valve and guide clarification

[Dick Eastman]

Do the valve guides press out from the combustion chamber toward the tappet cover? I presume the circlips on the guide can remain in place to do this, after heating the cylinder head. I have contemplated removing the circlips and pressing out from the tappet side down because of possible corrosion, etc on the combustion side scoring the guide bore. Any thoughts/recommendations here? The circlips are in a somewhat constricted area.
Also, I have been going through the valves I have on hand, and noticed some of the exhaust valves are non-magnetic on the head only [stems are magnetic], and others are entirely non-magnetic. When did Honda make this change, and which are preferable for a rebuild?
Thanks,
Dick

[G-Man]

Dick

I got my head cleaned up first and then pushed the guides out from the inside. Pretty difficult to get those circlips off when they are still in the head.

As for the valve, I would think it was a cost-saving measure. Austenic stainless for the head and a cheaper alternative for the stem. Probably friction-welded together.

G

[Dick Eastman]

Dick

I got my head cleaned up first and then pushed the guides out from the inside. Prettu difficult to get those circlips off when they are still in teh head.

As for the valve, I would think it was a cost-saving measure. Austenic stainless for the head and a cheaper alternative for the stem. Probably friction-welded together.

G

Thanks, Graham.
From stated above, the earlier exhaust valves were entirely stainless?
As for the guides, I noticed I could get some movement on one of the guides when I had heated the head up to remove the cams, but my objective at the time was cam removal, not guides. BTW, the cams came out very easily after heating the head in the oven @ 250 deg for about 45 minutes - I do not like driving parts out of interference fits. I did mic the cam bearings, and set a bore gage to that diameter, and measured the cam bearing bores: they were .0003" larger than the bearings. Honda cast a clearance at the 12 o'clock position in the cam bearing bores, and I would presume that when the head is torqued down, the bearing bores close minutely to lock the bearings down.
I'm going to turn up a piloted driver for the guides [7mm pilot], and warm the head up again, and try removal. I do have some pitting on the combustion side of the guides, and my primary concern is scoring the guide bores - I'll have to go gingerly to avoid that.

[Nick]

Don't know if this is feasible on the Honda head, but on Triumphs, etc. (and airplane engines) it's common practice to machine off the top of the guide, then bore it out, and only then knock it out the same direction it went in, thereby eliminating what you hinted at above: damaging the head by knocking out a guide coated in carbon, etc.

Of course, this all takes a lot of time and effort, so most people don't bother--but then maybe that's why one of your guides is loose.

[G-Man]

Dick

Yes - I guess that the earlier valves would have been all stainless. Not so good as a bearing material in the guide but better for the head in contact with hot gases.

I understand your feelings fro driving out the guides but the aluminum will expand more than the cast iron guide so will release the interference a little.

Here is a picture of the tool I made to knock my guides out and the guides themselves.

G

Dick

I got my head cleaned up first and then pushed the guides out from the inside. Pretty difficult to get those circlips off when they are still in the head.

As for the valve, I would think it was a cost-saving measure. Austenitic stainless for the head and a cheaper alternative for the stem. Probably friction-welded together.

G

Thanks, Graham.
From stated above, the earlier exhaust valves were entirely stainless?
As for the guides, I noticed I could get some movement on one of the guides when I had heated the head up to remove the cams, but my objective at the time was cam removal, not guides. BTW, the cams came out very easily after heating the head in the oven @ 250 deg for about 45 minutes - I do not like driving parts out of interference fits. I did mic the cam bearings, and set a bore gage to that diameter, and measured the cam bearing bores: they were .0003" larger than the bearings. Honda cast a clearance at the 12 o'clock position in the cam bearing bores, and I would presume that when the head is torqued down, the bearing bores close minutely to lock the bearings down.
I'm going to turn up a piloted driver for the guides [7mm pilot], and warm the head up again, and try removal. I do have some pitting on the combustion side of the guides, and my primary concern is scoring the guide bores - I'll have to go gingerly to avoid that.

[LOUD MOUSE]

Hello Dick.
I have a couple of questions about the guides and cam bearings.
What was the reason to replace the guides?
The wire Cir Clip is a limiter to stop the depth of the guide to an exact depth as the guide is installed from the top.
I've found "2" bad guides in all the heads I've rebuilt.
Both were intake and both had cracked in halt at the lower groove made to allow air to inter when the valve opens. (not much air and after time HONDA removed that from the guide/head.)
All the actual HONDA valves I have are the same as to magnetism. (I have plenty here and they usually have a "B" cast on the head but not all the exhaust but most do have the "B".
All of the intake is steel which is drawn to the magnet.
All of the exhaust will not draw to the magnet.
Beware of the CHEAP after market valves on eBay.
HONDA shows using a piece of wood and rubber mallet to drive the cams out.
I use Brass or Aluminum rod.
Did the 250 degree heat ruin the neoprene on the advance weights?
Do you think there may be a possibility that the steel dome may come loose if the head is heated several times? (I've had 2 leakers and I hadn't heated either of them.)
. ....................lm

Dick

I got my head cleaned up first and then pushed the guides out from the inside. Prettu difficult to get those circlips off when they are still in teh head.

As for the valve, I would think it was a cost-saving measure. Austenic stainless for the head and a cheaper alternative for the stem. Probably friction-welded together.

G

Thanks, Graham.
From stated above, the earlier exhaust valves were entirely stainless?
As for the guides, I noticed I could get some movement on one of the guides when I had heated the head up to remove the cams, but my objective at the time was cam removal, not guides. BTW, the cams came out very easily after heating the head in the oven @ 250 deg for about 45 minutes - I do not like driving parts out of interference fits. I did mic the cam bearings, and set a bore gage to that diameter, and measured the cam bearing bores: they were .0003" larger than the bearings. Honda cast a clearance at the 12 o'clock position in the cam bearing bores, and I would presume that when the head is torqued down, the bearing bores close minutely to lock the bearings down.
I'm going to turn up a piloted driver for the guides [7mm pilot], and warm the head up again, and try removal. I do have some pitting on the combustion side of the guides, and my primary concern is scoring the guide bores - I'll have to go gingerly to avoid that.

[LOUD MOUSE]

What caused the HEAT RING?. ................lm

Dick

Yes - I guess that the earlier valves would have been all stainless. Not so good as a bearing material in the guide but better for the head in contact with hot gases.

I understand your feelings fro driving out the guides but the aluminum will expand more than the cast iron guide so will release the interference a little.

Here is a picture of the tool I made to knock my guides out and the guides themselves.

G

Dick

I got my head cleaned up first and then pushed the guides out from the inside. Pretty difficult to get those circlips off when they are still in the head.

As for the valve, I would think it was a cost-saving measure. Austenitic stainless for the head and a cheaper alternative for the stem. Probably friction-welded together.

G

Thanks, Graham.
From stated above, the earlier exhaust valves were entirely stainless?
As for the guides, I noticed I could get some movement on one of the guides when I had heated the head up to remove the cams, but my objective at the time was cam removal, not guides. BTW, the cams came out very easily after heating the head in the oven @ 250 deg for about 45 minutes - I do not like driving parts out of interference fits. I did mic the cam bearings, and set a bore gage to that diameter, and measured the cam bearing bores: they were .0003" larger than the bearings. Honda cast a clearance at the 12 o'clock position in the cam bearing bores, and I would presume that when the head is torqued down, the bearing bores close minutely to lock the bearings down.
I'm going to turn up a piloted driver for the guides [7mm pilot], and warm the head up again, and try removal. I do have some pitting on the combustion side of the guides, and my primary concern is scoring the guide bores - I'll have to go gingerly to avoid that.