TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - 1968 390/343 X heads
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

1968 390/343 X heads

 Post Reply Post Reply
Author
Message
H60 View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Aug/09/2014
Location: Wister,Ok
Status: Offline
Points: 164
Post Options Post Options   Thanks (0) Thanks(0)   Quote H60 Quote  Post ReplyReply Direct Link To This Post Topic: 1968 390/343 X heads
    Posted: Oct/25/2020 at 7:03pm
Does the X mean anything, located just forward of front or rear spark plug depending on side? My original 390 has them and a set of 69 343 has them. Just curious.  Mike
Mike 1968 Blazerblue 390,4sp AMX
Back to Top
SC397 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/30/2009
Location: Michigan
Status: Offline
Points: 5428
Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 3:40am
No.  I don't remember seeing a pair without the X.
Back to Top
PHAT69AMX View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/07/2007
Location: West Virginia
Status: Offline
Points: 5905
Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 5:09am
Think the AMC "X" Heads that might have something different have a cast-in X under the valve cover?
Don't remember for sure but did save this picture.




Edited by PHAT69AMX - Oct/26/2020 at 5:12am
Back to Top
mramc View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/12/2007
Location: United States
Status: Offline
Points: 3217
Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 3:19pm
NASCAR "X" heads , I had a set on my 390 AMX engine that got stolen. The intake and exhaust port should be 0.125 of an inch bigger then standard AMC heads. LRDaum
LRDaum
Back to Top
PROSTOCKTOM View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar

Joined: Jun/20/2010
Location: Indiana
Status: Offline
Points: 2427
Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 4:56pm
It would be my guess that the X is actually an added structural component to the casting. There is not much in the way of support since the ports are below and a thin divider between them. It may have also been added to reduce the chill in that area when the heads are poured. Since thin areas tend to coll off quicker and if they cool to fast they crack. 

Personally I think it's more of the above than anything to do with something "SPECIAL"

Tom
Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods

1969 AMC Rambler Rouge Race Car
1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project
Back to Top
Rebel Machine View Drop Down
AMC Addicted
AMC Addicted


Joined: Jul/03/2007
Location: Western Il
Status: Offline
Points: 5118
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 5:51pm
Years ago I had a '69 Javelin with a 290. It also had the 'X' cast in the heads. Doubt there's anything special about them.

-Steve-


Back to Top
H60 View Drop Down
AMC Apprentice
AMC Apprentice
Avatar

Joined: Aug/09/2014
Location: Wister,Ok
Status: Offline
Points: 164
Post Options Post Options   Thanks (0) Thanks(0)   Quote H60 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/26/2020 at 6:28pm
I knew probably not special but they went to extra effort to out them there. Just curious. Thank guys love this forum. Mike
Mike 1968 Blazerblue 390,4sp AMX
Back to Top
Hurst390 View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/20/2008
Location: secret
Status: Offline
Points: 5752
Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/27/2020 at 4:09pm
Originally posted by mramc mramc wrote:

The intake and exhaust port should be 0.125 of an inch bigger then standard AMC heads. LRDaum
On the big x head(nascar).125 bigger maybe ported but I dont believe they are cast that way. I have a set here and they can be ported a little more than an oem casting..


Edited by Hurst390 - Oct/27/2020 at 4:11pm
SC/Hurst Rambler

11.62 120

100% Street Legal
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.109 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or