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#1
01-10-2003, 04:58 PM
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this 71 block i have has 30over domed pistons (1/4 inch). bought block from girl and she had no clue. checked it out and it has new crank bearings pistons etc... every thing mics out ok so which heads should i use.... have a lunati cam it is th 703 ram air 5 replica and roller rockers....
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No GTO doesn't mean garbage truck option! |
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#2
01-10-2003, 04:58 PM
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this 71 block i have has 30over domed pistons (1/4 inch). bought block from girl and she had no clue. checked it out and it has new crank bearings pistons etc... every thing mics out ok so which heads should i use.... have a lunati cam it is th 703 ram air 5 replica and roller rockers....
__________________
No GTO doesn't mean garbage truck option! |
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#3
01-10-2003, 06:42 PM
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6X heads with the '4' on the machined pad that holds the A/C compressor if the head were instlled on the passenger side, and toward the back on the driver's side.
TIGER EFI - Electronic Fuel Injection for the Traditional Pontiac Engine. bill@tigerefi.com
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Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same. -RONALD REAGAN 462 cid/ 6x-4/ TH400/ 3.36:1/ 28x10.5/ 3880#/ 12.35 @ 109.36/ 1.69 60 ft/ 4 wheel disc brakes/ 15 mpg  |
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#4
01-10-2003, 07:05 PM
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Thank you.. As it turns out i have 3 sets of these (2sets ready to go) and 2 sets of the 4x heads with the gm2. what are these heads good for?
__________________
No GTO doesn't mean garbage truck option! |
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#5
01-11-2003, 07:40 AM
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6X are keepers, 4x aren't.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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#6
01-11-2003, 08:48 AM
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Skip Fix
"4x aren't" Are you including the 4x's(98cc)on the 73/74 400's also?They're just as good as 6x's when doing a 455 buildup,right? 
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#7
01-11-2003, 09:34 AM
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I meant the 118 cc 455 heads. The smaller 400 are OK. I think you'll find the equivalent 6X wil flow better with less work.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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#8
01-11-2003, 10:48 AM
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The 4X's are secondary identified just as the 6X's are. The 4X-3H and 4X-7H are 98 cc heads with 2.11/1.66" valves and should both have screw in studs. Regardless, any head after May 7, 1973 should have screw in studs.
The 4X-1H is the 114cc 455 head with 2.11/1.66" valves. The 4X-4H is the 98cc 400 2bbl heads with 1.96/1.66" valves. Both will have pressed stud until around mid-May cast date. |
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#9
01-11-2003, 10:52 AM
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I did some checking and the 4xgm2 heads that i have are the same as the 6xgm4 same big valves screw in studs etc.. except the chamber is 87cc.. wouldn't that make a higher compression ratio??? I would think that these might be even better than 6x heads on a 455 or to use with domed pistons...
__________________
No GTO doesn't mean garbage truck option! |
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#10
01-11-2003, 11:29 AM
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You're not looking in the right spot. The "GM2" and "GM4" casting numbers you found are only the foundry numbers where the heads were cast. Look at the attached picture I stole from GTO Ken and then look at the heads you have.
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#11
01-11-2003, 11:57 AM
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jeez that number is well hidden, yeah i stand corrected they are the 98 cc heads. (4-h) can they be milled down and made useful? I hate to think any heads with those great big valves are useless.
__________________
No GTO doesn't mean garbage truck option! |
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#12
01-11-2003, 12:19 PM
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These are 4X-4H or 6X-4? If they're 4X-4H, they shouldn't have big valves. You can mill them down to about 88cc by milling .060" off them but you'd still have to install the 2.11" intake valve.
What is the date code on them? Pressed stud or threaded studs? |
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#13
01-11-2003, 04:28 PM
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Actually the 4x 4h heads have screw in studs and the same valves as the 6x 4 heads. today i got 2 sets of 6x 8 heads and they have the same valves and screw in studs but one set has funky nuts with allen lockscrews in them. maybe there are endless variations... I think the set of 4x 4h heads have been worked on. the set of 6x 8 heads with the locking nuts have stainless valves and elongated pushrod holes and the rockers appear to be 1.65 instead of the stock. would these be better then the 6x 4 heads???
__________________
No GTO doesn't mean garbage truck option! |
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#14
01-11-2003, 04:50 PM
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The lock nuts you're describing are called poly-locks. They're an aftermarket item and allow infinite adjustment of valve settings unlike the stock setting where the nut bottoms out against the shoulder of the rocker stud.
Looking at the 4X-4H, I would have to agree they have had some work at some point. They should be small intake and 1.66" exhaust valve. I have factory documentation that shows the actual part number of the intake valve for this head and it's definitely a 1.96" intake valve'd head. What is the date code on the ledge parallel to the valve cover rail? Not sure what size block you're going to use these on but if you want compression, the 6X'4's would be the way to go. If the 6X-8's are in good shape, you could bolt them on and have medium compression. What you really should do is measure the combustion chamber volume so you know what kind of compression you'll be looking at and if they've ever been cut before. With all the goodies, they may be a better choice but you have to look at the whole picture. 1.65 rockers may yield too much valve lift and overtax the springs. Lots of variables. |
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#15
01-11-2003, 04:59 PM
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6Xs
 SECOND AMENDMENT: AMERICA'S ORIGINAL HOMELAND SECURITY. I Misus Rash'!
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SECOND AMENDMENT: AMERICA'S ORIGINAL HOMELAND SECURITY! |
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#16
01-11-2003, 10:35 PM
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The 4x-1H I have have screw in studs, and it definitely is factory from the sludge on the heads.They have a deeper chamber than my 6X-8s.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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