Flathead blower cam WITHOUT the blower

OK, it's is really looking like somewhere down the line I'll be putting a 4-71 on top of a flathead. Besides beefing up the caps & forged pistons, should I install a blower specific cam during the rebuild?

I know Joe Albin likes the 400Jr, some guys run the Winfield SU-1A with a blower with great success. Both of these cams are also good street cams. But other guys like George @ Clay Smith, Crower, & Tatum sell flathead blower cams. Without posting specs & getting into that whole deal, would a blower cam (in theory) work OK on a normally asperated motor?

Thanks

 

To overr simplify, a blower blows the mixture in, where a normal engine the cam allows the cylenders to create suction to **** the mixture in.

 

Yes.

 

I would imagine that would mean a "blower cam" would have less valve overlap so the pressure isn't initially just blowing out the exhaust, but it can handle more intake duration, even past BDC on intake.?

Sorta like a "RV" cam as in very mild top end if it doesn't have the blower packing it in.

 

You won't hurt anything by running a "blower" cam in a normally aspirated motor. Special blower grinds usually open up th lobe center so that you capture more of the mixture. For example, If there is a lot of overlap, part of the pressurized air/fuel mixture gets "blown" out of the exhaust port when both the intake and exhaust valve are open, so widening the lobe center helps trap that mixture. Blower cams also tend to have less lift and duration (on the intake side especially). This lessens the strain on the valvetrain, and captures more of that precious mixture in the combustion chamber.

A blower cam in a naturally aspirated motor should act a little like an RV cam. It should idle real smooth, build cylinder pressure early, smooth out the torque curve and move the torque peak up slightly.

Or, I might be crazy, but that's how I understand it

 

Oops, DrJ beat me to it!

 

Blower cams do have less overlap - and the duration on the intake is typically less, as you're relying on the blower to pack the cylinder on the intake stroke.

If I recall right - a good blower grind has a longer exhaust duration to allow the xtra mix 'unpack' into the exhaust tract.

 

I ran a 400Jr in my Merc flattie for 6 years with 3-97's then pulled the intake and installed a Joe Abbin kit 4 years ago. No problems either before or after and averaging 4-5K miles/year.

Joe also likes the Max 1 it develops more torque in the mid-range than the 400Jr.

 

Yes; main difs in blower specific cam as pointed out would involve overlap, implying earlier/later events bracketing that point...if you want LOTS of detail on implications of moving different cam events, with specific chapters on supercharged applications, look at Dave Vizard's book on small block Chevy cams. It will give you the mental fuel to really think it all through. And probably a headache.

 

Was just over at Joes this week & we actually talked about this quite a bit - he does indeed like the Max-1. His old engine was running one - his new engine runs a 400Jr.

 

OK, this is just what you need for that blower motor..............plus I have a nice 4"Merc Crank.............some C.A.T. rods

That way you can build your "Street Motor" and be motoring............at the same time building the "Blower Motor" as time and money permits.

One of the nicest 8BA blocks you will ever see, and it is standard bore!!!!!!
OH........did I forget to say the block has a Doug King girdle and billet main caps with studs...........................all for you.

 

Thanks to all:

A Chopped Coupe- You are the man! Thanks.