Sticking valves?

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules

Topic author
RGould1910
Posts: 973
Joined: Tue Jan 22, 2019 8:16 am
First Name: Richard
Last Name: Gould
* REQUIRED* Type and Year of Model Ts owned: 1910 touring, 1912 roadster , 1927 roadster
Location: Folsom, CA

Sticking valves?

Post by RGould1910 » Mon Jul 27, 2020 11:22 am

What are the symptoms of sticking valves? Unsuccessfully trying to diagnose rough idling and once smoke emanating from the throttle arm hole in the valve cover on a newly rebuilt engine. I've gone thru the coils, carburetor, timer, plugs, all the easy stuff to no avail. Car runs strong at higher rpm.
I get different compression readings by hand cranking. Don't know if its my technique.
I do recall sticking valves on a 1910 on a new engine I rebuilt years ago that was cured when I cleaned the valves and guides and opened up the guides a few thou.
As always, any help appreciated.

User avatar

Rich Eagle
Posts: 6789
Joined: Fri Jan 04, 2019 10:51 am
First Name: Richard
Last Name: Eagle
* REQUIRED* Type and Year of Model Ts owned: 1909 TR 1914 TR 1915 Rd 1920 Spdstr 1922 Coupe 1925 Tudor
Location: Idaho Falls, ID
MTFCA Number: 1219
Contact:

Re: Sticking valves?

Post by Rich Eagle » Mon Jul 27, 2020 11:26 am

It's easy to take the valve cover off and watch them as the engine is turned over. I have seen new valves stick if the engine has sat for a while.
Rich
When did I do that?

User avatar

RajoRacer
Posts: 4305
Joined: Sun Jan 06, 2019 12:18 pm
First Name: Steve
Last Name: Tomaso
* REQUIRED* Type and Year of Model Ts owned: 1914 Touring, 1919 Centerdoor, 1924 TT C-Cab Express, 1925 Racer
Location: Longbranch, WA
MTFCA Number: 14972
MTFCI Number: 15411
Board Member Since: 2001

Re: Sticking valves?

Post by RajoRacer » Mon Jul 27, 2020 12:56 pm

Richard - for a proper compression test, remove all 4 spark plugs with the throttle wide open & crank away


Bruce Compton
Posts: 576
Joined: Thu Jan 10, 2019 11:23 am
First Name: Bruce
Last Name: Compton
* REQUIRED* Type and Year of Model Ts owned: 1921 Coupe, 1925 Coupe
Location: Kemptville

Re: Sticking valves?

Post by Bruce Compton » Mon Jul 27, 2020 1:13 pm

A sticking valve may not show up at cranking speed as it has lots of time to get closed. Having said that, if the engine runs strong at higher RPM, valve sticking is probably not the problem. A rough idle (especially on a fresh rebuild) is more likely fuel mixture, or one or two valves set a bit too tight. I'd check the clearances again (0.012 int. and 0.015 exhaust) and then look for a vacuum leak at the intake/block fitting. I'm assuming you're using the brass ring and steel sleeve gaskets to achieve a proper seal and prevent exhaust manifold sag. As I rebuild a lot of carbs, I use an intake with a vacuum fitting installed so I can connect my vacuum gauge which can expose any mixture or valve issues instantly . Good luck : Bruce


Topic author
RGould1910
Posts: 973
Joined: Tue Jan 22, 2019 8:16 am
First Name: Richard
Last Name: Gould
* REQUIRED* Type and Year of Model Ts owned: 1910 touring, 1912 roadster , 1927 roadster
Location: Folsom, CA

Re: Sticking valves?

Post by RGould1910 » Mon Jul 27, 2020 4:10 pm

Steve, I did best I could. Removed all the plugs, opened the throttle and hand cranked. I don't have a starter on the car.
I went thru each cylinder 6 times to make sure I got the highest reading before moving to the next cylinder. I got readings varying between 42 and 60 psi. That may be indicative of a newly rebuilt engine, I don't know.
Reluctant as I am to do this, I will remove the head and manifolds/valve cover and check things out. I have questionable threads in the head at the water outlet so I'll use the opportunity to install either a helicoil or solid insert. In addition to any valve work, I may decide to change rings. If so I dread getting under the car trying to remove the caps and keep everything in place.
The problems I am experiencing certainly suggest a carburetor problem, but I've substituted carbs known to be good with the same result. Really puzzling.

User avatar

RajoRacer
Posts: 4305
Joined: Sun Jan 06, 2019 12:18 pm
First Name: Steve
Last Name: Tomaso
* REQUIRED* Type and Year of Model Ts owned: 1914 Touring, 1919 Centerdoor, 1924 TT C-Cab Express, 1925 Racer
Location: Longbranch, WA
MTFCA Number: 14972
MTFCI Number: 15411
Board Member Since: 2001

Re: Sticking valves?

Post by RajoRacer » Mon Jul 27, 2020 4:52 pm

How "new" of a rebuild is it ? I'd attempt to squirt a small amount of motor oil in the low reading cylinder and check it again to verify the reading.


Roz
Posts: 79
Joined: Fri Feb 15, 2019 7:53 pm
First Name: Dennis
Last Name: P
* REQUIRED* Type and Year of Model Ts owned: 1925 Coupe, 1925 TT, 1927 Speedster, 1931 Model A
Location: Humboldt TN
MTFCA Number: 31449
MTFCI Number: 24373
Board Member Since: 2012

Re: Sticking valves?

Post by Roz » Mon Jul 27, 2020 7:30 pm

I vote for vacuum leak at the intake manifold. I would not pull the pistons to change the rings at this point. Also, you said there was some smoke coming out of the hole in the valve cover. That would indicate to me loose valve guides, which would be less likely to make a sticky valve. Before you tear anything apart, spray some carb cleaner around the intake ports while it is running and see if the idle changes.


Topic author
RGould1910
Posts: 973
Joined: Tue Jan 22, 2019 8:16 am
First Name: Richard
Last Name: Gould
* REQUIRED* Type and Year of Model Ts owned: 1910 touring, 1912 roadster , 1927 roadster
Location: Folsom, CA

Re: Sticking valves?

Post by RGould1910 » Mon Jul 27, 2020 9:14 pm

All ideas/suggestions good food for thought. I'll check for a vacuum leak before I do anything.

I rebuilt the engine last year and had the car running in October. I had to pull the engine because the .080 os pistons were hitting the head and I wanted to recheck all my work.

Since 2 of the rods were bent from the pistons hitting the head I pulled the pistons and aligned all 4. One mistake I may have made was I reused the rings thinking the car had run so few minutes, it would not be a problem. Now I wonder.

Like I said earlier I tried running 3 other carbs on it with the same result, two of which were known to be good running carbs. I'm running an nos roller timer and new Champion X plugs. I've checked the wiring for continuity and the rebuilt coils checked out perfectly on the Strobo meter. Im running out of ideas.

User avatar

Novice
Posts: 584
Joined: Tue Jan 08, 2019 12:25 pm
First Name: Jim
Last Name: Davis
* REQUIRED* Type and Year of Model Ts owned: 1926 Touring. 1923/26 Open Express. 1920 depot hack
Location: Tomball,Texas
MTFCA Number: 49832
MTFCI Number: 24686
Board Member Since: 2017

HOW MUCH SMOKE IS TOO MUCH SMOKE

Post by Novice » Mon Jul 27, 2020 9:29 pm

How much smoke is too much smoke! coming out of the throttle linkage hole ? I have a little after the engine warms up at idle.

User avatar

Susanne
Posts: 1043
Joined: Sat Apr 13, 2019 6:06 pm
First Name: Susanne
Last Name: Rohner
* REQUIRED* Type and Year of Model Ts owned: Late '15 touring, "Angel".
Location: Valfabbrica, (central) Italy
MTFCA Number: 464
MTFCA Life Member: YES
Board Member Since: 1999
Contact:

Re: Sticking valves?

Post by Susanne » Tue Jul 28, 2020 2:17 pm

A little is fine - it's blowby from your engine and oil vapor off the drain holes in the bottom of the spring chamber. If it's more than a little, then I'd be concerned as you have issues starting to develop - worn valve guides, rings, etc...


Bruce Compton
Posts: 576
Joined: Thu Jan 10, 2019 11:23 am
First Name: Bruce
Last Name: Compton
* REQUIRED* Type and Year of Model Ts owned: 1921 Coupe, 1925 Coupe
Location: Kemptville

Re: Sticking valves?

Post by Bruce Compton » Tue Jul 28, 2020 2:51 pm

Richard: I'm getting mixed signals. You say it's a "rebuilt" engine while suggesting changing the rings, talking about bent rods and as well as pistons hitting the head so I'm confused. If you have correctly checked the plugs, timer, timer wires, coils, coil box, carburetor and possible leaks at the intake manifold the only things left are valves/compression. I really doubt that you could get 60 psi in a stock T and cranking by hand, and I also question the huge variance from 60 to 40 even with 0.080over pistons so something's screwy. To verify any piston/ring issues, squirt some oil in each cylinder and repeat the compression test ( I'm assuming you have help with someone holding the gauge while the other guy does the cranking). If your piston/rings are ok the readings should be the same as the earlier test, and if so , the problem in with the valves, either not seating properly ,sticking, or set way too tight .


Topic author
RGould1910
Posts: 973
Joined: Tue Jan 22, 2019 8:16 am
First Name: Richard
Last Name: Gould
* REQUIRED* Type and Year of Model Ts owned: 1910 touring, 1912 roadster , 1927 roadster
Location: Folsom, CA

Re: Sticking valves?

Post by RGould1910 » Tue Jul 28, 2020 6:13 pm

Bruce the engine was finished initially in October. A total rebuild. When I ran it, I discovered the os pistons were hitting the head. I decided to remove the engine and go thru it again fearing the piston contact had bent the rods. I was right . Two of the four were bent so I realigned them. I beveled the tops of the pistons on a lathe to achieve clearance and put things back together after rechecking the valves just to be sure all was OK. Since the rings were practically new, I reused them.
When I started the engine back up in December I was confronted with the problems I describe above. I put things on hold due to medical issues and have been trying to remedy the problem for the last couple weeks.
Just today I performed an intake vacuum leak and found a significant leak on the 1-2 intake port. I think I found the problem. If not THE problem, a significant part. Thanks to all those who offered suggestions and advice.

Post Reply Previous topicNext topic