Thanks for the info. As for a photo.... Click on "Upload a File" found under the comment box. Find your file and just drag and drop it down into the comment box.
E: Engine Big End Replacement
- Thread starter Cyborg
- Start date
Thanks for the info. As for a photo.... Click on "Upload a File" found under the comment box. Find your file and just drag and drop it down into the comment box.
So tuning for Speed says that if there is any more than .002" diametral clearance, it is too much. Anyone have any thoughts on this. Presumably if I end up with .001 it will be ok. It states that the rod should just slide into place, but wondering if .0005 is too snug.
If I was going to be doing this more often... although the expanding mandrel quite well, I would likely break down and buy one from this fellow. There is some reading material on his site about lapping.
http://www.americanlap.com/Internal Laps.htm
http://www.americanlap.com/Internal Laps.htm
Could you have got away without doing anything ?, Was it out of round ?, Cheers Bill.
Short answer is: No I had to remove material and yes it was out of round.
The long answer is: The Alpha big end that I used was NOS.. as in very old and had the standard OD on the outer race. Since that wouldn't allow me the option of honing the rod big end eye to make it round, I figured (there once was a man from Nantucket) I would just press in the new outer race and hope for the best. In an effort to get the new outer race in straight, I machined up a round piece of MS with a hole big enough to accept the old outer race while supporting the rod. I drove the old race out only by about 1/8 and then put the rod in the oven at 200f. The new outer race went into the freezer. The new outer race was then pressed in, using a flat piece of steel on top. The thought being that when using the new outer race to press out the old one, the old one would help guide the new one in straight. As for rods being out of round, if they are inherently weak in that area, then when you hone the old rod round and press in a new outer race who's to say it won't go out of round again. Maybe in some cases, if it's minor you can ignore the out of round rod and just deal with it after the race is pressed in. Anyway, after it was pressed in, the race was slightly out of round plus it needed material removed to get it to correct size. Because I did it this way, I don't know how much the rod would have been out of round. There is no doubt some luck was involved given this was my first one, but definitely happy about the way it turned out. It's round and it fits. Again, I was surprised how well the "hone" worked. An old rod and valve lapping compound was used to true it up. The only painful part was cleaning it repeatedly between grades of compound. As long as the hone was kept snug in the race, there was no problem moving the rod back and forth in perfect alignment. No rocking or bell end. I just let the rod run up against the bed of the lathe.
The long answer is: The Alpha big end that I used was NOS.. as in very old and had the standard OD on the outer race. Since that wouldn't allow me the option of honing the rod big end eye to make it round, I figured (there once was a man from Nantucket) I would just press in the new outer race and hope for the best. In an effort to get the new outer race in straight, I machined up a round piece of MS with a hole big enough to accept the old outer race while supporting the rod. I drove the old race out only by about 1/8 and then put the rod in the oven at 200f. The new outer race went into the freezer. The new outer race was then pressed in, using a flat piece of steel on top. The thought being that when using the new outer race to press out the old one, the old one would help guide the new one in straight. As for rods being out of round, if they are inherently weak in that area, then when you hone the old rod round and press in a new outer race who's to say it won't go out of round again. Maybe in some cases, if it's minor you can ignore the out of round rod and just deal with it after the race is pressed in. Anyway, after it was pressed in, the race was slightly out of round plus it needed material removed to get it to correct size. Because I did it this way, I don't know how much the rod would have been out of round. There is no doubt some luck was involved given this was my first one, but definitely happy about the way it turned out. It's round and it fits. Again, I was surprised how well the "hone" worked. An old rod and valve lapping compound was used to true it up. The only painful part was cleaning it repeatedly between grades of compound. As long as the hone was kept snug in the race, there was no problem moving the rod back and forth in perfect alignment. No rocking or bell end. I just let the rod run up against the bed of the lathe.
I notice during this thread no mention being made of side clearance. This is just as important. If the oil cannot escape it will "stay around" for too long and cook. Wrecking all your hours of work. If it can't escape, no fresh can enter. As the prophet said-think on.
I have another rod and someone ground 2 grooves per side 180 apart to let oil escape. Seemed to me to be a strange thing to do given the side clearances I have seen. I don't know yet where the side clearance will end up on mine, but figured there would be plenty. Installing new thrust washers, so will make sure it is sufficient.
Last edited:
I checked and with new thrust washers and new big end, side clearance looks like it will be fine. Being a Comet crank it's easier to deal with. Pressed the pin into the drive side flywheel, which showed slightly less interference fit than the timing side. Quite happy with the amount of force it took to press it home.
Here I am thinking out loud again.... not having any sort of jig for aligning the flywheels, I'm thinking of putting the drive side into a chuck mounted to the bed of the mill, centring it with the quill, (using the centre in the inboard side of the mainshaft and confirming with running a dial gauge around the circumference of the flywheel) , mounting the timing side flywheel mainshaft in the quill with a collet, make sure it is running true, zero the DRO. Then lower the timing side down (going to try and set the quill up so it is totally neutral) and using a slightly modified puller, get the pin into the timing side flywheel as far as possible, then finish in the press. Feel free to rain on my parade or make suggestions. I think I can get as close this way as using some of the frightening alignment tools I have seen on the inter webs.
Here I am thinking out loud again.... not having any sort of jig for aligning the flywheels, I'm thinking of putting the drive side into a chuck mounted to the bed of the mill, centring it with the quill, (using the centre in the inboard side of the mainshaft and confirming with running a dial gauge around the circumference of the flywheel) , mounting the timing side flywheel mainshaft in the quill with a collet, make sure it is running true, zero the DRO. Then lower the timing side down (going to try and set the quill up so it is totally neutral) and using a slightly modified puller, get the pin into the timing side flywheel as far as possible, then finish in the press. Feel free to rain on my parade or make suggestions. I think I can get as close this way as using some of the frightening alignment tools I have seen on the inter webs.