Compression and flow

3W Hank said:
About compression in a FH.
Old speedparts heads had high compression as the Canada heads and to Kogel both cast iron and aluminium.
So idea must have been that compression got a stronger engine.
But this engines had a terrible flow around the piston so one can questionise if not a lower compression get more flow to spark, so more power in reality.

I has a set of the ’10 to 1’ L&S heads and Ross domed pistons.
Heads is at 59 CC and measure 10.5 mm or 0.413” deep chambers.
They get 10 in compression with 1/8” bore and a 4” stroke and a 0.04” thick gasket in a 59BA.
My cam is a Potvin 425 ( 425” lift ) so I might get away with this.
But I might has to mill the chambers or go with a thicker gasket.

-So the question is, do this engine like compression or do they make more power less compression.
That would cure all piston to head and valve to spark plug issues aswell.

In my case I’m not after max power, just like the sound and feeling and old parts.
So question is more technical.
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Hank I’m curious what the exact true lift of your Potvin cam is? Is it a genuine Potvin or a regrind knockoff? Legendary cam grinder Pete told me he has seen several original ones and none were ever .425” lift. I own an original and have looked at 3 others and again none had .425” lift.
 
Tim Ayers said:
I can't see for I don't have Facebook, but that could be Dale's (Bored&Stroked) motor. He was involved in the FlatCad racing team a few years ago
Click to expand...

Could likely be him then. He mentions “flat cad” and resurrecting it from about 5 yrs ago.
 

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Yep - you found me! LOL. I designed and built this engine (is in my shop as I write).

The FlatCAD engine is a very purpose-built racing engine that uses a lot of flow work and boost to make horsepower. The block has a couple hundred hours of porting and valve work done in it. The result are huge ports and a LOT more flow than you can even get close to with a Ford flathead. This is strictly due to the design of the engine and the amount of material I had to work with.

The only component that is original is the block, everything else was designed in 3D CAD and a lot of "ideas" came from Harley KR race engines.

Also, with the exhaust ports coming out of the TOP of the block, this gave me a way to port the heck out of them (impossible without welding new ports on a Ford).

It would be interesting to see what sort of HP it could achieve in naturally aspirated form, but we'll never go that direction.

Back to Bonneville: We're not going to make Bonneville this year (yet again), but the team sure seems to want to make it back in 2027. It will come down to the amount of time and $$$ it takes to complete our complete rebuild of the car, engine, suspension, etc..

Here is a peek at the deck and some port pics:

69307461615__97C022F7-6F82-42A6-AEA3-A38098F42659.jpg

LongIntake.jpg

TwoIntakePorts.1.1.jpg

ExhaustBowl.jpg

OutsideExhaustPort.1.1.jpg

On the dyno - quite the beast! Best tune on gas was 570 HP, best on Alcohol was 654. The interesting thing is that at 5500 RPM, the HP was still going up - that tells you that it has enough flow to make more HP. We also did a pull with about 10% nitro, but had head gasket failures. LOL

With the long stroke, it is a torque monster. Notice it has over 700 ft. lbs. way down at 4000 RPM. It is really fun to drive!

dyno 3.jpg

BestRun-AlcoholTune.jpg
 
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My ’Potvin’ cam is a cast cam for 8 BA.
It is not at .425” lift maybe .415”.
Its marked Potvin 425 but who knows who made it, maybe Moon (?) and according to seller it came from a old inventory in LA.
It’s used.

That cam will go in my ’race’ FH with a ported Merc 41 block ( old pro port work from LA ) but vales is still 1.5” but reviled ( 3.5/16” bore )
Baby stroked 4” crank.
Kong dist.

My other Mec 41 block with a baby stroked 3.75” crank might get a Potvin 3/4 cam as Weiand x 2 intake ( LZ/ Kurten dist ) If it works..

Ideas is still on me on less comp ( better flow ? ) but idea is not on the 3.75 crank engine ( std steel heads ) but the race engine.

Anyone has a Potvin 3/4 cam over ?
 
I've never seen or had a Potvin 3/4 cam. What are the specs?

I do have and swear by the Potvin 3/8 cam for street flatheads. Has a great sound, fun idle and pulls really well in any 276" or larger flathead. I put one in a 304" ported flathead (1.6" valves) - runs extremely well with 3 97's on the top.

I also have the Potvin Climax 400 cam . . . have not ran it as of yet.

I ran a Potvin/Moon 425 in my 34 sedan when I was a kid (284" ported flathead) - it ran pretty well on the street. It was a reground cast cam. Given the sharp "nose" on the 425 grind, using a reground 32 billet core isn't a bad idea. I had my friend Pete grind me one of those.
 
Bored&Stroked said:
I've never seen or had a Potvin 3/4 cam. What are the specs?

I do have and swear by the Potvin 3/8 cam for street flatheads. Has a great sound, fun idle and pulls really well in any 276" or larger flathead. I put one in a 304" ported flathead (1.6" valves) - runs extremely well with 3 97's on the top.

I also have the Potvin Climax 400 cam . . . have not ran it as of yet.

I ran a Potvin/Moon 425 in my 34 sedan when I was a kid (284" ported flathead) - it ran pretty well on the street. It was a reground cast cam. Given the sharp "nose" on the 425 grind, using a reground 32 billet core isn't a bad idea. I had my friend Pete grind me one of those.
Click to expand...

I also run a Potvin 3/8th's cam in 292 ci flathead. It's a blast to drive and has power from start to finish. Great, great street cam.

I also have two of Tony's Kiwi 100's that I will be trying out next to do side by side comparisons.
 
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