oversize valve stem question

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Wayfarer
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oversize valve stem question

Post by Wayfarer » Sat May 30, 2020 11:03 pm

tore into the engine in my '23 center door yesterday and today, and was disappointed to find the condition of the seats, valves and guides.

The valves are already "second oversize", which is advertised as .342". In measuring the non-wearing areas above and below the guide contact area, my valves were .3400" to .3404".

the guides measured .3437" to .3448" in the centers, bellmouthing notwithstanding

I searched for a stem-to-guide clearance spec for Model T, and didn't find one, so using a generic .001" to .003" - all the guides are out of spec for .340" valves. They'd be juuust at the limits if the valves were truly .342"

I've read a bunch of old posts about using 1.50" head diameter / .341" stem diameter Chebby valves, so my question is :

anybody ever go to oversize stem Chebby valves ? If I use a .344" stem, I can ream the guides to .346" Should be good for a long time, and then at the next rebuild I'd have to do liners or full guides.


Allan
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Re: oversize valve stem question

Post by Allan » Sun May 31, 2020 2:52 am

Cory, work with your machine shop. They should be able to install a set of K liners to take up the wear and give you a neat valve guide at the same time.

Allan from down under.


Les Schubert
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Re: oversize valve stem question

Post by Les Schubert » Sun May 31, 2020 10:48 am

LOTS of people have installed Chevy valves in the T


Topic author
Wayfarer
Posts: 97
Joined: Fri Jan 03, 2020 10:04 pm
First Name: Cory
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* REQUIRED* Type and Year of Model Ts owned: 26 engine on a stand, Canadian '23 center door
Location: Colorado Springs CO
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Re: oversize valve stem question

Post by Wayfarer » Sun May 31, 2020 11:33 am

Allan wrote:
Sun May 31, 2020 2:52 am
Cory, work with your machine shop. They should be able to install a set of K liners to take up the wear and give you a neat valve guide at the same time.

Allan from down under.
I've installed k liners before in OHV heads, and I like them (some people don't)
I tried to put them in a Flathead six Mopar a long time ago, and found the end result lacking, due to the inability to dress the ends of the guide inside the valve chamber.

I agree they would be a great solution.


Scott C.
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Re: oversize valve stem question

Post by Scott C. » Sun May 31, 2020 11:38 am

Have you considered knurling the valve guides? If done properly, it is gives better oil retention. Though when I was in the business, I only worked on one Model T engine. I converted it back from a Fronty set up. I reamed the guides out to accept a 3/8" valve stem and used the larger stemmed exhaust valves from a 350 Chevy. I had plenty of used ones from cracked heads. We put in adjustable lifters and used the Chevy retainers, if I recall correctly.


Topic author
Wayfarer
Posts: 97
Joined: Fri Jan 03, 2020 10:04 pm
First Name: Cory
Last Name: Woerth
* REQUIRED* Type and Year of Model Ts owned: 26 engine on a stand, Canadian '23 center door
Location: Colorado Springs CO
Board Member Since: 2020

Re: oversize valve stem question

Post by Wayfarer » Sun May 31, 2020 12:40 pm

Scott C. wrote:
Sun May 31, 2020 11:38 am
Have you considered knurling the valve guides? If done properly, it is gives better oil retention. Though when I was in the business, I only worked on one Model T engine. I converted it back from a Fronty set up. I reamed the guides out to accept a 3/8" valve stem and used the larger stemmed exhaust valves from a 350 Chevy. I had plenty of used ones from cracked heads. We put in adjustable lifters and used the Chevy retainers, if I recall correctly.
I've definitely been considering it


Topic author
Wayfarer
Posts: 97
Joined: Fri Jan 03, 2020 10:04 pm
First Name: Cory
Last Name: Woerth
* REQUIRED* Type and Year of Model Ts owned: 26 engine on a stand, Canadian '23 center door
Location: Colorado Springs CO
Board Member Since: 2020

Re: oversize valve stem question

Post by Wayfarer » Mon Jun 01, 2020 7:17 pm

as a follow up - I spoke with Steve at Lang's today - new 1/32" over T valves are .340" stem diameter. It is the GUIDE that would be .342", not the valve.


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Re: oversize valve stem question

Post by Adam » Mon Jun 01, 2020 8:07 pm

I’ve worked on a couple engines that had the spiral style knurling and they they had moderate but noticeable issues. The issues were oil burning and the equivalent of high vacuum intake leak (lean mixture at high vacuum conditions). Bear in mind that the T doesn’t have any valve seals and because of that should have smooth, precision valve guides. If you can't utilize the second oversize, then you should have a smooth bore 5/16” guide installed and standard valves.


Kerry
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Re: oversize valve stem question

Post by Kerry » Mon Jun 01, 2020 10:03 pm

The block I'm re-building at the moment, all 8 are cast iron valve guides pressed in and then reamed to what ever valve stem size being used.
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