone knows what the real compression ratio of this setup would be or knows another company other than Cometic that offers larger than stock headgaskets, I'de like to know. Hope this was helpful in any way.
 
garagemonkey said:
Hello all, this is my first post on any site and I thought I would start with you guys.

I have read lots of stuff in these forums saying that the pm3s will not work in a d16 becuase they stick out of the hole, however no one ever tried it....until now.

I had a spare d15b2 and a d16a6 bottom end and alot of time so I said wtf lets see. The d15 was trash and the d16 had no head, dissassembly began on the d15 and I pulled and cleaned any parts I wanted as extra, mainly the pistons. Then I pulled the rods and pistons from the d16.

Next was the pita part...swapping pistons and rods. I cut a slice along the wrist pin journals of the junk rods (d15), to ease tension and gently pushed out the pins. Then I took one of those junk wrist pins and shaved the diameter down so that when I used it to press out the d16 pins, it would not be stuck in the rod.

Since the d16 pistons were junk, I just placed them in a vise with wood on one side and the junk pin on the other, and pressed the pin out to the edge of the piston. Then I stacked two of the d15 rods with slits cut into them on that side so that the wrist pin would have somewhere to slide into, and with a little muscle and patience, my pm3's were out and my d16 rods were free.

On a side note, the pm6's appeared unscathed but who knows. To press the d16 wrist pins back onto the d16 rods with the pm3's, I put the pins in the freezer for twenty minutes and heated the rod ends with a propane torch for a few minutes. After that I quickly lined up the piston and rod, and pushed the pins in by hand like butter-- if you are carefull you can get them to just the right endplay, you need to be quick before the pins start to heat up once removed from the freezer.

I kept good record of which rings came from where and put the original d16 rings on the pm3's. I installed them into the a6 block in the same holes they originally came from to keep the bearings in check, and at TDC they do stick out about .5 to 1 mm-- not sure had no measuring devices.

I only had the used stock head gasket (.048) so I put it on and put the head on and set timing. I did not torque the head all the way down since I was going to remove it again, but it was pretty tight. Then I just turned it over by hand and I didn't notice any clearance problems with the pistons and valves.

So if all was done correctly, this set up should work, I plan on using a slightly larger .078 Cometic headgasket just to be sure clearance is'nt an issue. Im not sure of the compression ratio becuase I'm having trouble with the numbers, I put in all the corresponding info, plus .078 for head gasket thickness, and -0.7 is what

I came up with for piston to deck height, and it comes out to negative 11.504:1? Now the only problem i have is how to test this setup seeing how i no longer have a honda. Hopefully one of my friends will need an engine soon and I'll let you know how it goes.

If anyone knows what the real compression ratio of this setup would be or knows another company other than Cometic that offers larger than stock headgaskets, I'de like to know. Hope this was helpful in any way.


Welcome to Hondaswap.

Just a tip for web boards in general - Use spaces when typing a lenghty message. If your message is to long, not many people will read it. To be honest, I didn't even read the whole thing eventhough I spaced it out for ya.
 
Nice writeup! I'm getting 10.87:1 compression on a compression calculator with your stock gasket, and taking into account the compression height difference between the PM3 and PM6 pistons. It says that the PM3 pistons will stick up out of the hole 0.7mm, so if you have the room from the head gasket thickness and the bottom of the combustion chamber, you'll probably be ok. The only thing I would be worried about is using a head gasket that doesn't exactly match the bores of the cylinders, and the possibility of the pistons crashing into the head at high revs when the rods stretch.
 
Oh- I got 0.028in sticking out of the hole which is the same as 0.7mm using the D series compression calculator. The compression with your .078 Cometic gasket will only be 10.1:1.

On gasket choices- I've always used Cometic for custom sizes, and I've never been disappointed.
 
I have no idea. The car the engines were for sold and I'm either waiting for a friend to blow thiers or until I can pick up a cheap one at auction.
 
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