Timing gears and chain

T

thomas g. warner

New member
Mar 24, 1998
1,863
0
0
Jim since you mentioned timing chain I have a question about it. I am going
to change my timing chain and gears in the next month or so to a cloyes set.
Is it possible to do it without removing the transmission and final drive?

>Hey Man,
>I've always been here but I've been so burried with new work and the
>hundreds of direct Emails that I have had a hard time staying awake enough
>to get into any of the net threads. Sorry bout that chief!
>
>Does the pump fit, does it line up, gasket surfaces mate, offset of the
>shaft measure right and heater hose complement correct? Well the "Bookem
>Danno".
>
>One bobo I ran into on the last job was the gasket did not follow the mate
>surface at the to and left a gap, yes it did leak and yes we did have to go
>back in and change the gasket, bummer. The time chain set had several
>water pump gaskets to choose from so we had the prob. solved OK, but really
>check that out.
>
>Hope this helps,
>
>Jim bounds
>--------------------------
>

>>Jim
>>
>>Nice to see you back. Glad you care about us-----nobody else seems
>>to. The other day I found a water pump in my motorhome. It does not have
>>the right casting #s on the housing but it does have a 4 1/4 inch
>>cast impeller. Do I keep it or throw it away?
>>
>>Take Care
>>Arch
>>
>>>
>>> Mark,
>>> I just completed a job which included a new water pump. I ordered a new
>>> one through GM and recieved a steel impeller that was 3 1/2". I then
>>> ordered a rebuild and told my supplier to open the boxes and tell me the
>>> size of the impeller. He came back and said he had ones on the shelf with
>>> the same number with cast & stamped impellers, how about that! The OEM
>>> impeller on the water pump I pulled out was a 4" cast one.
>>>
>>
>>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
Tom,

Yes, you can change the timing chain without removing the trans and final
drive. We changed the timing chain at the same time we changed the intake
and cam when we first got our GMC. We didn't take out the trans or final
drive, but I remember we had to remove the radiator to install/remove the
cam. I don't think that would be necessary for just the timing chain. It
would be a very good time to change the cam though :).

Zak

>Jim since you mentioned timing chain I have a question about it. I am going
>to change my timing chain and gears in the next month or so to a cloyes set.
>Is it possible to do it without removing the transmission and final drive?
 
Zach:

What prompted you to change the cam? What brand and type of cam did you
install?

You say "...intake ... I assume as in "manifold"???? What brand intake did
you install?? What did that require in the way of a carburetor????

Lastly, what did all of the above do for performance and what do you notice
different now?

Paul Bartz

From: Zachary Zehnacker [mailto:zakz]
Sent: Friday, December 11, 1998 11:36 AM
Subject: Re: GMC: Timing gears and chain

Tom,

Yes, you can change the timing chain without removing the trans and final
drive. We changed the timing chain at the same time we changed the intake
and cam when we first got our GMC. We didn't take out the trans or final
drive, but I remember we had to remove the radiator to install/remove the
cam. I don't think that would be necessary for just the timing chain. It
would be a very good time to change the cam though :).

Jim since you mentioned timing chain I have a question about it. I am going
to change my timing chain and gears in the next month or so to a cloyes set.

Is it possible to do it without removing the transmission and final drive?
 
Paul,

>What prompted you to change the cam? What brand and type of cam did you
>install?

3.5 MPG towing from NJ to Florida with original cam/intake/carb prompted
the quick change. It did get about 12 MPG not towing though which was
pretty good. We went with the Edelbrock Performer cam as we had good
luck using them on past tow and other vehicles.

>You say "...intake ... I assume as in "manifold"???? What brand intake did
>you install?? What did that require in the way of a carburetor????

Edelbrock Performer intake. That first Edelbrock one cracked after
several years and many miles of use. It could have been from being too hot
from the cross-over, or from the burned valves we had. Apparently,
Edelbrock discovered it to be a fairly common problem, as they now include
cast iron block-offs in the intake kit which fit in the heads and block the
cross-over. They strongly recommend using them on race engines and
hardworking engines (they actually mention motorhomes). We only have
14,000 miles on it so far with the new intake and block-offs (our engine
guy drilled 1/4" holes through them as Edelbrock recommends) so I don't
know if it will last longer or not. I believe that the first one
cracked due to the burned valves (probably caused by trying to adjust
Holley Pro-Jection) anyway since it didn't happen for the first few years,
so I don't think that the problem will happen again.

IIRC, the new intake requires a Holley pattern carb. You might be able
to get an adapter for the Quadrajet, but we never liked the Quadrajet
anyway. The primaries on the Quadrajet are too small for a hard working
engine. This leads to the huge secondaries being open a lot of the time
which leads to poor gas mileage (at least in our experiences).

We switched over to a Holley 4-barrel carb. The Holley carb has
acceptably sized primaries, so the secondaries are not really needed. We
actually pinned shut the secondaries (did the same thing to van and class C
motorhome tow vehicles as well when we used them). This seems to pick
up the gas mileage and keeps the motor from lugging/droning/sucking gas as
it would with the secondaries open. I assume that a Holley 2-barrel might
offer similar results, but we always had the 4-barrels "in-stock" in our
race car parts bin, so we used them. With this combo installed, the
towing gas mileage went from the 3.5 mentioned above to about 7 when towing
the same one-car trailer.

We had switched over to the 2-barrel Analog Holley Pro-Jection with
Oxygen Sensor kit. While the unit picked up the MPG (up to about 8.5 with
one-car trailer, 6 with two car trailer), it was hard to keep tuned
correctly, and did not seem to be as reliable as we would have liked.
This probably led to the burned valves.

After our motor rebuild last winter, we switched to the Accel TBI fuel
injection which has much better control capabilities. It also has an
Idle Air Controller which improves convenience A LOT. Now we just turn
the key to start in any weather conditions (no stepping on gas pedal).
The idle is rock solid and we can program it for any RPM. The idle
gradually decreases to normal after startup instead of a drastic kick-down
that a carb or analog Pro-Jection uses. It can idle at low RPM both in and
out of drive rather than having to have a high "Park" idle to compensate for
a lower "Drive" idle. This unit also controls the timing with a knock
sensor, which eliminated our manual MSD adjustment. This system has made
our GMC much more like a modern vehicle. Just turn the key and drive.

>Lastly, what did all of the above do for performance and what do you notice
>different now?

The cam/intake/carb combo REALLY increased the performance and towing MPG.
I don't think that most would see the need for higher ratio final drives if
they installed these items. We were actually considering putting in the
2.73 final drive when we were only towing the one-car trailer. The
non-towing mileage didn't improve much, but we were getting a lot more
power for the same gas mileage. I can't say for sure which of the
cam/intake/carb had the most benefit since we did them all at the same
time, but it was probably a combination affect anyway. The original stock
cam was a quick fix for the smog laws. The original stock intake was
designed to keep the hood low on the Toronado and the engine cover flat on
the GMC but was not designed for performance. The new intake will require
a raised section in the engine cover for the air cleaner. Ours is about
2-3" high. You should give yourself some room for growth, since we had to
make ours a tiny bit taller when we put the Pro-Jection in. The Accel TBI
also needed the extra height we created for the Pro-Jection.

Other performance related improvements we have made.

Ragusa intake air scoop :

Recommended - lowers intake air temp by about 40 degrees on normal days.

MSD ignition and coil and timing control:

Not installed anymore.
Worked ok : Manual timing control a pain. Took out whole MSD system and
used Accel HEI parts instead with the new fuel injection. This allows
troubleshooting to much easier and allows stock GM HEI parts to be used
easily in a pinch.

Water injection :

Not installed anymore.
Worked ok : Pain to fill up the water tank at every gas stop, but did
allow us to use quite a bit more timing advance which increased the gas
mileage.

Spearco system we used was not well designed and had poor reliability. We
wanted to try the Edelbrock system, but they had already stopped making
them. Would like to try a better system, but probably never will get
around to it.

Headers and 3" exhaust :

Work good for towing. Louder than stock. Probably hurt the non-towing
gas mileage a little. May be a little easier to keep from leaking than
exhaust manifolds. Not recommended for non-towing or quiet applications.
Would do again. Edelbrock mufflers have made it quieter, but still not as
quiet as original. Will go with stainless steel exhaust system next time
since this one is getting pretty thin due to rusting.

3.42 Final Drive:

No real improvement noticed by us. Motor is at higher RPM/louder when
highway driving. MPG a little worse. Makes about as much difference as
changing tire size would. Maybe our other engine improvements make higher
ratio unnecessary? Now have peace of mind that we have a freshly built
final drive that was assembled correctly and should last a long time.
Probably would not do again due to high cost.

Heads:

On the engine rebuild, we went with Mondello E heads. They don't seem to
make a lot of difference on the low end, but the high end >3000 RPM does
seem to be better. Hard to give accurate comparison since done on total
engine rebuild. Only have 14,000 miles on these.

Overall, the cam/intake/carb was probably one of the best upgrades we have
made to our GMC. It doesn't cost much if you can do it yourself, and
really woke up the 455. We were really worried about our GMC decision
after getting 3.5 MPG all the way to Florida. These improvements quickly
removed those worries. The engine cover is really the only downside to
this upgrade.

The new fuel injection has added convenience and MPG, but is expensive for
those that only use their GMC every once in a while. Since we put about
14,000 miles a year on ours, we felt it was worth it. We will recoup
some(not all) of the expense in gas mileage, but the improved driveability
was worth every penny anyway.

Just some of our experiences YMMV,

Zak
 
Zak thanks for the information. Still not sure how to do it! The
maintenance manual, page 6A-50 says that the oil pan has to be removed to
take off the front cover. You also need to remove the bolts from the front
motor mount to the engine.

How did you remove the front cover without removing the oil pan ? I really
don't want to remove the tranny and final drive unless I have to.

Help.

>Tom,
>
> Yes, you can change the timing chain without removing the trans and final
>drive. We changed the timing chain at the same time we changed the intake
>and cam when we first got our GMC. We didn't take out the trans or final
>drive, but I remember we had to remove the radiator to install/remove the
>cam. I don't think that would be necessary for just the timing chain. It
>would be a very good time to change the cam though :).
>
> Zak
>
>

>>Jim since you mentioned timing chain I have a question about it. I am going
>>to change my timing chain and gears in the next month or so to a cloyes set.
>>Is it possible to do it without removing the transmission and final drive?
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
Tom,

Service manuals have a tendency to overdo things. They have to write them
so anyone could follow the instructions and get good results. They may
also be made to scare owners into taking their car/motorhome to the dealer
for service. If something like "remove trans and final drive" is the first
item on the list, not too many people are going to attempt it themselves
:). There are many things that can be done faster, more easily, or without
special tools with a little thought.

It was a long time ago (>6 years), so I don't really remember the details.
I know we didn't remove the trans or final drive. I'm almost positive we
didn't drop the oil pan. I tried looking through our frame off pictures,
but there weren't any shots good enough to see the details of the timing
cover. I should be able to find out more details this weekend. I'll write
back if/when I do.

Zak

>Zak thanks for the information. Still not sure how to do it! The
>maintenance manual, page 6A-50 says that the oil pan has to be removed to
>take off the front cover. You also need to remove the bolts from the front
>motor mount to the engine.
>
>How did you remove the front cover without removing the oil pan ? I really
>don't want to remove the tranny and final drive unless I have to.
 
Thanks

>Tom,
>
>Service manuals have a tendency to overdo things. They have to write them
>so anyone could follow the instructions and get good results. They may
>also be made to scare owners into taking their car/motorhome to the dealer
>for service. If something like "remove trans and final drive" is the first
>item on the list, not too many people are going to attempt it themselves
>:). There are many things that can be done faster, more easily, or without
>special tools with a little thought.
>
>It was a long time ago (>6 years), so I don't really remember the details.
>I know we didn't remove the trans or final drive. I'm almost positive we
>didn't drop the oil pan. I tried looking through our frame off pictures,
>but there weren't any shots good enough to see the details of the timing
>cover. I should be able to find out more details this weekend. I'll write
>back if/when I do.
>
>Zak
>
>

>>Zak thanks for the information. Still not sure how to do it! The
>>maintenance manual, page 6A-50 says that the oil pan has to be removed to
>>take off the front cover. You also need to remove the bolts from the front
>>motor mount to the engine.
>>
>>How did you remove the front cover without removing the oil pan ? I really
>>don't want to remove the tranny and final drive unless I have to.
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
Love to drive it. Does my Professional Driving course partially qualify me.
Driving those big red fire trucks all the time has to count for something. I
promise, no scotch till after the race. Darren

> ZAK
>
> You cant do this to me! I thought I was the only one who could not
> remember details of days gone by. Are you sure you can drive our
> 1000 HP GMC? Damn we just get it and you flake out! Dont
> know how old you are but I can promise you one thing IT ONLY
> GETS WORSE! Thats what I cant think.
>
> Take Care
> Arch 76 GB IL
>
> >
> > It was a long time ago (>6 years), so I don't really remember the details.
> > I know we didn't remove the trans or final drive. I'm almost positive we
> > didn't drop the oil pan. I tried looking through our frame off pictures,
> > but there weren't any shots good enough to see the details of the timing
> > cover. I should be able to find out more details this weekend. I'll write
> > back if/when I do.
> >
> > Zak
 
>Love to drive it. Does my Professional Driving course partially qualify me.
>Driving those big red fire trucks
Me Too, But ours are Lime-green.


John
Louisville Ky
73 GMC
 
The front oil pan seal is a #%&* getting in but with a little persuasion
and red Permatex she sealed up fine. I did loosen the first 2 bolts on the
pan but I really don't think it made the job any easier.

Jim Bounds
- -------------------

>Jim since you mentioned timing chain I have a question about it. I am going
>to change my timing chain and gears in the next month or so to a cloyes set.
>Is it possible to do it without removing the transmission and final drive?
>
>
>

>>Hey Man,
>>I've always been here but I've been so burried with new work and the
>>hundreds of direct Emails that I have had a hard time staying awake enough
>>to get into any of the net threads. Sorry bout that chief!
>>
>>Does the pump fit, does it line up, gasket surfaces mate, offset of the
>>shaft measure right and heater hose complement correct? Well the "Bookem
>>Danno".
>>
>>One bobo I ran into on the last job was the gasket did not follow the mate
>>surface at the to and left a gap, yes it did leak and yes we did have to go
>>back in and change the gasket, bummer. The time chain set had several
>>water pump gaskets to choose from so we had the prob. solved OK, but really
>>check that out.
>>
>>Hope this helps,
>>
>>Jim bounds
>>--------------------------
>>

>>>Jim
>>>
>>>Nice to see you back. Glad you care about us-----nobody else seems
>>>to. The other day I found a water pump in my motorhome. It does not have
>>>the right casting #s on the housing but it does have a 4 1/4 inch
>>>cast impeller. Do I keep it or throw it away?
>>>
>>>Take Care
>>>Arch
>>>
>>>>
>>>> Mark,
>>>> I just completed a job which included a new water pump. I ordered a new
>>>> one through GM and recieved a steel impeller that was 3 1/2". I then
>>>> ordered a rebuild and told my supplier to open the boxes and tell me the
>>>> size of the impeller. He came back and said he had ones on the shelf
with
>>>> the same number with cast & stamped impellers, how about that! The OEM
>>>> impeller on the water pump I pulled out was a 4" cast one.
>>>>
>>>
>>>
>>
>>
>Tom & Marg Warner
>Vernon Center NY
>1976 palmbeach
>
>
>
 
You must log in or register to reply here.
GMCMI Fall 2026 Rally
Applied GMC

Share this page

Share this page
Top Bottom
Back