401 rebuild specs and other info

P

projectbeaumont

Newbie
I'm planning on rebuilding a 401 for my 31 Ford A coupe hot-rod project, and have a few questions.

Most importantly, does anyone know a good resource for all the dimensions and clearances for reassembling these motors? I would like to "blueprint" this engine as much as possible while I assemble it. I'm looking for a very reliable, long lasting motor for the street and highway, that I can beat on once in a while (but never abuse)

Has anyone had any experience converting Nailheads to internal balance? Are there any performance or durability tricks specific to these engines? I have worked on (and killed) a few SBCs but this will be my first Nailhead build. This will also be the first time I assemble the rotating assembly and valve-train by myself.

I've been reading a lot of cam advice with differing opinions. I'm looking for a cam that sounds a little lumpier than stock, but don't want to give up the great low and mid-range torque these engines are famous for. I'm curios to hear more debate on what cam shaft would be ideal for my combo.

I plan on running a 700r4 trans with a mild 1800-2000 stall converter, 3x2 carbs, cleaned up stock heads, and modern HEI style ignition. Obviously with a '32 style grille, the rad won't be very big. It will be a light car with big rear tires. I'd love to get as much power over stock as I can. but not at the cost of reliability or low end torque. This motor will be built for pump gas.

Any help is greatly appreciated!
 
projectbeaumont said:
I'm planning on rebuilding a 401 for my 31 Ford A coupe hot-rod project, and have a few questions.


I've been reading a lot of cam advice with differing opinions. I'm looking for a cam that sounds a little lumpier than stock, but don't want to give up the great low and mid-range torque these engines are famous for. I'm curios to hear more debate on what cam shaft would be ideal for my combo.
Click to expand...

If you use a cam that has a narrow Lobe Separation Angle (less than 110 degrees), you increase
the valve overlap giving you a lumpy idle and the low rpm sound you are looking for.

However with a narrow LSA, the intake valve closes sooner and the exhaust valve opens later which increases low end torque.
You can have lumpy idle and low end torque as a bonus

The downside of a lot of valve overlap is lower manifold vacuum for power brakes.

The Comp Thumper series is based on this principle.
This cam will give you a lot of midrange torque.

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1515&sb=2

A 9.5:1 static compression ratio with the above cam will give you a dynamic compression ratio of 7.7:1
for good pump gas tolerance without detonation.

Paul
 
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Thanks for the help guys!

Bob, I'm ordering a couple books, including a reprint of the chassis manual. I knew they existed, just wasn't sure how specific the drive-train info was in them. The resources and info you have made avail here on the site never ceases to amaze me! I used the Nailhead casting #s resource quite a bit when buying all the components and looking at used blocks and heads. You guys have put together a fantastic site, Keep up the good work!

Paul, thanks for the cam advice. I was pretty much headed in that direction, but it's always reassuring to hear it confirmed by someone more knowledgeable. I have heard people refer to "dynamic compression" before, but I don't understand it's relationship to Static Compression. I usually shoot for a 10:1 static compression when building motors (we have a station near us that sells 94 octane).
Are there any assumptions I might be making from my experience with SBC motors that are not transferable to the nailhead?

Also if anyone else out there has any Nailhead specific words of wisdom, I'd be extremely grateful.

Has anyone had any experience converting a Nailhead to internal balance? I'd like to know if it's worth the trouble, or even feasible at all...

Thanks again
 
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