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Topic Review (Newest First)
01-05-2013 03:06 PM
LATECH 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.
01-05-2013 02:59 PM
LATECH 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.
01-05-2013 02:41 PM
cobalt327 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.
01-05-2013 02:09 PM
LATECH 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.
01-05-2013 01:03 PM
cobalt327 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:

01-05-2013 12:12 PM
Originally Posted by LATECH View Post
Chill out.
Good point, I'll take your advice myself.
01-05-2013 11:43 AM
LATECH [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.
01-05-2013 11:20 AM
bullheimer 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 tho. and they are the people to ask questions about anything pontiac.

01-05-2013 09:59 AM
cobalt327 Cutting the deck is all well and good, but you do not depend on cutting the deck for raising the compression as much as the deck is cut to obtain a good quench figure. That the compression may be raised is secondary to that. Get a clue.

Surely you must realize that the quench distance should be about 0.040". That is done regardless of compression ratio. The chamber volume and dish/dome volume is where the compression ratio is 'made'- NOT the head gasket thickness or deck height, except as a secondary effect to getting the quench right. Get a clue.

A Pontiac 455 can make well over 450 HP on 9.5:1 CR. 450 HP can be done w/9:1. This is NOT a SBC!!! Cutting a Pontiac head 0.060" most certainly WILL do something, AFA compression ratio is concerned. Get a clue.

One more time: The lower compression ratios of the '70s were NOT related to mileage- it was done for emissions. If mileage was a concern, they'd have used different cam timing and a different piston design. And higher compression can potentially get better mileage than lower.

Get a clue!!!
01-05-2013 08:10 AM
vinniekq2 from what I have read about the heads,there is not enough flow to generate 450. I do see a large amount of torque and its not another sbc.Go for it.
01-05-2013 07:00 AM
LATECH I was thinking that a set of 4X heads off a 400, with the 98 CC chambers would work well. They still say 4X on them and would appear original. But it seems the OP probably wont go for that option. Cutting .060 of the heads he has would put them close to 100 CC which would also work.
A comp cams XE 262 would do pretty well in that combe with a tall gear and stock converter. An XE 268 would also work, just reduce the dynamic a Tad
Static CR would be 8.88 and Dynamic would be 7.53 with cam installed straight up. This is also without decking the block or milling the heads, using flat top pistons with 6 CC reliefs, .042 Head gasket
Not sure that would put it at 450 horses, but on a 455, with a Qjet, Headers and duals, recurved dizzy, I would think it would be close.Just sayin
01-05-2013 12:08 AM
Originally Posted by blakethechop View Post
i hope to get 450 hp with head ported and milled new comp cam new edelbrock rpm intake 800cfm carb roller rockers.i have read that pontiac under rated the horsepower on the 455 during the fuel crisis is that true
The compression changes were made due to emissions standards being tightened. This meant no (or reduced) amounts of lead in the gasoline, which lowered the octane ratings, which led to lower compression. It had nada to do w/mileage.

Again- you need to CC the heads (both of them) first to try to determine if they've been milled before you got them. After that, mill the heads so the chambers are equal to one another (both heads match). When you're done, the compression ratio you will have depends on what heads you started out with and how much was milled. I don't cut them more than 0.050", personally.

If the heads have screw in studs, you may be in luck as far as the chamber size. Pressed studs are going to be the too-large 455 chambers. But screw in studs began to be used in more heads after mid '73, so that's not always going to help as an identifier. Pressed studs are a no-no, regardless.

Or just read up on them, instead of listening to me or anyone else: 4X Cylinder Heads - How to Pick the Right 4X Heads for your Pontiac - High Performance Pontiac Magazine

The factory ratings are not anything you need to concern yourself with IMO. Some were too high, some too low, some about right. But so what? What matters to YOU is how your engine is assembled, and it is not going to be the same as any factory engine anyway.
01-04-2013 04:41 PM
blakethechop i hope to get 450 hp with head ported and milled new comp cam new edelbrock rpm intake 800cfm carb roller rockers.i have read that pontiac under rated the horsepower on the 455 during the fuel crisis is that true
01-04-2013 04:30 PM
V8&4spd Stock a 455 with those 4X heads is only rated at 250hp. How much does the book say you will make with the recomended changes?
01-04-2013 03:50 PM
Originally Posted by WDCreech View Post
You don't read very well, do you? He had posted that changing heads was NOT an option!
Oh well, changing the pistons, paying for machine work to mill the heads and special head gaskets is a option. There is more than one way to skin a cat.
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