Blown Flathead Cam Options

M

movingviolation

Junior Member
Hey folks

In the process of building a stroked flathead with a 4-71 blower. Anyone out there with experience in these?? If so what cam shaft options are being used?

Rotating assembly is the 4.25 with Scat Hbeams and Scat Crank. Offenhauser heads, and Mooneyham 4-71 set up..

Currently looking at the custom grind H&H flatheads has..

Thanks
 
It kind of depends on the rest of the package, weight of the car, intended usage, etc.. Are you looking for fairly rough idle and lots of higher RPM power, or is this more of a HotRod on the street? What flywheel, transmission and rear-end gears?

A blower will effectively tame a bigger cam and will give you more low-end power (under boost) than a naturally aspirated engine (depending on when the boost comes in and how much).

What bore is the engine, what valve sizes, ported, relieved??? Give us a bit more to go on. Also, what grind in H&H recommending (they don't grind cams, so whose is it?).
 
I have a similar motor in my 2700 lb '34 coupe. B&M 144 blower, offenhauser 425 heads.
I am running a Schneider cam which is pretty much a Potvin super 3/8. Idles at about 800 RPM. Max boost is 5lb. Holley 600 cfm carb. A great combo, incredible pull as soon as you hit the gas and revs real quick to 6000 rpm. Make sure you run a boost retard ignition, mine backs off the timing 2d for every lb of boost. Total timing is 26d which is reduced to 16d @ 5lb boost. I would give Schneider cams a call. They really know these engines.
 
The Potvin 3/8 grind is one of my favorites - and would work well on any street blower setup. What I do is have a stock cam reground by 'Pete' on this forum. He does really quality work and I've used his cams in a lot of larger cubic inch street engines - all the way up to a 304 CI build.
 
Like B&S said,
Pete does beautiful work,,,,he reground a cam and put a Potvin 3/8 profile on it for me .
The grinding looks like a work of art.

Schneider does excellent work also,,,,and others .
But,,, Pete is here on the board ,,,and has an excellent price to boot .

Tommy
 
The only recommendation I would have for the blower is to open the LSA considerably. I used 106 degrees for the NA Bonneville style engine but I think AT LEAST 113 degrees is appropriate for a blower.
 
During my learning years running my GMC blown flathead on the street and drag racing the car as well the cam i ran was the Potvin 3/8 super I actually purchased the first one from Dean Moon back in 1977. In 1975 Paul Kosma set the XF blown street roadster record at Bonneville running the 3/8 super. The cam is perfect for what your doing.
I build lots of flathead 471 blower combinations have a dozen blowers in stock at the moment.
Ronnieroadster
 
Ronnie is your man for blown flathead advice. I have sold several of my KiWi-L100 cams for blower flathead engines. Customers have liked them.
Cheers
Tony
 
KiWinUS said:
Ronnie is your man for blown flathead advice. I have sold several of my KiWi-L100 cams for blower flathead engines. Customers have liked them.
Cheers
Tony
Click to expand...

I have one of Tony's L100B cams and it works great for my application which is street with some stompin'! No racing or side stepping the clutch here.
 
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