: I thought the head bolts were 7/16"?

: DOH! I looked in my handy-dandy 1999 Mopar
: Performance book, again. The 1968 Torque
: Specification table calls for the 9/16-14
: bolt (page 302, PLEASE look if you have the
: book and tell me I'm not crazy). HOWEVER, a
: few pages back is the 1974 Torque
: Specification table. IT calls for a 7/16-14
: bolt.
:
: Would this make the later cylinder heads
: non-compatible w/ the older blocks? I've
: never heard of this. Maybe it's a typo in
: the 1968 table.
:
: I rechecked Doc's info on the ARP studs. All of
: that info calls for the 7/16-14 thread.
:
: Back to the original question. Can you increase
: the bolt size? I dunno. Sorry if I lead this
: thread astray.
:
: Gilly

: "has anyone ever tried increasing the head
: bolt diameters to 1/2" for increasing
: the clamping force?"
:
: The /6 has a 9/16-14 cylinder head bolt. For an
: improvement to the clamping and sealing, I'd
: suggest looking at the ARP head studs. I
: also like to take a skim cut (0.005" or
: so) just to make sure the block and head are
: true.
:
: In the Mopar performance book they caution:
: "When milling cylinder head and deck,
: don't make them too smooth or you could have
: gasket sealing problems. A typical
: production surface (100 micro-inches) should
: be your guide."
: Gilly

: I'm guessing it's a misprint. I have an '81
: head on a '68 block with 7/16" bolts.
: I've never really seen anyone have head
: gasket trouble unless they were over 13 to 1
: compression. Later! Dennis

: The "9/16" call-out is a typo, I have
: seen that mistake "carried-over"
: to a number of places.
: All the SL6 blocks are tapped 7/16 - 14 unc and
: this works well with the stock bolts up into
: the 10 to 1 compression range. You do need
: to prep your surfaces well and use a good
: quality gasket.
: I use 70 ftlbs on stock head bolts. (this spec
: is also called-out as 65 ftlbs in most
: places)
:
: The ARP head stud are the next step if your
: working with 11 to 1 ++ compression, I
: torque these to 80 ftlbs and again, surface
: prep and gasket type is key and *different*
: depending on the gasket you are using. Most
: super high cylinder pressure applications go
: to receiver grooves and copper O-rings but
: stay with the 7/16 - 14 block holes.
:
: I have done one of the 1/2 - 13 unc oversize
: "retrofits" just because I had a
: nice block with a couple of messed-up tapped
: holes. It can be done but drilling-out the
: old threads "on centerline" and
: re-tapping is a "time bandit". (do
: it on a big drill press or end mill)
: This is a "it can be done but there is no
: real need to" kind of up-grade.
: DD

:
: Hi Doug;
: I have always wondered about the same question.
: I now have over 40 runs on my new 13.5-1
: engine. My season is over and I want to tear
: this engine down to inspect it. I used 7/16
: ARP studs,copper head gasket with a
: stainless steel o-ring's in the cylinder
: block. So far I have had no problems ? ? ? I
: have a fairly big roller cam and I also want
: to inspect that. Before I tore the engine
: apart I did a cranking compression check and
: had 305 PSI on all the cylinder ! Maybe
: that's why the car ran good this year. I'll
: let you know what I found.
:
: Dave

: No kidding! I've seen it on several 'stock'
: sl/6's. Though, I couldn't tell you what may
: have brought about that event; you know,
: operator error, or poor assembly procedures,
: or what.