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#1 |
Registered User
Join Date: May 2013
Location: Colorado Rocky Mountains
Posts: 263
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Re: 1972 307 cam selection... HELP!
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 |
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#2 | |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,496
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Re: 1972 307 cam selection... HELP!
Quote:
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.
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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#3 |
Registered User
Join Date: Mar 2005
Location: 10-Uh-See
Posts: 5,609
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Re: 1972 307 cam selection... HELP!
Found the article!! It was Super Chevy magazine, not Car Craft.
http://www.superchevy.com/how-to/eng...ne-performance
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#4 |
Senior Member
![]() Join Date: Jul 2000
Location: North Texas
Posts: 3,496
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Re: 1972 307 cam selection... HELP!
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:
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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