new 225 v6 pistons and installing them

A couple years ago when building my jeep, all i had was bunch of parts. Most of it was never together in one vehicle before, so I decided to just go through it all and rebuild it as best I could.

My engine is from a 65 or so Buick skylark. Its a pre jeep 225 odd fire. I got it cheap and it was complete carb to pan minus the flywheel because it was an automatic. The PO told me it ran and I'm sure it did at one point. I decided to rebuild it. I took it apart and took it to a machine shop to magna flux the heads and hot tank the block. They charged me 300 bucks to do that and that alone. I was so peeved that I decided to just do it all myself. I did take the crank to a crank guy and for 100 bucks he polished the journals and told me it was good to go.

I bought an engine kit from Northern Auto parts because it was the cheapest. No lie. Thats why i went with them. The kit was complete with cam lifters, pistons and all bearings and seals. Didn't come with any head parts, so i just lapped the valves myself. I decided to install new pistons myself...

This is where i ask questions. What I did worked, but not without destroying a couple new pistons in the learning curve. I am used to wrist pins being held in with cir clips or a bolt in T slot pistons. These are not like that at all. The wrist pins will press out just fine, but if you try and press them in without the correct fixture you will wreck the pistons. I know from experience.

So, what i did was to take a propane torch and heat the small end of the connecting rod, freeze the wrist pin and assemble the connecting rod, wrist pin and piston by pushing the wrist pin through the piston and into the connecting rod while wearing a glove. Whats the correct way to do this?

This engine runs fine, no funny noises, good power and good oil pressure. The vacuum gauge shows no flutter so valves are ok etc..

thanks

 

Engine shop I took the #8 piston to the guy punched the wrist pin out and heated it to get it back in then cooled it. It was good to go from there.

 

I built a fixture to hold the piston that included an adjustable stop to keep from over inserting the piston pin. Then I do the same as you suggested by heating the rod slightly and freezing the pin. When ready, I place the piston in the fixture, heat the rod end and while holding the rob in alignment, slide the pin in until it hits the stop. Once cooled, everything is perfectly aligned and set.

I also broke a number of pistons before figuring this out. ;-)

 

so really, is this the right way to do it? I did it and it worked and funs fine, but I might want to do it again to another engine and never really will have enough money to get it done by a shop.

 

There are two accepted ways to install press fit pistons.

The pro shops with lots of capital investment use special press tooling to align the rod and pin so that they can be pressed together exactly square and cleanly. Most of the guys I know who have that ability still freeze the pins first and warm the rods.

Warming the rod ends and cooling the pins is a very common method for pin insertion. So common in fact that there are specialty heaters available for bringing the rods up to temp safely and in a controlled fashion.

The biggest risk one runs is over heating the rod end. I use an oxyacetylene torch with a rosebud to warm my rods, being VERY careful to not heat too much. Over heating could weaken the small end.

The other risk is not centering the pin properly on the rod when inserted. You only have a few micro-seconds before the parts lock together. That's where my fixture comes into play. It assures the pin is centered perfected every time.

I also fabricated a piston pin arbor for removing pins safely without damaging the pistons or rods. I could theoretically use this to install pins, but I can't be 100% certain it's square.

Paul

 

It cost me 4 dollars for the one to be removed and the new piston put on.

 

thank you for taking the time to reply. this is good stuff.

I used a propane torch to do mine. It can only get so hot. I was concerned about the centering of the pin in the rod as well. Mine seemed to turn out alright without any fixtures, probably from luck more than anything else.

 

When I first got my pile of parts it came with 2 flathead engines. I took them to a machine shop that did lots and lots of crank work and everything else. They did caterpillar stuff all the way down to car stuff. Huge machines, giant lathes. It was awesome. So much work was being done. Those blocks had the normal crack at IIRC the #3 exhaust valve.

I went back to get them to do work on my crank and only one guy was left and he was working in basically the closet of the old building with one crank polishing machine and 1 submerged flux machine for welding journals. he was the owner of the old shop. Said that even though he did good work at a fair price guys undercut. suchh is business i guess.