Showing posts with label gap. Show all posts
Showing posts with label gap. Show all posts

Monday, February 24, 2014

Engine Assembly: Installing The Pistons

Next task on the assembly list was installing the pistons. First they needed to be ringed though. The ring gaps had been inspected so I got on with it. Oil ring assembly was first. They were made from spring steel so installation tools were not needed. I just spread the expansion ring and pushed it in the bottom groove. The side rails followed. I was not worried about the gap positions for now. I'll set them right before installing the pistons.

The compression rings are a bit harder so I bought pliers for them. They were only a few euros and made installing the rings really easy. I just had to make sure the moly faced ring was installed to the top groove and that they were installed the correct side up. This was indicated by a dot on both rings.


Then it was time to insert the pistons to their cylinders. Before the final install, I wanted to check the bearing clearance though. I did that only for the first piston as testing all of them would have been somewhat pointless. First the bearings.


Then pieces of rubber tubing over the bolts to protect the bores.


And installation. I had a cheap ring compressor that I screwed around the piston. I sprayed WD-40 on everything and then tapped the piston in. The compressor unfortunately got stuck a bit and broke as I pulled it out. So much for cheap tools. At least I got the clearance measured with Plastigage again.


As with the main bearings, the result was about 0.002 inches. Acceptable range should be 0.002 - 0.003 inches so I was fine.

I did some reading and apparently the best tool for installing pistons is a tapered aluminium ring that is precision tooled for a single bore size. So I went an bought one by Moroso.


You can only use it for 4.030 inch bore size but I don't think I'll be building another engine any time soon. After pulling the first piston out again, I prepared it and the crankshaft for final install. This meant spreading some assembly lube on the journals and bearings...


...then turning the correct journal to bottom dead center (BDC), oiling the bore, locating the ring gaps and using the tool to tap the piston in. For ring gap positions I used the ones instructed in Millers book.




I have to say that the installation ring was an excellent tool! I did not have a single problem with any of the pistons. They just smoothly slipped in the cylinders. I pushed the piston in until the bearing contacted the journal.


Final step before placing the cap on the rod was checking that the locating tab on all the bearing faced towards the center of the block.


This meant that the rod had been installed correctly on the piston. Everything was OK in that front so I torqued the cap nuts to 24 ft-lbs. And after a few hours of work, all the pistons were in!



Turning the crank was naturally much harder now but everything still moved smoothly so this job was done!

Thursday, February 6, 2014

Engine Assembly: Piston Ring Gaps

After the first few visual checks it was time to get serious. The Sealed Power piston rings that I had bought were pre gapped but I was following "How to Rebuild Small-Block Ford Engines" book by Tom Monroe and it instructed to check everything. So I got busy.

I pushed each ring in its respective cylinder and then squared it with one of the old pistons. I removed the top ring from it and then just pushed the new ring in with it.




Then it was time to check the gap with feeler gauges. After going through every ring, they all seemed to have 0,40 mm (0.0157 inch) gap. I did some reading and it was maybe a little tight. Also, I found more modern suggestions that the bottom ring gap should be a bit larger so any pressure that goes through the top ring is not trapped between the rings.

I clamped a fine toothed file to my table and went through the rings once more. I filed a tiny amount at a time and measured again many times until all top rings had 0,45 mm (0.0177 inch) gaps and bottom rings 0,50 mm (0.0197 inch). Finally I removed the sharp edges from the filed end with 600 grit sandpaper.

I will install the rings to the pistons later when it's time to put them in the cylinders.