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Old 01-06-2014, 10:57 PM   #1
Pete1stark@yahoo.com
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307 Chevy motor

I read an article about the 307 engine being a 350 cast block with a small (3.875) bore & the only reason the 307 got a bad rap was because the cam was mad from very soft material causing the cam to flatten really quick which made it sluggish. This giving it a bad rap. Am I wrong.
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Old 01-07-2014, 12:13 AM   #2
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Re: 307 Chevy motor

Cam was no different than any other small block. They where sluggish due to the smaller bore and longer stroke. Made for low end torque and not high rpm.
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Old 01-07-2014, 12:15 AM   #3
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Re: 307 Chevy motor

307 will work for a truck for torque and daily driving but if spending cubic inchs rule, so at least spend on a 350, same parts more torque yet and power. Mileage is about the same.
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Old 01-07-2014, 12:15 AM   #4
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Re: 307 Chevy motor

I believe the 307's had smaller valves than the 350's too.
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Old 01-07-2014, 12:42 AM   #5
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Re: 307 Chevy motor

305'S had the cam problem in the 80's. 307's were dogs, they worked hard, were loyal but nothing fancy
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Old 01-07-2014, 12:43 AM   #6
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Re: 307 Chevy motor

307s git a bad rap from the bigger is better mentality They are actually a longer lasting motor than a 350.
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Old 01-07-2014, 01:03 AM   #7
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Re: 307 Chevy motor

I had a 307 in a 1968 Chevelle with a 2sp auto behind it. It ran great and after I put headers on it the gas mileage went up by around 5%-10%.

I sold it to my sister. She ran it into the ground and thru a rod thru the side of the block. My brother and brother-in-law talked her into letting them put in a 327. It was a total gut-less POS after that (so she said) and sold the car. She said that it just was not the same anymore. She liked the low end torque of that 307.
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Old 01-07-2014, 01:07 AM   #8
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Re: 307 Chevy motor

My 71 has one. I've only driven it home from buying it but if the compression is good I'm going to fix some oil leaks and run it so I can spend my time and money on other parts of the truck. With the 3.08 rear gear I'm hoping for some road trip worthy mileage.
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Old 01-07-2014, 01:52 AM   #9
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Re: 307 Chevy motor

Quote:
Originally Posted by Pete1stark@yahoo.com View Post
I read an article about the 307 engine being a 350 cast block with a small (3.875) bore & the only reason the 307 got a bad rap was because the cam was mad from very soft material causing the cam to flatten really quick which made it sluggish. This giving it a bad rap. Am I wrong.
I've heard that to. Also that you could bore it out 4.00 (350).
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Old 01-07-2014, 08:26 AM   #10
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Re: 307 Chevy motor

A 307 has the same stroke as a 327 so if you have a good 350 block (4" bore) you can make a 327.
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Old 01-07-2014, 09:07 AM   #11
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Re: 307 Chevy motor

Not to Steal your thread but i Have a question for these guys too.I've heard I can use the 307 piston in my i6 250 is that true?
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Old 01-07-2014, 10:52 AM   #12
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Re: 307 Chevy motor

307 uses the 327 crank with a 3.25 stroke
307 has a 3.875 bore
350 has a 4.00 bore is
230 has same stroke and bore as 307, so pistons should fit-check part numbers
250 bore is 3.915 not 4.00
you could bore out the 307 to 4.00 but need thick cylinder walls (different 307's have diiferent thickness) so you need a sonic check

Last edited by ho70; 01-07-2014 at 10:58 AM.
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Old 01-07-2014, 12:45 PM   #13
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Re: 307 Chevy motor

A 307 was a 283 bore with a 327 crank. 3.875 bore & 3.25 stroke. This made for more torque than the 283, but less potential than the 327. Overall these were a base-line engines and have never been popular for performance because of the odd CID. And chances are you cannot bore these blocks out to a 4.00 bore of a 302/327/350. You are better off finding a 4" bore block and starting from there.

Conversly, a 302 is a little monster. Lower torque, but very high RPM and very quick revving potential making it perfect for the short track in a lighter car
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Old 01-07-2014, 03:27 PM   #14
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Re: 307 Chevy motor

I've always wondered how a 307 with a 3.75" stroke crank would behave compared to a 383.
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Old 01-07-2014, 05:05 PM   #15
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Re: 307 Chevy motor

Quote:
Originally Posted by Unionwelder View Post
Not to Steal your thread but i Have a question for these guys too.I've heard I can use the 307 piston in my i6 250 is that true?
I have heard that also many times. It raises the comp. ratio.
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Old 01-07-2014, 07:15 PM   #16
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Re: 307 Chevy motor

No real magic with a 307, As stated above it's a 283 with a 327 crank. Think of it as a factory 283 "stroker" but with mild compression and a tame cam. Personally I think I would rather own a 307 then a 305. You could wake it up with a stouter cam, but I don't know if higher comp pistons are available. Build what you like, but a 350 is always a great cheap way to engine happiness. All the best, Dirk
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Old 01-07-2014, 08:20 PM   #17
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Re: 307 Chevy motor

I think the 307 is a great engine as long as you have reasonable expectation. It's never going to make the power or torque a 350 would, but the bore and stroke sizes are pretty good when you compare it to other engines of similar size. I wouldn't want to try to bore one to 4.00", you would never be able to hone the cylinders straight because there wouldn't be enough cylinder wall left to keep the bore stable. And if you did manage to get the engine together, it would collapse a cylinder very quickly.
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Old 01-07-2014, 09:57 PM   #18
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Re: 307 Chevy motor

Why bore a 307 to 4.00 when there are so many 350 blocks out there already? I built a 307 with an RV cam,1.94 valve 64cc heads,stock 4 bbl manifold,Holley 450cfm(can't recall,but performance not economaster),HEI,and double roller timing chain in a '71 K/20 work truck with 4.57s and 37/14.50 mud tires. That thing hauled and moved out like a 350 and got 13 mpg
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Old 01-08-2014, 09:56 AM   #19
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Re: 307 Chevy motor

My 307 was a crate motor purchased for a T bucket. It got 25 miles put on it when the guy decided to go Rat Motor. Since I've got a good complete motor I just wanted to perform it as much as I could without messing with the block and rotating assembly. I read that sometime after 68 Chevy was using the 350 block casting and boring the cylinders at 3.88, substantially increasing the wall thickness. And another article, head change, cam change with a Performer intake, & 650 edelbrock netted 315 horses @5800 rpm & 330 ft/lbs at 3800 rpm. That's kinda what I'm looking for. Thanks for all the input!
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Old 01-08-2014, 04:58 PM   #20
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Re: 307 Chevy motor

The 307 was a little work horse of an engine. My 69 GMC came from the factory with a 307 and TH400. It spent most of it's working life on a farm, pulling overloaded trailers through muddy fields, hauling hay, and earning it's keep as a work truck. When I got it, I pulled the tired little 307 out and replaced it with a SB 406. The 307 was still running pretty good even after 20 years of hard service, and would have probably gone much farther, but I just wanted more power.
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Old 01-08-2014, 05:36 PM   #21
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Re: 307 Chevy motor

My 72 Blazer 4x4 4"lift and 33's had a 307 with 2 barrel, and that thing would absolutely get it..Of coure I wasn't out there dogging it, But it was a daily driver... was very happy with it...My truck 64 has a 307 in it with mild cam and 4 barrel still under construction so It's not on road so don't know how it's gonna do yet..
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Old 01-08-2014, 05:39 PM   #22
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Re: 307 Chevy motor

Way back, I had a '69 Chevy 307 with an SM465 and 4.10 gears. The guy that owned it from new was a tree trimmer. He pulled a triple axle dump trailer with it. He went over the scales loaded at 13,000 lbs! Forget power, how the hell he every STOPPED that thing is beyond me! But I digress... The truck is owned by my neighbor to this day and has over 400,000 miles on the third 307 (and still stock tranny and rear end). And BTW, the only reason the 2nd engine gave up the ghost was the bonehead ran it with no AIR FILTER for 3 years!! He finally sucked a rock or something into the engine and lunched it.

I now have a '70 Chevy 1/2 ton with a 307. I've got some bugs to work out with it, but if I get that resolved, I'll run it until it's blowing more oil than fuel. Then I'll dump a 350 with a 700R4 in it and keep it for another 100 years.
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Old 01-08-2014, 06:33 PM   #23
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Re: 307 Chevy motor

Well... Now I'm crying. I just found out that my 307 turned out to be a 305. Now I have a boat anchor. Too much money to get even 300 horses out of this dog. ��
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Old 01-08-2014, 07:14 PM   #24
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Re: 307 Chevy motor

Dont bash the 305. A different set of heads, good intake and cam designed for the 305 and it will surprise you.
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Old 01-08-2014, 09:34 PM   #25
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Re: 307 Chevy motor

Like I said. Too much money for not enough gain!
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