1972 307 cam selection... HELP!

[gvw5400]

Spiced Ice Pirate,
Don't over think your build!!! Of course you can do any of the
many ideas offered here by everyone offering their thoughts to help.
We are all good at spending your money! You might consider taking a simpler
cost effective approach, install 3.73 as others have recommended or (4.10 gears with Bigger Tires) free up the exhaust side of the 307, ( might be good enough now).
Give it a great tune on ignition and carb.
Unless you really want a huge project, $$$ and the 307 is basically sound now,
just do the gears.
Have fun driving your truck !!, get it on the road and have Fun !!!!
All The Best,
Dirk

[MikeB]

Originally Posted by gvw5400

Spiced Ice Pirate,

Give it a great tune on ignition and carb.
Unless you really want a huge project, $$$ and the 307 is basically sound now,
just do the gears.

Dirk

Have to jump in again and say my 69 C10 had a totally stock 307 with single exhaust. I installed duals (only 2" pipes) with generic turbo mufflers, and installed a used Q-jet manifold with a 450 cfm 4bbl Holley Economaster carb. What a huge difference that made!

As I recall, fuel mileage around the suburbs, with some highway, went from 10-11 mpg to 12-13 mpg. And the engine felt so much better when accelerating and at highway speeds, like it went from asthma to breathing freely. Back in 1990 it was the best $250 I ever spent.

[68Stepbed]

Found the article!! It was Super Chevy magazine, not Car Craft.

http://www.superchevy.com/how-to/eng...ne-performance

[MikeB]

Interesting article from Super Chevy, but they were wrong about GM producing a 307 with a small journal crank. Quite unusual for them.

Here's an excerpt from Hot Rod Magazine. It's the second paragraph.
https://www.hotrod.com/articles/ccrp...-engine-specs/

And here's a Wikipedia article on small blocks. Read the first and last paragraphs under the section entitled "3.875 in. bore family (1955–1973)".
https://en.wikipedia.org/wiki/Chevro...l-block_engine

Finally, go halfway down the page here:
http://chevellestuff.net/qd/crank/crank.htm

Bottom line is I think GM needed a new block for the 307 with more "cast-in" clearance for rods (due to .25" longer stroke). And why cast a brand new block with small journals, when they were moving to medium journal cranks on all other small blocks (302, 327, 350)?

I did find a list of crank castings at Mortec.com that shows only three castings used for the 307, and they were also used for 327s. So, they were the same raw castings but machined differently for balancing with different piston weights.

3911001....307,327...cast....medium journal...3.25" stroke
3911011....307,327...cast....medium journal...3.25" stroke
3941174....307,327...cast....medium journal...3.25" stroke

A couple pictures of my 307 crank rebalanced for 327 (+.030") pistons and SCAT rods: