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Old 02-04-2009, 08:50 PM
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307 spring perches??

anybody know if a 1968 307 spring perch would be capable of holding a spring off of a bigger 350 or somthing...I'm wanting to throw a 280 cam in one of these lil motors, and it's got .480 lift...and i have the right springs too, I'm just worried they won't fit the perches....any insight? thanks

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Old 02-04-2009, 09:29 PM
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The spring seats on a 307 cylinder head will accept up to a 1.26" diameter spring including the comp 981 springs. All factory 307's have a low compression ratio that is not going to work with a comp 280H cam. Its going to be a dog.
Either get the cr up or pick another cam with much shorter duration.
You need a real 9.5:1 cr or more. You'll need a much higher rear gear ratio and a very high stall converter for a auto trans with the 280 cam.
The stock 307 heads suck. All are 70cc+ chamber volume. Most have very small valves and crappy restrictive ports. A swap to a small chamber head would be a step in the right direction, if you actually expect the 280H cam to make any real power.
big cam+ low compression ratio+ crappy low flow heads = low performance at all rpms.
You can make a 307 go good. You can even build a good 307 around a 280H cam, but you need the other supporting components to the puzzle.
Compression ratio + cylinder head airflow, exhaust system,+ gears.+ converter stall speed.

Start by id'ing the cylinder head casting number.
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Old 02-05-2009, 12:44 AM
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I agree with F-Bird fully. Installing a set of 305 416 castings would be a step in the right direction. They have smaller 58cc chambers which will raise your compression ratio up to around the 9.5:1 area. They also have ports in the 160cc size, a good port clean up and bowl porting helps alot. The valve size is slightly larger at 1.84. From the factory, the 307 was presented as a economy torque engine with the bore of a 283 and the stroke of a 327. They came with small valve 1.71 heads, wheezer 8:1 compression ratio, corked single exhaust, 2 barrel carbs and slow ignition timing. The only good thing was they used a 300 horsepower 327 camshaft, but, this was also a curse, as chevy had run a bad batch of these and many of the cams went flat and the cast iron contamination took out the rest of the engine with it. If it were me I wouldn`t use the 280 cam since you have to remember your only dealing with 307 cubic inches. I would use a comp magnum 268H cam with the 416 heads and a .028 thickness GM head gasket. Add a double roller timing set, a set of small tube headers with dual exhaust, aluminum intake and a Quadrajet carb, a HEI ignition with good parts such as spiral core wires, a better coil and module with a dialed in advance curve. Tune the combo in and your 307 will come to life. The whole idea is the combo must work together as a team to make it`s best power and this combo would give it good street manners and decent economy.
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Old 02-05-2009, 09:29 AM
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hey guys, good replys, thanks for the info. Here's a lil info bout what i'm doing just so you'll know. First of all i'm in college, i'm after a ME degree at Clemson. This is sucking all my funds up. I was in the middle of a rather respectable 400 build I started on this past summer, but finacial deals changed and now i'm not gonna be able to finish that project. Soooo I've got my el camino sitting with no motor, and the 400 won't be done until after graduation.
I began to rack my brain, and remembered the ole 307 I have sitting in the corner of my step-dad's garage, it's the motor we pulled outta this car back when i was 16...now it's been just sitting here collecting dust, but it should run fine, so i'm gonna just put that motor back in the car so i can drive it around still until i graduate. That being said I started thinking about the parts pile I have just laying in the shop, and was wondering how i could swap said parts on the 307 and make a motor that at least sounded good. I mean even if she is a dog, The main thing I don't want is for my el camino to sound like a truck hauling off the trash on saturday...if ya know what i mean...I'll list some parts i have, and see if anybody has any more suggestions..., Thanks again yall

AFR 180cc heads
882 heads, with three angle valve job, pocket and port cleaning done.
comp cams 280H
Holley contender intake, High rise dual plane (like old z28)
650 holley double pumper
1 5/8 headers, leading to a 2.5" dual system (pretty free flowing)
petronix flame thrower dist.


I wonder if i could trade somebody my 882 casting heads for a set of the 305 heads that would make my lil 307 wake up? think anybody would go for that?
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Old 02-05-2009, 10:04 AM
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You can usually get the 305 heads in the junkyard for $25 a pop there so common. But I`m sure somebody would trade you. You have a good parts list that should work well with your 307. The 268 Magnum cam will give it a lopey idle without killing off the low end torque, perfect for a daily driver.
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Old 02-05-2009, 10:14 AM
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Quote:
Originally Posted by elsky79

AFR 180cc heads
882 heads, with three angle valve job, pocket and port cleaning done.
comp cams 280H
Holley contender intake, High rise dual plane (like old z28)
650 holley double pumper
1 5/8 headers, leading to a 2.5" dual system (pretty free flowing)
petronix flame thrower dist.
put on the 180cc afrs, holley intake/carb, the headers, and ignition.

then get a summit cam with 205 to 210 degrees duration at 0.050" if you plan to use the stock converter and a 2.73 to 3.08 gear.

a 307 should make a solid 300hp/325 ftlbs with those heads, exhaust, intake, and mild cam.
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Old 02-05-2009, 10:21 AM
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I had a 51 ford Vic. that I put a 307 auto trans in then I put a 280 cam in it with a aluminum intake with a eldebrock 650 and it run really good no stall it sat in gear when running I twisted the drive shaft out of it once I sold it and I wish I had it back Oh well
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Old 02-05-2009, 03:44 PM
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I was thinking i couldn't use the AFR's cause the bore was so small on the 307. am I wrong?

Oh yeah it's got a muncie in it, with a 3.73 out back. so that'll help matters some...

Hey I just found some 267 heads...are they worth while? ofcourse if i can squeeze the AFR's on there i'll do that...
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Old 02-05-2009, 04:15 PM
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Hey I just found some 267 heads...are they worth while?

no small valves and ports.

save the 180's for a 350
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Old 02-05-2009, 07:14 PM
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I agree with F-Bird. The AFR heads would be overkill and a waste of effort on the 307. They come in 65cc and 75cc chambers, both too big for the 307. Same goes for the 882s. You would be best off with the HO 305 heads, usually around 55cc chambers and plenty of breathing for the 307.

You will be able to make the 307 run good and have decent power. It just won't compare to a similarly prepared 327 or 350.

tom
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