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  #46 (permalink)  
Old 11-26-2012, 09:42 PM
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self porting,I only ported the exhaust side of the heads and only about an inch into the port.
Now a days with flow benches,I wont touch anything at all. Porting does make a difference,but exactly what tech just posted,,
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  #47 (permalink)  
Old 11-27-2012, 05:40 AM
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Good point. Doing the obvious things like the lip below the seats and removing any casting flash/irregularities should be the extent of it unless you have experience and/or a lot of time and a flow bench- along w/enough heads to find out what is helping and what is hurting. After all, if you remove too much or from the wrong place, the head is now scrap; you cannot add the metal back and welding is in no way cost effective on these commonly available heads.

FWIW, there have been good builds using the L30 305 Vortec heads on the small bore SBC engines. One member here has them on a 283 and likes them just fine. Takes a Vortec intake, self aligning rockers, centerbolt valve covers, and a spring and retainer change.

Some info and photos of the L30 5.0L Vortec head can be seen at NastyZ28.com Vortec Cylinder Heads: The Definitive Guide, post 478.
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  #48 (permalink)  
Old 11-27-2012, 07:40 AM
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One of the keys to learning to port your own heads is to not take advice from people who admitedly cannot port heads or are afraid to. Its like taking advice on baseball from some one who cannot swing the bat. You got to swing the bat to get a hit.

You learn by doing. These are an excellent head to learn on. And if you do the whole port they will flow a good bit more than when you started.. You really cannot mess it up.

There are many good books on general porting and SBC heads specificely.

Just don't grind the (*&^ out of the floor of the port. This area just needs a clean up.
The port needs to be made taller and a bit wider. That valve guide boss needs to be thinned and streamlined so the
air can go around it. The push rod pinch needs to be opened up a bit too. The port opening at the flange does not need to be huge. felpro 1205 gasket size is just right.


These heads respond very well to generous complete hand porting and the larger 1.94 valve.
They will flow a lot more air when you are done than when you started.

This is not rocket science. And you don;t need a flow bench.

I have flow tested these heads after porting. The flow bench testing did not get the gain in flow...THE HAND PORTING DID.

Last edited by F-BIRD'88; 11-27-2012 at 08:06 AM.
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  #49 (permalink)  
Old 11-27-2012, 08:18 AM
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Some pictures of ported 305 heads
http://www.hotrodders.com/forum/atta...1&d=1347917576

http://www.hotrodders.com/forum/atta...5&d=1199151813

http://www.hotrodders.com/forum/atta...8&d=1227570680
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  #50 (permalink)  
Old 11-27-2012, 09:35 AM
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Quote:
Originally Posted by ChevelleSS_LS6 View Post
Found an article on a 307 build. Not superhero power, but I'll bet you could actually afford to drive the thing how fuel prices are (grrrr!).

307 Chevy Dyno Test - Super Chevy Magazine
This 307 could have made a lot more power if better parts and attention to details
had been done.

The resulting engine compression ratio was less than 8.5:1

8.5:1 is way too low... you want 10:1 with that cam on a 307.

This engine should have had a supercharger on it.

if the heads had been milled to 51cc (.041" gasket) or 56cc with a .015" gasket to get the compression up it would have made a lot more power and torque. 10:1 minimum compression ratio.
A finished 10.5:1 compression ratio would not be too much for this motor. (92 octane gas)

Bad intake and carb choice. The lowly performer manifold and 600cfm carb are bad choices when you want power. even on a 307.

A Performer RPM high rise dual plane and 750cfm carb will make more power and torque. Always.

This engine could have made well over 350hp if attention to details and parts choices had been better.
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Old 11-27-2012, 01:49 PM
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The bottom line is that F-BIRD'88 will continue to advise grinding on your heads and I will continue to nay-nay it.
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  #52 (permalink)  
Old 11-27-2012, 02:59 PM
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Quote:
Originally Posted by techinspector1 View Post
The bottom line is that F-BIRD'88 will continue to advise grinding on your heads and I will continue to nay-nay it.
There are many who say "hog this", "grind that" and that you don't need a flow bench, etc. The guys who want to follow that advice are just setting themselves up for disappointment. And that will happen AFTER they spend untold hours trying to duplicate what they think they see- in a picture!

I'm not saying that hand porting cannot be done successfully. I was fortunate enough to have made some templates out of brass from a GOOD set of fuelie heads. Using them I can do a pretty good rendition of those heads and they show an improvement at the track.

By eye I can get a little improvement as well- being as how I've done this so many times. But a first timer? Good luck until you've made some goofs- and the goofs will cost you a casting every time unless you have a bench to show you what's happening. And /o a bench you have to port a PAIR of heads, bolt them on and take it to the track, then remove them, port some more, or port another set of heads, repeat until you're happy w/the results or you decide you'd rather spend your time earning some coinage to buy a decent set of aftermarket heads or at least for some time on a flow bench.

Last edited by cobalt327; 11-27-2012 at 03:07 PM.
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  #53 (permalink)  
Old 11-27-2012, 07:31 PM
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Im not going to tell you to not port your own heads,,,
I wont do any porting for a few reasons
I want to know the flow numbers so I need a flow bench:\without a flow bench how do I know that I have similar flow in all my ports?:
If it takes 25 hours to port a set of heads? I know that I can make more money doing something else than I can save.
I work with engines that make more than 350 horse power and the castings cost quite a lot more than I want to risk ruining:::
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  #54 (permalink)  
Old 11-27-2012, 10:22 PM
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This is probably the most civil 307 thread I have ever read.

I opted to use an old, unrebuilt, early 70s 307 in my 66 elky.

All I did was put a q-jet and intake manifold on it.

The car has a 5-speed (TKO 2.87 first) and is plenty peppy even with the 3.08 rear gears.
And gets better than 25mpg on the hiway to boot.
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