Ad Radar
High Performance Pontiac
Click here to find out more!

Better or worse heads for 76 Trans am w Pontiac 400.

  
High Performance Pontiac
1 |  2 |  Next   | Last 
Item Posts    Sort Order

Better or worse heads for 76 Trans am w Pontiac 400.

 
jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/11/14
09:55 PM

Hey Guys,
I am actually restoring two cars at once now! I know, crazy!! The 69 GTO is coming along well and I am adjusting the fenders and doors and endura bumper and all to prepare for painting, blocking and so on!! The question I have is about the motor that I am having rebuilt by my friend Brett. This is a numbers matching 76 Trans am white with black interior pontiac 400 with automatic.  The heads on the motor are 6S heads. I have a set of 6X heads that I could use instead. Any suggestions?? Oh, the 6X heads have had the new hardened seats put in and have been rebuilt about a year ago. Thanks guys and I will post some photos of what Iam doing with both cars!! You all are the best as usual!! JB  

bigD bigD
User | Posts: 134 | Joined: 05/14
Posted: 06/11/14
11:18 PM

If that '76 is a "557" block, and you feel you must use it to be numbers matching, build it for low performance, and don't try to wind it up after it's built. Some guys have got away with 400hp builds. But many others were not so lucky. My neighbor was in the last bunch.  Frown Eqmg
Jdro  

bigD bigD
User | Posts: 134 | Joined: 05/14
Posted: 06/12/14
04:39 AM

I've tried to find info on the 6s heads. It seems that there isn't much to find. All the head charts show these to be A.I.R. heads. Well, I didn't even know what that meant. So I looked it up. It stands for either Air Injection Reactor, or Air Injection Reaction. It's a system which began in Pontiacs in 1966. It was started, of course, in CA, to reduce exhaust emissions. I read that in about 1975 CA required both the A.I.R. system and a catalytic converter on all new vehicles sold there.

This system consisted of a belt driven air pump, which we called a "smog pump", and all sorts of plumbing to force this air into the exhaust ports of the cylinder heads, to help burn any unburnt gas in the exhaust. Most guys use to just take the pumps off and throw 'em away. I have not been able to find a single article about modifying these A.I.R. heads like the 6s. But I assume that if you get rid of all the plumbing and seal off the holes to the outside, these heads should be as good as the 6x heads.

If anybody has any links to good info about using the A.I.R. heads please post them here.   Smile

http://smog-era.com/pollution-control-devices-explained/air-injection-reaction-a-i-r-explained/

http://ericpetersautos.com/forum/showthread.php?7188-How-they-kneecapped-cars-in-the-70s  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 466 | Joined: 11/13
Posted: 06/12/14
01:03 PM

hello

if you want any type of perf engine, those must all go in the trash. the chamber is way too big to get decent compression. you need heads with 72 - 76 cc's.

heres the specs below.

4 6X 93.74 cc's 2.11/1.66 valve 4.86" 350
6 6X 124.51 cc's 2.11/1.66 valve 4.71" 455
6 6H 124.51 cc's 2.11/1.66 valve 4.71" 455
7 6S (AIR) 100.04 cc's 2.11/1.66 valve 4.86" 400
8 6X 100.04 cc's 2.11/1.66 valve 4.86" 400
9 6S (AIR) 93.74 cc's 2.11/1.66 valve 4.86" 350
1977 4 6X 93.74 cc's 2.11/1.66 valve 4.86" 350 / 400 W72
8 6X 100.04 cc's 2.11/1.66 valve 4.86" 400
1978 8 6X 100.04 cc's 2.11/1.66 valve 4.86" 400
1978/79 4 6X 93.74 cc's 2.11/1.66 valve 4.86" 400 W72


cyl head info

http://ronspontiacpage.com/reference-pages/stockheadspecs.htm  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 466 | Joined: 11/13
Posted: 06/12/14
01:14 PM

Icon QuotebigD:
If that '76 is a "557" block, and you feel you must use it to be numbers matching, build it for low performance, and don't try to wind it up after it's built. Some guys have got away with 400hp builds. But many others were not so lucky. My neighbor was in the last bunch.




was this a stroker or 400 ci?

did the rod come off or did the crank break?  

jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/12/14
01:34 PM

As usual guys, thanks for all the help!!! I really appreciate all the input! But Im a little confused with "Shy"'s post. So if I read your first post right I need to toss both sets of heads in the trash? But you list the 6X heads as ones to have, and those were the one set I have? Help!! Confused JB  

jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/12/14
01:34 PM

As usual guys, thanks for all the help!!! I really appreciate all the input! But Im a little confused with "Shy"'s post. So if I read your first post right I need to toss both sets of heads in the trash? But you list the 6X heads as ones to have, and those were the one set I have? Help!! Confused JB  

jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/12/14
01:35 PM

Guys I dont know why my posts are getting put out twice!! Dammit! JB  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 466 | Joined: 11/13
Posted: 06/12/14
02:08 PM

lol, yes you are confused.

that list is all trash heads for a 400, there are more trash heads than that.

there is a second number on most heads by the valve cover on a flat spot. this tells the app and cc of the heads. this number is on the trash list. look for this number on your 6x heads and you can see exactly which trash version of 6x heads you have, lol.


I POSTED THIS LINK FOR YOU BUT I GUESS YOU DID NOT LOOK AT IT.

cyl head info

http://ronspontiacpage.com/reference-pages/stockheadspecs.htm    

4zpeed 4zpeed
Enthusiast | Posts: 368 | Joined: 04/13
Posted: 06/12/14
03:14 PM

Hi JB,

I think all Shy is saying is that you won't get enough compression with those heads to build a strong performance engine.

First though, you need to back up and address big D's reply to your post. The 500557 castings of the 400's were weaker with thinner webbing in the block, therefor if using the original block you may want to limit the build anyway, depends on your expectations.

BTW thanks for making that a quick link Shy.

Blocks
Year            Displacement     Casting Number
1975                350                     488986 (early) 500810 (late)
                       400                     488986 (early) 500557 (late)
                       455                     500813

1976                350                     488986  
                       400                     500557
                       455                     500813

1977                301                     525934
                       400                     568557

1978-79           400                     568557

Heads
The 6X castings started being installed on engines after about 2/21/75

•6X-4 350(and 77-79 T/A 6.6), 93cc, 2.11/1.66"

•6X-8 400, 101cc, 2.11/1.66"

•6H-6 455, 124cc, 2.11/1.66"

•6S-7 350 w/AIR, 93cc, 2.11/1.66"

•6S-9 400 w/AIR, 101cc 2.11/1.66"


The 6X-4 and 6X-8 were the only heads used after 1976.


1975 Engine Codes  

Code Application Displacement Compression Horsepower Transmission Heads Camshaft Carb
WT                          400              7.6:1           185             Manual       5C         67     4 bbl
WX                          455              7.6:1           200             Manual       6H         67     4 bbl
YA                           350              7.6:1           155               Auto         5C        555    2 bbl
YB                           350              7.6:1           155               Auto         5C        555    2 bbl
YH                           400              7.6:1           170               Auto         5C        266    2 bbl
YM                           400              7.6:1           185               Auto         5C         66     4 bbl
YN                           350              7.6:1           195             Manual        5C       555     4 bbl
YO                           350              7.6:1           195             Manual        5C       555     4 bbl
YS                           400              7.6:1           185               Auto          5C        66      4 bbl
YT                           400              7.6:1           185               Auto          5C        66      4 bbl
YU                           455              7.6:1           200               Auto          5I         67      4 bbl
YW                          455              7.6:1           200               Auto          5I         67      4 bbl
ZP                           350              7.6:1           195               Auto          5C        555    4 bbl
ZT                           400              7.6:1           185               Auto          5C         66     4 bbl
ZU                           455              7.6:1           200               Auto          6S         67     4 bbl      
ZW                          455              7.6:1           200               Auto          6S         67     4 bbl

1976 Engine Codes  

Code Application Displacement Compression Horsepower Transmission Heads Camshaft Carb  
WT                          400              7.6:1           185             Manual        6X         67     4 bbl
WX                          455              7.6:1           200             Manual        6H         67     4 bbl
X4                           400              7.6:1           170               Auto          6X        255    2 bbl
XP                           350              7.6:1           160               Auto          6X        254    2 bbl
XZ                           350              7.6:1           165               Auto          6X        555    4 bbl
Y3                           455              7.6:1           200               Auto          6H         67     4 bbl
Y4                           455              7.6:1           200               Auto          6H         67     4 bbl
Y6                           400              7.6:1           185               Auto          6X         66     4 bbl
Y7                           400              7.6:1           185               Auto          6X         66     4 bbl
Y8                           455              7.6:1           200               Auto          6H         67     4 bbl
YA                           350              7.6:1           160               Auto          6X        254    2 bbl
YB                           350              7.6:1           160               Auto          6X        254    2 bbl
YC                           400              7.6:1           170               Auto          6X        255    2 bbl
YJ                            400              7.6:1           170               Auto          6X        255    2 bbl
YP                           350              7.6:1           160               Auto          6X        254    2 bbl
YR                           350              7.6:1           160               Auto          6X        254    2 bbl
YS                           400              7.6:1           185               Auto          6X         66     4 bbl
YT                           400              7.6:1           185               Auto          6X         66     4 bbl
YY                           400              7.6:1           185               Auto          6X         66     4 bbl
YZ                           400              7.6:1           185               Auto          6X         66     4 bbl
Z3                           455              7.6:1           200               Auto          6S         67     4 bbl
Z4                           455              7.6:1           200               Auto          6S         67     4 bbl
ZA                           400              7.6:1           185               Auto          6S         66     4 bbl  
ZB                           455              7.6:1           200               Auto          6S         67     4 bbl
ZF                           350              7.6:1           165               Auto          6X        555     4 bbl
ZK                           400              7.6:1           185               Auto          6X         66     4 bbl

1977 Engine Codes

Code Application Displacement Compression Horsepower Transmission Heads Camshaft Carb  
WA                          400               8:1             200             Manual        6X       431     4 bbl
WB                          301              8.1:1           135             Manual         1        868     2 bbl
XA                           400              7.6:1           180               Auto          6X       793     4 bbl
XB                           350              7.6:1           170               Auto          6X       793     4 bbl
XC                           350              7.6:1           170               Auto          6X       793     4 bbl
XD                           400              7.6:1           180               Auto          6X       793     4 bbl
XF                           400              7.6:1           180               Auto          6X       793     4 bbl
XH                           400              7.6:1           180               Auto          6X       793     4 bbl
XJ                            400              7.6:1           180               Auto          6X       793     4 bbl
XK                           400              7.6:1           180               Auto          6X       793     4 bbl
Y6                           400               8:1             200               Auto          6X       112     4 bbl
Y7                           400              7.6:1           180               Auto          6X       793     4 bbl
Y9                           350              7.6:1           170               Auto          6X       793     4 bbl
YA                           350              7.6:1           170               Auto          6X       793     4 bbl
YB                           350              7.6:1           170               Auto          6X       793     4 bbl
YH                           301              8.1:1           135               Auto           1        868     2 bbl
YK                           301              8.1:1           135               Auto           1        868     2 bbl
YW                          301              8.1:1           135               Auto           1        868     2 bbl
YX                           301              8.1:1           135               Auto           1        868     2 bbl

1978 Engine Codes

Code Application Displacement Compression Horsepower Transmission Heads Camshaft Carb  
WC                          400              8.1:1           220            Manual        6X        402     4 bbl
X7                           400              8.1:1           220              Auto          6X        402     4 bbl
XA                           301              8.1:1           140              Auto           1         471     2 bbl
XB                           301              8.1:1           140              Auto           1         471     2 bbl
XC                           301              8.1:1           140              Auto           1         471     2 bbl
XD                           301              8.1:1           140              Auto           1         471     2 bbl
XF                            301             8.1:1            150              Auto           1        464     4 bbl
XH                           301              8.1:1           150              Auto           1         464     4 bbl
XJ                            400              8.1:1           180              Auto          6X        471     4 bbl
XK                           400              8.1:1           180              Auto          6X        471     4 bbl
XU                           301              8.1:1           150              Auto           1         464     4 bbl
XW                          301              8.1:1           150              Auto           1         464     4 bbl
YA                           400              7.7:1           180              Auto          6X        471     4 bbl
YU                           400              7.7:1           180              Auto          6X        471     4 bbl



Grin  
Poncho huggen gear snatchen posi piro.

jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/12/14
08:41 PM

Shy, I tried to look at it and it wouldnt let me. It said unknown page and something or other. JB  

jbmacneil jbmacneil
Enthusiast | Posts: 542 | Joined: 07/09
Posted: 06/12/14
08:45 PM

Thanks to 4Zpeed, I know my engine is the 1976 ZA. The car is a numbers matching 1976 trans am 400 with automatic and the 6S heads. I dont know if this helps anyone with recommendations. Also, I should have stated this upfront. I am just looking to keep the T/A fairly stock with the exception of the motor and I would like to have around 400 horses at the crank and Im not sure just what I will need to do to accomplish that. I just want to run pimp gas and just want her to run good!! JB  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 466 | Joined: 11/13
Posted: 06/12/14
09:15 PM

hi

here's one option

76 cc heads

frankspontiacprts.com might have some

port the bejesus out of them but it still might not be enough

arp screw in studs

flat top forged 2 valve relief pistons

lunati voodoo 60204 cam.

arp rod bolts.

roller timing chain

eddy rpm intake

750 cfm annular booster carb either vacuum or mechanical secondary. a 4500 holley is nice but has no choke.

scorpion roller rockerst

msd 6al-2 box

stock hei ignition with timing curved

balance eng

ati damper or cheap pioneer/powerbond damper

melling hp oil pump


this set up will give you around:

10.0 static compression

8.0 dynamic compression

160.0 cylinder cranking pressure.

This is easily low enough to use 91 thru 93 octane with the proper timing.

You also loose around 5 psi in cylinder cranking pressure for every 1000 ft increase in elevation so if you sre at 4000 ft you need eveb more than 10.0 static compression.






look at this

http://forums.highperformancepontiac.com/70/8747136/the-general-discussion/dawnas-406-433-build-a-tribute-heaven-can-wait/page9.html


look sat ronspontiacpage.com for 67 and newer head specs  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 466 | Joined: 11/13
Posted: 06/12/14
09:15 PM

hi

here's one option

76 cc heads

frankspontiacprts.com might have some

port the bejesus out of them but it still might not be enough

arp screw in studs

flat top forged 2 valve relief pistons

lunati voodoo 60204 cam.

arp rod bolts.

roller timing chain

eddy rpm intake

750 cfm annular booster carb either vacuum or mechanical secondary. a 4500 holley is nice but has no choke.

scorpion roller rockerst

msd 6al-2 box

stock hei ignition with timing curved

balance eng

ati damper or cheap pioneer/powerbond damper

melling hp oil pump


look at this

http://forums.highperformancepontiac.com/70/8747136/the-general-discussion/dawnas-406-433-build-a-tribute-heaven-can-wait/page9.html


look sat ronspomtiacpage.com for 67 and newer head specs  

bigD bigD
User | Posts: 134 | Joined: 05/14
Posted: 06/12/14
11:53 PM

Icon Quotejbmacneil:
Thanks to 4Zpeed, I know my engine is the 1976 ZA. The car is a numbers matching 1976 trans am 400 with automatic and the 6S heads. I dont know if this helps anyone with recommendations. Also, I should have stated this upfront. I am just looking to keep the T/A fairly stock with the exception of the motor and I would like to have around 400 horses at the crank and Im not sure just what I will need to do to accomplish that. I just want to run pimp gas and just want her to run good!! JB

Well, if you don't have to keep the motor numbers matching, that changes everything. But you can get real close to your goal and still use 6x heads. They just need to be milled down to produce about 9.25 CR. When this is done, the intake side of the heads also need to be milled the exact same amount as the chamber side, so that the intake manifold bolt holes will still line up. You don't want to cut the intake manifold itself, because then it won't fit other motors and if you decide to change to a different manifold, it will have to be cut to fit. I'd hate to have to cut a brand new $250 intake manifold.  Frown

Another way to help get the CR up to 9.25 is to cut the block deck down some. Many suggest "zero deck", but I would leave at least .005-.010, for possible future builds which might require a clean-up cut on the deck. The amount to cut will depend on the length of the rods you use and the comp distance or pin height of your pistons. Many stock Pontiac engines came with the top of the pistons at least .020 or more down in the hole. And if you use resized cast rods, they will be slightly shorter than before resizing. Since the Chinese forged rods are less than $300, most choose those over the cast rods.

The only way to know for sure, exactly how much can safely be cut off the deck is to measure everything. Then if you cut more than .010 off the deck, you also need to add that amount to how much you cut off the intake side of your heads. Any amount cut off the deck, will lower the intake bolt holes of the head, in exactly the same way as removing material from the chamber side of the head.

Another way to increase CR is to use a thinner Cometic head gasket or at least one with a smaller bore size. I think the popular Fel-Pro gaskets have a bore size of about 4.30 inches. If you have a .030 over 400, the bore is about 4.150. That's .150 difference.  4.30 - 4.150 = .150. Cometic makes several bore sizes which will increase CR. They show a 4.160 and also a 4.20, in case you bore .060 over. They also come with allowances for the the cylinder chamfers if you have 'em, or without, if you don't. Of course, if you don't, the round bore gaskets will provide slightly more CR.

http://www.spottsperformance.com/cometic%20head%20gaskets

http://www.jegs.com/i/Cometic-Gaskets/245/C5711-027/10002/-1?parentProductId=1288713

http://www.jegs.com/i/Cometic-Gaskets/245/C5711-036/10002/-1?parentProductId=1288713

http://www.jegs.com/i/Cometic-Gaskets/245/C5769-027/10002/-1?parentProductId=1288713

http://www.jegs.com/i/Cometic-Gaskets/245/C5769-030/10002/-1?parentProductId=1288713

http://www.jegs.com/p/Cometic-Gaskets/Cometic-Pontiac-Cylinder-Head-Gaskets/1288713/10002/-1

Just to prove that what I'm saying is possible, here's a 385hp 9.25 CR pump gas 400 crate motor with 6x heads. This one has resized rods. But for about $4000 I'm sure they would sub some Chinese forged rods.

http://lenwilliamsautomachine.com/400_Long_Block.html

Of course, the exact final HP of your motor will depend on, cam, intake, carb, ignition & timing, and exhaust system.  Smile  

1 |  2 |  Next   | Last