Valve guide clearance

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Robert Bente
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Valve guide clearance

Post by Robert Bente » Thu Jan 24, 2019 8:23 pm

I’m replacing my old two piece valves with modern stainless valves. They are original standard .312 valves. I measured the guides at varying places and it’s a pretty consistent .317. Should I stick with the standard size, or ream .010 over and get the 10 over size valves?
The 1916 engine appears to Have very little wear. Standard size bore with standard size cast pistons and rings.
Just for fun I pulled the rear end to check for Babbitt vs bronze thrust. Lucked out, someone replaced with bronze, probably in 1955?
r/s Bob

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Re: Valve guide clearance

Post by RajoRacer » Thu Jan 24, 2019 8:35 pm

Currently available valves are .015 or .030 oversize. S.S. Chev. valves are .030 over and have a slightly larger head diameter for worn original valve seats but one must use adjustable lifters.


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Re: Valve guide clearance

Post by Kerry » Thu Jan 24, 2019 8:45 pm

It will run OK with .005" clearance, also it's possible that your bronze thrust washers are original, they changed to white metal in 1916.


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Re: Valve guide clearance

Post by rgould1910 » Fri Jan 25, 2019 1:25 pm

Speaking of thrust washers, my former Jan or Feb 1916 touring car had the original thrust washers. They were bronze not babbitt.


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Re: Valve guide clearance

Post by Steve Hughes » Fri Jan 25, 2019 4:11 pm

How did you measure the guides? I have never figured out how to measure the ID of a small bore. Thanks.

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Re: Valve guide clearance

Post by Ruxstel24 » Fri Jan 25, 2019 4:21 pm

There's various styles of bore gauges.
This is the less expensive type...
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Re: Valve guide clearance

Post by Steve Hughes » Fri Jan 25, 2019 4:32 pm

Thanks for the reply, Dan. I have those, and can measure the larger bore diameters like cylinders. But how do you measure a small bore like valve guides? He said he was measuring a consistent .317". That is a much smaller diameter than can be measured by one of the telescoping bore gauges that you show.
Last edited by Steve Hughes on Fri Jan 25, 2019 4:39 pm, edited 1 time in total.

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Re: Valve guide clearance

Post by Ruxstel24 » Fri Jan 25, 2019 4:35 pm

Steve Hughes wrote:
Fri Jan 25, 2019 4:32 pm
I have those, and can measure the larger bore diameters. But how do you measure a small bore like valve guides?
One set I have goes down to 5/16"...
Some go down to near zero, but those are a little pricey...


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Re: Valve guide clearance

Post by Steve Hughes » Fri Jan 25, 2019 4:42 pm

I was editing my post while you were typing. I had no idea that there were gauges like that that were so small. I will have to check to see what my smallest gauge will measure.


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Re: Valve guide clearance

Post by Steve Hughes » Fri Jan 25, 2019 4:48 pm

Just checked my gauges, and my set does go to 5/16". I'll be darned. Learned something today. Thanks for the input.


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Re: Valve guide clearance

Post by Kerry » Fri Jan 25, 2019 4:54 pm

A ball gauge, set to bore size and measure with mic.
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Re: Valve guide clearance

Post by Scott_Conger » Fri Jan 25, 2019 5:11 pm

Ball gauge per Kerry is the tool to use. Measure top, middle, bottom of the bore. Mic the OD of the fixed gage when withdrawn from bore.
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Re: Valve guide clearance

Post by Scott_Conger » Fri Jan 25, 2019 5:11 pm

OOPS...per Frank, above, not Kerry
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Re: Valve guide clearance

Post by Ruxstel24 » Fri Jan 25, 2019 5:29 pm

Scott_conger wrote:
Fri Jan 25, 2019 5:11 pm
Ball gauge per Kerry is the tool to use. Measure top, middle, bottom of the bore. Mic the OD of the fixed gage when withdrawn from bore.
Scott, wouldn't the other style show out of round better ?
The style Frank showed would only show taper, IMHO.


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Re: Valve guide clearance

Post by Scott_Conger » Fri Jan 25, 2019 5:34 pm

Three measurements will show taper or not. Whether or not round is of no consequence, really, as the out of roundness for this particular location is minimal in any event. Simply twisting the gage in the bore will find if out of round or not if that is a real concern. These gages are not sprung like telescoping gages. They are fixed to size by wedge action of the adjuster. If it is gently snug and you rotate slightly and it goes slack, well then, you've found out of round and can fix it to that size and measure it. Still, the problem is "is it oversize and by how much?", not "is it round?"
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Re: Valve guide clearance

Post by Ruxstel24 » Fri Jan 25, 2019 5:38 pm

Scott_conger wrote:
Fri Jan 25, 2019 5:34 pm
Three measurements will show taper or not. Whether or not round is of no consequence, really, as the out of roundness for this particular location is minimal in any event. Simply twisting the gage in the bore will find if out of round or not if that is a real concern. These gages are not sprung like telescoping gages. They are fixed to size by wedge action of the adjuster. If it is gently snug and you rotate slightly and it goes slack, well then, you've found out of round and can fix it to that size and measure it. Still, the problem is "is it oversize and by how much?", not "is it round?"
I can agree with that, but either style will give you a close enough reading. If Steve has the telescoping version, I see no need to get the others. :)


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Re: Valve guide clearance

Post by Scott_Conger » Fri Jan 25, 2019 5:52 pm

Dave

for this application, I agree with you. However, the ball-type is a fixed wedge and once set to a measured size will not alter itself one whit. Telescoping gages are best used where they can be made "large" and inserted to the bore then swept from side to side so that the "smallest" size is recorded by the gauge. Real care is then exercised to not bump them to close them or allow them to re-expand and give false reading in any case.

I would never take the first reading of a telescoping gage as gospel...I'd take multiple readings to ensure correct and careful use. The ball gages are far less suceptible to to error or eroneous use. For small holes that I must have an accurate reading, ball gages are my go-to tool.
Scott Conger

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Re: Valve guide clearance

Post by Robert Bente » Fri Jan 25, 2019 9:04 pm

I think I was blessed with a low mileage engine. The second owner bought it in 1955 and was told at the time, 1955, that it was driven less than 1000 miles. He put new piston rings in. I bought this from him, my first T, three years ago. I was sold by his story, about him and his Dad, finding it in Nebraska, buying it for 50 dollars, and trailering behind there Desoto to the west.
I bought it with that info and last ran in 1975.
I believe it’s a very low mileage early feb. engine with an aluminum hogs head.
Thank you all for your responses.
r/s Bob


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Re: Valve guide clearance

Post by Scott_Conger » Fri Jan 25, 2019 10:43 pm

Robert

Let me answer your initial question directly: I believe that an original engine that is running well, will be just fine with standard diameter valves at least for now. I say this, because to do otherwise right now will entail reaming the valve guides. This is not a big job for someone ready with the tooling but is a daunting job to do accurately for the first time and without specialized tooling.

Some will say the valve should be close enough fit to "pop" when you block off the guide and you pull the valve out. That's true. You also want the valve face to completely seat in the block, and brother let me tell you between "popping" and seating, you can live with no POP, but not "no seat". When you ream the guides, the valves now follow THAT path and it will be a miracle if the valve heads are still concentric to the valve seats and will still seat. Now What? Well, you get to cut new seats! More expensive tooling with NeWay Cutters or grind with an old valve seat grinder that has beat up used up pilots. Sounds fun, Yeah? In any event, you may need to kiss the seats with compound as they are likely rough.

Maybe you'd like adjustable lifters? So pull the cam, replace the lifters and you STILL may have to shorten the valves to work with the lifters! So keep it simple, change the valves, kiss the seats and see how it runs. Valves are cheap and if you're unhappy with the results, you can spend lots of $$ and time later.
Scott Conger

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Re: Valve guide clearance

Post by Steve Hughes » Sat Jan 26, 2019 12:06 am

Thanks for the lessons in bore measurements guys. And sorry for hi jacking the thread for a while. Don’t think I will be getting ball gauges for now. I am working on an engine in about the same condition as Robert’s but I am doing a full bare block rebuild.


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Re: Valve guide clearance

Post by Adam » Sat Jan 26, 2019 10:04 am

.005” clearance is a bit too much. It will run ok, but will run much better if you properly ream and properly fit new valves.


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Re: Valve guide clearance

Post by FordModelT9 » Sat Jan 26, 2019 10:40 am

I knurled mine That worked great for me. That way you keep everything std. size.


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Re: Valve guide clearance

Post by HaroldRJr » Sat Jan 26, 2019 2:30 pm

Don - Never had any experience with knurling valve guides, however, it seems like a good idea to me! And if those that know a lot more about it than me also think it's a good idea, it seems like you, or "someone", should share the valve guide "knurling process" with everyone here on the forum, as "worn guides" are a very common problem for so many of us.

In thinking that knurling sounds like a good idea to me, I'm thinking that besides a "gentle way" to take up a bit of "slop" that really has not prevented a worn engine from running, tightening up the guides a bit by knurling will also help hold bit of oil, and I would think that that would also be a good thing too!

How about it Don? Or "somebody",....tell us more about this "knurling" process,....anybody?

For what it's worth,.....harold


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Re: Valve guide clearance

Post by Adam » Sun Jan 27, 2019 1:16 pm

The T valve guides can generally get very loose before the valves actually start having problems sealing against combustion.

However, there is an issue here that many people overlook. Wider stem to guide clearance on the intake valves are a vacuum leak. This is the same as having a leaky throttle shaft on your carburetor. Vacuum leaks cause your fuel/air mixture to run excessively lean during high vacuum conditions (like during idle or cruising along on flat straightaways at moderate speed). It often doesn’t take much of a vacuum leak to cause an intermittent rough running situation, which for most hobbyists can oftentimes be difficult to properly diagnose. The intermittent rough running from leaky valve guides or throttle shaft often are mistaken for coil, timer, or magneto issues.


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Re: Valve guide clearance

Post by HaroldRJr » Sun Jan 27, 2019 3:14 pm

Adam - I am of the same opinion as you in that valves can indeed become quite loose due to worn guides, however, still seal compression as well as ever for a good running engine, but with some oil consumption and rough idle due to vacuum pulling oil up thru' the worn intake guides. Years ago, I made some very effective intake valve seals that work very well to solve oil burning and rough idle due to vacuum leaking thru' the worn intake valve guides:

I merely purchased three standard hardware items (four of each for just the 4 intake valves) from Lowes and assembled the seals as part of a "valve job". They did (and still do) work very well. These "seals" consisted of just a small, thin felt washer made from little round "dime-sized" felt, each of which I punched a valve stem sized hole in, and a plain flat washer about the same size, held up against the bottom of the valve guide by a soft spring about 2" long which holds the felt & plain flat washer up against the bottom of the intake valve guide. (The little thin felt discs are the type normally glued to the bottom of a table lamp to prevent scratching the table or whatever.)

Obviously, these are only needed on the four intake valves (not the exhaust valves) as the intake valves are the only ones with vacuum leaks thru' the worn guides. The seals are of course not needed on the exhaust valves and the exhaust valve are too hot for the felt washer to survive anyway!

For what it's worth,.....harold


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Re: Valve guide clearance

Post by HaroldRJr » Sun Jan 27, 2019 3:37 pm

Well, one other little "detail"......

I probably should have said that the only really critical detail is that the hole that you punch in the little thin felt washer should be of a diameter just barely "snug" against the valve stem, but not so "snug" as to restrict valve motion. Also, the steel (or brass, or aluminum) flat washer should also have a hole just barely big enough to provide clearance for valve movement, but small enough to provide adequate support for the felt washer.

Also, for what it's worth, I think that the felt washers retain enough oil to provide good lubrication for the valve stem,....a "good thing" in my opinion,.......harold


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Re: Valve guide clearance

Post by SurfCityGene » Sun Jan 27, 2019 4:03 pm

Harold, I like your idea of the felt washers. I've seen this work before for quite a long time.
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Re: Valve guide clearance

Post by Will_Vanderburg » Sun Jan 27, 2019 4:59 pm

when I did my first engine over 18 years ago, I just sleeved my valve guides back to standard .312 and put standard sized valves in it.

It may or may not have been the right thing to do, but it runs. Currently sidelined for a knock i cannot find. And has been for 5 years. So I run an older engine.
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Re: Valve guide clearance

Post by Roar_Sand » Mon Feb 04, 2019 10:28 pm

Manufacturing numbers for MOPAR cast iron engines was 0.001 to 0.003 diametrical clearance for intakes and 0.002 to 0.004 for exhaust.

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