Hopped up Briggs twin build

[Gregor 4,838]

1 hour ago, Greentored said:

He was actually OVERscavenging during the overlap phase and pulling so much incoming mixture through, it was going right out the pipe and wasting it.

I don't know enough about engines to really understand the "scavenging" effect, but...........  Maybe if the valve to tappet clearance was increased slightly on both valves, they would both open slightly later, and close slightly sooner, and possibly reduce, or eliminate the overlap. Then again, maybe this would cause more problems than it solved.

Or maybe just the intake valve

 

 

Edited July 20, 2021 by Gregor

[Greentored 3,196]

50 minutes ago, Gregor said:

I don't know enough about engines to really understand the "scavenging" effect, but...........  Maybe if the valve to tappet clearance was increased slightly on both valves, they would both open slightly later, and close slightly sooner, and possibly reduce, or eliminate the overlap. Then again, maybe this would cause more problems than it solved.

Or maybe just the intake valve

 

 

That is absolutely a way engine builders will 'fine tune' race engines. Playing with valve clearance will alter the cam opening, closing, overlap events to dial it in.

I often run less valve clearance on the small engines than called for to make the engine 'think' its got a bigger cam.

[Greentored 3,196]

2 hours ago, ebinmaine said:

That is pretty cool and adds even more thought now...

Makes me wonder if a slightly different cam design would be able to utilize even more of the available fuel. 

Yep!

...and thats how it all starts

[MikMacMike 479]

On 7/9/2021 at 9:22 AM, Gregor said:

My C-175 came with the Briggs 18 Twin on it. Model # 422437 Type 1049 01. I have not seen a C-175 with the Kohler on it, so I cannot tell you the differences between the two. I can say that the shaker plate was completely removed, and the frame re-drilled for the Briggs. I replaced the belt. I am 99% sure it is an 85" belt, but it's been a while. (still waiting on parts) All of the safety switches had been by-passed. I am using the brake pedal safety switch, but not the PTO switch. I don't plan on having any implements on the tractor at this time. The Briggs has magneto ignition, and has the correct ignition switch. I don't know what the Kohler is.

It looks to me as though the PTO Housing Rod has been cut off at the top. I don't know why anyone would have done this, but it just seems short to me.

 

I ordered a new carb, and also bought a rebuild kit for the old one. The rebuild kit came with the parts necessary to rebuild the integrated fuel pump also. It cleaned up well, so I reused the old carb.

When I check the tracking number for my parts from Lincoln, it simply say, "In Transit  Arriving Late" It has said that for the last 6 days.

Where you said the rod seems short at the top I had the same thing. the split pin on the bottom of mine was the same as yours too, so I added an 1/8" washer which brought it back up to hieght. Now I should mention though!!! watch your centers where it conects to the shaft to the bearing, that should be as close to center as possible.

[Gregor 4,838]

This is my fix. I turned the cotter pin upside down in the PTO rod, and drilled a hole in the PTO housing rod, and added a cotter pin there. Bought a generic spring, and all is good I think.