Valve guide insertion

I got the old guides out no problem after heating the head & useing a double drift . I stuck the new guides in the freezer overnight & re-heated the head for about 3 hours. I managed to hammer one guide in although it was hard going - very tight. I immediately started to hammer the other guide (exhaust) in but only got about two-thirds of the way. The drift started bending & no matter how hard i hit, the guide refused to go any further. Then the drift got stuck in the guide & I had to remove it useing pliers. When I tried the valve in the guide, the valve became stuck as well. I wonder if the guide has become miss-shaped? (its a well fitting drift)and it appears the valve stem may be slightly bent as it won't go in the other guide unlike the other valves.
Anyway, Can the inlet guides be fitted useing the drift method without removeing the rocker spindle etc?
By the way, the guides are std size as I checked them against the old one with the calipers.

Wow! they normally tap in quite easily if the head is hot enough and they are the right size. What temperature did you heat it to and what sort of caliper?


Cash

I wonder if the guide has become miss shaped, :?: quit now while you still have cylinder head and go and get quality professenal help

Once the guides are in place they will need reaming using a 5/16" reamer, but the old valves will be bigger than they should be at the top where the rocker has been hammering them, so the valves will need dressing at the top before refitting. But if you are fitting guides I would be going for new valves. You best get the head seen to by a professional, you could end up ruining a head that is going to cost loads of loot to replace if you try anymore hence my orginal post on your request for help.

Thanks for your replys, Cash, i heated the head to 180 c & used a digital micro caliper to measure. I also gave the top edge of the stems a light rub with emery before i tried them in the guide. Hope I've not knackered my head :roll: :shock:

chiefdeal said:

I stuck the new guides in the freezer overnight & re-heated the head for about 3 hours. I managed to hammer one guide in although it was hard going - very tight. I immediately started to hammer the other guide (exhaust) in but only got about two-thirds of the way. The drift started bending & no matter how hard i hit, the guide refused to go any further.

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If you are doing this job for the first time and therefore (quite understandably) being a little overcautious, then you could be working too slowly?

Maybe you needed to get the head a bit hotter to start with, I don't know? But the key to getting the guides in is - SPEED!

You need to work quite quickly, as every second the cold guide is in contact with the head it will be heating up and expanding. So get the head nice and hot, and get the guides in as quick as you can.
If you start to feel a guide getting tight as you knock it in, then knock it out immediately, then re-heat the head, cool the guide, and try again.

I'll agree with Lab you need the head nice and hot {oven} guides in freezer and as Lab has pointed out must be done quickly or heat transfer to guides will cause expansion to guide and they will jam on the way in knock back out and start over .. Doxford

The guide may be getting cocked if using a drift to install. There is a proper tool for this in which one part is seated on the valve seat and then the valve guide is drawn into place by tightening a nut on a threaded rod.

Russ

batrider said:

The guide may be getting cocked if using a drift to install. There is a proper tool for this in which one part is seated on the valve seat and then the valve guide is drawn into place by tightening a nut on a threaded rod.

Russ

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Have you ever worked with an awkward 200* cylinder head :?:

Well I've had the tool for about 30 years and have baked the head 3-4 times in that period. I use heavy fireplace mitts that come up to my elbows. No problem mon!

batrider said:

Well I've had the tool for about 30 years and have baked the head 3-4 times in that period. I use heavy fireplace mitts that come up to my elbows. No problem mon!

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Welding gloves work good too.



At 3 pair for $10 there's not much excuse to not have some.

LAB, I did try as quick as possible to get the guides in but should maybae have re- heated the head after getting the first one in? Anyway, I got the head heated up again & knocked out the guide that didn't get right home. When I try to insert the valve into the guide, it will go in but gets tight about halfway inside the guide but will go in. I think the guide has become warped inside rendering it useless. I
By the way, i've been using welding gloves.

The last guide I did on a B44 head did the same, ie it tightened up after insertion. I put a 5/16" reamer down and it took a small slither of material out and the valve freed up. You only get so many goes at removing and reinserting a guide, each time you do it you remove metal from the head guide bore, better to get the one you have in working than to subject the head to more pain. If after reaming it still is no good eg it needs to much cut off the valve seat to get a seal then go for another guide.

I've thrown in the towel & took the head round to the guy I mentioned in a previous thread. He works on classic race bikes & knows what hes doing. Hes got valve cutting equipment etc. I'm not going to risk anything else. Thanks again for all your help.

That's probably money well spent. If he does it every day you shouldn't end up with stuff I've seen like cracked head or jammed valve hitting a piston.