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  #16 (permalink)  
Old 01-05-2013, 11:20 AM
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Like LaTech said, they made more than one chamber size of 4X heads. If you have 113 cc's i would toss them, or your idea of making 450hp. Could still maybe reach that mark, but not w/o alot of work that i don't think is worth it.

i did exactly like what you said on my 061 heads for my 400. i think there is a pic of them somewhere in my album. i couldn't possibly have removed more than 2 or 3 cc's in my uneducated opinion. you HAVE to cc them and then use c.r. formulas to come up with how much of a piston you will need. Since most of those came with greatly dished pistons, you could get to around 9 (8.8 was stated above) with a flat top with valve reliefs, then with that 268 cam it might still fly somewhere in the 400hp range or more. i took it straight out of jim hands book, the arp bolts on stock rods, etc. i did not port my heads tho. i dont have the confidence since i never did it before. the machine shop did put the largest valves on earth in it tho, and i dont really know if he pocket ported them or not. i did not ask as it is a long shot to whether i will ever see this motor run..

i think my heads were around 101cc's and with a 6cc piston i was going to get almost 9:1 on my 455. so with a 113 cc head, i think you will have to getta pop up piston. but i am just blowing this out my arse as it's been years now since i did the math. but that is what you have to do. as Cobalt said. there is a c.r. calculator at www.sdperformance.com tho. and they are the people to ask questions about anything pontiac.

FOUND THIS THERE. ALL PONTIAC DUDE READ: http://www.sdperformance.com/moreTech.php?newsID=41

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Last edited by bullheimer; 01-05-2013 at 11:39 AM.
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  #17 (permalink)  
Old 01-05-2013, 11:43 AM
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[QUOTE=hcompton;1630899] Zero decking the block will give you more cr increase than cutting the heads. [QUOTE]

That is absolutely backwards. Most heads have a quench area in the chamber, milling an open chamber head verses decking would result in the same amount of CR change, with a poncho head, because it has a quench pad (even small) you gain more raise in CR thousanth per thousanth milling the head than decking the block.
Also, engines today wont run at 300 degrees in the cooling system.Damage will occur. Absolutely.
I like your enthusiasm here but stick to the facts.
And Cobalt is RARELY incorrect, if you have a valid point ..OK. As of yet I dont see that. Chill out.
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Old 01-05-2013, 12:12 PM
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Originally Posted by LATECH View Post
Chill out.
Good point, I'll take your advice myself.
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  #19 (permalink)  
Old 01-05-2013, 01:03 PM
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All I have to say is to the OP is:

"Warning: Be sure to verify all Pontiac info found in print, by word of mouth, or on the internet (including here). There's a LOT of erroneous and misleading info out there."

What the OEMs are doing w/"modern" engines has little to do w/a Pontiac V8 that was out of production >35 years ago.

As for cutting a deck being preferable to milling a head, I stand by my previous statement regarding milling blocks vs. heads, and will leave it at that.

Pontiac used the same engines/heads/pistons/CR regardless of application in the smog years w/only a few exceptions like the W72 and 301 turbo engines used in the F-body.

And of course the Pontiac 4X and 6X heads, etc. have a quench pad- regardless of chamber size, shown below:

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Old 01-05-2013, 02:09 PM
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Even with the tiny almost non existant quench pad, it is still a larger gain milling the head than the deck, as the bore is a concentric hole.
Still negating your argument.
Even though you said "water" I am assuming you mean "coolant". If coolant is 300 degrees, they must be running something special and /or using about 40 psi cooling system pressure.
You should eleaborate more on your statements, if in fact what you say is true. Nothing backs the truth like good ol physics.
Decking the block is NOT preffered for raising CR as much as milling heads, or using pop up pistons. Substantial Milling of the deck on some engines Like the SBC can weaken them considerably
Also when milling heads , if you mill to raise CR, then you most likely will be milling .030 or more, Milling the intake side of the head is a better way to fly. That allows you to run ANY intake you want . Milling an intake is a backwards way to approach the issue.
Lower CR in the early 70s was due to emissions and the cat wizz gas they started making. Low octane wont support High CR. Gas mileage suffered as a result.
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Old 01-05-2013, 02:41 PM
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Pontiac engines have made good power/torque w/the compression ratios obtainable w/flat top pistons and the 400 chamber heads, like the 6X-4. I never had my 455 on a dyno but going by my weight and quarter mile speed/ET I estimate it was right at 450 HP. 6X-4 heads w/FT pistons.

The OP lives overseas, he's stuck w/the 4X 455 heads. He can get to 450 or damn near it if he ports the heads and maximizes the CR w/the 455 4X heads and does his homework regarding quench and picks a good split pattern cam and runs 4-tube headers.

The OP's 4X 455 heads w/a 0.060" cut and FT pistons and a 0.041" quench will give him right at 9.1:1; 9.5:1 is the max I, or anyone who knows what they're talking about regarding Pontiac engines w/iron heads would recommend he use, anyway.

BTW, just because YOU cannot make 450 HP- even w/ round ports- doesn't mean it's impossible for the rest of the world, even w/iron D-ports. Because not only is it not impossible, it's common.

I'd ask what happened to the idea that you cut the block to gain compression instead of the heads, or what about the quench pad that didn't exist, or what happened to "455's don't use 4X heads"? Et cetera. But all I really need to say is: Just stick to the facts.

I don't know what you are talking about when you say closed chamber heads and 88cc, but the early pre-emissions Pontiac heads were around 72cc. If you're talking about the 400 size chamber smog heads, they're not "closed chamber" heads by any stretch of the imagination. 88cc heads on a FT 455 would put the CR too high anyway.

Last edited by cobalt327; 01-05-2013 at 02:46 PM.
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  #22 (permalink)  
Old 01-05-2013, 02:59 PM
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I had my heads milled, it only ran about 30 bucks extra to have the intake side shaved. It was well worth it.
I have 3 different intakes , not sure which one I am gonna run, yet.
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Old 01-05-2013, 03:06 PM
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I have been pretty relaxed with my build, time is no biggee. My Machinist is slammed right now. All his roundy round guys have there plants at his place getting freshened up, dynoed etc.
He has a 400 of mine there right now, I told him no rush. I have no place to store it soo...
My 389 (punched to 4.12 ) is at the shop, awaiting its final assembly.
I have a set of cabinets at the house to finish next week, and a couple engines to change before I can get back on it. But I will have it ready by spring for its home in the 64.
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