Home » Public Forums » GMCnet » How to change cylinder heads on a 455 engine (First Part)
| How to change cylinder heads on a 455 engine [message #90653] |
Thu, 01 July 2010 09:54  |
Michael Bozardt
Messages: 367
Registered: January 2007
Location: College Station, Texas
Karma: 1
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Senior Member |
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Having three "bad" valves, I have decided to change cylinder heads. One shop wanted $2000 to do it-if you can believe that.
Needing knee replacement surgery and battling the heat/humidity of Houston, I decided to have a go at it anyway. I was fortunate to move things around to get the GMC inside my shop out of the sun and it is so much better inside.
First, I got the engine up to top dead center(TDC). Then, I drained the radiator and oil.
So far I have unbolted the air conditioning compressor and laid it aside without disconnecting the freon lines. I also removed the upper A/C bracket that attaches to the intake manifold and the right cylinder head. I removed the alternator and alternator brackets. One bolt of the alt. front bracket is behind the power steering unit. To get the front bracket off, I removed a few nuts from the power steering fluid container. Then I was able to move it forward toward the front of the coach without removing it or disconnecting the fluid lines.
I have removed the L and R upper shroud brackets which are bolted to the fan shroud, intake manifold and the front of the cylinder heads.
I disconnected the upper radiator hose from the thermostat housing. I also removed the vacuum line to the distributor and disconnected the wire from the dist. to the coil. After checking that the rotor is pointed correctly, to the number 1 spark plug wire, I removed the distributor.
There is one more A/C bracket to be removed before I can remove the intake manifold with the carburetor. Earlier this year, I changed the carb and added an aluminum intake manifold so I have been there and done that.
Remaining to be done:
remove the valve covers
remove the rocker arms-keeping them in order to replace them where they originlly are.
remove the push rods, again, keeping them in order.
remove the cylinder head bolts and remove the heads.
I will replace these heads with two "J" heads that I sold to a "customer" in California. He returned them saying his machinist told him they were no good. As they had obviously been rebuilt before I acquired them, I figured he was, as a minimum, mistaken. So I kept the heads and now, in my time of need, I had them checked by a machine shop that builds race engines. You guessed it, the heads are good. Explanation! He found some cheaper heads elsewhere. But, as usual, God knew I would need these heads, so he had them returned to me. You know, if we look, we will see these minor miracles happening all the time.
I also will replace the plug wires and dist. cap with some Springfield Ignition stuff from Dick Paterson; also, the intake manifold gaskets, cylinder head gaskets and valve cover gaskets.
Will post later as the experience goes.....Michael at GEMRECS
There are three GMC parts coaches available at $500 each.
They have a number of usable parts like engine, trans, final drive, drive axles, CV joints, front and rear hubs, front knuckles, 1 dash, steering columns, some windows, 1 entry door, bunk/sofas, 1 late style driver's seat. Also good for body parts.
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| Re: [GMCnet] How to change cylinder heads on a 455 engine [message #90656 is a reply to message #90653] |
Thu, 01 July 2010 10:02  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Michael,
Did you drain the block of coolant using the plug on the passenger side -- even if you drain the radiator enough coolant stays in the heads to leak into the cylinders as you remove them.
Dennis Sexton
73 GMC
Germantown, TN
USA
-----Original Message-----
From: Michael Bozardt <ilse@earth-comm.com>
To: gmclist@temp.gmcnet.org
Sent: Thu, Jul 1, 2010 9:54 am
Subject: [GMCnet] How to change cylinder heads on a 455 engine
Having three "bad" valves, I have decided to change cylinder heads. One shop
anted $2000 to do it-if you can believe that.
eeding knee replacement surgery and battling the heat/humidity of Houston, I
ecided to have a go at it anyway. I was fortunate to move things around to get
he GMC inside my shop out of the sun and it is so much better inside.
First, I got the engine up to top dead center(TDC). Then, I drained the radiator
nd oil.
So far I have unbolted the air conditioning compressor and laid it aside without
isconnecting the freon lines. I also removed the upper A/C bracket that
ttaches to the intake manifold and the right cylinder head. I removed the
lternator and alternator brackets. One bolt of the alt. front bracket is
ehind the power steering unit. To get the front bracket off, I removed a few
uts from the power steering fluid container. Then I was able to move it forward
oward the front of the coach without removing it or disconnecting the fluid
ines.
I have removed the L and R upper shroud brackets which are bolted to the fan
hroud, intake manifold and the front of the cylinder heads.
I disconnected the upper radiator hose from the thermostat housing. I also
emoved the vacuum line to the distributor and disconnected the wire from the
ist. to the coil. After checking that the rotor is pointed correctly, to the
umber 1 spark plug wire, I removed the distributor.
There is one more A/C bracket to be removed before I can remove the intake
anifold with the carburetor. Earlier this year, I changed the carb and added an
luminum intake manifold so I have been there and done that.
Remaining to be done:
emove the valve covers
emove the rocker arms-keeping them in order to replace them where they
riginlly are.
emove the push rods, again, keeping them in order.
emove the cylinder head bolts and remove the heads.
I will replace these heads with two "J" heads that I sold to a "customer" in
alifornia. He returned them saying his machinist told him they were no good.
s they had obviously been rebuilt before I acquired them, I figured he was, as
minimum, mistaken. So I kept the heads and now, in my time of need, I had
hem checked by a machine shop that builds race engines. You guessed it, the
eads are good. Explanation! He found some cheaper heads elsewhere. But, as
sual, God knew I would need these heads, so he had them returned to me. You
now, if we look, we will see these minor miracles happening all the time.
I also will replace the plug wires and dist. cap with some Springfield Ignition
tuff from Dick Paterson; also, the intake manifold gaskets, cylinder head
askets and valve cover gaskets.
Will post later as the experience goes.....Michael at GEMRECS
There are three GMC parts coaches available at $500 each.
hey have a number of usable parts like engine, trans, final drive, drive axles,
V joints, front and rear hubs, front knuckles, 1 dash, steering columns, some
indows, 1 entry door, bunk/sofas, 1 late style driver's seat. Also good for
ody parts.
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MCnet mailing list
ist Information and Subscription Options:
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] How to change cylinder heads on a 455 engine [message #90659 is a reply to message #90653] |
Thu, 01 July 2010 10:16 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Jul 1, 2010, at 8:54 AM, Michael Bozardt wrote:
>
> I will replace these heads with two "J" heads that I sold to a "customer" in California. He returned them saying his machinist told him they were no good. As they had obviously been rebuilt before I acquired them, I figured he was, as a minimum, mistaken. So I kept the heads and now, in my time of need, I had them checked by a machine shop that builds race engines. You guessed it, the heads are good. Explanation! He found some cheaper heads elsewhere. But, as usual, God knew I would need these heads, so he had them returned to me. You know, if we look, we will see these minor miracles happening all the time.
>
Michael
When I had my engine rebuilt while returning from the Goshen rally in October 2004 the rebuilder was able to find a brand new set of J heads. I had them pocket port them as recommended by Dick Paterson in his tech session at Goshen. This is where they use a piloted J cutter to just smooth out the casting in the area in the heads just behind the head of the intake valve (the "pocket"). Dick feels that this results is a good performance increase by letting the engine breath better without the necessity of doing any other work on the heads or any additional porting.
He did not feel that one should do any additional porting as the turbulence caused by the rest of the head air channels was desirable to mix the air and gas and, at the RPM of our engines, any more porting would really not give any noticeable results. Dick also said the exhaust passages were fine in an unported casting, again referring to the low RPM of our engines. If we were running 4 or 5000 rpm then full porting would give an advantage.
At the time, someone on the GMCnet had stated that the J heads were the worst heads to put on the 455 so I contacted Dick Paterson. He is what he said to me:
Emery the J heads are perfectly OK for our use---I have used them for 99%
of my motors---racers called them "smoggers " because of their era--and the
small a.i.r. bumps in the exh port.. (even grinding out these bumps is a
waste of time for a GMC application.---- the 2.00 inch intake is common to
most olds big block heads---some aftermarket perf valves are 2.07 the
common exh are 1.62 and the racer guys can get 1.71 ---in my opinion --
there are several parameters that balance the adequacy of the stock valve
sizes (int2.00---exh 1.62) -------- 1. the need for low rpm -max torque
(int and exh tract "flow "___velocity__) 2. the int and exh port size and
capacity in cc 's or cubic inches---the restrictions here result in the
flow being maxed out or "stalled " at around .430 valve lift--so no matter
how big a valve you put in you cannot overcome these restrictions.---- 3.
the poor design of our depressed intake mfld (relys on high velocity to
offset its poor design.)-- a larger valve will slow low rpm
velocity --the same as a thorough porting job will.-----4. the cfm demand
of our motor operating in its cruise rpm band (1500 -3500 rpm) cfm
requirements for a 455 motor at 1500 rpm is 195 cfm---at 3500rpm the
requirement is 456cfm ---a larger valve will not have any effect on that
demand- now remember my comments on this subject
are directed at our gmc application only--- --not to the theory of bigger
valves for making more power------ if I were building a 455 for competition
in a light vehicle or boat and wanted to run around 5500 rpm --then I would
definetly go to larger valves (maybe even in a set of ported J heads) to
take advantage of the other requirements -or changes made to up the rpm.
.Put in a wild-ass cam --- throw away the intake mfld and put on an open
plenum high rise .----get a good set of of headers (not the tri Y
esign ---and let the motor breathe up high in the power
band---mean-while --I,ll just make my 495-500 lbs. ft of torque in the rpm I
use with my pocket ported --stock valve sized "J" heads ------- just my
humble opinion ---- Regards Dick---
Emery Stora
77 Kingsley
Santa Fe, NM
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