Engine rebuild has begun

T

tyler

Active member
Jun 22, 2013
516
96
28
Many folks across NC, FL, and TN have listened to my now 8000 mile, PO rebuild by a non GMC shop to diagnose the knock that was mainly evident on hot
restart. With no definite answers from some of the best mechanics, it is coming out to check the innards before a catastrophic or inconvenient
failure. The warm week here has been favorable (though wet) to start. A local GMC'er that already had a trolley built is helping me, and I'm hoping to
have the last few accessories off today to swing the 455 through the kitchen and cherry pick it out the door. I'm taking video and pics and will
probably do some across Youtube, Facebook and the GMC photo site.

The first problem that I have found is a significant crack on the passenger side stock exhaust manifold. Anyone have a spare?

Stay tuned! I'll add a more in-depth post to this thread about the "why" of this rebuild...hoping for an answer to the main concern of the knock! Care
to claim a cause this early in the process? Is it A) main bearing B) thrust bearing C) thrust plate D) broken piston sleeve E) other?

Tyler

--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
 
Thrust bearing issue can be easily checked by using a dial gage on the
crank and levering a pry bar carefully at the harmonic balancer and push
and pull.

On Thu, Jan 16, 2020 at 5:52 AM Tyler via Gmclist
wrote:

> Many folks across NC, FL, and TN have listened to my now 8000 mile, PO
> rebuild by a non GMC shop to diagnose the knock that was mainly evident on
> hot
> restart. With no definite answers from some of the best mechanics, it is
> coming out to check the innards before a catastrophic or inconvenient
> failure. The warm week here has been favorable (though wet) to start. A
> local GMC'er that already had a trolley built is helping me, and I'm hoping
> to
> have the last few accessories off today to swing the 455 through the
> kitchen and cherry pick it out the door. I'm taking video and pics and will
> probably do some across Youtube, Facebook and the GMC photo site.
>
> The first problem that I have found is a significant crack on the
> passenger side stock exhaust manifold. Anyone have a spare?
>
> Stay tuned! I'll add a more in-depth post to this thread about the "why"
> of this rebuild...hoping for an answer to the main concern of the knock!
> Care
> to claim a cause this early in the process? Is it A) main bearing B)
> thrust bearing C) thrust plate D) broken piston sleeve E) other?
>
> Tyler
>
>
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmcrvparts.com
1-800-752-7502
 
I thought mine had a knock too, until further investigation with a hose stuck in my ear pinpointed it to an exhaust leak at the choke stove cover
plate. Mine did not go away after warmup, but a cracked exhaust manifold will sound like that and then go away after it gets hot and closes the gap.
Seen it several times on small block Ford trucks, probably caused by water splash from front tires, but not on my GMC as I still have the inner
fenders installed.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
The crack in your exhaust manifold just might be the cause of your
knock. I had that exact issue on a 472 Caddy motor. How far apart do
you have it? Can you swap out the manifold and try it before going any
further?

-Dave
1978 Transmode near Pittsburgh
 
Bet you have never heard this one. I built a 455 for a customer, which he
and some non GMC helpers installed. As he was a very knowledgeable
mechanic, and I gave him explicit installation and break-in procedures,
which he followed to the letter, I had no concerns that he had dotted all
the i's and crossed all the t's.
So, it surprised me a whole lot when he claimed that my engine had a
sharp knock. I drove to his location, verified that he indeed did have a
knock. So, I had him deliver the coach to my location in order for me to
repair it. I pulled the engine, and very carefully disassembled it,
measuring everything very carefully. After completing the teardown, I
installed another different 455 into his coach, and as I was inspecting the
flex plate from his old engine that I was re-using on the new engine, I
noticed that the slotted holes to the torque converter looked very shiny
where the heads of the bolts met the flex plate.
Hmmm? So, I checked the torque converter lugs with an inspection
camera, and lo and behold discovered that the bottoms of the holes were
marked by the fasteners. Turns out, he had replaced the torque converter
fasteners with new very high quality ones, but did not match the lengths of
the OEM fasteners that he discarded. Seems the new, high zoot bolts were a
touch too long. They bottomed in the holes before they clamped the flex
plate to the torque converter, and the firing impulses of the crank caused
the bolts to move laterally, making one hell of a knock. There wasn't
anything wrong with the original engine, that's why i could not figure out
where the knock was coming from. Go figure.
Jim Hupy
Salem, Oregon

On Thu, Jan 16, 2020, 10:49 AM Dave Stragand via Gmclist <

> The crack in your exhaust manifold just might be the cause of your
> knock. I had that exact issue on a 472 Caddy motor. How far apart do
> you have it? Can you swap out the manifold and try it before going any
> further?
>
> -Dave
> 1978 Transmode near Pittsburgh
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I had a knocking sound in a '63 Avanti. Sounded just like a rod knock.
It turned out to be a cracked flex plate by the transmission.
Hopefully yours will be something simple.
 
Call cinnebar for an exhaust manifold. Brand new About $300 to your door.

Good luck. One of our local club members had a low knock on a rebuild as well. He drove it a bit trying to verify it was indeed a knock and hoping
it was something else. Eventually started on the engine build.

He had a new engine dyno'd sitting on an engine stand and on the way to the shop to get it installed it let go and busted everything including the cam
in 1/2. No core refund for him.

So I am sure you have the right people involved now. Good luck.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Turns out my bad engine knock was also a cracked left side exhaust manifold.

Jerry
--
Jerry Sitzlar..... 77 Eleganza II, Twin bed, dry bath......
Lenoir City, TN (near Knoxville)
 
And the winner is....number six rod bearing.
There was plenty of trash in this motor - one piece of a casting was as big as the end of my pinky finger. There were bits of metal scored and trapped
in some of the other bearings, but the number six had moved. Silver/nickel color surface was worn off to gouges of copper evident on number six and
one other rod bearing.

Took it to the machine shop and his first comments were that it looked like it had the wrong valve guides and springs.

Time to start ironing things out! Not all is lost...full assessment next and do what it needs for clean and to specs.

Oh, and the timing chain - with only about 8000 miles it had major slop. Did they put new gears and use original chain? Do not know the answer to that
or several other things that have led to this rebuild!

--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
 
Bob, you hit on something! You guys are awesome...

So I'm guessing that's why the bolts are two sizes, to put the one with a hole in the right place.

AND guess where a piece of debris lodged? I went out to garage and looked after I read your reply. Yep...the bolt does have a hole, but it is 100%
blocked with one of those metal spits. Don't know which came first, but a slew of not goods that shall be remedied.
Thanks
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
 
Tyler, et al,

What am I missing? Apparently I, exclusively on the mailing list, have
missed at least one posting, that from "Bob" describing some potential
engine problem which you verified. Please let me in on the "secret". And
if anyone understands how I might have failed to receive that posting,
please let me know.

Ken H

On Mon, Jan 20, 2020 at 9:25 PM Tyler via Gmclist
wrote:

> Bob, you hit on something! You guys are awesome...
>
> So I'm guessing that's why the bolts are two sizes, to put the one with a
> hole in the right place.
>
> AND guess where a piece of debris lodged? I went out to garage and looked
> after I read your reply. Yep...the bolt does have a hole, but it is 100%
> blocked with one of those metal spits. Don't know which came first, but a
> slew of not goods that shall be remedied.
> Thanks
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
I'm on email and I don't see bob's posting either
________________________________
From: Gmclist on behalf of Ken Henderson via Gmclist
Sent: Tuesday, January 21, 2020 6:54 AM
To: GMC Mail List
Cc: Ken Henderson ; Tyler
Subject: Re: [GMCnet] Engine rebuild has begun

Tyler, et al,

What am I missing? Apparently I, exclusively on the mailing list, have
missed at least one posting, that from "Bob" describing some potential
engine problem which you verified. Please let me in on the "secret". And
if anyone understands how I might have failed to receive that posting,
please let me know.

Ken H

On Mon, Jan 20, 2020 at 9:25 PM Tyler via Gmclist
wrote:

> Bob, you hit on something! You guys are awesome...
>
> So I'm guessing that's why the bolts are two sizes, to put the one with a
> hole in the right place.
>
> AND guess where a piece of debris lodged? I went out to garage and looked
> after I read your reply. Yep...the bolt does have a hole, but it is 100%
> blocked with one of those metal spits. Don't know which came first, but a
> slew of not goods that shall be remedied.
> Thanks
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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