valve guide reaming

[sgellis]

Rebuilding stock 36h heads. Installed new valve guides and run ream through them.

The new valves seem tight but I have no experience with guides. I need to give the valves a very light push all the way in or out (no lube). I was expecting them to drop in/out with just gravity. Did a very quick measure and they appear to be within spec.

How do new stainless valves feel when putting them in newly reamed brass guides? I am going to take the time to do accurate measurements and go by that but it is nice to have some idea of what things should feel like.

If they are a little tight could I run a hone through them to get to spec?
https://www.amazon.com/Research-FLEX-HONE-Cylinder-Abrasive-Diameter/dp/B002XUL19Y

Thanks
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My camper interior build
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[Brian_e]

The intakes should have .0015" clearance, and the exhausts should have .0025" clearance.

If they are the slightest bit tight now, they will bind up and stick once its running. The valves should fall in and out of the heads dry.

I tried a lot of things, but found a AV&V carbide reamer to work the best. reagular HSS reamers will just sieve up in the guide.

Any real engine machine shop should be able to quick hone a few tenth's out for you.

I am pretty sure the ball hone will get you an hourglass shaped guide before you finish.

Brian
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[modok]

If the stem has the right clearance is ok, yet is not free.... then the guide must be curved.

This is why we like carbide reamers or diamond hones.
HSS reamers sometimes not rigid enough to fix curved holes.

I can't explain how it feels. Learn to use a micrometer.

[Vanapplebomb]

Same experience with HSS, even in soft materials like aluminum. Smaller HHS reamers have a really bad tendency to follow a hole when going deep.
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1800 Type 4 Berrien 295

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[sgellis]

[sgellis]

[modok]

What size does the reamer measure?
Straight or reverse flute?

If the reamer does not work from day one, there is no trick, other than get one that does work.

There might be some tricks to get the most holes without it wearing out, or to squeeze the last few holes out of it, or resharpen it, or getting the rpm and feed right.
but if it doesn't work then quit doin it. It's just going to get worse. Bronze is springy and grabby, you need a really sharp edge to cut it clean.

Or is it the wrong size?
Who sold it to you? Ask them what it's supposed to do.

[mark tucker]

reamed guides need to be honed with proper hone.and no not a fucking dingle berry hone. a small burr /bump /dent on stem will drag also. Ive seen guides reamed too big have too much drag and too much clearance..

[jimmyhoffa]

As for honing I've used one of those Sunnen P-190 Honall sets on guides very successfully a few times when I was an engineer there, but Sunnen also makes what they call a "MMT" hone which is this multi-stone mandrel hone thing that works sorta like a tiny-ass version of their normal rigid cylinder hones. I used some that had 3 and 4 stones and they both worked INSANELY well at sizing and truing the guides. I just figured I'd mention them here since they pop up on Ebay and stuff all the time sometimes super cheap from industrial surplus/tooling sellers who don't know what they are. They remove material way faster than the occasionally agonizing but effective Honall, which satisfies my total lack of patience in general.
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[dogmeat]

Modok hit the question... what size reamer (and what is the stem diameter). you do not need to hone the guide if you have the right reamer and use it correctly. But... this will depend on the available reamers and how tight you want to hold the clearance.

you WILL need to surface the valve seats to true them to the new guides. and no, lapping will not do it, they need to be recut (well... 1 in a 100 might be close enough to lap but don't count on that)

[sgellis]

Spent some time tonight with the heads.

I reamed by hand the first time. Decided to use a drill at about 2-400 rpm with lots of cutting oil. Didn't make much difference but all holes are the same size.

Did both heads. Exhaust valves fall in and out but don't have enough clearance.

Three of the for intake guides are curved. Valves push in so not curved by much. Seam to be curved where they exit on the combustion side. The guide comes through the casting at an angle so suspect that pushed the end off center. Added photo but it doesn't really show the casting angle well.

Is there a trick to preventing the curve or is this normal and a good reame would fix it anyway?

All holes measure 6.95mm
Exhaust valve stem 6.93
Intake valve stem 6.94

Reame is a .275" - 6.98mm. Odd it is only cutting a 6.95 hole.

Looking at the spec and a hole between 6.99 and 7.01 would work for both. At that clearance I wouldn't have noticed the curve.

So what to do... Definitely need a bigger reame or something to cut the holes.

This engine will get about 500 very easy miles a year so perfection in not exactly needed. I could get a 7mm HSS reame cheap and hope for the best. I don't really want to spend 500 or more for a tool to do a perfect job when I could get by less on an engine that will get little use... But I also don't want a cloud of smoke trailing behind me.

_________________
My 64 Kombi restoration
My camper interior build
My 54 standard restoration
The Nova Scotian Barndoor (YouTube)
The Nova Scotian Barndoor (CAD drawings)

[modok]

Nice. You are learning fast.
yes indeed the hole can be that much smaller than the reamer.... How much is the guide expanding and how much is the reamer squeezing? some of both!

The guide bore coming out at an angle isn't good. Next time use a little oval carbide burr to go in there and relieve the press on the long side so the end of the guide bore is 90 degrees.

Still a bit too tight, but almost there, will have to keep doing something until they aren't... and that could end better or worse but it's better than doing nothing. try both directions? 500rpm, slow feed with solvent for coolant? Valve getting stuck in the guide is a common problem, see reports of that all the time. Why did my pushrod fall off the rocker? Some of that is guide problem, also lubrication. I advise to lube with gear oil.
"One pass diamond hones", hones, carbide reamers, all do help to make a straighter hole. A very sharp straight flute steel reamer can do pretty good until it gets dull, but quality varies. it is a PITA for sure.
i don't even have a go-to brand anymore. But just slightly larger reamer would be good to have. OR
I haven't tried one of these yet but they might be......worth the money
https://www.ebay.com/itm/183918594238?chn=ps&_...2398c7db7d

[RandyV]

Part of the problem is that reamers need something to take a bite out of. Not sure if you measured the guides beforehand but reamers want something between 3-5% of their target left in the hole to ream properly. In this case .265" or less. Once a hole is reamed....trying to get small sub-1% increments afterward becomes very difficult.

You could try "lapping" the rest in with some lapping compound and an old valve as that's about what you have left to clear and the valve stem and compound will work to blend those spots of resistance thru the bore.

It sounds like you're close and you might waste money jumping up in reamer sizes until you found one that "bit" enough to make a difference and might only find out you went too far at that point.

My $.02

[sgellis]

Thanks. Appreciate the help

Thought on it a bit. I could get a 7mm carbide ream for $240 and be done with them.

Could get a larger HSS ream at $55 and get my clearance but will likely keep a bit of curve. Also the expanding diamond ream but also likely to keep some curve. Shouldn't be a problem for the valves though the guides may ware faster than normal. My concern is seat grinding. If the pilot is held at more of an angle than the valve runs then it will be off. Pilot being tapered will try to hold more at the bent end I think. Maybe it wouldn't be enough to matter.

Other option is remove the intake guides, cut casting to get 90º exit for guide. New guides and larger HSS reamer. That should get a good job and be inexpensive compared to a carbide ream.

The lapping compound sounds interesting...

Typing this I think I decided to try the lapping compound on the intakes as I believe replacing them is likely the best option for me. If lapping compound actually works and I feel confident the grinding pilot will set correctly then great. If not I just replace the intake guides and get a larger HSS ream.
_________________
My 64 Kombi restoration
My camper interior build
My 54 standard restoration
The Nova Scotian Barndoor (YouTube)
The Nova Scotian Barndoor (CAD drawings)

[Brian_e]

Lapping steel on steel is one thing, but using lapping compound with steel in soft bronze doesn’t sound like a good idea to me. Sounds like you will be imbedding lapping compound into the bronze forever, and then wearing the valve stem down every time the engine is running.

If it was me, I would bite the bullet and do new guides, and a correctly sized reamer. You might be able to get by with a HSS reamer for the small quantity you are doing. I spent a while trying to get HSS to work, and never could get it. It never wants to bite, and seems to grab more than cut. Turning it slow with no lube might be your best bet.

If it’s hackery you want just to get it on the road, why not just spin the valve stem in a drill on a worn belt sander? That is just as crude as the other incorrect methods.

Brian
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[modok]

Lapping! right
Except mainly the abrasive will stick in the bronze and wear the shaft down.
But it's a good idea, just need to work on it a bit. How can this be solved?

How about diamond abrasive
nickel plated onto a steel shaft

now we are cooking

but it might still need some means of adjusting the size as it wears down,

that's what the threaded thing on the end is for.

[sgellis]

Haha

Do you think the diamond reamer will take enough curve out to allow good seat grinding? I guess worst case the valve doesn't seat and I change the intake guides.

Little concerned the 7mm diamond reamer will fit in a 6.95 hole. It doesn't state any range. Maybe I can find some size specs somewhere on these.
_________________
My 64 Kombi restoration
My camper interior build
My 54 standard restoration
The Nova Scotian Barndoor (YouTube)
The Nova Scotian Barndoor (CAD drawings)

[modok]

It should work very nice, I just can't vouch for the quality of the Ukrainian diamond hone. Been waiting for an opportunity to try it myself.
I have a few different sytles of one pass hones and they do all make a very straight hole. The main downside is they only take out about .001" per pass, anymore and they try to jam, so ideally you want two or three of them so you can step up the size gradually.

I have bought some Russian diamond grinding wheels and they work fine, at 1/3 the price of the competition.

[RandyV]

There are specific lapping compounds safe for brass/bronze/copper etc.

They will cut, then diminish, then dissolve. Perfectly safe and still the smartest way I think to accomplish what you're after.

https://www.newmantools.com/lapping/time.htm

There are also diamond compounds that could be used similarly and may accomplish what modok is thinking too.

At least a couple good options. And NO WAY should you pay $240 for a carbide reamer of that size (solid *or* tipped)....that's WAY too expensive!!

[Jason37]

Maybe a little unconventional, but with you being from NS, I would ask these guys who they use to rebuild their heads. http://www.britcycle.com/ cause every brit bike I have owned or worked on needed guides.