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Discussion Starter · #1 ·
hi i have a pontiac firebird 455 with 4x heads 113cfm i want to port heads and have read jim hands book has any body ported 4x heads and would you do chamber as in jims book or would this lower cr i want to keep heads and would appreciate info should i use higher cr pistons smaller head gasket mill heads ?any help would be great. i live in australia so locating different heads is a impossibillity and dont want to spend 3 grand on new heads shipped from usa
thanks blake
 

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113 CFM??? Do you mean 133 CC chambers?
What is your project goal? street car? strip?
I have to agree with Hcompton, having spent some change on head work.
 

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Grumpy Old Goat Herder
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Blake, Have those heads milled. For every .005" that they are milled, you will reduce the combustion chamber by about 1cc. I wouldn't go more than .060" and you'll need to have the intake side of the head milled an equal amount so that you won't have trouble putting any intake manifold on that engine.

Bill
 

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Discussion Starter · #4 ·
thanks for replies the car is for street and i would like to port heads myself could anyone give me what they would do with the 4x heads what pistons what gaskets how much to mill of heads would they reshape combustion chamber changing heads is not an option i am going to put an xe 268 comp cam and a edelbrock rpm intake 750 carb .would love some ideas
 

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WFO
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thanks for replies the car is for street and i would like to port heads myself could anyone give me what they would do with the 4x heads what pistons what gaskets how much to mill of heads would they reshape combustion chamber changing heads is not an option i am going to put an xe 268 comp cam and a edelbrock rpm intake 750 carb .would love some ideas
If the heads are from a 455, the chambers are too big. If it was me, I'd find a set of smaller chamber heads like the well known 6X-4 or 4X heads from a 400. I used a set of these on a 455 in a '81 Camaro and was very satisfied w/the results.

I didn't go w/the 1.77" exhaust, either. Stock valve sizes. Much is made of using the bigger exhaust valve, and that's fine if the budget allows. But my way of looking at it is, every penny you spend on a set of iron production heads is a penny better spent on a set of aftermarket heads. Not saying you cannot get good results from iron heads- but keep the expensive mods out of the picture.

The best results are sometimes the cheapest: owner bowl work and porting, careful attention to quench, as well as other areas of the valve train.

Cleaning up the bowls by removing the lip just below the last angle of the valve seat (see image below) will help as much as anything. The valve guides have to be right before doing the valve job. The guides, valve job (three angle, but do not be tempted to change the intake seat from 30 to 45 degrees), and milling the heads to help compression are the only things I would recommend outsourcing. Everything else you can do yourself.



Choose a head gasket to raise after you've measured the piston deck height (as well as the actual combustion chamber volume) during the mock-up phase of the build.

Rods are bound to come up any time a performance Pontiac build is mentioned. If you have the budget, buy a set of forged rods for peace of mind if nothing else. But an iron head 455 is not going to make power past about 5200 unless you've done a lot of porting and have the cam to match. FWIW the stock cast iron rods are what I used- with ARP bolts and resizing- and they worked just fine. And according to Hand, he also thinks the cast iron rods are OK at that level.

From a recent post:
...(my 455/Camaro) was the tamest, easiest to drive anywhere, everyday, regular gas, 3.31 rear gear, 650 DP, all steel, full interior, 12 second vehicle you'd ever want to see.

I mean, how many cars w/those specs can stage in Drive, mat the gas from an idle and let the tranny shift out on its own (no governor work) and still run 12's on street tires? With a 10-bolt 3.08 run the same way (in Drive) it went 13 seconds flat in the quarter. Oh, and it had a 4777 Holley on a Performer intake (not the RPM, it hadn't come out yet). It was a ball.
The engine shifted out at about 4400 rpm by itself. For the best ET I shifted it at 5000 rpm.

Some Pontiac info:
Info/sites
Pontiac engine info
 

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WFO
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4X was used on 400 and 455 Pontiac engines. Fortunately, Pontiac engines are not overly sensitive to lower than "normal" compression ratio.

Pontiac production rods are mostly either just OK (cast iron, need ARP bolts) or real pos (forged production rods used in 1959-'62). There were decent factory Pontiac $uper Duty rods, but why even think about them when there's cheap aftermarket forged rods everywhere.

I'll reserve comment on "slapping cars together with left over parts", except to say GM might have lost their balls, but Pontiac didn't. Pontiac stuck to their guns longer than anyone else- they had a 455 Firebird as late as '76 IIRC. Yeah, it had low compression, but the raw material was there at least.
 

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Discussion Starter · #11 ·
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
 

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WFO
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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.;)
 

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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
 

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WFO
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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!!!
 

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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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Zero decking the block will give you more cr increase than cutting the heads.
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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WFO
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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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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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