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Old 08-21-2007, 02:47 PM
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Heads and at home machining

A friend of mine found that instead of buying $900 performance heads that if he took his dremel with carbide bits and artfully reduced the flashing and molding in the stock heads and cut around the valve guides he could attain equal or better power than these hi-performance ungrades. With winter coming around my camaro will be garaged (damn salted Ohio roads). I want to stay sharp with my new hobby and thought that if its possible to keep the engine in the car why not do this. Could this be done and if so should it? or am I gonna end up driving a screw driver through my eye from the shear stress?

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Old 08-21-2007, 03:07 PM
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Best advice I can give is don`t waste your time, and the reasons are:
If you have no experience, then there`s a good chance of making it worse than better. If you have no flow bench to test the air flow with you won`t know if it made it better or worse, or if you don`t have a dyno to show the results again you won`t know if it`s better or worse. There`s alot more to head porting than just taking a carbide bit to it. The expensive after market heads are often CNC ported that a human hand can`t come close to duplicating such precise tolerences.
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Old 08-21-2007, 04:23 PM
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While I can understand the desire to do your own porting, I will side with DV's advice. 30 years ago, I ruined a perfectly good set of Corvair Turbo heads by trying to improve them without knowing where to remove aluminum and how much to remove.

If you're gonna do it anyway, maybe I can offer some guidance. I would start with a decent set of heads in the first place, not with heads that were cast 30 or 40 years ago with old technology. My choice would be '96-up Vortecs off a 5700 V8. These should be plentiful in the boneyards by now. They can be identified by the hacksaw blade looking casting on the front of the heads and by the casting numbers under the valve covers. Two numbers I think are valid are 10239906 and 12558062. There may be others. These are thinwall castings, so clean them up real well and have them magnafluxed for cracks before you spend any time on them. While it's true that you must use a Vortec manifold with them (and rail rockers if you don't plan to install guide plates) and that adds to the cost of using them, they're still the best cast iron head that Chevy has produced in the last 50 years in my opinion.

Standard Abrasives has provided some guidance for the procedure because, of course, they want to sell the abrasives that you will use. You will note in the instructions that they said a 300 hp motor should pick up about 19 hp with their suggested mods. While that isn't enough to write home about, if you are using otherwise idle time to do it, why not?
http://www.sa-motorsports.com/diyport.aspx
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Old 08-21-2007, 04:41 PM
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A dremel tool wont cut it aswell.
you need a good die grinder and a good air supply.
if you do wanna go that route get a junk set of heads to practice on and there is a few good books on head porting.
I port my heads but it only took me 20+ years to get good at it.
I suggest buying the 900 buck heads and not worry about porting.
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Old 08-21-2007, 04:42 PM
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I used to port iron and aluminum heads but not any more. You can buy heads that will make more power than any stock head for cheap. I'm talking Dart SS, Iron Eagle, WP II. Even the Bowtie Vortecs. The amount of time involved in hand porting to achieve only fair results compared to CNC or as cast is not practicable in my mind. Especially iron. And without a flow bench, youre just guessing.

Get a part time job and save up for some heads. Maybe some good used ones.
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Old 08-21-2007, 05:40 PM
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I would suggest getting another set of sbc head castings to work on.
Some factory heads are just not worth the time and cash to modify. Some others are. When you're all done just swap heads.
What is the casting number on your heads?

A Dremel does not have enough power to effectively port a cylinder head.
You need a real electric die grinder that takes 1/4" shank cutting bits.
About $100. Often on sale at tool supply outlets for less.
www.harborfreight.com
www.princessauto.com
www.eastwoodco.com
You want to get carbide cutting bits with long 6" shafts to allow you to reach deep into the ports with out damaging the valve seats with the collet of the grinder. You only need 2, maybe 3 different bit head styles to do small block heads. You need 1 3/8" cylinder shaped with a rounded end. 1tree shaped and 1 flame shape is nice to.
Then you'll need a head porting kit which includes a selection of mounted stones and sanding/polishing cartridge rolls and drill arbor.
If you follow the advice and pictures in of the many books and online articles on doing basic cylinder head porting on small block chev heads, you can get pretty good results. It takes time and patience. Won't get done in 1 day.
But will keep ya busy for quite a few cold winter nights. Good lighting and eye protection is a must. Nice to start on a old scrap head to gain hand skill before you dive into your heads.
I like working with the 305 HO heads. They are cheap, plentyfull and have small combustion chambers and the ports are unrestricted. They have hardened ex seats. With full porting and larger 1.94x 1.60" valves they flow pretty good when done.
A good upgrade from a stock 76cc smogger head like 624 or 882 castings on a budget 350 motor.
There are a few more desirable stock heads that can be had for low $$$'s , but many are just not worth the bother.
You'll pick up 15 to 20 hp on a stock or near stock mild motor and up to 50-60-70 hp over the stock head on a racey motor with all the supporting horsepower parts. To get more power than that from these heads takes welding,heavy reshaping and flow bench verification. At that point a new aftermarket casting is much more desireable as a starting point.
By doing some of the modifications and upgrades and final assembly yourself you can finish them for a reasonable cost. I get my machinist to do the hot tank, valve guides (if nessessary) valve job and resurface as nessessary but save money by doing the rocker studs and final cleaning and assembly myself.
You'll have to decide for yourself if the time and effort is worth it for you.

Last edited by F-BIRD'88; 08-21-2007 at 05:52 PM.
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Old 08-21-2007, 06:06 PM
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Quote:
Originally Posted by Urbanfarmer
A friend of mine found that instead of buying $900 performance heads that if he took his dremel with carbide bits and artfully reduced the flashing and molding in the stock heads and cut around the valve guides he could attain equal or better power than these hi-performance ungrades. With winter coming around my camaro will be garaged (damn salted Ohio roads). I want to stay sharp with my new hobby and thought that if its possible to keep the engine in the car why not do this. Could this be done and if so should it? or am I gonna end up driving a screw driver through my eye from the shear stress?

Well I don't know about achieving equal or better performance with some stock head and a Dremel tool; but since it's a long winter here's some fireside reading by David Vizard for you to get before becoming the Micheal Angelo of cylinder heads.

"How to Build & Modify Chevrolet Small-Block V-8 Cylinder Heads"

"How to Build Max Performance Chevy Small Blocks on a Budget"

Bogie
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