Carb issues
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Topic author - Posts: 989
- 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
Carb issues
When I am driving down the road and throttle down before coming to a stop, the engine rhythmically surges. Not heavy but noticeable. It doesn't do that when I increase the throttle above an idle position while still slowing down. It also doesn't do that with the car slowing down in neutral. I've noticed this on a couple cars I've owned. What could be the cause? I'm sure I'm not the only one who has experienced this.
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- Posts: 4967
- Joined: Sat Jan 05, 2019 1:57 pm
- First Name: Mark
- Last Name: Gregush
- * REQUIRED* Type and Year of Model Ts owned: 1925 cutdown PU, 1920 Dodge touring, 1948 F2 Ford flat head 6 pickup 3 speed
- Location: Portland Or
- MTFCA Number: 52564
- Board Member Since: 1999
Re: Carb issues
Try opening (running too lean) or closing (running too rich) the spray needle and retard the spark some, see if that helps. Question, what carb are you running? Have you checked for vacuum leaks?
I know the voices aren't real but damn they have some good ideas!
1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup
1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup
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- Posts: 4095
- Joined: Tue Jan 08, 2019 1:39 pm
- First Name: Norman
- Last Name: Kling
- Location: Alpine California
Re: Carb issues
They idle better with the spark retarded. Not all the way up but about 3 or 4 notches above where it runs well at cruising speed. It could also be the carb mixture as posted above. Some carburetors have an adjustable idle jet. In that case you can try adjusting it for smoothest idle.
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Topic author - Posts: 989
- 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: Carb issues
Thanks for the input. I continue to work thru the vaccuum leaks. I am running a swaybuck NH carb allegedly restored but I have my doubts. I do hope it is a vaccuum leak issue and will clear up once I get that resolved. I have tried different needle and spark positions, also adjusted the float to where it starts easiest and runs good above idle.
Re vaccuum leaks, It could well be the steel rings that hold the manifolds to the car are bottoming out before fully compressing the copper washers. The mating surface of the block was surfaced to remove pitting and the lips inside the ports were recessed to restore the original distance, but Ive heard some reproduction rings were made too thick. I may try running the car with the fiber gaskets that come with the gasket sets you buy not using rings to see if that solves the problem. If so I'll figure out how to reduce the thickness of the rings before switching back to the copper washers.
Re vaccuum leaks, It could well be the steel rings that hold the manifolds to the car are bottoming out before fully compressing the copper washers. The mating surface of the block was surfaced to remove pitting and the lips inside the ports were recessed to restore the original distance, but Ive heard some reproduction rings were made too thick. I may try running the car with the fiber gaskets that come with the gasket sets you buy not using rings to see if that solves the problem. If so I'll figure out how to reduce the thickness of the rings before switching back to the copper washers.
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- Posts: 4967
- Joined: Sat Jan 05, 2019 1:57 pm
- First Name: Mark
- Last Name: Gregush
- * REQUIRED* Type and Year of Model Ts owned: 1925 cutdown PU, 1920 Dodge touring, 1948 F2 Ford flat head 6 pickup 3 speed
- Location: Portland Or
- MTFCA Number: 52564
- Board Member Since: 1999
Re: Carb issues
Try fitting the rings with out the coppers and see how it fits.
I know the voices aren't real but damn they have some good ideas!
1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup
1925 Cut down pickup
1920 Dodge touring
1948 Ford F2 pickup
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- Posts: 584
- 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: Carb issues
I still think that your timing is too far advanced and what you are experiencing is pretty much to be expected. A vacuum leak should have little effect on an unloaded engine decelerating, and for sure not enough to be able to feel it from the driver's seat. Surging at cruising speed will occur from either too lean a mixture or too far advanced timing but the surge you're describing has to come from timing.
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- Posts: 6496
- 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
- MTFCA Number: 16175
- MTFCI Number: 14758
- Board Member Since: 2007
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Re: Carb issues
Gene, there's no law against adding a little hi-temp RTV to those copper rings. I do that because my block hasn't been surfaced to remove the pits.
The inevitable often happens.
1915 Runabout
1923 Touring
1915 Runabout
1923 Touring