Should I install new valves?

Sun Feb 16, 2014 7:47 pm

Hello Team,

A friend asked me to help him install new valves in his cub engine. He claimed it was smoking and since, after taking off the head, he felt a little slop when he wiggled the valve, he order a complete valve kit. I don’t think I have the tools to replace the valve guides so I have a dilemma. Do I install the new valves into the old guides and lap the valves as best I can or should I use the old valves, since they don’t look bad and lap them good.

I’m concerned that I’m not going to be able to lap the new valves into the existing block and we don’t have plans on taking it to the machine shop. I do plan on installing new rings since the measurements and condition of the piston and bore seem fine.

Any advice would be appreciated.
:mrgreen:

Re: Should I install new valves?

Sun Feb 16, 2014 10:36 pm

I have never changed them, but I do not think it needs any specialty tools to do a valve job, HOWEVER, this is a flat head, so worn guides have very little to do with smoking or oil consumption.

Re: Should I install new valves?

Sun Feb 16, 2014 10:53 pm

isnt smoking typically a sign of bad piston rings? Oil getting past them and burning?

You're gonna need a valve spring compressor, but thats all I know.

Re: Should I install new valves?

Mon Feb 17, 2014 8:50 am

"this is a flat head, so worn guides have very little to do with smoking or oil consumption." John, I had not known that fact. However now that I see it, it is apparent why that is so. Thanks

Re: Should I install new valves?

Mon Feb 17, 2014 9:54 am

to replace the guides you have to remove the engine and remove the cam shaft. The guides need to be pressed out from the top. with the cam in place it doesnt allow room to get the guides out. worn guides will causes excessive wear on the seats and valve face. I have yet in 40 years seen a valve out of a cub not need to be faced on a valve machine. If the guides are excessivly worn it can contribute to oil burning in a small way.

Re: Should I install new valves?

Mon Feb 17, 2014 10:51 am

Thanks for the advice and it’s good to know the valve guides are not likely the cause of the engine smoking.

My dilemma is, since I’m not grinding the valve seats: do I use the old valves, which appear okay or install the new valves. I’m afraid the new valves and worn seats will not match as well as the old valves and therefore I’d be better off using the old valves. In either case i plan to lap the valves.

It would be interesting to know where I could buy a valve seat grinding tool that would allow me to grind the block in my garage. I thought I saw one once that used a pilot stem, which went into the valve guides and then allowed you to drop a sanding tool over the valve seats. Does anyone know where I can get one of those?

Re: Should I install new valves?

Mon Feb 17, 2014 11:04 am

Do a search for Neway valve seat cutter. Easy to use.

Bob

Re: Should I install new valves?

Mon Feb 17, 2014 12:07 pm

Valve seat cutter/grinder. They are portable. Try one of the small engine shops and see if the mechanic will stop by after work to touch up your valve seats.

Actually, I would try lapping the valves and seats first to see what happens.

Re: Should I install new valves?

Mon Feb 17, 2014 1:25 pm

I pulled my guides out from the top, without removing cam shaft. Used a bolt, and assorted washers...they came rite out...then I put the new guides in the freezer overnight, warmed the block...and the new ones went in easily...

Re: Should I install new valves?

Mon Feb 17, 2014 4:57 pm

Time to check pistons, rings, and bore, for the cause of the oil burning. It likely isn't valves.
Ed

Installing Valve Guides

Mon Feb 17, 2014 8:56 pm

Thanks for all the great advice. I did test fit the new valve into the new valve guide and there is a noticeable difference regarding play in the old ones compared to the new ones. Since I have the new valve guides in hand, I think I’m going to try and remove the old guides with a nut and bolt described above. That is:

Place the head of the bolt (with washers enough to cover the valve opening on the flat head) down the value guide from the top. Place the nut onto the bolt under the valve guide and turn the nut and hopefully it will force the guild upwards. What do you think?

My next question is what kind of jig do I need to make to make sure the valve guide is replaced to the proper depth?

Thanks again, I really enjoy messing with these old engine. :D

Re: Should I install new valves?

Mon Feb 17, 2014 9:50 pm

I used a 6" long metal ruler marked off in 64th of an inch increments and a sliding "T" head. This was on a 50 chev 6 cylinder engine.

Measure the height of the installed valve guides and install the new guides to the same height.

Re: Installing Valve Guides

Tue Feb 18, 2014 7:51 am

Virginia Joe wrote:Thanks for all the great advice. I did test fit the new valve into the new valve guide and there is a noticeable difference regarding play in the old ones compared to the new ones. Since I have the new valve guides in hand, I think I’m going to try and remove the old guides with a nut and bolt described above. That is:

Place the head of the bolt (with washers enough to cover the valve opening on the flat head) down the value guide from the top. Place the nut onto the bolt under the valve guide and turn the nut and hopefully it will force the guild upwards. What do you think?

My next question is what kind of jig do I need to make to make sure the valve guide is replaced to the proper depth?

Thanks again, I really enjoy messing with these old engine. :D


Yes that will work..if I remember correctly..once the nut on the bottom reaches the block, you will need to remove the nut and add some spacers that are smaller in diameter than the guide to finish pulling it all the way out...Warming the block and Putting the new guides in the freezer overnight worked like a charm when re-installing..take them out of the freezer one at a time when installing...I used an old guide and bolt as an alignment tool to gently drive them back in...they should go in real easy to the depth you measured on the originally installed guides....Tom

Re: Installing Valve Guides

Tue Apr 29, 2014 11:56 am

Tractorboy3 wrote:
Virginia Joe wrote:Thanks for all the great advice. I did test fit the new valve into the new valve guide and there is a noticeable difference regarding play in the old ones compared to the new ones. Since I have the new valve guides in hand, I think I’m going to try and remove the old guides with a nut and bolt described above. That is:

Place the head of the bolt (with washers enough to cover the valve opening on the flat head) down the value guide from the top. Place the nut onto the bolt under the valve guide and turn the nut and hopefully it will force the guild upwards. What do you think?

My next question is what kind of jig do I need to make to make sure the valve guide is replaced to the proper depth?

Thanks again, I really enjoy messing with these old engine. :D


Yes that will work..if I remember correctly..once the nut on the bottom reaches the block, you will need to remove the nut and add some spacers that are smaller in diameter than the guide to finish pulling it all the way out...Warming the block and Putting the new guides in the freezer overnight worked like a charm when re-installing..take them out of the freezer one at a time when installing...I used an old guide and bolt as an alignment tool to gently drive them back in...they should go in real easy to the depth you measured on the originally installed guides....Tom


Just finished removing all of my old valve guides. Used a 5/16-24 x 4 inch grade 8 bolt, fender washers stacked on top of block. Pulled the guides up to where the nut was close to the underside of the block. Made a spacer by using a 1/4 inch pipe nipple drilled out to fit the bolt, and about 3/4 of an inch long. Buy one long enough you can cut the threaded portions off. Remove enough washers on top till the spacer will fit on the bolt and allow the nut a full thread and keep turning. Had all mine out in a couple of hours.

Re: Should I install new valves?

Tue Apr 29, 2014 3:03 pm

I use a 5 lb slap hammer with a bolt on the end and nut, pulls all the guides out in 10 minutes
Tim