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Old 08-31-2008, 09:07 PM   #1
Aunt-Jemima
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1972 chevy 1/2 ton 307

ok i have a 1972 chevy 1/2 ton 307/auto. its wrecked i need a whole front end clip passenger bed side doors and the frames bent. someone put a floor shift auto in it be the colum was getting stiff and they didnt know how to put it on the fllor so they switched it out for a auto i have no idea what kind it is. im deciding on whether its worth rebuilding or not. if i do i want to know what would be better gas millage a 350 or the 307 but either will be built to around 300 horse. help me decide whether its worth it or not.
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Old 08-31-2008, 09:21 PM   #2
Longhorn Man
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Re: 1972 chevy 1/2 ton 307

welcome to the forums!
There have been many MANY reports of the 'ole 307 getting outstanding MPG on here... 13 - 16 seems realistic with that engine.

Last edited by Longhorn Man; 08-31-2008 at 09:22 PM.
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Old 08-31-2008, 11:28 PM   #3
Indyuke
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Re: 1972 chevy 1/2 ton 307

Sheet metal can be easily replaced... a bent frame is tougher to deal with.

The 307 is a good engine. I've got a 350 coupled with a 700r4 tranny and it gets about 15mpg average. Strictly highway is about 17mpg.
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Old 09-01-2008, 09:54 AM   #4
LONGHAIR
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Re: 1972 chevy 1/2 ton 307

In theory the fuel usage is directly related to horsepower, meaning that you can only get so much power from a given amount of fuel...and under perfect conditions. So, again theoretically the cubic inch factor doesn't matter....now, you might have to be a bit more radical to get 300HP from a 307, but if the horsepower is equal, the fuel used should be similar. Of course this is all sounds good, but in practical application?

Mileage is more about the efficient use of that power. You can only push a brick wall with a certain degree of efficiency, and 300HP is more than enough. These trucks are heavy and aerodynamically huge, efficiency was not a concern when they were designed and there isn't much that can be done about it at this point.
Low-end torque to get it rolling w/o a lot of throttle, proper gearing and over-drive....along with driving style will get you the best you are going to get.
The milder 350 would probably drive better, more torque with the longer stroke.
You can squeeze some more out by eliminating some brake drag/rolling resistance and a manual transmission, still with overdrive. The cost of all off this might take a long time to recover though.
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Old 09-01-2008, 01:39 PM   #5
Aunt-Jemima
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Re: 1972 chevy 1/2 ton 307

I wasn't expecting to make 300 horse out of the 307 but in that area. is it posible to put a 350 crank in it to make it a stroker?
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Old 09-01-2008, 02:39 PM   #6
LONGHAIR
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Re: 1972 chevy 1/2 ton 307

Probably....buy why? You would need cu$tom pi$ton$ to make it work. All that for 328 cubic inches? Unique, yeah (just because you can, doesn't mean you should)
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Old 09-01-2008, 02:48 PM   #7
88JRFAN
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Re: 1972 chevy 1/2 ton 307

A 350 crank will not fit in a 307. The 307 is an animal all it's own. A 350 crank will fit in a 305 though.
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Old 09-01-2008, 04:06 PM   #8
LONGHAIR
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Re: 1972 chevy 1/2 ton 307

Quote:
Originally Posted by 88JRFAN View Post
A 350 crank will not fit in a 307. The 307 is an animal all it's own. A 350 crank will fit in a 305 though.
Sure it will. Any of the large journal cranks will fit in any of the large journal blocks. Anything after the journal change in the 327s will work except the 400, they are bigger yet.

265, 283, early302, and early 327 all had small main journals (2.300)
Late 302, late 327, 307, 350 have larger (2.450)
400s are all alone at (2.650)

Besides a 350 crank and a 305 crank have the same stroke anyway. You wouldn't gain a thing.

305s have valve clearence issues with the cylinder wall, so bigger heads are a problem with them. AFAIK the slightly larger bore of the 307 doesn't have a problem with this.

You can do it, but it is not a stock combination, so special piston with a lower compression height would be required. Someone may make them as a stock item, but again it's gonna cost for no real benefit. The same money would get you a lot farther in a 350.
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Old 09-01-2008, 04:48 PM   #9
88JRFAN
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Re: 1972 chevy 1/2 ton 307

OK, i stand corrected. Learn something new every day. Thanks Longhair.
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