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03-17-2023, 07:56 AM | #1 |
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Power slot in an model a engine?
Hi everyone.
I saw a Ford v8 engine beeing machined on youtube. They made a groove between the cylinder and valves - a so called Perfoemance Slot. They said that i Pulled mutch better from this. Is there any merrit to this and is this aplicable to the Model A? Johan Ottosen Toudor early 1929 |
03-17-2023, 09:00 AM | #2 |
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Re: Power slot in an model a engine?
I believe in the old days of hotrodding they called that "relieving". It was supposed to add power to hopped-up V-8 blocks. Like the Beach Boy song "Little Deuce Coupe" goes: "She's ported and relieved and she's stroked and bored."
Marshall |
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03-17-2023, 09:03 AM | #3 |
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Re: Power slot in an model a engine?
Good one Marshall.
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03-17-2023, 09:46 AM | #4 |
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Re: Power slot in an model a engine?
Porting was necessary in Flathead V8s with hi-compression heads.
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03-17-2023, 10:04 AM | #5 |
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Re: Power slot in an model a engine?
Y-Blockhead -
In my life at various times I've been "relieved", I've been "stroked" and I've been "bored". But I have never, ever been "ported". Marshall |
03-17-2023, 10:51 AM | #6 |
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Re: Power slot in an model a engine?
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03-17-2023, 11:21 AM | #7 |
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Re: Power slot in an model a engine?
The valves in an A sit up more flush with the block deck so there is nothing really to relieve in the block. Much more beneficial to make sure the head is open around those "big" valves that you instaled to unshroud them
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03-17-2023, 11:46 AM | #8 |
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Re: Power slot in an model a engine?
I believe the V8 valves are slanted which would make the relief needed.
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03-17-2023, 12:23 PM | #9 |
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Re: Power slot in an model a engine?
Relieving a V8 block only reduces compression ratio. In my opinion it doesn't help the Model A or V8 engine.
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03-17-2023, 01:06 PM | #10 |
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Re: Power slot in an model a engine?
This is the most informative thread I've found on relieving the V8 block:
https://www.fordbarn.com/forum/showt...1427&showall=1 |
03-17-2023, 01:12 PM | #11 |
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Re: Power slot in an model a engine?
I think in the early days of the post WWII hot rodding era, it was an ego thing to be able to brag that one's "mill" (engine) was "relieved". 'Didn't impress those who really knew engines, but it bowled over the non-automotive types, who didn't know what the heck "relieving" meant. I also read that relieving was finally recognized as not being cost-effective or created any significant additional horsepower, and sometimes it actually decreased the engine's performance. But it sure sings when you say: "She's ported and relieved." Come to think of it, that could also apply to several girls I used to date.
Marshall |
03-17-2023, 02:16 PM | #12 |
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Re: Power slot in an model a engine?
Relieving a model A block will definitely help if you are building a flathead configuration for all out racing. You need to lower the transfer area in the head to match. It all has to do with flame front speed and distance travel.
This is also one reason why a deep relief in a V8 makes it go faster. Not much help on a wimp street engine. |
03-17-2023, 03:04 PM | #13 |
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Re: Power slot in an model a engine?
It doesn’t help to thin out the deck which is o-2-thin to begin with
Getting the valves up high out of the seats makes more sense and flow Chamber design is crucial for performance J
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03-17-2023, 03:21 PM | #14 |
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Re: Power slot in an model a engine?
Ford generally only relieved the truck engines and like the photo in post #1, it was just a basic straight cut relief. Racers took it to an art form.
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03-17-2023, 04:04 PM | #15 |
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Re: Power slot in an model a engine?
Thanks all. You have been very enlighening! I will stick to leveling the deck :-)
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03-17-2023, 04:23 PM | #16 | |
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Re: Power slot in an model a engine?
Quote:
The old full width and full depth all the way works best. I was going to try moving the valves and cam closer to the cylinders but never got around to it after I switched to V8's.. I also had plans for combining pieces of an Olds quad 4 and a model B block so it still qualified as a vintage block but had all the attributes of the quad 4. |
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03-17-2023, 08:22 PM | #17 |
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Re: Power slot in an model a engine?
Head design has everything to do with power. Two heads with the same compression ratio but with different chamber design will perform differently. The intake air has to get past the valves and then down into the cylinder in the smoothest way. And the squish area has to create the most turbulence for ignition without creating a dead pocket or a chilled area. Racing flat heads are the best examples to follow. Relieving the block, in my opinion, is not going to gain much for a Model A engine. It is better to create a smooth path for the air in the head. The intake air already has some momentum upwards as it exits the valve.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-17-2023, 09:10 PM | #18 | |
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Re: Power slot in an model a engine?
Quote:
A good example of one of these engines was several years ago a FLATHEAD B engine won top eliminator in the vintage 4 cylinder dragster class at the Antique Nationals 2 years in a row. The OHV engines just couldn't do it. |
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03-18-2023, 10:52 AM | #19 | |
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Re: Power slot in an model a engine?
Quote:
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03-18-2023, 01:22 PM | #20 | |
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Re: Power slot in an model a engine?
Quote:
While welded in tubing was the first way tried for that, a much easier and better way was found later by hogging the whole area between the ports out and attaching a divider plate to the header plate. Ended up with considerably larger port. |
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