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Reaming bronze valve guides

General engine tech -- Drag Racing to Circle Track

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Nut124
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Reaming bronze valve guides

Post by Nut124 » 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?

hoodeng
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Re: Reaming bronze valve guides

Post by hoodeng » Mon Jun 29, 2020 11:39 pm

K-Line Bronze lube is one of the best. A low speed electric drill is better to drive a reamer as it keeps rotation constant, stop and start hand reaming is tough on reamers.

Cheers.

BCjohnny
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Re: Reaming bronze valve guides

Post by BCjohnny » Tue Jun 30, 2020 3:53 am

As you've found out, the cutting pressure of the reamer tends to swage the bronze out in the unsupported areas, and to a lesser extent it will relax back in afterwards, the worst of both worlds

I've not used some of the more recommended guide reamers, but you have to keep all reamers moving consistently, with the better cutting fluid you can get locally

A lot of people clean to size with honing afterwards, stone or diamond, for obvious reasons

I've a few select Sunnen diamond sleeves and they're chalk and cheese compared to stones
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon

hoodeng
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Re: Reaming bronze valve guides

Post by hoodeng » Tue Jun 30, 2020 4:29 am

BC that is how i do my c/i or bronze guides. K-Line reamer in drive head to .001"-.0015" under-size then finish with Sunnen hone , check throughout with pin gauges, no hour glassing, taper or out of round. I have checked in the past with internal bore gauges but the consistency has proved that step superfluous.
Sounds like op only has reamers.

Cheers.

BCjohnny
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Re: Reaming bronze valve guides

Post by BCjohnny » Tue Jun 30, 2020 5:33 am

hoodeng

Yes, and no slight on the OP at all but some jobs are not as simple as they may initially seem, rarely are ....... to the guy's credit though he's worked it out

Educational at worst :wink:
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon

hoodeng
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Re: Reaming bronze valve guides

Post by hoodeng » Tue Jun 30, 2020 7:36 pm

One of the most feared statements by a prospective machinist is,,

" Piece of piss mate, how hard can it be"

Cheers.

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