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Old 12-01-2005, 09:44 PM   #1
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Car: 1991 Z28 vert, 1988 GTA
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Need help with Vortec 305 Heads

I'm thinking about getting some heads for my 305 and was wondering how the Vortec 305 heads were. The casting number I have found for them is 12552520. Anyone have specs on these? How good would they be on a stock 85 305 TPI? I'll more than likely throw a cam in there too while I have the engine broken down that far. Probably a XE262H or something like that. Thanks for the help

Kevin
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Old 12-01-2005, 09:45 PM   #2
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Mortec doesnt show crap all for info on these...

12552520...97-up...305..........Vortec, truck
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Old 12-01-2005, 09:50 PM   #3
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Yeah thats where I found the casting number but they have jack on info about em.

Kevin
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Old 12-01-2005, 09:52 PM   #4
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You don't want them, they are not like 350 vortec heads. Its not worth it.
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Old 12-01-2005, 10:02 PM   #5
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The 520s are different than the 350 castings, the 509s that came off the later Express vans are not. They are identical except the chamber is scaled down and the intake valve is .010" smaller. They still flow a paltry 235 CFM on the intake and identical to the 350 on the exhaust. They also have the kidney bean shaped chamber as well.

You have to remember the 305 vortec express make 235 FWHP and 290 ft/lbs of torque and that is with the MILD B-body LT1 cam. Had GM given it the F-body LT1 cam and a better intake/exhaust this engine would have easily made 310-320 ft/lbs and 260 FWHP.
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Last edited by Fast355; 12-01-2005 at 10:06 PM.
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Old 12-02-2005, 07:04 AM   #6
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Quote:
Originally posted by Fast355
The 520s are different than the 350 castings, the 509s that came off the later Express vans are not. ....


The differences, ALL the differences, among all the (Gen 1 type) Vortec heads would make an interested thread... especially if coupled with the iron and aluminum LT1 heads.

Quote:
You have to remember the 305 vortec express make 235 FWHP and 290 ft/lbs of torque and that is with the MILD B-body LT1 cam. Had GM given it the F-body LT1 cam and a better intake/exhaust this engine would have easily made 310-320 ft/lbs and 260 FWHP.
Scale the L30 (305 Vortec) up to a 350 using the same Bcar cam:

235 fwhp *(350/305) = 269 fwhp (which is very close to the 255 fwhp of the L31 Vortec, which used the Bcar cam)

IHI has flow data for the 305 Vortec heads, linked in this post. I don't remember them getting anywhere near 235 cfm. 199 cfm was the peak airflow that I recall.
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Old 12-02-2005, 08:33 AM   #7
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thanks for the replies. basically, i checked out the post on the 305 vortec heads and decided that's not the way i wanna go. i think i'm gonne get the 062 castings, get the .020 milled off to clear the bore, and put them on my motor with the SD TPI intake. the 062 castings are fairly cheap and easy to find so hopefully this will be a good mod for not a whole lot of money.

By the way, how well does the stock 85 TPI cam work with these heads?

Kevin
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Old 12-02-2005, 08:33 AM
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