Valve guide wear? And valve job with new valves?

How do I determine if I need to have the guides done on my 906 heads? I assume there is a measurement to check the play? The play in the valves seems pretty equal in all directions, with the exhaust valves seeming a bit loose compared to the intakes. When I cover the guide at the top and pull the valve out the intakes generate a very loud pop when they come out of the guide, the exhausts aren't as loud but still make a pop. I would think the exhausts might have a looser tolerance.

Also, the seats and original valves look to be in very nice shape. I want to replace them with one piece stainless valves though. What is the opinion on new valves on an old seat? Obviously a valve job would be better but is it necessary? I have hand lapped new valves into old seats before on a late model turbo application(~20 psi) with 115k miles and the car ran flawlessly. I would think if it could hold up on a boosted application it shouldn't be a problem naturally aspirated.

hi
almost always is a good idea to install new guides in ex side and check the intakes for play .

you got away with the laping on the turbo cars as they were newer and had hard valve seats for unleaded fuel which wear much slower than 906 soft cast seats .

get new hardened seats installed in the 906 and do a 5 angle valve job and they will hold up way longer !

Are you planning on keeping the engine your installing the heads on ?? If you are planning on keeping it wouldn't you be much happier knowing you have a great set of rebuilt heads on the engine rather than just a lap job to get you through ? Do it right and have a good valve job done that correctly locates the valve seat wigth on the valve face for better seating and performance. If your changing out the valves they will vary in diameter compared to your existing valves, so valve guide I.D.'s will need to be checked. Intake stem to guide clearance should be .0015 and exhaust .0015-.002.
Your saying you hear a loud pop when you remove the valve ? Is that being done with oil on the stem or a dry valve ? With oil on any stem it will pop but that isn't a good test of valve guide condition. With experience over time a rebuilder can judge the condition by feel.

logan426

What is a good replacement valve guide type, cast iron, bronze, helicoil or ? and is this something that can be done at home?

Chrysler had a procedure to measure guide wear by measuring the amount of side-to-side motion between valve and guide. You should be able to find that.

Whenever you replace the valve guides you must cut the seats to be concentric with the guides.

Years ago I used the aluminum bronze guides, 0.502" or 0.503" in diameter pressed into 0.500" reamed holes which were drilled using a drill bit with a pilot the size of the valvstem, then reamed to size. You can find all of this stuff in Goodson's website. The problem is that try as you might you are drilling the old guide out using the worn hole and you'll be off a little bit.

I used Neway cutters to cut the seats.

I was building smallblock chevies and using Manley economy valves. I'd take them out of the box and put them in the valve grinder and about 8 out of 10 needed a touch-up to get the valve head concentric with the stem. What a disappointment.

Maybe valves are better now.

I have no experience with spiral inserts or sleeves.

Unless you have a fortune invested in your 3/8 stem valves, I'd seriously consider moving to an 11/32 stem with cutdown shank in the bowl.

R.

Take your heads to a good shop near you and have the guides checked out or replaced before putting in new valves and have a valve job done. I also have the replacement bronze guide liner tooling in my Radiac Abrasive catalog and web-site under Automotive aftermarket at www.radiac.com but you need to have experience when boring, installing and sizing valve guides.

logan426

The heads would be getting replaced not too far down the road, so I'm just trying to keep investment in them minimum. If I have to sink much into them I will be much too tempted to buy aluminum, but at this point I'm just trying to get the engine back together and running if you get my drift.

If you are just trying to get a year or two out of it, and they pass the finger pop test, and you are lapping them in, I would try it. Have done it in the past. Get some standard equipment valve stem seals, being sure to put the deeper seals on intakes.

I agree. If you are just trying to get another couple of years before an upgrade then put on new stock seals, make sure the valves are seating all the way around and run it.
R.