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Old 08-14-2008, 11:29 AM
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Vortecs on a 400 SB, the cheapest way

Gents; After all these years of hanging in there with the old smog heads, I finally gave into the hype and bought a set of very used Vortec's (906's) for 200 bucks. They will be going on my 400 SB that has the old "993" heads, on it, that I home ported ten years ago which ran surprisingly well. Now for my questions...I have been reading info relating to the Vortecs that state you "home porters" with a beer close by the die grinder had better beware before you go hog wild into those Vortec castings. Ordinarily, I would ignor those statements and port those heads like there was no tomorrow, especially after having such good results from porting my 993 castings. However, after looking at the Vortec ports, they look to be somewhat different than the older heads, so before I reach for my die grinder and six pack, I thought I better get an opinion from you gents....can any of you "David Vizards" out there tell me if I'm wasting my time by porting the Vortec's. If I'm not wasting my time then here is my plan....obtain 1.6" exhaust valves and have the machine shop cut a 30 degree back cut on them. Leave the 1.94" intake valves alone. Pay attention to the throat of the exhaust port and smooth out any sharp lips down from the seat. Clean up and smooth out both of the intake and exhaust ports. Slightly, open up the exhaust exit ports (like I did to my 993's). Install a set of "Z-28" springs and use the Vortec retainers and keepers and then (I read this on the site!) discard the stock Vortec seals and install 1986 Dodge Daytona umbrella seals for valve guide oil control. That way I can run my old Summit 224/234, 4.88" lift cam. Is this a sound plan or have I had one beer to many?! Thanks gents

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Old 08-14-2008, 05:55 PM
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I personally would not touch the Vortec head ports. Porting, if not done correctly can make less power than stock ports. The only sure way you would know if your work is making a difference is to flow bench test them. This of course too is only a "ballpark" figure unless you use a wet flow bench which many shops DO NOT have. Personally, I would leave them alone. Those heads stock are better than some good aftermarket heads.
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Old 08-14-2008, 06:11 PM
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Old 08-14-2008, 06:40 PM
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I fully concour with the last 2 posts, and much of what you`ve given is all you need. If they were mine, I would install some necked down stainless valves and thats it. The ports of vortec heads are far superior to that of the old head designs. The combustion chamber is also far more efficient. Make sure you have the decks of heads checked for straightness or have them skim milled to assure flatness, then have the steam holes drilled, if they are not drilled it will overheat and you won`t be happy. Once you finish and retune it and jet the carb properly, hang on, you`ll be dealing with a completely different beast. If I`m not mistaken, you will also have to clearence the valve guides if you plan to run a .488 lift cam. Lastly, make sure you install a quality vortec intake like a edelbrock, don`t waste your money on the professional products made in china junk.
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Old 08-14-2008, 07:14 PM
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Quote:
Originally Posted by dallam11
Gents; After all these years of hanging in there with the old smog heads, I finally gave into the hype and bought a set of very used Vortec's (906's) for 200 bucks. They will be going on my 400 SB that has the old "993" heads, on it, that I home ported ten years ago which ran surprisingly well. Now for my questions...I have been reading info relating to the Vortecs that state you "home porters" with a beer close by the die grinder had better beware before you go hog wild into those Vortec castings. Ordinarily, I would ignor those statements and port those heads like there was no tomorrow, especially after having such good results from porting my 993 castings. However, after looking at the Vortec ports, they look to be somewhat different than the older heads, so before I reach for my die grinder and six pack, I thought I better get an opinion from you gents....can any of you "David Vizards" out there tell me if I'm wasting my time by porting the Vortec's. If I'm not wasting my time then here is my plan....obtain 1.6" exhaust valves and have the machine shop cut a 30 degree back cut on them. Leave the 1.94" intake valves alone. Pay attention to the throat of the exhaust port and smooth out any sharp lips down from the seat. Clean up and smooth out both of the intake and exhaust ports. Slightly, open up the exhaust exit ports (like I did to my 993's). Install a set of "Z-28" springs and use the Vortec retainers and keepers and then (I read this on the site!) discard the stock Vortec seals and install 1986 Dodge Daytona umbrella seals for valve guide oil control. That way I can run my old Summit 224/234, 4.88" lift cam. Is this a sound plan or have I had one beer to many?! Thanks gents
You can pick up a little on Vortecs, but they start so much better it's hard to see the kind of gains you did with the 993's. You have to realize that the Vortec uses a lot of the LT-1 and 4 ideas, it really is a cast iron version of the aluminum Fastburn head with some production compromises in the valve train area as it was for a truck engine. But the ports and chambers are most similar to the heads I referenced. I'm sure that much of the work you did on the 993's was in the pockets, when you open up the Vortec heads, you'll see the pockets already look like what you did.

So you can grab a beer and do a little cleaning, but without a flow bench to really start getting beyond what the home porter can reasonably do, you're mostly going to just spend your time rubbing off the signs of the ports being shaped in a sand cast mold.

Bogie
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Old 08-15-2008, 04:00 PM
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The Vortecs flow more than the ported 993s, and probably do it with less volume. Bolt them on, shred tires, and make nice power to 5000 rpm.

I'd leave well enough alone.
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Old 08-15-2008, 05:16 PM
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jump in!

I know all of this is hard to believe, but honest, these heads work really swell right out of the box!

I used Z28 springs, and Teflon seals. The heads were milled 45 thou as well. I used a 15 thou head gasket and flat top pistons.

These heads will not disappoint.

Rubber & smoke from a standing start is fun!
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Old 08-15-2008, 05:58 PM
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Well here's the deal. I've got the heads and I've got the grinder....I have to do SOMETHING to them! There are without a doubt ridges just below the seats that I would like to tackle and I really believe those valve stem bosses could be contoured. And lastly, I think a smoothing out of the combustion chamber would not hurt things. Please, tell me I'm on track here....it's just not normal to accept bone STOCK heads! One last thing, does anyone know what book David Vizard has out that addresses the Vortec's. Thanks again
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Old 08-15-2008, 10:08 PM
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Vizard's book about SBC engines on a budget has a section on the Vortec heads. Read it before you crank up the grinder. What works on old heads won't necessarily work on Vortecs.

Meanwhile, you could always polish the combustion chambers and maybe deburr the outside.
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Old 08-15-2008, 11:07 PM
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On the intake port the typical "pocket port" job will get you notta. (but it looks pretty) So don't waste your time. (or don't expect gains from your time)
You are best to leave that alone. The only way you are going to see more flow on the intake is a full port job. The inake port is very good as is.
Like you said you can contour the valve guide boss and the two flow paths around it to good effect. cleaning up the walls and raising the roof of the port from gasket flange to bowl helps. Minor widening the pushrod pinch helps a bit too. The general port shape is very good. Do not get carried away.
The idea is to gain about 10-12cfm peak without wrecking the very good low/mid lift flow and velocity. Do not get all carried away.
The exhaust port can use the full work up. You'll gain a lot more on the ex port then the intake side from your port efforts.
The idea is to make a better vortec head,not a huge port head. If you want huge ports , go buy huge 220cc port heads.
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Old 08-15-2008, 11:14 PM
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I put a set of Vortecs on my 406. I left the valve sizes alone and did not grind any on the intake or exhaust ports except for deburring a bit. I did open the pockets a bit right under the seat and slimmed the valve guide a bit. Polished the chamber a little and drilled the steam holes. Checked them for straightness.

I'm using PC seals on the intakes and umbrellas on the exhaust. Regular Comp springs retainers and keepers can be used but you have to have the spring seats machined. I also had the heads fitted with screw in studs with pushrod guide plates.

Here is a little twist about Vortecs, regular pushrod guide plates will not work. Maybe by now there is someone who makes them. I've since seen a set of adjustable guide plates for sale in one of the catalogs.

I could not find any for the Vortec heads so had to use Crane roller rockers that are self-centering. They work fine.

The cam I'm using has a .490 valve lift, XE274H.

I am very satisfied with the heads. My 406 pulls very hard to 5500RPM, after that it just flattens out. I shift it at 5000-5200 and it seems to love it.

You'll like them.
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Old 08-16-2008, 12:50 AM
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This is a very good thread about the Vortecs>
http://www.nastyz28.com/forum/showthread.php?t=56505

http://www.chevytech.com/2c42o2.html

http://www.gregsengine.com/350to400.htm

http://www.chevytech.com/2c42o1.html
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Old 08-16-2008, 01:16 PM
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Now, we're on the same sheet of music! OK, I'll contour the guide bosses on the intakes and just clean up the ports then leave the intake side if things alone. Then I would like to install a larger 1.6" valve in the exhaust side, which brings me to a question...will enlarging the hardened exhaust seats ruin it's induction hardness? I heard yes and no and also that with after market stainless steel valves installed, there will be little or no problem because stainless steel won't "weld" to the seats like milder steel valves will. Lastly, can I open up the exhaust exits (gasket match) like I did to my 993s? Thanks again gents.
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Old 08-17-2008, 03:01 AM
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Gasket-matching might be counterproductive. The ledge where the port empties into a larger header tube can lessen the tendency toward reversion.

I'm gonna leave my intake ports alone, but I'll probably do something to the exhaust side. I saw in an old Circle Track mag where they put 1.6" exhaust valves in a Vortec head, and it picked up a decent amount of flow. They put 2.02" intakes in, and it picked up a little at the lowest lift tested, but it decreased flow across the board from there up.
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