6-71 on a flathead

6-71. mechanicly too big, visually too big, takes too much power to run it.

 

All I can add to this discussion is that the quickest and fastest flathead dragster in the world and the only one to run in the sevens is 4-71 blown. Seems like just the right size.

 

The best suited would be the 4-71, but the 6-71 looks cool to me. I know it's a bit big and some say cartoonish....but in Hot Rodding, isn't bigger always better?

On a serious note, if you run the 6-71, you need to under-drive it about 25% for the street. You can do what the old-timers did for an intake, convert an Edmunds. Mill off the top, hog out the center and weld on a plate. That's what I'm doing for my Flathead.

Matt

 

You can buy billet main caps -- from Doug "Ardun" King, more wild and expensive stud girdles from Tony Baron, probably Tatum as well, etc.. The more money you spend . . . the more "stuff" you can put on the bottom end. Heck, Flathead Jack will probably take your first born and sell your one of his "ghost main" setups that a billet crank and 5 mains. If you're running a blown motor (on low boost), you can get away with the stock mains or maybe just a strap. If you start getting over 6 lbs on a regular basis, then you might consider the Doug King setup (you'll have to align bore and hone the block & caps). You should also replace the original studs with something like ARP. Of course . . . then there is the rods . . . enough . . . that's for another day . . .

 

This link posted on the Fordbarn site for flathead blower intakes:

http://www.austinrodshop.com/Ford_Flathead.html

 

Problem with a strap over the centre main , is that its still all hanging on 2 inches of thread !Like pouring a cemant flat roof on a house without upgrading the walls to take it . You gotta use the pan bolts to tie the whole gizmo together .

 

I are bulding a flathead with a 3-71 blower to my shoebox



It will have multirib belt drive and a size of bore 3.312" and stroke 4.125" (284 cu in)
i have made belt wheels for 13% overdrive of the blower

/Stefan

 

6 X 71 = 426, True. But in any theoretical calculations remember that 671 GMC/Detroit's are two strokes, take a gulp of air every revolution.

By nature Roots blowers tend to be high volume/ low pressure pumps, tend to start ****ing up HP to drive 'em big time as RPM's go up. Big Daddy's '64 edge was to drop boost [save drive HP], increase compression ratio to compensate, made for a more efficient combination then.

Chasing sweet spots is ongoing for racers. Rumor has it a buddy is replacing a 471 with a 671 on his blown Flathead coupe for the coming LSR season. Be interesting to see the tale the time slips tell....