valve and guide clarification

[G-Man]

I use a butane gas torch to heat up the head.

G

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.

[G-Man]

I use a butane gas torch to heat up the head.

G

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.

[LOUD MOUSE]

OK.
What was wrong with the guides?. ..............lm

I use a butane gas torch to heat up the head.

G

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.

[Dick Eastman]

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.

Good point, Nick.
The manual calls for heating the head for guide removal, and while it was still hot from the cam removal op, the guide with the least corrosion [on the combustion side] would move about 1/8", the others were tight - more corrosion on ends? I'll have to be careful, in any event.

[Dick Eastman]

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
Thanks, Graham.
That tool is what I have in mind - piloted brass. The pics of the guides are helpful - thanks!

[Dick Eastman]

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

Thanks, lm
I am considering making new valve guides from SAE no. 62 hard bronze - an excellent material for severe use. The ends of my guides are pitted, and I am concerned with carbon build up around the stem.
All of my exhaust valves with a "B" are entirely non-magnetic - is that your preference, lm?
250 degrees is only 38 deg above boiling, hot enough for the aluminum to expand, and less than the operating temps of the head. I put a couple of pennies on the point cam under my vise grip jaws to protect it, and the cam came out with little effort. The same for the opposite cam. The cam bearings are a press fit on the cam, and I have always been hesitant driving bearings out, whereby the races and balls take the shock load.
As for the neoprene on the advancer weights, they do not seem to be affected; besides, I am using the Sasche-Elektronic crank-mounted ignition, and removed the weights and point cam from the camshaft, and will cover that end with a cl77 cam end cover. I cut off the tach drive from the l.h. cam, counter bored the end, and made a tool steel washer to fit the counter bore. I shortened the expander bolt, re-threaded it, and made all to fit under a cl77 l.h. cam end cover. BTW, the weight of the stock points system parts I removed was 269 grams [ about 9.5 oz ].

[G-Man]

They were very loose on the new valves I put in.

G

OK.
What was wrong with the guides?. ..............lm

I use a butane gas torch to heat up the head.

G

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.