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post #1 of 22 (permalink) Old 12-31-2011, 06:52 AM Thread Starter
 
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62 heads

I currently have 4x heads on 455 bored .30 over, there are some 62 heads in the area I will be later today. How much better are the 62 heads, if any? He is asking $450, I have not inspected them. When I was rebuilding my 455, I notice a rocker arm, rocker stud and push rod guide plate was damaged (about $30 in parts)

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post #2 of 22 (permalink) Old 12-31-2011, 09:59 AM
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Not good for your application. Compression ratio will be too high for pump gas.... They're around 72cc...... 87cc would be about ideal...



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post #3 of 22 (permalink) Old 12-31-2011, 10:06 AM
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All the "large valve" Pontiac d-port heads (2.11 intake, 1.77 exhaust, screw-in rocker studs) are pretty much the same in terms of the port configuration, size, shape, and stock flow. The main differences are in chamber sizes, shapes, and configurations. At 72 cc's nominal those #62's would turn it into a "leaded race gas only" engine unless you also changed out pistons and other components to get the static compression ratio back down --- and the ports in those 62's are nearly identical to what you already have. All that's possible to do, but unless you have some overriding passion to run those heads and spend the money it would take to do it, my opinion is that it wouldn't be worth it.

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post #4 of 22 (permalink) Old 12-31-2011, 10:09 AM
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Those #62s with a .030 overbore would put you around 11.8cr, 87cc would be pushing it at 10.2cr, 92cc will get you under 10cr(9.8 which is better for the pump.....), 96cc will be at 9.5cr and will have larger valves than the 92s.



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post #5 of 22 (permalink) Old 12-31-2011, 11:09 AM Thread Starter
 
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Recommed use

Well I was hoping to use the 62's because they where only $450, but 93 octane would not work with that compression ratio.

I currently have 4x heads off a 1973 GTO 400 that need a new rocker, rocker stud and guide

Also I have 66 heads off a 1971 GTO 455 that is a bare block that someone started changing to screw-in studs.

What would be my best choice? Or should I just by some edelbrock 87 cc heads for $2200?

I'm trying to do a budget build, but I want a GTO with some HP.
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post #6 of 22 (permalink) Old 12-31-2011, 11:21 AM
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The 87cc Edelbrock heads would be perhaps the least hassle, if they are ready to bolt on. You will have over 10: 1 compression, which is fine for an aluminum headed engine. Not so with iron heads, which are thermally more efficient. It takes 10:1 with aluminum to equal the amount of energy produced by a 9:1 iron head. That said, you can do the research and get a set of cheap heads that cc out at about 96-100. I recently sold a set of 66's (114cc chambers) for peanuts. They are a 1971 455 head, and you could mill them just a bit to bring them down to 100 cc's or so and be set. That's probably what I'd do. $450 for a set of 62's is not a great deal, in my opinion, unless they are totally professionally re-worked and ready to bolt on. Plus, they are NG for a 455 with normal pistons. All cast iron Pontiac heads '68 -up flow about the same. All can be upgraded to screw in studs and bigger valves. The important thing is to find the right chamber size for your combo if you're running regular flat top pistons.
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post #7 of 22 (permalink) Old 12-31-2011, 12:18 PM
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"It depends" If youv'e got the budget for them, aftermarket aluminum heads have the most power potential. The best way is to buy them "bare" then have someone who really knows what they're doing to prep them with good valves, springs, some port work, etc. The components on the "ready to run" heads aren't all that great. Going the bare head route will net you the most power if you build the rest of the engine to take advantage of the heads, but it's also the most expensive solution. By the time they're done you'll spend double (or more) the cost of the bare heads. To really wake them up you'll want a roller cam, good headers, etc etc etc... depending on how rowdy you get with the cam choice, 600, 650+ horsepower out of 455+ inches ain't hard at all. You'll be up into forged crank territory easily. You'll also have way yonder on the far side of $10K into the engine. If that's your destination, that's the cost of the ticket to get there

Like A.J. Foyt once said, "Speed is just a matter of money. How fast do you want to go?"

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post #8 of 22 (permalink) Old 12-31-2011, 02:05 PM Thread Starter
 
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Heads

I think I will try to rebuild the one of the heads I have. if I'm trying for close to 100 cc, should I use 73 GTO head that has 98 cc? Maybe put larger valve in it? Or have it tricut?

I talked to the machine shop and they said they cannot machine the 66 heads to 100cc.

Would it be better to use the 4X heads or 66 heads, taking into account the above info?


Thanks

Joe

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post #9 of 22 (permalink) Old 01-01-2012, 12:24 PM Thread Starter
 
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Found some 96 heads off a 71 GTO 400. I'm going to try that set up.

Thanks for the info
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post #10 of 22 (permalink) Old 01-01-2012, 01:25 PM
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There are quite a few web sites out there with information on the various Pontiac cylinder heads. Google "Pontiac cylinder head codes" to find a bunch of them. Just about any d-port head with an appropriate chamber volume will be a good starting point as all the ports are pretty much the same. If you're on a budget the trick is to find some heads that don't need a bunch of work/machining. In general, aim for a set of heads that already have the "large valves" (2.11 intake, 1.77 exhaust) and screw-in rocker studs (with pushrod guide plates) as opposed to pressed in rocker studs. Heads can be modified to have both those features but why spend money for parts and machining if you don't have to? The one aspect that's not easily modified is the combustion chamber shape and size, so that should figure significantly in your selection criteria.

Also, learn how to cc heads yourself. It's not hard. I used a flat piece of plexiglas, some grease, a large plastic graduated syringe, and colored windsheild washer fluid. I measured every chamber 3 or 4 times and averaged all the results to ensure I was getting accurate measurements. It's important because just a couple of cc's makes a difference in compression ratio, and Pontiac heads are known to vary a lot from the published factory chamber sizes. This is an area where you want to be positive you know where you stand.

If you have Excel available, I have a spreadsheet I can send you that does all the calculations necessary for compression ratio --- there are also web sites out there that can do it too. For a +0.030 455, assuming "standard" head gasket compressed thickness of 0.042 and a "usual" piston deck clearance of 0.020, a total clearance volume of 114 cc's will put you at about 9.3:1 - a good spot for iron heads. Making up that 114 cc's are 4.5 cc's from deck clearance, 9.45 cc's from head gasket, 6 cc's in the flat top piston valve pockets, and 94 cc's in the chambers. Zero-deck the block and you lose 4.5 cc's, upping compression to 9.65:1 - so you'd need to get those 4.5 cc's "back" from somewhere (like dishing the pistons, using a different head with 98.5 cc chambers, or using (much) thicker head gaskets. Using thick gaskets though is going to effectively eliminate the very beneficial cylinder "quench area" so that's not a preferred choice. That's why having a tool to work with compression ratios is nice. It lets you see the effects of various changes and parts combinations easily before you start putting out the cash.

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