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Old 12-05-2022, 03:43 PM
Brewster G Brewster G is offline
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Default 73 4X head identification

My early 73 T/A 455 has 4X heads dated H182. Yes and? I hear you ask.

Well up to press (I have owned the bird about a year) I had assumed these to be the original large chamber 455 application heads, especially since the block is also H182 dated.

However I have just found the secondary stamping on the heads to be "3", which I believe to be early 73 400 application with 98cc chambers.

Am I a lucky sun of a gun or could these still be large chamber 455 heads. The identical casting date is making me doubt my findings.

Any info would be greatly appreciated.

John

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Old 12-05-2022, 06:28 PM
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Are both heads same secondary stamp?
I'd say it is the 400 (98cc) heads, should make the 455 around 9:1 CR.
Until the head comes off and checked may never know.
I quess you could get some one to 'pump' the engine to see what it shows?


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Old 12-05-2022, 07:11 PM
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I believe that the 1973 98cc heads were in fact the 400 heads;
If my memory serves me the published compression for 1973/1974 was 8.2:1.
(vs 1971/1972 advertised compression of 8.4:1, then 1975/1976 compression of 7.6:1)

All that being said though, if the date codes align it wouldn't seem completely unbelievable for 98cc heads to have been used;
I have heard more about 75-77 heads either being different castings/combustion chamber size from left to right - so that doesn't seem like a giant stretch...
But I'll default to believing anyone more knowledgeable in this stuff...

When I had my '73 Formula (350/350 car), the plan was to build it as a 1973 Formula 455, so I sourced the correct 4X-1H(114cc) heads for it;
After I gave the car back to my brother he decided to acquire 1974 4X-4H heads;
The heads he bought were the 98cc castings, but if my memory serves me, after a given date early in the 1974 model year all 4X heads received screw in studs (as opposed to the pressed-in studs that all(?) 1973-4X heads had) - the heads he bought need nothing, as they were previously rebuilt, but swapped out for aluminum heads, and left at the shop.

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1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.


1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)
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Old 12-06-2022, 12:29 PM
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Those heads I have found on early '73 cars and with the pistons used and deck at .022, they are around 110 CC and come in around 8.2:1 as unruhjonny has said .
You will not see these typically after the ( EPA mandated) engine change over in March/April and the new Intake, EGR etc.

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Old 12-06-2022, 04:14 PM
Brewster G Brewster G is offline
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Hi guys,

Many thanks for your replies. I have been basing my assumptions that a secondary stamping of 3 is a 98cc head from a 400 4bbl MT on the following: http://pontiacpower.org/4xheads.htm

Both heads are most definately stamped "3", both H182 casting date same as the 455 block. The motor has been apart before so I can't be sure the combination is original, but it seems ulikely a previous owner found a set of 400 heads cast on the very same day as the block.

It would therefore seem Formulabruce's observations may more likely translate and these "3" heads have larger chambers.

My next steps will be to check the compression and check for press or screw in rocker arm studs before ultimately removing to cc a head.

Thanks again for your advice

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Old 12-06-2022, 04:48 PM
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Incase it is worth elaborating, according to my Pete McCarthy book here the secondary stampings used on 1973-4X heads are:
1H (455) 114cc or 112cc
3H (400-4bbl) 98cc
4H (400-2bbl*) 98cc
7H (400-4bbl) 98cc

I know this reference source has some errors - I have a page that Mr McCarthy compiled about 1973/1974 engines somewhere here...

*According to Pete's book, the 4H was only on 2bbl motors, and my guess was that these were small valve heads;
I decided to investigate further, and went over to John's site - and sure enough, it indicates that the 4H was a small valve head;
Johns site also suggests that some of the secondary stampings were missing the letter code - so "3H" could have been stamped as "3" - ditto on the other secondary stampings.

Pete's book also suggests that the "3H" stamping was only used on manual transmission engines - while "7H" was used on automatic engines, and if Pontiac engines from a couple years earlier are any indicator, maybe there is a combustion chamber difference between the two??

http://www.wallaceracing.com/headsearch.htm

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1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.


1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)
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Old 12-07-2022, 10:27 PM
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Rocky Rotella Rocky Rotella is online now
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This will explain most everything needed to know about 4X heads.

https://www.motortrend.com/how-to/03...-racing-heads/

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Old 12-09-2022, 01:56 PM
Brewster G Brewster G is offline
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Thanks again for all the info and links. I pulled a valve cover and found screw in rocker studs so I everything seems to tally with the various sources for 98cc's.

Now I just need to find a copy if Jim Hands book for so I can port them.

Is there a recomended maximum that can be skimmed from these heads to further reduce the chamber volume. I guess there will be a point where this becomes counter productive if piston to valve clearance becomes close and the piston needs more valve releif.

Also would these heads benefit from 1.65 rockers. I would be looking to combine them with something along the lines of a RA4 041 cam.

Cheers
John

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Old 12-09-2022, 02:06 PM
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Quote:
Originally Posted by Brewster G View Post
Thanks again for all the info and links. I pulled a valve cover and found screw in rocker studs so I everything seems to tally with the various sources for 98cc's.

Now I just need to find a copy if Jim Hands book for so I can port them.

Is there a recomended maximum that can be skimmed from these heads to further reduce the chamber volume. I guess there will be a point where this becomes counter productive if piston to valve clearance becomes close and the piston needs more valve releif.

Also would these heads benefit from 1.65 rockers. I would be looking to combine them with something along the lines of a RA4 041 cam.

Cheers
John
I could be wrong, but I have understood that typically a 041 cam needs much more compression than you make to work properly;
unless you plan on zero decking the block, cc'ing the heads, and calculating for which head gasket you intend to use (all to get the proper compression needed) I would advise against it.

I believe that Cliff Ruggles did some extensive testing of a 9.0:1 (or very close) 455 build with a 041 cam, and some others - which may be of great benefit to you.

There are also a couple members here that have shared seemingly basic builds, and have netted stellar results - it's all about with attention to detail, and matching parts;
You really might be interested in some threads relative to "pure stock" type builds.

I say all this because I have understood that although an 8:1 engine can make a bunch of power, it can also be a dog if over cammed.

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1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.


1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)
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Old 12-09-2022, 02:34 PM
SD455DJ SD455DJ is offline
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I have a 461 (400 + .030" with a 4.25" crank) with 9.5 to 1 compression (6X-8 heads with a .060" cut), .040" quench, zero deck with flat top pistons with a 041 clone-cam that is pretty rowdy at idle. It still makes amazing torque just off idle, so no problem roasting the tires and making vacuum for the power brakes. I wouldn't go less than 9.5 to 1 static compression on any 455 if you're considering a RAIV style cam.

Dennis

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Old 12-09-2022, 05:40 PM
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unruhjonny unruhjonny is offline
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Quote:
Originally Posted by SD455DJ View Post
... I wouldn't go less than 9.5 to 1 static compression on any 455 if you're considering a RAIV style cam.

Dennis
BINGO!

Unless you really pay attention to how it's all assembled, it can fall way short of there.

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1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.


1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)

Last edited by unruhjonny; 12-09-2022 at 05:46 PM.
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Old 12-10-2022, 02:15 PM
Brewster G Brewster G is offline
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I would be aiming for at least 10:1 comp on iron heads, hence why I was asking how much the 98cc heads can be skimmed down.

If its not feasble to acheive this compression with these heads I will most likely go with alloy heads and aim for 11:1. This is what I was aiming to do when I thought I had the original 455 112cc heads.

Cheers
John

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Old 12-10-2022, 02:50 PM
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unruhjonny unruhjonny is offline
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fair enough.

I wanted to touch on something you said earlier - I waited to see if somone more knowledgable might speak up:

Quote:
Originally Posted by Brewster G View Post
My early 73 T/A 455 has 4X heads dated H182. ...
the block is also H182 dated....
I have just found the secondary stamping on the heads to be "3", which I believe to be early 73 400 application with 98cc chambers. ...
The identical casting date is making me doubt my findings. ...
I was hoping someone more versed in casting dates of components might speak up, but with no one saying anything, I just want to say it so that it has been said;

I have my doubts these are the original heads to your cars engine.

Since you've only had the car a year, I would guess that odds are a previous owner bought those heads because:
1) more compression
2) date matched to block

Now I don't want to seem to undermine anything previously stated;
I still think it's possible that those are original heads, but considering the following, I think it's rather improbable:

1) I have understood that once a drive train was certified, that if manufacturers are caught building cars/drivetrains that are incongruent with epa certification they were subject to heavy fines ect.
Just look at the 1973 Pontiac EGR fiasco - in that instance they were not breaking any rules, but they were more bending the rules, because of how the testing to gain certification was done.

1b) If a casting (1/1H) was already created specifically for ALL 1973-455's;
And those heads were a component of the EPA certification;
odds are those were the only castings intended to be used on 455.
...but I've learned to never say never.

2) casting dates;
I have understood that blocks, heads, and intakes (the three parts everyone looks at for casting dates) were all created in batches, and often the block preceded the heads by weeks, if not much more;
I have also understood that more often than not supplies of blocks and intakes exceeded that of heads - maybe because the heads required more time to complete finishing work(?), so shortblocks, and intakes were awating heads.
I have understood that often the intake will be closely dated to the block.

3) The history (or lack there of) on your car which you have shared with us.

So although possible, I believe it to be improbable.

... and none of this takes away from your intentions of your build, or the stock appearance of the engine components.

That's probably a VERY fun car.

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1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.


1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)

Last edited by unruhjonny; 12-10-2022 at 02:58 PM. Reason: spelling/punctuation ect
  #14  
Old 12-10-2022, 03:02 PM
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Formulabruce Formulabruce is offline
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Keep in mind, no matter the head CC , the final CR was around 8.2:1. Piston edges were rounded off so the same heads could be used, piston head types changed too.

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Old 12-10-2022, 05:46 PM
Brewster G Brewster G is offline
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unruhjonny - Thank you, that is just the kind of insight I was initially looking for. I too have now come to the conclusion that these were not the original heads and as you say they were most likey sought out by a previous owner seeking to add some much needed compression, I see this as a bonus

Also very interesting how head casting dates would usually be later than engine casting dates on original pairings. I had my suspicions that they would not necessarily match exactly. Again not a problem, I know its been apart before.


Thanks again to all. I appreciate you taking the time to educate me further on an interesting topic

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