Reaming bronze valve guides
Posted: Mon Jun 29, 2020 10:55 pm
Had my first experience reaming bronze valve guides today.
This is a Fiat twincam aluminum head in which I drove the new guides. The reamers are K-Line bronze guide finish reamers, HSS. I reamed by hand with some gear oil.
A few observations:
- Reaming by hand was hard and slow,but was totally OK with me.
- Reamed finish seems very nice.
- Reamed guide appears smaller in ID than the indicated reamer size by 1/2 thou or more.
- The top of the guide, where the guide OD is not in a bore in the head remains tighter than the rest of the reamed guide by approx 0.0002(?). It appears that the reamer pushes outward the ID of the top of the guide rather than cutting it. The same applies to lesser extent to the unsupported bottom end of the guide.
- This may not be so bad considering that I'm planning on cutting the seats with Neway cutters, which use tapered dead pilots.
- Initial testing with dychem seem to indicate that the guides are pretty well concentric with the existing seat cut.
What fluid or oil should be used when reaming bronze guides?
This is a Fiat twincam aluminum head in which I drove the new guides. The reamers are K-Line bronze guide finish reamers, HSS. I reamed by hand with some gear oil.
A few observations:
- Reaming by hand was hard and slow,but was totally OK with me.
- Reamed finish seems very nice.
- Reamed guide appears smaller in ID than the indicated reamer size by 1/2 thou or more.
- The top of the guide, where the guide OD is not in a bore in the head remains tighter than the rest of the reamed guide by approx 0.0002(?). It appears that the reamer pushes outward the ID of the top of the guide rather than cutting it. The same applies to lesser extent to the unsupported bottom end of the guide.
- This may not be so bad considering that I'm planning on cutting the seats with Neway cutters, which use tapered dead pilots.
- Initial testing with dychem seem to indicate that the guides are pretty well concentric with the existing seat cut.
What fluid or oil should be used when reaming bronze guides?