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Old 03-25-2008, 07:06 PM
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307 yay or nay

I already have the chevy 307 in the truck but its tired. Has 160k on it. I dont have any problems with it currently.
I know it wont just take a slap rebuild like a rering kit and it will need to be machined, but would any of you guys bother or just go the 350 route.
I was thinking of putting in all the parts that came off the 350 i built that bit the dust.
It would have tons of cam 224 @ .50 / 470 with 1.5s.
Compression would have to come up for sure with some machining or some aftermarket or even some 305 heads.
I am not looking for 400 horsepower just somethin fun for the streets with either a 4.11 or 3.73 rear gear.

So yay or nay? Tell me what ya think.

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Old 03-25-2008, 07:24 PM
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If you are wanting to run those type of gears. I would go with the 350 SBC.
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Old 03-25-2008, 07:25 PM
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You can pretty well build a 307 the same way you would go about budget building a 305. A 224 cam in a 307 will want to rev. It will want 4.10's+ and a 3500+stall as the torque curve is going to get up there a bit. The low end torque below 3000rpm will be soft. You'll need compression and head porting. Don't be shy on the compression and rear gearing. 4.56's are not too much.
A budget 9.5" race converter is not too much.

Your typical 10" "3500 stall" converter will give you about 3100-3200 stall behind a 307ci motor. I would not use less than this.
What makes you think you can't freshen it up with rings and bearings?
Do what I did on my Junkyard Dawg 350. Just redneck rebuild it.
Hone it, clean up the pistons, get the 307 crank turned 10-10, new rings and bearings and gaskets.



If you must play with the 307 I would max flat mill a 305 HO head down to 52cc
(right down to the intake valve seat edge/spark plug boss)
and use a .015" head gasket to maximize the cr using the stock 307 piston.
You'll want to max shim up the valve springs as its going to want to rev.
Drill and roll pin the rocker arm studs. Fully home hand port the 305 heads. More is better (short of busting thru a port wall). They work pretty good if you get serious with the porting.
May want to play with the cam installed position (cam advance) to maximize torque. You want to get the cranking cylinder pressure as high as possible.
If your "224 cam" is on 110LSA, advance it a bit more than usual. (103-105 intake C/L).

If you have to do a full rebuild with machining, get a 350 to start with.

Could be a lot of fun if done right. Spend you money where it will do the most good. (cylinder heads, compression, induction, exhaust)

Last edited by F-BIRD'88; 03-25-2008 at 08:19 PM.
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Old 03-25-2008, 07:26 PM
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yeh 307

i had a 307 in my nova i put vortec heads on it and a 224@.050 470 lift.cam. a summit dual plane intake and 650 carb. i was surprised how much power it had....but there is so much more you can do with a 350.
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Old 03-25-2008, 07:34 PM
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Sbc 307

When GM cast the 307 blocks they did not use very much nickel in the cast iron mix. Because of this, these blocks are prone to excessive wear. I am surprised to see it went 160000 miles with no cylinder problems. Most had oil consumption problems starting at about 60000 miles. Even with this problem, the 307 is a good engine and will run circles around a 305. It is worth rebuilding or just find a 350, which is cheaper to rebuild.
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Old 03-25-2008, 07:35 PM
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I was expecting the RPM range to go way up like you stated.
The mag 270 was 2000-5500 in a 350 so i was thinkin it would be high 2k to 6.5k in the 307. I have a 2500 holeshot that I would be using for this application.
I may go even crazier with the rear gear I have yet to make up my mind. This isn't a daily driver (obviously), just a cruise night vehicle.
I haven't been actively looking for a 327 or 350 block lately but I have a word in with a couple people to let me know if they find one.
Just lookin for a cheap-ish build that will be fun and somewhat different from the last 350 i built.
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Old 03-25-2008, 07:52 PM
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Quote:
Originally Posted by DeathRattle
I was expecting the RPM range to go way up like you stated.
The mag 270 was 2000-5500 in a 350 so i was thinkin it would be high 2k to 6.5k in the 307. I have a 2500 holeshot that I would be using for this application.
I may go even crazier with the rear gear I have yet to make up my mind. This isn't a daily driver (obviously), just a cruise night vehicle.
I haven't been actively looking for a 327 or 350 block lately but I have a word in with a couple people to let me know if they find one.
Just lookin for a cheap-ish build that will be fun and somewhat different from the last 350 i built.

The "2500 stall" will not be enough. The actual stall behind a 307 will be less than 2500. Plan on 400-500 rpm less than the "rated stall" when using on a 305 or 307Ci motor. (off the shelf converters are rated for stall behind a 350ci motor.)
If you want to use that stall , use less camshaft. 211 to 218@.050" It's easy to over cam a small motor. Get a low buck dirt cheap Jegs 10" 3500-3800stall for a 224 cam. You won;t hurt that with a 307. The converter is critial.
If you want ton use a 224 cam sell your converter and get the right stall for the 224 cam used in a small motor. the rated rpm range of a cam is for a larger motor. The torque curve will be much higher in a small motor. Needs more gear and stall than a 350 would.

If you do this right, you'll suprise a lot of people, including yourself.

what vehicle is this going in?

Last edited by F-BIRD'88; 03-25-2008 at 08:02 PM.
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Old 03-25-2008, 08:11 PM
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http://www.hioutput.com/tech/343hp/343hp.html

You can use this very similar, simple 343hp 305 budget build as a guide and inspiration.
notice in the dyno test peak torque occurs at 4250rpm. Peak power is at 6250.
Your 307's torque curve won't be any different. needs more than 3000rpm actual converter stall . 3800rpm actual stall is not too much.
Needs 4.10's minimum. You want to get the measured cr as close to 10:1 as possible.
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Old 03-25-2008, 08:43 PM
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The rear gear is gonna be really key, because it is going in a truck. So weight is equivalent to a like a full size car on this application.
The 307 as it sits right now scoots along real well on the highway cause of the 2.55 or 2.73 gears the truck currently has. Can take first gear to 40-50, second to 80-90, no more after that the speedo only reads 85 so who knows.
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Old 03-25-2008, 09:05 PM
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A cammed up small ci motor in a heavy vehicle needs a high rear gear ratio.
If you want a fun saturday night machine, gear it up. 4.56's are a starting point.
How tall are the tires? Sticky tires? junk tires?
the rear gear ratio/tire diameter and stall match are critical. Especially in a heavy vehicle.
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Old 03-25-2008, 09:07 PM
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If I ran the current tire(Probably not), I am pretty sure as its been a very long time since I measured it was 30 or 31"
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Old 03-25-2008, 09:09 PM
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Quote:
Originally Posted by DeathRattle
If I ran the current tire(Probably not), I am pretty sure as its been a very long time since I measured it was 30 or 31"
You should be thinking 5.13's
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Old 03-25-2008, 09:17 PM
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Quote:
Originally Posted by F-BIRD'88
You should be thinking 5.13's
Haha, I already knew that one was comin. Thats why I included the probably not in the previous post. I never got to anything else after I blew up the 350. The axle was gonna get a 3.73 gear set but never did cause I installed the stocker nova 307 after the 350
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Old 03-25-2008, 09:49 PM
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Personally, I would not rebuild a 307 for performance. Lots of cast parts and a 350 is probably more affordable to build even if you have the 307 already.

The 307 belongs in your 60 year old old aunt's 71 Malibu.
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Old 03-25-2008, 10:24 PM
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Hot Rod built a 315 horsepower 307. These engines can hold there own given the right parts. The low tin and nickel is just a rumour, I have had two 10/20 307 blocks. If you want original, build the 307, and if you can get away with standard do so, as aftermarket cheapy pistons are destroked, meaning they have .020 removed from the overall deck height. if you want to go faster cheaper, go 350. If the bores mic'd out okay on the 307, you can do a hone job and replace the rings and build from there but make sure you scrub the bores clean of hone residue. as been said good heads, cam, intake and exhaust all have to work as a team to build power. The 307 got a bad rap cause it was never a performance engine, the factory version had low compression, small valve smogger heads, a 2 barrel carb and single exhaust, worst of all was the cams in them wore out very quickly. There is much you can do with a 307, you just have to select the proper parts to do so.
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