Higher RPM Miss?

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Model T Ford Forum: Forum 2016: Higher RPM Miss?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Pat Kelly Montana on Sunday, June 05, 2016 - 10:08 pm:

When I hit about 35 mph the motor starts to miss and it does the same thing pulling a hill. It acts like I'm dragging a cylinder at times. No back firing no black plugs. Below that speed it hits on all four and runs and idles good. Ideas? PK

12v battery, stock coils. No mag.
Simmons carb.
Prus head. 14mm plugs.
Newday timer.
Chevy 350 valves, T springs.
7.5* advance gear on a stock cam.
Balanced motor.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Pawelek Brookshire, Texas on Sunday, June 05, 2016 - 10:41 pm:

For starters it may be a weak spring in the timer that does not hold the brush on the contacts well enough at higher speeds. Also check the contact area inside the timer cap to make sure the transition from grounded to non grounded areas is smooth. Finally make sure the grounded areas inside the cap are clean and not glazed over.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Barrett in Auburn Ca. on Monday, June 06, 2016 - 12:18 am:

Agree with Michael, look at the timer. Almost certainly an ignition problem. Make sure the connections in your coil box are tight. If the brass upper contacts where they touch the coils are loose you will have no end of trouble. Take them apart and solder the contacts to the studs. While you sure there, rebuild the coil box with one of Regan's Fun Projects kits. The best thing thing you can do for a buzz coil ignition T. It goes without saying that your coils need to be up to the task as well.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Monday, June 06, 2016 - 04:37 am:

That happened to me. i examined my ignition system several times and found nothing. Then i found an air leak in the manifold.
If the timer, coils and plugs test as ok then test for an air leak.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, June 06, 2016 - 05:21 am:

That's odd, Kep? Usually when I have an intake leak, it's running the worst at idle and better at higher rpms?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Monday, June 06, 2016 - 01:17 pm:

I also say check the timer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, June 06, 2016 - 02:04 pm:

The reproduction black New Day timers with the "S" on them wear out in no time because they are made out of some really soft plastic.

Here's a photo of one of the crap black ones next to an original Brown one:



I got a reproduction New Day from Tom Carnegie a while back that appears to be made of a much harder material. Been running it in the '10. So far it has almost 100 miles with no sign of wear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, June 06, 2016 - 04:28 pm:

It could be your timer as suggested above, but another clue which is suspicious is that it misses at high speed and while climbing hills. This clue could indicate a clog in your fuel line. If you are using an in line filter, it will almost always starve for fuel in those two cases. So if it were mine, I would remove an in line filter and clean the fuel line and sediment bulb.

Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Pat Kelly Montana on Monday, June 06, 2016 - 07:38 pm:

Timer it was! The rotor brush spring was week. I checked my spare rotor and it had quite a bit more tension. First I put a stock Ford roller timer on to check performance. It ran smooth at all speeds. I went back to the Newday and the back up rotor and it ran great. I did notice that the car has much more power with the Newday over the roller timer. Why is that?
Norm, fuel was the first thing I checked. I did as you suggested and drained the tank and went through every thing. No junk.
Thanks to all for the help. PK


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, June 06, 2016 - 09:34 pm:

You might check the timing. Each timer has a little different point where it is timed. I have run the older New Day and find it's a very good timer. I have one on one of my T's and I also had one on another T, but the brush had worn on an angle. I think the hole in the brush holder was too wide causing the brush to wear on one side. That car ran rough and I installed an Anderson. Now it runs very well.
Norm


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