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Old 11-03-2008, 06:01 PM
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1956 powerpack heads

Hello,
Does anybody know what the first generation powerpack heads that came out on 265s spec in at? The combustion chamber looks very small with a shrouded spark plug.
Any info is appreciated
Brandon

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Old 11-03-2008, 06:08 PM
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If you have the head numbers, ck at http://www.mortec.com for info.
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Old 11-03-2008, 07:43 PM
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I think the first power pac heads were in 57?- might be wrong on that, look at the casting dates on your heads. I do know most power pacs (57-67) and early 55-56 heads had 137cc intake runners, 1.75 1.50 valves and 58cc chambers.

The early 55-56 heads had a combustion chamber shaped like this below

____
/ 0 0 \ --- the 'o' s are supposed to be intake and exhaust valves...

The power packs had the reshaped combustion chamer that is visually similar to double hump heads.
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Old 11-03-2008, 08:00 PM
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Thanks for the replys. I do not have the heads, but was considering getting a set for a 283 (future build) for nostalgia purposes. I've had good luck with milling and porting 896 powerpack heads that really woke up a 307 I tinker with. The small chamber of the 265 head almost resembles a hipo (ford) 289 head and looks like it would really wake up a small cube engine.
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Old 11-03-2008, 08:12 PM
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You want to wake up a small cube engine. Go to the boneyard and get a pair of 062 Vortecs off a '96-'99 5700 truck motor. Playing with my DynoSim, I made 638 hp with 'em on a 302.
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Old 11-04-2008, 08:19 AM
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I mean, they work well for a 265/283 very mild build... I built one for a friend that we dynoed and it made a respectable 245hp and 287ft.lb. of torque. I smoothed the transitions from the valve seat throat into the chamber and very lightly massaged the short side... 204/214 .420/.444 112CL cam, edelbrock dual plane, and comp roller 1.5 rockers. About 9.1:1 compression.

But a vortec head would be clearly superior.
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Old 11-04-2008, 11:35 AM
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I just sold a set to a guy thats doing the same thing, I'm pretty sure they are 1.72 X 1.50. You could do some pocket port work and radius the short side but you would still be choked a little by the int. valve.

I wouldn't go to the expense of installing bigger int. valves ....if thats possible on these heads, the performance gain, if any just wouldn't be worth it. A 283 punched to a 292, Vortec heads, Comp 268 magnum, E'brock Performer and a Holley 570 Street Avenger carb....or a million other combos similar and you would have a nice healthy, reliable street engine.
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Old 11-04-2008, 11:45 AM
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327Nut- that's exactly what I'm saying! Those were my thoughts exactly but it seems like everytime vortec heads are mentioned someone has to say..."Hey you might as well buy aftermarket aluminum heads for the price of some vortecs, the vortec specific manifold, vortec specifci bolts, vortec specfic gaskets, and not to mention the work needed to the heads to swap out the springs..." so I just don't mention them any more hardly when recommending heads.

Anyway, with that build you are recommending, the only thing I would add would be a set KB hypereutectic pistons with a very slight dome, +4cc I think, to bring the compression with larger vortec 64cc heads to around 9.7:1. That thing would run!
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Old 11-04-2008, 08:16 PM
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Well I wasn't REALLY "recommending" per se, just making a suggestion....if there's a difference?? You'll see some guy's on here that are just "dreamers" talking smack about building an 800 hp sbc for the street when in reality they probably have never built anything. And yes I know it can be done....

Most builds are dictated by the amount of $$$$$$$ you have to spend, if you can afford a nice set of alum. heads then by all means do it....as long as it fits your engine parts combination. If you want to build a high perf. street engine then you will usually have to buy a decent set of heads, intake man., bolts and all the related parts that go with it. There's lots of good used parts at swap meets and on Ebay, or go to the boneyard, pick up a set of Vortecs and just have a GOOD machine shop rebuild them...not expensive.

Like I said there's a million combo's and you don't have to build some exotic, expensive engine to have fun with in your hot rod....keep it simple!

Re-read your last post.... Use what you like but I'm a BIG fan of Speed Pro coated hyper pistons and their moly faced rings. Also The domed pistons??, I would do a lot of figuring before you buy those. My 331" has Speed Pro flat tops .010 in the hole, .039 compressed Fel Pro gasket and 64cc E,brock heads. It computes out to 9.52:1, be careful.....

Last edited by 327NUT; 11-04-2008 at 08:29 PM.
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Old 11-04-2008, 09:29 PM
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right, right... agreed. I like Speed Pro's stuff too...especially their rings...cast, molys or plasmas the rings I don't think can be beat. The only reason I mentioned KB was because Speed Pro simply doesn't have too many alternatives for a 283 these days- I think the only piston is a 4 valve releif type. Which if you are working with a .025 deck height only gets you around 9:1 (maybe a wee bit more with a .015 steel shim). And as you know that limits cam duration.

That combo you mentioned was just a build that I had in my mind, maybe a bit more cam but pretty much on target...

And yes there are sooo many parts out there on the cheap... I bought my vortec heads, intake, and valve covers off a guy for $300. He took them off a gm 330 horse 'delux' 350 crate engine and it only had 500 miles on it.
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Old 11-05-2008, 01:24 AM
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You guys are right, vortecs are the best, but only if you want to buy an intake and valve covers along with it. And the 268 comp cam seems to be very popular as well for 283s and 307s.
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Old 11-05-2008, 07:50 AM
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You can do this... same volume as 56 powerpak heads.

http://tri5chevy.proboards19.com/ind...lay&thread=135
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Old 11-05-2008, 08:11 PM
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Yeah, that guys set up was really cool, and those 305 heads he mentioned actually spec out around 55cc. I've had 305 four barrell heads on my 307 and it ran commendable, but they were a larger cc version. With a Performer intake and 280dur .440lift cam ran very well (and 305 heads), with single plane intake and duntov 30/30 cam ran like crap, but compression was not enough, I admit.
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Old 11-05-2008, 08:30 PM
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12558060 (12558062 casting) Vortec heads are hard to beat for the money. Here are the flow numbers from Scoggin-Dickey....
0.100 70 48
0.200 139 101
0.300 190 129
0.400 227 140
0.500 239 147
Those numbers are with 1.94"/1.50" valves. I mean, that's gettin' after it for an OEM cast iron head that you can rescue from the boneyard. A 350 with these heads and the proper supporting parts can make well in excess of 400 hp and a very streetable motor.
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Old 11-06-2008, 08:53 AM
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Please note the 400hp figure that TechInspct is refering too is most likely a 350ci engine... 400hp out of a vortec headed 283 can be reality but it's gonna take a lot of cam and probably a compression ratio that likes more octane than pump gas.
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