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Old 07-30-2020, 12:50 PM   #1
Cape Codder
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Thumbs down Port & Polish Engine

Does anyone Port and Polish their engine when rebuilding or afterwards? Is there any real advantage to doing this on a Model A Engine?

Last edited by Cape Codder; 07-30-2020 at 01:04 PM. Reason: Incomplete Title
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Old 07-30-2020, 01:05 PM   #2
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Default Re: Port & Polish Engine

Why is there a "thumbs down" symbol next to the title in my post?
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Old 07-30-2020, 01:09 PM   #3
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Default Re: Port & Polish Engine

No clue on the thumbs down...


As far as port and polish. I doubt it would make much difference, if any, in a stock engine. In a performance engine where you're trying to eek out as much power as you can then it probably would help.
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Old 07-30-2020, 01:09 PM   #4
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Default Re: Port & Polish Engine

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Does anyone Port and Polish their engine when rebuilding or afterwards? Is there any real advantage to doing this on a Model A Engine?

Porting and polishing are just one part of a high performance build. On a stock or near stock engine there is no gain, unless there's a casting flaw to smooth out.
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Old 07-30-2020, 01:19 PM   #5
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Thumbs up Re: Port & Polish Engine

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Why is there a "thumbs down" symbol next to the title in my post?
I believe you are the only one that can edit your title. Perhaps you mistakenly hit the down thumb button? (notice my up thumb).

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Does anyone Port and Polish their engine when rebuilding or afterwards? Is there any real advantage to doing this on a Model A Engine?
Only porting I would suggest is opening up the 'A' manifold when using a 'B' carby.
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Last edited by Ruth; 07-30-2020 at 01:26 PM.
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Old 07-30-2020, 02:37 PM   #6
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Thumbs up Re: Port & Polish Engine

Well I must give all three of you a "THUMBS UP" for responding and answering my post!
Thanks again!!
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Old 07-30-2020, 02:39 PM   #7
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Default Re: Port & Polish Engine

Yes to port and polish, but, I never have with a Model A.
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Old 07-30-2020, 03:33 PM   #8
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Default Re: Port & Polish Engine

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Does anyone Port and Polish their engine when rebuilding or afterwards? Is there any real advantage to doing this on a Model A Engine?
Indirectly, yes we do when we install oversized intake valves as we enlarge the bowl area by 0.100". Port matching is another area to gain performance. One thing that I will share with you is the technology of polishing has changed where that is not what is typically done. Blending and dimpling (-think surface of a golf ball) is where the most advantage is gained on high-performance engines.
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Old 07-30-2020, 03:52 PM   #9
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Default Re: Port & Polish Engine

A definite increase in hp can be had by porting and PORT MATCHING on a stock engine.
Bigger is better. A larger ID intake manifold and carb will add more hp. A exhaust header will add more.
Brent mentions the best type surface finish for intakes but in lieu of that a stone finish is next. The exhaust should be polished smooth as possible.
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Old 07-30-2020, 03:52 PM   #10
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Old 07-30-2020, 04:17 PM   #11
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Default Re: Port & Polish Engine

I think larger intake valves help more than porting. I have them and they give good power. I also have a Stipe cam and HC head. It all works together.


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Old 07-30-2020, 08:39 PM   #12
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Default Re: Port & Polish Engine

IMO, porting and polishing a stock Model A engine doesn't make much difference but it does help - a little.
For a real boost to performance, there are the three Cs". Carb, Cam and Compression. A little on each will give amazing results. Porting and polishing helps with the "Carb" part of that.
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Old 07-31-2020, 06:15 PM   #13
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Default Re: Port & Polish Engine

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Does anyone Port and Polish their engine when rebuilding or afterwards? Is there any real advantage to doing this on a Model A Engine?
Pete gives you best information, that addresses the question asked ! And is what I've practiced for many years.
Your choice !
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Old 08-01-2020, 10:35 AM   #14
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Default Re: Port & Polish Engine

I enlarged the intake ports a bit before installing a dual updraft intake manifold and model B carbs on my roadster . I don't polish intake ports on engines that run updraft carbs .
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Old 08-01-2020, 10:51 AM   #15
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Default Re: Port & Polish Engine

Hmmm, I posted agreeing with Brent and Pete. Don't know where it went. But it was probably my fault.
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Old 08-01-2020, 11:08 AM   #16
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Default Re: Port & Polish Engine

This video is for a single cylinder Flathead motor, but it is similar to the configuration of a cylinder in a Model "A" engine. https://www.youtube.com/watch?v=s-Li-mwjvlg
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Old 08-01-2020, 12:04 PM   #17
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Default Re: Port & Polish Engine

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This video is for a single cylinder Flathead motor, but it is similar to the configuration of a cylinder in a Model "A" engine. https://www.youtube.com/watch?v=s-Li-mwjvlg
Bob, what he is calling "shaving the eyebrows" was originally what was the relieved part was back in the 40s & 50s when they said 'Port & Relieved on a flathead Ford.

The biggest two things that I came out of this video is; 1) there is not any flow numbers on the before and after to see whether he actually did any good. Often times, you can hurt flow by grinding away metal.

And 2), the Briggs do not deal with reversion like the Model-A/B engines do because of the Ford's shared intake port. I first became educated on serious horsepower of a flathead from my son's early racing days with a kart and a jr. dragster. The R&D that has been spent in the Briggs world is unreal.

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Old 08-01-2020, 12:58 PM   #18
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Default Re: Port & Polish Engine

'The R&D that has been spent in the Briggs world is unreal.'


Boy, I guess so. A good friend became 'crew chief' for his son starting with mic-rods and then go-karts. It surprising how far these guys have taken these B&S engines since I was playing with them in the early 60s.
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Old 08-01-2020, 01:16 PM   #19
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Default Re: Port & Polish Engine

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Boy, I guess so. A good friend became 'crew chief' for his son starting with mic-rods and then go-karts. It surprising how far these guys have taken these B&S engines since I was playing with them in the early 60s.
We have not been around Jr. racing in over 15 years, but back then the single-cylinder Briggs engine in our dragster made a tad more horsepower than a stock Model-A engine, and back then those engines cost about what a rebuilt long-block Model-A engine did. I feel certain these engines are making well over 50 hp today.
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Old 08-01-2020, 02:49 PM   #20
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Default Re: Port & Polish Engine

Amazing. I thought if we were getting 7-8 HP out of a 5 HP we were doing good. I think in my friends time they were doing around 20 HP. I can't even think about 40-50 !
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