Miss and breaking down at higher rpm
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
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 - Posts: 46
- Joined: Tue Aug 22, 2023 2:04 am
- First Name: Bill
- Last Name: Hurman
- * REQUIRED* Type and Year of Model Ts owned: 1914 Touring car
- Location: Australia
Miss and breaking down at higher rpm
Hi folks,
I am quite new to the Model T scene although I am experienced with old cars of other makes. I have recently got my 1914 touring car on the road and it's going great and makes me smile every time I drive it. One problem that I do have is the engine misses and loses power at high (high for a T anyway!) revs. My roller timer has a lot of play in the roller (about 1/8") and I was wondering if this could be the problem? I am in Australia and parts are a bit more expensive to get and ship so just wanted to get advice before I buy parts. Best regards, Bill
I am quite new to the Model T scene although I am experienced with old cars of other makes. I have recently got my 1914 touring car on the road and it's going great and makes me smile every time I drive it. One problem that I do have is the engine misses and loses power at high (high for a T anyway!) revs. My roller timer has a lot of play in the roller (about 1/8") and I was wondering if this could be the problem? I am in Australia and parts are a bit more expensive to get and ship so just wanted to get advice before I buy parts. Best regards, Bill
-
- Posts: 318
- Joined: Sun Jan 06, 2019 5:08 pm
- First Name: Chris
- Last Name: Barker
- * REQUIRED* Type and Year of Model Ts owned: 1926 Coupe
- Location: Somerset, Eng;and
Re: Miss and breaking down at higher rpm
Fuel may not be getting through. Some modern float needle valves have a hole smaller than the original. Adding a fuel filter to the Model T's system which relies on gravity is not good - or the original filter below the tank may be blocked. The easy check for all these is to remove the carb bowl and time fuel flow into a jar. I calculate that 100cc/minute should be good.
Timers can certainly cause the problems you describe. It's normal to have a slack roller. Look hard at the track around the casing. Wear often occurs adjacent to the junctions between metal and insulation. Check that the spring is pushing the roller. You may need to find a lathe and clean up the track. Maybe try to find someone who will lend you another timer?
If you decide to buy, Henry's offer the Anderson, which is good (but POA) or the New Day. A good New Day can be good but there are some modern replicas which wear quickly.
https://henrystaparts.com.au/wp-content ... E-2023.pdf
And last but not least, coils. What do you know about their history? Have they been set up on one of the special devices designed to get the best performance? As an absolute minimum, have you checked that they generate good steady sparks across a gap of about 6mm and take about 1.3A when fed with 12v DC?
Timers can certainly cause the problems you describe. It's normal to have a slack roller. Look hard at the track around the casing. Wear often occurs adjacent to the junctions between metal and insulation. Check that the spring is pushing the roller. You may need to find a lathe and clean up the track. Maybe try to find someone who will lend you another timer?
If you decide to buy, Henry's offer the Anderson, which is good (but POA) or the New Day. A good New Day can be good but there are some modern replicas which wear quickly.
https://henrystaparts.com.au/wp-content ... E-2023.pdf
And last but not least, coils. What do you know about their history? Have they been set up on one of the special devices designed to get the best performance? As an absolute minimum, have you checked that they generate good steady sparks across a gap of about 6mm and take about 1.3A when fed with 12v DC?
Last edited by Chris Barker on Tue Jan 21, 2025 6:18 am, edited 1 time in total.
-
- Posts: 4082
- Joined: Sun Jan 06, 2019 4:06 pm
- First Name: Jerry
- Last Name: Van
- Location: S.E. Michigan
Re: Miss and breaking down at higher rpm
The first step is to replace the timer, as you suspected.
-
- Posts: 5009
- Joined: Tue Jan 08, 2019 7:31 pm
- First Name: Dan
- Last Name: Hatch
- Location: Alabama
Re: Miss and breaking down at higher rpm
First step is get the Service Manual if you don’t have one. Then replace the timer.
-
- Posts: 303
- Joined: Sun Sep 01, 2024 8:57 pm
- First Name: John
- Last Name: Maxson
- * REQUIRED* Type and Year of Model Ts owned: 1926 model t coupe
- Location: Old Saybrook, CT
Re: Miss and breaking down at higher rpm
Could be a clogged main jet which you can acess from under the car by removing the float bowl and chasing the jet oriface with some stranded wire. If it runs fine cold until it heats up and then sputters, I would suspect condensers.
-
- Posts: 1863
- Joined: Sun Jan 06, 2019 8:20 pm
- First Name: Robert
- Last Name: Jablonski
- * REQUIRED* Type and Year of Model Ts owned: 1926 Runabout
- Location: New Jersey
- MTFCA Life Member: YES
- Board Member Since: 1999
Re: Miss and breaking down at higher rpm
Original14T..... Do yourself a favor, do check to see if there is a chapter or other Model T owners in your area. Firsthand knowledge and experience will be helpful for you.
-
- Posts: 2814
- Joined: Sun Jan 06, 2019 5:25 pm
- First Name: George
- Last Name: House
- * REQUIRED* Type and Year of Model Ts owned: ‘10 Maxwell AA, ‘11Hupp Model 20, Two 1914 Ford runabouts, 19 centerdoor, 25 C Cab,26 roadster
- Location: Northern Caldwell County TX
- MTFCA Life Member: YES
- Board Member Since: 1999
Re: Miss and breaking down at higher rpm
G’day Bill,… along with all the other good advice, are you advancing the spark after the engine is running ?
A Fine is a Tax for Doing Something Wrong….A Tax is a Fine for Doing Something RIGHT 
-
- Posts: 4082
- Joined: Sun Jan 06, 2019 4:06 pm
- First Name: Jerry
- Last Name: Van
- Location: S.E. Michigan
Re: Miss and breaking down at higher rpm
As suggested above, your trouble could stem from any number of issues. However, without a good timer, (and good coils), as a starting point, those other issues will be hard to diagnose. From your description, we know your timer is bad. Start there, (or start with acquiring the manual, as Dan Hatch suggests).
-
Topic author - Posts: 46
- Joined: Tue Aug 22, 2023 2:04 am
- First Name: Bill
- Last Name: Hurman
- * REQUIRED* Type and Year of Model Ts owned: 1914 Touring car
- Location: Australia
Re: Miss and breaking down at higher rpm
Thanks for all the good advice guys, much appreciated. I will hunt down a service manual. I have gone through the carby and fuel supply which is in good order, it does feel like a spark problem as there is no backfire through the carb from leaning out. My coils have had new points fitted in the past but I don't know to what extent they have been set apart from myself checking the clearances. I do advance the timing and move it around to find the best spot on mag and battery George, the car certainly performs better on mag, no doubt from the extra advance of the mag. I will replace the timer roller and skim the timer surface as suggested as the insulation surface is slightly below the metal contacts which could be promoting some bounce. Best regards, Bill
-
- Posts: 1863
- Joined: Sun Jan 06, 2019 8:20 pm
- First Name: Robert
- Last Name: Jablonski
- * REQUIRED* Type and Year of Model Ts owned: 1926 Runabout
- Location: New Jersey
- MTFCA Life Member: YES
- Board Member Since: 1999
Re: Miss and breaking down at higher rpm
Replacing the timer roller is okay and also cleaning the contacts inside the commutator cap... If you decide to install a new timer, regardless of manufacturer, please follow the instructions for set ting the initial timing.
-
- Posts: 1230
- Joined: Sun Jan 06, 2019 5:39 pm
- First Name: James
- Last Name: Golden
- * REQUIRED* Type and Year of Model Ts owned: 1926 Model T Roadster
- Location: Bowie, MD
Re: Miss and breaking down at higher rpm
The surface inside the timer must be smooth with a complete even surface or the roller will hop up and down at high speeds and cause those misses.
A week spring holding the roller against the Timer circuit path will cause the same action, along with a worn shaft that the roller rides around on.
A week spring holding the roller against the Timer circuit path will cause the same action, along with a worn shaft that the roller rides around on.
-
- Posts: 7237
- Joined: Fri Jan 04, 2019 9:37 pm
- First Name: Steve
- Last Name: Jelf
- * REQUIRED* Type and Year of Model Ts owned: 1923 touring and a few projects
- Location: Parkerfield, Kansas
- Board Member Since: 2007
- Contact:
Re: Miss and breaking down at higher rpm
We don't know which carb you're using. If it's a Holley NH, check the float valve to confirm that the opening is .125", not .100" as some are mistakenly made. The wrong size can lead to fuel starvation.
The inevitable often happens.
1915 Runabout
1923 Touring
1915 Runabout
1923 Touring
-
- Posts: 7391
- Joined: Sun Feb 14, 2021 10:08 pm
- First Name: Pat
- Last Name: McNallen
- * REQUIRED* Type and Year of Model Ts owned: 1926-7 roadster
- Location: Graham, Texas
- Board Member Since: 2021
Re: Miss and breaking down at higher rpm
Original type timers require occasional cleaning and frequent oiling with a light oil, like 10 W motor oil or Marvel oil. I believe Ford advised oiling the timer every 200 miles. A worn or dirty timer will often cause erratic performance at higher engine speeds. If the entire ignition system, including all 4 coils and all related switches and wiring, as well as the entire fuel system, is in good order, weak valve springs could be a problem.
-
- Posts: 1863
- Joined: Sun Jan 06, 2019 8:20 pm
- First Name: Robert
- Last Name: Jablonski
- * REQUIRED* Type and Year of Model Ts owned: 1926 Runabout
- Location: New Jersey
- MTFCA Life Member: YES
- Board Member Since: 1999
Re: Miss and breaking down at higher rpm
Would we be safe to assume that your 1914 ignition is running on magneto power? Even though the car does start and runs at speed, The the AC voltage should be checked to have at least 30 volts AC, at speed , ....., if it hangs around 15 - 20 volts AC, your magneto may have to be recharged. The lower AC numbers at speed will definitely give the problem you have.
-
Topic author - Posts: 46
- Joined: Tue Aug 22, 2023 2:04 am
- First Name: Bill
- Last Name: Hurman
- * REQUIRED* Type and Year of Model Ts owned: 1914 Touring car
- Location: Australia
Re: Miss and breaking down at higher rpm
Thanks for all the great advice folks, I checked the roller and timer again today and the roller has even more play than I first thought, so much so that it can foul on its carrier. I will order one and replace it first. The timer track is actually quite good with an even surface all around.
I really feel that the problem is spark related as the engine shows no typical signs of leaning out.
Best regards from downunder, Bill
I really feel that the problem is spark related as the engine shows no typical signs of leaning out.
Best regards from downunder, Bill
-
- Posts: 7391
- Joined: Sun Feb 14, 2021 10:08 pm
- First Name: Pat
- Last Name: McNallen
- * REQUIRED* Type and Year of Model Ts owned: 1926-7 roadster
- Location: Graham, Texas
- Board Member Since: 2021
Re: Miss and breaking down at higher rpm
Also check the timer wires to the coil box for any sign of bad insulation. The spark plug wires should be arranged so that they are at least 1" from each other or anything else. Worn spark plug electrodes can cause mis-firing at higher engine speeds, especially if the gap is on the wide side. Worn electrodes can often be filed to improve performance. Any wooden parts in the coil box that are exposed to high voltage can leak current and cause problems. This sometimes happens even if the parts look good, especially in damp conditions. It sometimes happens that the contact buttons on the individual coil boxes don't make a secure contact with the spring-like contacts inside the coil box. Cleaning them and tightening hardware may help. Often, placing cardboard or plastic shims between the coil units and the coil box to hold the coil unit firmly against the coil box contacts can fix the problem.