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Old 07-21-2010, 08:06 PM
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Really...another 307 build thread???

Hello gents,

I have been reading tons of threads and gathering tons of info for my L31 350 vortec build from this site. All the info has been great and I never felt the need to post a question as the search feature (and Google) always provided an answer.

However advice on a 307 build is sketchy other than the inevitable "swap in a 350" or "boat anchor" comments. So I would like to pick your brains and see what positive suggestions (I've heard all the negative) for spicing up my most excellent 71 307.

Parts I have to work with:
Bone stock 307 running engine, heads are slap wore out, but the bottom end is good, I cruise it every weekend once the valve guide/seal smoke clears up...
OEM 4brl 70ish cast iron intake
600CFM Edelbrock 1406
600CFM Edelbrock 1405
Rebuilt 098 64cc Vortec heads (un prepped - Bone stock)
305 swil port heads rebuilt
Performer intake for swirliy heads
K1103 cam kit
HEI dizzy
Cloyes timing set
Full Felpro gasket set with .039 head gaskets
1 5/8 mid length headers and a 2.5" Flowmaster exhaust to the bumper.

So this engine will be going into my wifes 67 Malibu. It will have a 700r4 behind it as it does now with a posi 3.08 rear end and 245/40/18 tires.

I drive it like I stole it and it sees WOT ALOT, 307s are slap ***** bulletproof. I know its not a huge power house which is why it's going into the WIFE'S Malibu, but I still want to be able to open her up on the interstate and get the ol' Malibu up and goin'

So now onto the engine, my thoughts are this: The 307 uses flat top 4VR pistons and are ~.025 in the hole (block is virgin)

With the 64cc Vortec heads and a .015 head gasket that would put my quench @ ~.040 and net me 10.0:1 SCR (Pump gas friendly)

Should I go to a .028 head gasket to drop the CR a bit and still have decent ~.053 quench?

The Summit K1103 cam has a 214/224 duration and .442/.465 Vortec friendly lift. or do you think this is too much cam?

I plan on running a 2500 stall convertor in the 700R4 as well as the corvette servos big boost valve and reprogramming kit.

With all this in mind, I'm thinking the Pro Parts Vortec Crosswind intake (RPM Airgap knock off)is a good choice (I have one on my yet to run L31)


I have a $500 budget so lets see what we can come up with with the parts and money listed....

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Old 07-21-2010, 10:49 PM
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I am seeing just a bit over 9:1 CR w/64cc heads, 0.015 gasket and the piston 0.025" in the hole, 6cc valve relief volume. Stock B&S.
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Old 07-22-2010, 12:11 AM
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You are absolutely right Cobalt... I had my DD2003 set to 350 not 307...9.0CR is better than 10.0 for a daily driver...Thanks

Any suggestions on the cam?
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Old 07-22-2010, 12:52 AM
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With 628 cc's in the cylinder, 64 in the chamber, 6 in the piston, 3.2 in the gasket and 4.83 in the piston deck, total ingested is 706.03, total squeezed into is 78.03, resulting in a 9.048:1 static compression ratio.

This is a good thing, not a bad thing. 9.0 is an excellent SCR for a daily driver with iron heads.

I just finished another post where I railed against you fellows ratcheting up the lift limit on stock L31 heads. NOW HEAR THIS. LIFT LIMIT FOR STOCK L31 CYLINDER HEADS WITH STOCK SPRINGS, SEALS AND RETAINERS IS 0.430". You can't use all the travel there is in there because you have to leave some for safety.

Crane offers a torque cam with acceptable lift that would work nicely in this motor at 9.0 SCR. Energizer 260H10, kit part number 100032. 1000-4600 RPM Power range, excellent low end torque, smooth idle, daily useage, fuel economy, 1600-2200 cruise rpm, 8.0 to 9.5 static compression ratio advised. Use with stock converter and stock rear gear. 204/204, 260/260, 110 LSA, 0.427"/0.427" valve lift, timing events -3/27/37/-13.

RPM HP TQ
2000 130 342
2500 161 339
3000 206 360
3500 247 370
4000 276 362
4500 294 343
5000 300 312
5500 258 246

By the way, if the piston in this motor looks like the thumbnail, don't count on any squish at all. Oh, and for headers, you said this "mid length headers". You need to use full length headers. This mid length, block hugger, etc. stuff is just a waste of time. You might just as well walk out to the street and throw your money in the gutter.
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Old 07-22-2010, 06:45 AM
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You have small cubic inches and heads with a sizeable runner of 170cc and you want to keep low end power in the balance. I would use this cam:
http://www.summitracing.com/parts/SUM-1069/
And as tech inspector suggested, use full lenth small tube headers, if you can get them in 1 1/2 tubes that`s what I`d use.
Make sure you get the springs to match the cam.
One issue I can see is, if you run thin head gaskets you have to remember, they won`t seal on decks that aren`t perfectly flat. This is why replacement fel pro gaskets are .041 thick. Before I would use a thin gasket I would have the heads and the block decked to assure flatness. Most of the time when someone is doing a 307 build we suggest 416 casting 305 heads as they have 1.84 intake valves that flow better on small bores and small 58cc chambers to keep the compression ratio up. If you were to use 416 heads that would cut some money off the table as there wouldn`t be the need for a special vortec intake or self aligning rockers. While it`s true they don`t flow like Vortecs do with a bowl clean up they will feed all your 307 needs for street duty.
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Old 07-22-2010, 07:25 AM
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If ever I was tempted into doing a 307, I swear I'd try a set of 059 L30 Vortec heads:

From the Stan Weiss flow chart:

Vortec L30 "059" casting:
Lift__Int Ex
.100 68 47
.200 128 103
.300 179 138
.400 205 152
.500 221 163

L30 305 head info- POST #487.
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Old 07-22-2010, 11:39 AM
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Guys----
I think this is the first thread I have ever seen on this subject that just did not beat the poor 307 to death-----.

Someone put a 307 in my 66 Elky years ago, and it is my intent to drive that til it quits. Getting good solid advice to spice it up is helpful.

Geeze, even the 64 Chev C-10 I will be building for my son will get a 305.
Hell, I might stick with the 250-6 just to irritate the kid
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Old 07-22-2010, 12:05 PM
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Quote:
Originally Posted by Bryan59EC
Guys----
I think this is the first thread I have ever seen on this subject that just did not beat the poor 307 to death-----.

Someone put a 307 in my 66 Elky years ago, and it is my intent to drive that til it quits. Getting good solid advice to spice it up is helpful.
IMO, the 307 has better fundamental specs than the 305. Its larger bore and shorter stroke appeals to me.

Years ago, before Chevy did the 307, guys would make one to use in class drag racing. Quite illegal and all, but it was done. I'd have rather kept the engine a straight 283/292, but some guys would rather cheat than compete. The point being, is that the engine was a "known quantity" even before Chevy produced the first 'real' one.

Quote:
Geeze, even the 64 Chev C-10 I will be building for my son will get a 305. Hell, I might stick with the 250-6 just to irritate the kid
Now you're just being mean! LOL

I have a soft spot for that gen truck, though. Had a '65 w/a 230/3-speed stick. For a while it did, anyway.
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Old 07-22-2010, 01:36 PM
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Thanks for the info so far guys....

To Clarify, I have no problems prepping the 098 heads for larger lift and bigger springs...its just cuts into the budget a bit...

Is the 1103 cam out of the question for the 307 in general or because it had too much lift for stock unprepped Vortec heads?

I assumed that the split duration and slightly higher lift would help the relatively weak vortec exhaust side evacuate the cylinder better?

I also have a set of 187 swirly 305 heads and matching performer intake...maybe I should go that route and save the Vortecs to replace the fuely heads on a future 327 project.

Keep throwin ideas at me....
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Old 07-22-2010, 04:06 PM
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Where I`m getting thrown off is I don`t know of any 098 heads. Are you sure this is the casting number?
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Old 07-22-2010, 04:46 PM
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tech posted dyno#'s:

"RPM HP TQ
2000 130 342
2500 161 339
3000 206 360
3500 247 370
4000 276 362
4500 294 343
5000 300 312
5500 258 246"

Wow that is pretty good for what most call an anchor, the torque numbers are especially good considering. I heard before that these 307's were/are popular in econo rail dragsters...is there any merit to that notion and why
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Old 07-22-2010, 05:54 PM
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Quote:
Originally Posted by DoubleVision
Where I`m getting thrown off is I don`t know of any 098 heads. Are you sure this is the casting number?
I hadn't paid any attention to this, but you're right. L31 Vortecs only came in two casting numbers, 12558062 and 10239906.
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Old 07-22-2010, 06:10 PM
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Quote:
Originally Posted by screamin_67
Is the 1103 cam out of the question for the 307 in general or because it had too much lift for stock unprepped Vortec heads?....
The duration will still work with 9.0:1, but the lift exceeded retainer to seal clearance, so I backed off to a shorter cam.

Quote:
Originally Posted by screamin_67
I assumed that the split duration and slightly higher lift would help the relatively weak vortec exhaust side evacuate the cylinder better.
Please scroll down here and read Tech Tip 2003. Then you will be able not only to know the TRUTH yourself, but will be able to amaze your friends and relatives with the TRUTH. Written by Iskenderian. (It won't get much better than that.)
http://www.iskycams.com/techtips.php

Quote:
Originally Posted by screamin_67
I also have a set of 187 swirly 305 heads and matching performer intake...maybe I should go that route and save the Vortecs to replace the fuely heads on a future 327 project.
Did you bump your head gettin' out of the car?
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Old 07-22-2010, 06:55 PM
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Quote:
Originally Posted by techinspector1
I hadn't paid any attention to this, but you're right. L31 Vortecs only came in two casting numbers, 12558062 and 10239906.
Maybe L98 TPI heads?
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Old 07-22-2010, 10:05 PM
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Heh Heh, Tech I guess you don't have any love for the 187 swirlies huh?...

Sorry guys the Vortecs I have are 906s... fat fingers and a fuzzy memory lead to erroneous info some times.

I included a pic of the unprepped set of 906s as well as the set we did with larger exhaust valves, screw in studs, cut for larger springs and .600" lift. etc. These are on my L31 build....I could have the same things done for the 307...probably wouldn't need the 1.60 exhaust valves though...
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