Featured Technical Best Flathead Build for a 150 HP+ Cruiser

banjorear · Dec 1, 2025 at 5:58 PM

3blapcam said: ↑

I agree with this statement. I don't care for copper gaskets though, I use those cheap composite ones and they seal up really well!

Studs, heat cycle, re-torque once or twice and drive it.

3blap.
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I'm the opposite. Copper gaskets with three coats of cheap as aluminum paint, slap them on as the third is still tacky.

banjorear · Dec 1, 2025 at 5:59 PM

Bandit Billy said: ↑

Like I said, flatheads don't breathe well stock. Fortunately, this is not a "stock" website, we hot rod **** here. I did relieve mine and did substantial porting, and put in large Chevy valves, and upped the CR ratio a bit, and decked the heads a bit, and added a 471 blower and made a fun, streetable engine out of it. They are just air pumps and the more efficient they are at it, the more fun they will provide. Most folk need to stick to crate engines from summit, but a few will take the road less traveled. For those that do, I'll see you out there.

That gets one of these and a . I used ARP studs, copper gaskets, SS acorns, washers, and I machined every mounting boss on the heads to be sure they were flat (because they weren't). One re-torque after initial heat cycle, never again. Thousands of miles and not all very kind! Zero issues other than a sticky input shaft/pilot bushing I had to remedy.

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Awesome, man. Love it! I still kick myself in the **** for selling my 4-71 and Navarro blower intake. What a mistake!

AmishMike · Dec 1, 2025 at 9:01 PM

Bandit Billy said: ↑

Like I said, flatheads don't breathe well stock. Fortunately, this is not a "stock" website, we hot rod **** here. I did relieve mine and did substantial porting, and put in large Chevy valves, and upped the CR ratio a bit, and decked the heads a bit, and added a 471 blower and made a fun, streetable engine out of it. They are just air pumps and the more efficient they are at it, the more fun they will provide. Most folk need to stick to crate engines from summit, but a few will take the road Great looking flathead envy of many. How about details? Cubes, comp ratio, boost lbs, hp @ rpm, cost to build, value today?less traveled. For those that do, I'll see you out there.

That gets one of these and a . I used ARP studs, copper gaskets, SS acorns, washers, and I machined every mounting boss on the heads to be sure they were flat (because they weren't). One re-torque after initial heat cycle, never again. Thousands of miles and not all very kind! Zero issues other than a sticky input shaft/pilot bushing I had to remedy.

View attachment 6586687
Click to expand...

AmishMike · Dec 1, 2025 at 9:06 PM

Screwed up post of my questions for bandit billy. Trust u see them. One other question: how many miles on it over what time period?

3blapcam · Dec 2, 2025 at 11:16 AM

AmishMike said: ↑

Screwed up post of my questions for bandit billy. Trust u see them. One other question: how many miles on it over what time period?
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On your post, there's an "edit" ****on next to the date & time at the bottom. You can fix it.

3blap.

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Featured Technical Best Flathead Build for a 150 HP+ Cruiser

banjorear
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AmishMike
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from Ephrata, Pa

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Featured Technical Best Flathead Build for a 150 HP+ Cruiser

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banjorear
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from Trinidad, Colorado