Heads for GTX
#2541779
08/26/18 11:09 PM
08/26/18 11:09 PM
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Joined: Feb 2015
Posts: 265 Philadelphia, PA
GTXKARL
OP
enthusiast
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OP
enthusiast
Joined: Feb 2015
Posts: 265
Philadelphia, PA
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Hi. I have a set of heads. They came with my 1970 Plymouth GTX. I want to put them on the current engine that is in the car because I want to take the numbers matching heads and eventually attach them back to the original engine that is sitting in my garage. The person who gave me the heads told me they were milled, and they were milled too much for the engine in the car currently. Is there a way I can find out how much they were milled? Also, can I use thicker head gaskets to make up the difference? Hope, this does not sound like a dumb question.
“Working on cars teaches you patience... and every curse word imaginable.”
1970 Plymouth GTX -- A true gentleman's coupe, but a serious muscle machine.
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Re: Heads for GTX
[Re: Cab_Burge]
#2541856
08/27/18 02:28 AM
08/27/18 02:28 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Karl there are no dumb questions & that for sure sounds like something that I would want to know if I was in the same situation. iirc the outer boss where the short head bolts is 1" thick on an unmilled head but others will clarify. As said do some measureing/cc ing & holler back with what you find out.
live every 24 hour block of time like it's your last day on earth
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Re: Heads for GTX
[Re: GTXKARL]
#2541950
08/27/18 11:41 AM
08/27/18 11:41 AM
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Joined: Jan 2003
Posts: 14,496 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,496
So. Burlington, Vt.
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The outer row of head bolt bosses are nominally 1.00” thick.
Using a caliper or a mic, measure several and average the results.
How much smaller that dimension is than 1.00” will get you really close to knowing how much has been milled off.
However, having them cc’d will be a more accurate way of determining if they’ve actually been milled “too much” for you to use.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Heads for GTX
[Re: GTXKARL]
#2541957
08/27/18 11:51 AM
08/27/18 11:51 AM
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Joined: Jan 2003
Posts: 1,908 Nebraska
4406bbl
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,908
Nebraska
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Here you go
915 closed chamber, .710-.730 to flat target area next to sparkplug. Lower row of headbolt bosses.955-1.010, this is average of 6 pair of 915 big and small valve heads.
906 open chamber, .729-.735 to flat target next to sparkplug, lower headbolt boss all were 1.00, with my chinese calipers only 4 heads with 1970ish date codes.
Now the real important measurement
Valve tip to outer unmachined valve spring seat area, 2.095-2.135. Stock low mile untouched heads measure 2.110 pretty co sistant. If you want your rocker arm geometry correct, with stock parts this is critical. Measurements are taken from a miller c3648 go no go tool that is mentioned in the service manual.
I have learned after 40 years if I walk in a machine shop to pick up my heads and they say, hey are you going to be running adjustable rocker arms on these? My heads are done wrong, may be ruined but will for sure need more work and $$$$ to fix. Give them a valve stem height that you need as they are not smart enough to measure it before they start.
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Re: Heads for GTX
[Re: GTXKARL]
#2541986
08/27/18 12:51 PM
08/27/18 12:51 PM
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Joined: Feb 2015
Posts: 265 Philadelphia, PA
GTXKARL
OP
enthusiast
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OP
enthusiast
Joined: Feb 2015
Posts: 265
Philadelphia, PA
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Good morning! I pulled the 906 heads off the shelf that I had in the garage. These are the numbers I found stamped on: 28161 and 21412. These were both stamped on the heads by the machine shop supposedly. Does anyone have any idea what these #'s mean? And I have no way to measure the thickness of the heads.
Last edited by GTXKARL; 08/27/18 12:51 PM.
“Working on cars teaches you patience... and every curse word imaginable.”
1970 Plymouth GTX -- A true gentleman's coupe, but a serious muscle machine.
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Re: Heads for GTX
[Re: GTXKARL]
#2542023
08/27/18 02:46 PM
08/27/18 02:46 PM
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Joined: Mar 2003
Posts: 4,848 Memphis
HemiRick
master
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master
Joined: Mar 2003
Posts: 4,848
Memphis
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Those are not the numbers we're looking for on top of the heads between the rocker shaft pedestals is a number cast into the head....
Take care, Rick 68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: Heads for GTX
[Re: RapidRobert]
#2542261
08/28/18 12:18 AM
08/28/18 12:18 AM
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Joined: Feb 2005
Posts: 4,313 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,313
Prospect, PA
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Karl there are no dumb questions.... Yes there are. No dumb questions is a little like everyone gets a trophy. That said, the OP's questions are not dumb.
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Re: Heads for GTX
[Re: BSB67]
#2543097
08/29/18 04:25 PM
08/29/18 04:25 PM
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Joined: Jan 2003
Posts: 75,005 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
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Karl there are no dumb questions.... Yes there are. No dumb questions is a little like everyone gets a trophy. That said, the OP's questions are not dumb. what he said ...
running up my post count some more .
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