Technical Best Flathead Build for a 150 HP+ Cruiser

banjorear · Dec 1, 2025

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

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 2, 2025

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. 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.

How about some details: how many cubes, compression ratio, lbs boost, max HP at what RPM, cost to build, value today? And how many miles driven in a month or year?
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AmishMike · Dec 1, 2025

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

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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Technical Best Flathead Build for a 150 HP+ Cruiser

banjorear
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from Garden State

banjorear
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AmishMike
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from Ephrata, Pa

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3blapcam
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Technical Best Flathead Build for a 150 HP+ Cruiser

banjorear Member from Garden State

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AmishMike Member from Ephrata, Pa

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3blapcam Member from Trinidad, Colorado

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banjorear
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from Trinidad, Colorado