Author Topic: Porting questions  (Read 36330 times)

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Offline outlawmower

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Re: Porting questions
« Reply #30 on: April 16, 2008, 06:29:29 pm »
Well I finally got around to getting that old 8 hp Briggs torn down and on my bench for some porting. I have about 3-4 hours totall in porting and I hope I did right.

Pictures-


 
looking inside the exhaust port.....



from the top of the exhaust.....



looking inside the intake.....


 
and last looking from the top of the intake.

Hopefully I did this right. Any thoughts? Comments? Any tips for the next time? Anything I did wrong?
Any comments appreciated.

Outlaw
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Offline kmowtion

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Re: Porting questions
« Reply #31 on: April 16, 2008, 06:48:36 pm »
Looks pretty dang good. Intake is not too smooth to allow fuel suspension and exhaust should allow good flow. I give it an A.
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Offline cycloneracer

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Re: Porting questions
« Reply #32 on: April 17, 2008, 01:26:23 pm »
Pics are hard to tell on porting.  But from what I see you enlarged both the intake and exhaust port.  That is a no no on a flat head briggs.  The Angle you put on the exhaust port will rob torque.  Taking out the valve guide was good, but the enlarging of the port will decrease the exhaust scavenging.

On the intake it looks like you enlarged the hole where the carb mounts.  That will create turblance if you don't match the intake to the port.  But if you did enlarge it is to big.  On a briggs you only want to make the path of the flow straighter.  Larger only hinders performance.

Like everyone said about the Kohlers, briggs are the same.  You are limmited by the valves.  Here is a tip.  Measure the inside of the valve seat.  Measure the valve stem.  Subtract the stem from the valve seat.  Now go and measure your port.   Understand?  Knowing that will help you with your porting.

At least you are trying.  Now reassemble that engine and see how it runs compared to stock.  If you want to do it yourself, you are going to destroy some blocks before you figure it out.

Later
Paul

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Offline outlawmower

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Re: Porting questions
« Reply #33 on: April 17, 2008, 06:50:24 pm »
Pics are hard to tell on porting.  But from what I see you enlarged both the intake and exhaust port.  That is a no no on a flat head briggs.  The Angle you put on the exhaust port will rob torque.  Taking out the valve guide was good, but the enlarging of the port will decrease the exhaust scavenging.

On the intake it looks like you enlarged the hole where the carb mounts.  That will create turblance if you don't match the intake to the port.  But if you did enlarge it is to big.  On a briggs you only want to make the path of the flow straighter.  Larger only hinders performance.

Like everyone said about the Kohlers, briggs are the same.  You are limmited by the valves.  Here is a tip.  Measure the inside of the valve seat.  Measure the valve stem.  Subtract the stem from the valve seat.  Now go and measure your port.   Understand?  Knowing that will help you with your porting.

At least you are trying.  Now reassemble that engine and see how it runs compared to stock.  If you want to do it yourself, you are going to destroy some blocks before you figure it out.

Later
Paul


Hey Thanks Paul for the tips! I have 2 vertical shaft 5 hp briggs still sitting here and ready for some porting. I will post pics as soon as I am done with those blocks. I understand about the measuring the valve and stem. Thanks for the help Paul and everyone!

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Offline outlawmower

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Re: Porting questions
« Reply #34 on: May 11, 2008, 08:55:57 am »
Here's a question/ comment for you guys-

I got to thinking about how the port works. It swirls the fuel around until it gets to the valve and dumps out. Kinda like a toilet right? It swirls the water until it drains out the bottom.... Now if you think about that it takes a certain amount of time to get the water down..... SO it takes a certain amount of time fopr the fuel to get there, Correct? Following me here? 
Now what if you instead of cutting the port round and waiting on the fuel to get there cant you try to cut in a shape of a "D" so that the fuel has to go right to the valve? It would not swirl and you wouldnt have to wait on the fuel to get there....And when you rev up the throttle on the kohler we run you wont have to worry about fuel starving correct?

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Offline George Herrin

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Re: Porting questions
« Reply #35 on: May 11, 2008, 09:10:46 am »
fuel starving is generally a result of carburetion or a lack there of.
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Offline outlawmower

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Re: Porting questions
« Reply #36 on: May 11, 2008, 09:53:15 am »
all right then! Thanks George!
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Offline Big daddy

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Re: Porting questions
« Reply #37 on: May 12, 2008, 12:24:47 pm »
outlawmower, you are on the right track for port shape for the Kohler K series. You want a D shape intake port, you might want to first weld/braze up the top above the flange square with the engine deck, even though you shape it into a "D" shape you still want to raise it as far as you can, and when you do and you have not built up this area then you will weaken the flange and break the flange off. The short side radius is the side for the flat, becareful around the head bold hole to the left side of the port, but if you grind through don't worry it is not the end of the world you can fill it with a stud and glue it in. The bottom of the intake port you just want to smooth and blend, knock only the front edge off the valve guide-maintaining the dia on the guide hole all around. When you make your intake manifold you will want to bore the carb. end 1/8" to 3/16" larger than the backside of our carb. then taper to the other end-matching a round diameter that your port would have been before you made the "D" shape then blend it to the port leaving no lips or sharp edges. As far as the dead spot on the Kohler engine you will get that on almost all Kohler carbs running racing gas or pump gas, there is no accelerator pump in the carb, and if you try to tune the idle circuit to run fat trying to get the dead spot out you will only cause the idle circuit to surge with the high speed circuit on top end, the Kohler carbs on gas are only good at idle and top end. I am hoping to get some pics of my stuff in the next few weeks, then I can show you better than explain what I am talking about. Stay with the "D" shaped ports for a Kohler K series. And don't let anybody talk you out of it
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Offline outlawmower

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Re: Porting questions
« Reply #38 on: May 12, 2008, 03:34:13 pm »
outlawmower, you are on the right track for port shape for the Kohler K series. You want a D shape intake port, you might want to first weld/braze up the top above the flange square with the engine deck, even though you shape it into a "D" shape you still want to raise it as far as you can, and when you do and you have not built up this area then you will weaken the flange and break the flange off. The short side radius is the side for the flat, becareful around the head bold hole to the left side of the port, but if you grind through don't worry it is not the end of the world you can fill it with a stud and glue it in. The bottom of the intake port you just want to smooth and blend, knock only the front edge off the valve guide-maintaining the dia on the guide hole all around. When you make your intake manifold you will want to bore the carb. end 1/8" to 3/16" larger than the backside of our carb. then taper to the other end-matching a round diameter that your port would have been before you made the "D" shape then blend it to the port leaving no lips or sharp edges. As far as the dead spot on the Kohler engine you will get that on almost all Kohler carbs running racing gas or pump gas, there is no accelerator pump in the carb, and if you try to tune the idle circuit to run fat trying to get the dead spot out you will only cause the idle circuit to surge with the high speed circuit on top end, the Kohler carbs on gas are only good at idle and top end. I am hoping to get some pics of my stuff in the next few weeks, then I can show you better than explain what I am talking about. Stay with the "D" shaped ports for a Kohler K series. And don't let anybody talk you out of it

Bigdaddy,
Thanks for all the information! Once you get those pictures up those will really help! Also I am going to try and get a picture of one of my ports soon as I get around to porting on of these blocks!

Thanks,
Outlaw
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Offline Big daddy

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Re: Porting questions
« Reply #39 on: May 12, 2008, 04:07:25 pm »
Just make sure you do all of your welding/buildup before machining the block, have the block hot tanked and use plenty of flux when welding. These blocks can be welded if you take the time and do it right.
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Offline outlawmower

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Re: Porting questions
« Reply #40 on: May 12, 2008, 04:15:58 pm »
I already had to do some welding to the exhaust port because it has a hole drilled in the exhaust port :omg: . But I successefully welded it in and gotta fixed...
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Offline outlawmower

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Re: Porting questions
« Reply #41 on: May 23, 2008, 08:31:58 pm »
Bigdaddy,
I know we were talking about "D" Shaped ports and I came across somthing similar today.




(clickable)

This is a old Briggs 6.5 HP vertical shaft OHV. A guy down the street brought it to me because they carb is gummed up and when I pulled the carb this is what found.... Is this what you are sorta talking about for a "D" shaped port? Should I make it similar? Or not quite that way?

Thanks,
Outlaw
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Offline Big daddy

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Re: Porting questions
« Reply #42 on: May 29, 2008, 04:33:49 pm »
Not quite, but the principle is the same. I did get some pics that I told you about here a few weeks ago. The only problem is the pictures are a little fuzzy, and I am afraid to get them to the size required to post on here you will not see that much. P.M me or E-mail me and I will E-mail them to you along with explainations of each. I also have a pic of an engine block that the tie down failed, and lets just say it
vents rather efficiently now! It is (was) a K341 16 hp. Kohler, the other engine I have pics of is my old Kohler modified class motor built back in 2000, we use aftermarket blocks now-much easier to deal with!!
  Jst for grins, here is the block that gave it up. (not much of it left!) :doh:
Bruce Litton

Offline kohler guy

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Re: Porting questions
« Reply #43 on: May 30, 2008, 09:02:36 pm »
Howdy,
New here and just had some quick questions for you kohler guys... When porting a kohler engine just for farm work do I need to take out the taper in the back of the port for more flow?

Pictures-



See the taper should I cut it out?

Next,
I did some rod modifying and was wondering how much cam it could take? It's a stock rod with the rough casting removed all the way arounf the rod....






Thanks,
Kohler Guy
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Offline FlatheadPuller

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Re: Porting questions
« Reply #44 on: May 30, 2008, 09:10:31 pm »
If its stock, on the governor just put a bearing insert in it and if the crank is in good shape it will run for a LONG time.

Dennis
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