Lean valve

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2018: Lean valve
Top of pagePrevious messageNext messageBottom of page Link to this message  By Ralph Fitz-Gerald - Vermont on Sunday, January 28, 2018 - 09:04 pm:

Today we pulled my motor from my 15 touring. When we pulled the head this what we found. Valve in cylinder 1+ 2 very rich and 3+4 very lean. I could use some help in trying to figure out what is going on.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dallas landers on Sunday, January 28, 2018 - 09:28 pm:

Sounds like a leaking intake manifold.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Sunday, January 28, 2018 - 10:43 pm:

Rather than post the same thing four times, why not just add to the original post? That will make it easier to find any answers you may get.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Art Wilson on Sunday, January 28, 2018 - 11:23 pm:

This is a common Model T problem with stock carb's and intake manifolds, especially if the inside passage of the manifold has been polished.
With a stock carburetor the fuel is drawn into the air stream from the bottom side of the air channel. This creates a situation where the fuel-air stream is lean on the top side and rich on the bottom side.
In addition, the design of the intake manifold has the bottom edge sweeping nicely up to the front intake port and the top edge of the manifold curving up and to the back to connect to the rear port. This design allows the rich part of the fuel-air mixture to flow along the bottom edge of the manifold up to the front port and the lean portion to flow along the top edge of the manifold to the rear port.
This condition is most prevalent when the inside of the manifold has been polished to achieve better air flow.
I found out about this problem the hard way. Years ago I polished the inside passage of an aluminum manifold for more power and could never get the engine to idle on all four cylinders. I could lean out the carburetor and it would fire on the front two cylinders or make it richer and the engine fire on the rear two cylinders. I switched back to a rough cast iron manifold and could get the engine to idle OK, but my plugs sill showed rich at the front and lean at the back.

From time to time there are pictures of old advertisements or devices to get better fuel economy from a Model T. A lot of the claims look to be over rated but I think if they can get the fuel air mixture to be better atomized as it comes out of the carburetor then they may actually work. The general consensus though is these devices rob power but that may not always be the case.

Art


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ralph Fitz-Gerald - Vermont on Monday, January 29, 2018 - 07:06 am:

Steve I was trying to post a photo of the valves. That why there was four entries
Fitz


Top of pagePrevious messageNext messageBottom of page Link to this message  By Lew Morrill on Monday, January 29, 2018 - 09:59 am:

Heated intake pipe used or not? Warm air might help vaporise the gas mixture and alleviate some of the symptoms?


Top of pagePrevious messageNext messageBottom of page Link to this message  By George n LakeOzark,Missourah on Monday, January 29, 2018 - 03:54 pm:

Another thought from the Late RDRichs was to use a thermostat . His theory was that with the thermo (BARF) system water cooled the front of the engine faster then the rear. The thinking is that the thermostat allows the front cylinders to get up to temp and even temps with the rear cyls. Since my car has no water pump I'm trying out the 160deg. thermostat as recommended by him.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ralph Fitz-Gerald - Vermont on Monday, January 29, 2018 - 07:53 pm:

Just located the reason for the lean valves. There are two very small holes on the backside of my exhaust manifold. The holes seem to be located in two very small foundry marks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Monday, January 29, 2018 - 10:59 pm:

Small holes in the exhaust manifold would not cause the engine to run lean or rich or difference in front to rear temps. or did you mean intake?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Hatch on Tuesday, January 30, 2018 - 03:56 am:

George: That is why the head gasket has a larger hole in the rear. Dan


Add a Message


This is a private posting area. Only registered users and moderators may post messages here.
Username:  
Password:

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration