1. Before the heads are removed
a. It is a good idea to turn the engine to TDC and measure
the lifter preload for a couple of cylinders - Lifter preload is how far
the pushrod cup in the lifter is compressed below the snap ring when
valves are fully closed (like TDC ) - this distance should be about .030"
- .050" - I believe that you will find that if you back off the rocker
a couple of turns and then re-tighten till the rocker arm just makes
contact with the valve stem - it will be about 1 full turn further down
when the rocker arm is fully tight (IIRC - measure with a feeler gauge
first - then check rocker arm bolt turns) - give this info to your rebuilder
- (see section 2)
2. After the heads have been removed
A. Measure the distance between
the head bolt boss and the deck surface of the head. the average
stock measurement is 2.200" to 2.220"
B. If the heads have been - or
will be surfaced - more than .030" (.050 is about the max limit for our
heads). Than choose one of the following. remember most replacement head
gaskets are almost that
much thicker than the OEM gaskets
so you have that much built in lee-way(sp) - The OEM shim style head gasket
would crush to .017" and the standard replacement Felpro crushes to .043"
1. Mill the
surfaces of the intake manifold a total of 1.3 times what ever was cut
from the head. ex .050 milled from head would indicate that
you want 1.3 x .050" = .065" milled (decked) from the manifold
2. Call Mondello and try to find a head
gasket set that will crush to a thicker dimension to compensate for the
heads being milled greater than .030
C. Lifter preload is an absolutely important factor
- - Your rebuilder needs to understand this completely - Mandello sells
a gauge HG-455 to check this clearance (if your heads have been milled
over .030 then this must be compensated for with the Mondello gauge).
There are other way to check for this clearance - most rebuilder have a
gauge that will measure the valve installed height - and with
the information obtained in step 1 - the rebuilder can calculate what the
installed height needs to be to get the lifter preload between .30" - .050".
3. Rebuilding the heads- here's what I did
I made sure they used all
NORTH AMERICAN parts (Fed Mogal - Speed Pro - same co. -- good solid
stuff)
A. Had the heads Magnafluxed(sp) for cracks
B. Made sure the heads are not warped
C. mill only the minimum amount off the surface
of the heads to get a smooth surface
D. milled the exhaust side - minimum for flat
surface
E. Had only the INTAKE valve bosses cut to
accept positive valve seals
F. I had my heads "POCKET PORTED" - which
removes most of the imperfections in the passages and enlarges the cambers
for better flow - this is one of the few things that directly effect LOW
END torque. I believe they used a chevy "J" cutter to do most of that work.
G. Installed "thin wall Manganese/bronze liner"
valve guides
1. intake valve guide clearance
to minimum .0020" - .0025" max.
a. - Mitrol(sp) positive valve seals
2. exhaust valve guide clearance
to minimum .0025" - .0030" max
a. - OEM
umbrella valve seals (for extra lubrication)
H. Measured valve springs & replaced if
neccesary
1. check rotators and replace
keepers
I. Used the largest intake valve possible
for MY engine - if you have 455- 1.995" try to get 455 - 2.072"
your rebuilder can help you select what will work
J. Use valve seats inserts - ONLY IF ABSOLUTELY
neccesary - and if you do - make sure there OLDS seats - not chevy seats
K. 3 angle valve job
L. After you get your heads back - place a
steel ruler across the tops of the valve stems - they should all
be within a few .001"s
4. Installing heads
A. prelub the pushrods
B. check preload (shim if too much - oversized
pushrod if too little (this should not happen - if your rebuilder did it
right)
C. I used Felpro header exhaust gasket because
they had the max amount of contact area - I coated them with
"NEVER-SEIZE"(sp) so that they would be more likely to slip when the manifold
cools
down and moves - (re-tighten
2 more times - each time after the engine has been allow to cool
down over nite)
5. Installing Intake manifold
A. I used Mondello block off plates - his
kit contains 2 sets because the cross-over port came in 2 different
sizes
I do not believe anything
else is required - no furnace cement - no alloy -no metal insets
- The only thing you must do is find an electric choke
I paint my intake manifolds OLDs blue - and as long as the paint stays a nice pretty blue - I'm assured that the plates are holding - I have many thousands of miles on both engines I've blocked off with only the plates - and the intake manifold is still ----unburned
B I use the OEM valley pan and cut out
a space big enough for the Mondello Block Off Plates to fit. This
prevents any doubling of gaskets
C I use Blue RTV (sensor safe - in case
you have O2 sensors) and apply a bead around every intake port and
water jacket hole. (Zeb Fredy has used this trick to correct many newly
rebuilt engines that were using excessive amounts of oil. Oil that
was being sucked up thru the valley into the intake ports.
(thrust me it works great)
D I do not use the supplied valley end
gasket (rubber or felt) because they can hold the intake manifold
from seating properly I used a heavy bead of blue RTV and let
it skin over (about a half hour) - then I believe that most intake manifolds
have 1 bolt hole that is a slot - I put a long bolt in the head &
use that bolt as a guide
to lower the head down with 2 hands. this methods lets me put the intake
manifold on with a minimum of movement of all that RTV stuff.
E. after everything is tighten down -- go
inside a come back the next day -DO NOT TRY AND START THE MOTOR -
the same day - you may blow the RTV out the valley edges - wait the one
day - you will not be sorry - this gives ALL the RTV a chance to work its
wonders.
I need to give credit to
Dick Paterson
Brent Covey
Zeb Frady
Joe Mondello
GMCnet
It was the combined input from all of the above. -- Thank
You do what you want - I just know what works for me I just want
to prevent anyone else from falling down the holes I already feel thru
- isn't that the whole purpose of this group
If I've missed anything - please feel free to email your corrections
Pete - Head nut here in the asylum