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[GMCnet] Comp Cam Break In [message #238653] Mon, 03 February 2014 16:26 Go to next message
USAussie is currently offline  USAussie   United States
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
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Senior Member
G'day,

I think I understand that for a flat tappet cam you should:

1) coat the cam and lifters with break in lube before you install them
2) set the engine at No. 1 TDC then insert the cam
3) time the cam before you install the lifters
4) install the distributor and set the ignition timing before you install the lifters
5) use single valve springs during the break in process
6) not turn over the engine by hand after the lifters have been installed
7) not use synthetic oil during the break in process
8) use engine break in oil (1400 ppm ZDDP) when breaking in the cam
9) run the engine at 2000 - 2500 rpm (varying the rpm's) for 20-30 minutes to break in the cam

However I never REALLY understood what the cam break in process accomplished. I called Comp Cams tech support and informed them
that I had a Caddy 500 with a Nitrided cam and asked if I needed to use the same procedure as noted above and was advised YES!

I then asked what does the break in process do to the cam and lifters. I was advised that it assures that the lifters are spinning
in their bores establishing the wear pattern on the cam lobes and lifter faces quickly which assures that the lifters will continue
spinning over the life of the engine.

I asked why do you need the 2000 - 2500 rpm; why can't a lower rpm over a longer period accomplish the same thing and was advised
that rpm range creates more force to overcome any resistance between the lifter and lifter bores to make sure the lifters are
spinning.

While poking around the Comp Cams website I stumbled on to this page; LOTS of good info here!

http://www.cpgnation.com/forum/comp-cams-product-tech.html

If I've missed anything or if you wish to comment or criticize PLEASE do so!

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426


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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Comp Cam Break In [message #238658 is a reply to message #238653] Mon, 03 February 2014 16:47 Go to previous messageGo to next message
Dennis S is currently offline  Dennis S   United States
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Registered: November 2005
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Senior Member
USAussie wrote on Mon, 03 February 2014 16:26

G'day,

I think I understand that for a flat tappet cam you should:

1) coat the cam and lifters with break in lube before you install them
2) set the engine at No. 1 TDC then insert the cam
3) time the cam before you install the lifters
4) install the distributor and set the ignition timing before you install the lifters
5) use single valve springs during the break in process
6) not turn over the engine by hand after the lifters have been installed
7) not use synthetic oil during the break in process
Cool use engine break in oil (1400 ppm ZDDP) when breaking in the cam
9) run the engine at 2000 - 2500 rpm (varying the rpm's) for 20-30 minutes to break in the cam

However I never REALLY understood what the cam break in process accomplished. I called Comp Cams tech support and informed them
that I had a Caddy 500 with a Nitrided cam and asked if I needed to use the same procedure as noted above and was advised YES!

I then asked what does the break in process do to the cam and lifters. I was advised that it assures that the lifters are spinning
in their bores establishing the wear pattern on the cam lobes and lifter faces quickly which assures that the lifters will continue
spinning over the life of the engine.

I asked why do you need the 2000 - 2500 rpm; why can't a lower rpm over a longer period accomplish the same thing and was advised
that rpm range creates more force to overcome any resistance between the lifter and lifter bores to make sure the lifters are
spinning.

While poking around the Comp Cams website I stumbled on to this page; LOTS of good info here!

http://www.cpgnation.com/forum/comp-cams-product-tech.html

If I've missed anything or if you wish to comment or criticize PLEASE do so!

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion



Rob

Comp Cams did offer a cam and lifter lube and a different lube (white paste) to be used on valve stem tips and push rod ends.

Dennis


Dennis S
73 Painted Desert 230
Memphis TN Metro
Re: [GMCnet] Comp Cam Break In [message #238659 is a reply to message #238653] Mon, 03 February 2014 16:51 Go to previous messageGo to next message
JohnL455 is currently offline  JohnL455   United States
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Location: Woodstock, IL
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All looks good to me but don't you also add the bottle of Comp Cams breakin lube they provide? That would be high on my list in addition to the assembly lube. I always thought that RPM range was for the best oil slinging without adding excessive inertial loads of going even faster while the final lifter foot and cam lobe finishing happens.

John Lebetski
Woodstock, IL
77 Eleganza II
Re: [GMCnet] Comp Cam Break In [message #238674 is a reply to message #238659] Mon, 03 February 2014 18:45 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Registered: July 2007
Location: Sydney, Australia
Karma: 6
Senior Member
John,

Good point! I will clarify what I was "saying."

I agree that the published info regarding the 2000 - 2500 rpm is to assure there is sufficient lubrication. The Comp Cam Tech Rep
added the bit about assuring that the lifter was spinning.

As I understand it there are two lubricants that should be used when installing and breaking in a cam:

1) A lube you apply to the cam and lifters during the assembly process.

2) Oil that contains a ZDDP level of 1400 ppm or an additive that brings the level of ZDDP in the oil you're using to a level of
1400 ppm.

Step 1) of the procedure noted:

1) coat the cam and lifters with break in lube before you install them

Step 8) of the procedure noted:

8) use engine break in oil (1400 ppm ZDDP) when breaking in the cam

Comp Cams sells break in oil by the quart:

http://tinyurl.com/nzzgaqt

http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=1590&Category_Code=

Comp Cams sells break in additive by the bottle:

http://tinyurl.com/l3nvjud

http://www.compperformancegroupstores.com/store/merchant.mvc?Store_Code=CC&Screen=PROD&Product_Code=159

Both of the products listed above state the following:

Due to government regulations, in recent years oil manufacturers have removed the zinc and many of the other additives from their
motor oil. However, using an "off-the-shelf" brand of oil during the critical break-in process can lead to a failure. Thus, COMP
CamsR Engine Break-In Oil Additive is designed to extend the durability of internal engine components including camshafts, valve
train components and all moving parts in your new or rebuilt engine. It does so by using a special blend of extreme pressure
additives no longer available in "off-the-shelf" motor oils. COMP CamsR Engine Break-In Oil provides added protection during the
break-in process and is compatible with any petroleum, synthetic or blended motor oil.

* Extend the durability of internal engine components including camshafts, valve train components and all moving parts
* Special blend of extreme pressure additives no longer available in off the shelf motor oils
* Provides added protection during critical engine break-in process
* Compatible with any petroleum, synthetic or blended motor oil

Conclusion: it is critical that the proper lubricants be used when assembling and building an engine and installing the cam. They
don't have to be Comp Cam products I only used them as an example because I have a Comp Cam and their products is what I'll use so
that IF I have a problem I can lay it in their lap! ;-)

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: John R. Lebetski

All looks good to me but don't you also add the bottle of Comp Cams breakin lube they provide? That would be high on my list in
addition to the assembly lube. I always thought that RPM range was for the best oil slinging without adding excessive inertial loads
of going even faster while the final lifter foot and cam lobe finishing happens.
--
John

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Comp Cam Break In [message #238725 is a reply to message #238653] Tue, 04 February 2014 08:57 Go to previous messageGo to next message
GMC_LES is currently offline  GMC_LES   United States
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Location: Montreal
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Senior Member
A bit off topic but i have always questioned the cam break-in procedure regarding the recommended 2000-2500 rpm. It is a general guide for passenger car type engines. What does one do on engines that don't rev that high such as governed industrial or agricultural engines? Many of the big diesels don't turn that fast, and there are some antique car engines that would be at their upper limits running that fast. I've never dug deep looking for an answer as i've not been in a position to need the info. Just wondering what is recommended for those engines?

Back in the early 80's, fresh out of highschool, i worked in a friend's garage where i witnessed many SBC cams get run in at 1500-1600 rpm. Those engines ran well for many years afterwards as we saw them for regular maintenance. I often questioned the practice, but always received the answer "never had a comeback doing it this way" i guess we were just lucky!

Later when i was running my own business i followed the correct procedures where ever possible, but have always questioned the recommendation.

Les Burt
Montreal
1975 Eleganza 26ft
A work in Progress


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Les Burt Montreal 1975 Eleganza 26ft A work in Progress
Re: [GMCnet] Comp Cam Break In [message #238726 is a reply to message #238653] Tue, 04 February 2014 08:58 Go to previous messageGo to next message
powwerjon is currently offline  powwerjon   United States
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When I was building motors on a regular basis in the late 60’s and most of the 70’s I used to put the lifters in can on end and cover them with the oil I was going to run for break in. I would also take a wooden dowel and push down on the lifters to get the air out. JWID

J.R. Wright
30' Buskirk Stretch
Michigan
On Location in Tucson

On Feb 3, 2014, at 3:26 PM, Robert Mueller <robmueller@iinet.net.au> wrote:

> G'day,
>
> I think I understand that for a flat tappet cam you should:
>
> 1) coat the cam and lifters with break in lube before you install them
> 2) set the engine at No. 1 TDC then insert the cam
> 3) time the cam before you install the lifters
> 4) install the distributor and set the ignition timing before you install the lifters
> 5) use single valve springs during the break in process
> 6) not turn over the engine by hand after the lifters have been installed
> 7) not use synthetic oil during the break in process
> 8) use engine break in oil (1400 ppm ZDDP) when breaking in the cam
> 9) run the engine at 2000 - 2500 rpm (varying the rpm's) for 20-30 minutes to break in the cam
>
> However I never REALLY understood what the cam break in process accomplished. I called Comp Cams tech support and informed them
> that I had a Caddy 500 with a Nitrided cam and asked if I needed to use the same procedure as noted above and was advised YES!
>
> I then asked what does the break in process do to the cam and lifters. I was advised that it assures that the lifters are spinning
> in their bores establishing the wear pattern on the cam lobes and lifter faces quickly which assures that the lifters will continue
> spinning over the life of the engine.
>
> I asked why do you need the 2000 - 2500 rpm; why can't a lower rpm over a longer period accomplish the same thing and was advised
> that rpm range creates more force to overcome any resistance between the lifter and lifter bores to make sure the lifters are
> spinning.
>
> While poking around the Comp Cams website I stumbled on to this page; LOTS of good info here!
>
> http://www.cpgnation.com/forum/comp-cams-product-tech.html
>
> If I've missed anything or if you wish to comment or criticize PLEASE do so!
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

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Re: [GMCnet] Comp Cam Break In [message #238731 is a reply to message #238725] Tue, 04 February 2014 09:14 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
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Location: Braselton ga
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Well, the industrial engines usually have positive valve rotators, so you'd figure the cam and lifters are designed with extra geometry to make them turn.  As I understand it, the idea is twofold, the main one to ensure a lifter doesn't decide not to turn and scuff the bore enough that it takes a set and doesn't want to turn.  In that direction lies early failure.  Our tower crews use winches with industrial engines... Waukesha is a common one.  They idle for six or eight hours at a stretch, and when they take load it's at6 maybe 1500 rpm max/  But, they sound liek there's enough room in the inside for a small rat to crawl through most of the passages and bearings anyway.  I suspect they hand lap the lifters at buildup.  My pipeline budydy says their big Nordberg and Gardiner-Denver pump engines run at 250 - 350 RPM anyway.  Auto engine speeds would destroy them.
 
Maybe one of the engine gurus can enlighten us... if you took a drill and oiled up the bore and then spun the lifter in the bore for a few minutes while raisng and lowering it, would ti then be less prone to problems at initial startup?
 
--johnny
 

From: Les Burt <gmc.les@gmail.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Tuesday, February 4, 2014 9:57 AM
Subject: Re: [GMCnet] Comp Cam Break In


A bit off topic but i have always questioned the cam break-in procedure regarding the recommended 2000-2500 rpm. It is a general guide for passenger car type engines. What does one do on engines that don't rev that high such as governed industrial or agricultural engines? Many of the big diesels don't turn that fast, and there are some antique car engines that would be at their upper limits running that fast.  I've never dug deep looking for an answer as i've not been in a position to need the info.  Just wondering what is recommended for those engines?

Back in the early 80's, fresh out of highschool, i worked in a friend's garage where i witnessed  many SBC cams get run in at 1500-1600 rpm. Those engines ran well for many years afterwards as we saw them for regular maintenance. I often questioned the practice, but always received the answer "never had a comeback doing it this way" i guess we were just lucky!

Later when i was running my own business i followed the correct procedures where ever possible, but have always questioned the recommendation.

Les Burt
Montreal
1975 Eleganza 26ft
A work in Progress



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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell
Re: [GMCnet] Comp Cam Break In [message #238733 is a reply to message #238653] Tue, 04 February 2014 09:18 Go to previous messageGo to next message
JohnL455 is currently offline  JohnL455   United States
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I would think that 1500- 2000 would be fine too. The higher range on a full rebuild assures that the new rings and walls are getting plenty of wash down from the crank throwing oil up there. But I'm not a rebuilder.

John Lebetski
Woodstock, IL
77 Eleganza II
Re: [GMCnet] Comp Cam Break In [message #238800 is a reply to message #238726] Tue, 04 February 2014 18:21 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Registered: July 2007
Location: Sydney, Australia
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JR,

I understand what you did and why you did it and it's a good idea.

However, part of the assembly process is to spin the oil pump until you get oil out of the top of the pushrods, oil is fed to the
pushrods through the lifters.

It seems to me that to make sure the lifters were full of oil you would not tighten the rocker arm nuts until it just came into
contact with the rocker arm. That way the piston in the lifter would be at its highest position and fill completely with oil when
you spun the oil pump.

Once you got oil out of all the pushrods you would go back and tighten the rocker arm nuts to the correct position which would
squeeze oil out of the lifter.

Comments / criticism please.

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: John Wright

When I was building motors on a regular basis in the late 60's and most of the 70's I used to put the lifters in can on end and
cover them with the oil I was going to run for break in. I would also take a wooden dowel and push down on the lifters to get the
air out. JWID

J.R.

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Comp Cam Break In [message #238820 is a reply to message #238800] Tue, 04 February 2014 22:00 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Damn!

I screwed up this email big time! It doesn't make sense! DOUH!

I'll try again below:

JR,

I understand what you did and why you did it and it's a good idea.

Part of the assembly process is to spin the oil pump until you see oil coming out of the top of the pushrods where they contact the
rocker arms.

As I understand the oil flow in an Olds 455 / 403 the oil pump feeds oil to the left and right main galleries; they feed the
lifters. Oil goes into the lifters and then heads up to the rocker arms through the pushrods. See MM X-7525 / Section 6A - ENGINE /
page 6A-2 / Figure 1 - Engine Lubrication. I have not mentioned the oil feed to the mains and rods as it is not relevant to this
discussion.

It seems to me that to make sure the lifters were full of oil you would tighten the rocker arm pivot nuts only until the rocker arm
just barely contacts the pushrod top. That would leave the piston in the lifter at the top of its bore and the chamber under it
would be fully filled with oil when you spun the oil pump.

Once you got oil out of all the pushrods you would go back and tighten the rocker arm pivot nuts to the correct position which would
squeeze oil out of the lifter.

Comments / criticism please.

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: Robert Mueller

JR,

I understand what you did and why you did it and it's a good idea.

However, part of the assembly process is to spin the oil pump until you get oil out of the top of the pushrods, oil is fed to the
pushrods through the lifters.

It seems to me that to make sure the lifters were full of oil you would not tighten the rocker arm nuts until it just came into
contact with the rocker arm. That way the piston in the lifter would be at its highest position and fill completely with oil when
you spun the oil pump.

Once you got oil out of all the pushrods you would go back and tighten the rocker arm nuts to the correct position which would
squeeze oil out of the lifter.

Comments / criticism please.

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: John Wright

When I was building motors on a regular basis in the late 60's and most of the 70's I used to put the lifters in can on end and
cover them with the oil I was going to run for break in. I would also take a wooden dowel and push down on the lifters to get the
air out. JWID

J.R.

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Comp Cam Break In [message #238821 is a reply to message #238653] Tue, 04 February 2014 22:08 Go to previous messageGo to next message
Chris Tyler is currently offline  Chris Tyler   United States
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Registered: September 2013
Location: Odessa FL
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" if you took a drill and oiled up the bore and then spun the lifter in the bore for a few minutes while raisng and lowering it, would ti then be less prone to problems at initial startup?"

No. That would only serve to wear a spot on the cam lobe. There was a discussion about this a few days ago. Neither the lobe and the lifter are actually flat, to impart the rotation that an earlier poster pointed out.


"It seems to me that to make sure the lifters were full of oil you would not tighten the rocker arm nuts until it just came into
contact with the rocker arm. That way the piston in the lifter would be at its highest position and fill completely with oil when
you spun the oil pump.Once you got oil out of all the pushrods you would go back and tighten the rocker arm nuts to the correct position which would
squeeze oil out of the lifter."

Aussie, I made the mistake of trying that on my GTO when I was a kid. It didn't work too well. My dads friend [who was my mechanical mentor], had me take the lifter apart and see how it operated so I could see how air got trapped. When you purge them in the can of oil, you can get all the air out front and avoid the engine sounding like two skeletons gettin frisky on a tin roof.


76 Glenbrook
Re: [GMCnet] Comp Cam Break In [message #238858 is a reply to message #238731] Wed, 05 February 2014 09:18 Go to previous messageGo to next message
mike miller   United States
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Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
Senior Member
Johnny Bridges wrote on Tue, 04 February 2014 07:14

... As I understand it, the idea is twofold, the main one to ensure a lifter doesn't decide not to turn and scuff the bore enough that it takes a set and doesn't want to turn.  In that direction lies early failure.  ...


Looking at websites for engine remanufacturers, That is one of the items they check. Video of one companies "SimTest" machine here:

<https://www.youtube.com/watch?feature=player_embedded&v=hBKJdKZlLIM>

As they do not have pans and manifolds for each and every engine... they really can not actually run the motors.


Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo' http://m000035.blogspot.com
Re: [GMCnet] Comp Cam Break In [message #238891 is a reply to message #238858] Wed, 05 February 2014 15:10 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Registered: July 2007
Location: Sydney, Australia
Karma: 6
Senior Member
Mike,

I had been directed to S&J awhile back and had a "discussion" with the individual that sent me the link noting that S&J only spun
the engine at 500 rpm which was way below Comp Cams recommendation of 2000 - 2500. I felt this was a critical point and not spinning
the engine at that rpm could lead to cam / lifter failure.

This "discussion" occurred before I spoke to Comp Cams and found out that that the reason for the 2000 - 2500 rpm was (a) to insure
that there was sufficient oil to the cam and (b) to make sure the lifters (and by extension the pushrods) were spinning.

For some reason the fact that S&J checks the pushrods during the engine spin test didn't register! DOUH! At any rate after you
calling this test to our attention and watching the video AGAIN I am no longer concerned by the fact that they only spin the engine
at 600 rpm.

However, while watching the video I noted a statement made by Jeff that I don't think is correct. When discussing the pushrod spin
check he said "if the pushrods are spinning the lifters are spinning which means we have the correct taper on the cam." I am fairly
confident that cam lobes are not ground with a taper. The lifters spin because they ride on the cam with the center offset.

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: Mike Miller

Looking at websites for engine remanufacturers, That is one of the items they check. Video of one companies "SimTest" machine here:

<https://www.youtube.com/watch?feature=player_embedded&v=hBKJdKZlLIM>

As they do not have pans and manifolds for each and every engine... they really can not actually run the motors.

Mike

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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Comp Cam Break In [message #238922 is a reply to message #238891] Wed, 05 February 2014 19:15 Go to previous messageGo to next message
Kosier is currently offline  Kosier   United States
Messages: 834
Registered: February 2008
Karma: 1
Senior Member
Rob,

Yes, cam lobes are ground on a taper on a flat tappet cam. They are flat on
a roller tappet cam for obvious reasons.
I have no proof, but I assume it is to keep the cam pushed to the rear
against the thrust face on the front of the block.
On the roller cam, you have to use a thrust button to keep the cam located
Also, just realized that if the lobe didn't have a taper to match the
lifter, the lifter would ride on the very center and
not rotate. Amazing the things you never consider until someone else
broaches the subject.

Gary Kosier
77 PB w/500 Cad
Newark, Oh

-----Original Message-----
From: Robert Mueller
Sent: Wednesday, February 05, 2014 4:10 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Comp Cam Break In

Mike,

I had been directed to S&J awhile back and had a "discussion" with the
individual that sent me the link noting that S&J only spun
the engine at 500 rpm which was way below Comp Cams recommendation of 2000 -
2500. I felt this was a critical point and not spinning
the engine at that rpm could lead to cam / lifter failure.

This "discussion" occurred before I spoke to Comp Cams and found out that
that the reason for the 2000 - 2500 rpm was (a) to insure
that there was sufficient oil to the cam and (b) to make sure the lifters
(and by extension the pushrods) were spinning.

For some reason the fact that S&J checks the pushrods during the engine spin
test didn't register! DOUH! At any rate after you
calling this test to our attention and watching the video AGAIN I am no
longer concerned by the fact that they only spin the engine
at 600 rpm.

However, while watching the video I noted a statement made by Jeff that I
don't think is correct. When discussing the pushrod spin
check he said "if the pushrods are spinning the lifters are spinning which
means we have the correct taper on the cam." I am fairly
confident that cam lobes are not ground with a taper. The lifters spin
because they ride on the cam with the center offset.

Regards,
Rob M.
Sydney, Australia

-----Original Message-----
From: Mike Miller

Looking at websites for engine remanufacturers, That is one of the items
they check. Video of one companies "SimTest" machine here:

<https://www.youtube.com/watch?feature=player_embedded&v=hBKJdKZlLIM>

As they do not have pans and manifolds for each and every engine... they
really can not actually run the motors.

Mike

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Re: [GMCnet] Comp Cam Break In [message #238930 is a reply to message #238922] Wed, 05 February 2014 20:08 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
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Registered: March 2007
Location: S.E. Michigan
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Kosier wrote on Wed, 05 February 2014 20:15

Rob,

Yes, cam lobes are ground on a taper on a flat tappet cam. They are flat on a roller tappet cam for obvious reasons.
I have no proof, but I assume it is to keep the cam pushed to the rear against the thrust face on the front of the block.
On the roller cam, you have to use a thrust button to keep the cam located
Also, just realized that if the lobe didn't have a taper to match the lifter, the lifter would ride on the very center and
not rotate. Amazing the things you never consider until someone else broaches the subject.

Gary Kosier

Gary,

The flat tappet cam specifications that I have seen have a taper of 1~2°. That and the 5~15' radius of the cam follower are to make the followers rotate. If they stop rotating, they wear very badly and fast. The axial thrust from this is pretty small. I have spun a flat tappet cam in a bare block with valve gear. It will snap from dwell to the next dwell even on a V-8 but it does not push out.

Prior to modern CCMs it was a real bear to measure and confirm either of these values. The OEs had special gages, but when you are measuring Brand C or F for a report to Brand G, it was often interesting.

Matt


Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
Re: [GMCnet] Comp Cam Break In [message #238956 is a reply to message #238653] Thu, 06 February 2014 09:15 Go to previous messageGo to next message
JohnL455 is currently offline  JohnL455   United States
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Location: Woodstock, IL
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While on the rotation theme, was Olds one of the first to advertise valve rotators? Blurry memory but thought it was about the time of lead free fuel to help prevent valve burning. If so was it the lifter that rotated the valve and how so? Do our 455 403 have this?

John Lebetski
Woodstock, IL
77 Eleganza II
Re: [GMCnet] Comp cam break in [message #238969 is a reply to message #238653] Thu, 06 February 2014 10:42 Go to previous messageGo to next message
BobDunahugh is currently offline  BobDunahugh   United States
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Location: Cedar Rapids, IA
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Valve rotators are mounted between the valve spring and valve spring keeper/ retainer. It rotates the exhaust valve. Used on lower RPM engines. As the extra valvetrain mass is only a problem at high RPM's.
Bob Dunahugh GMCMI Member78 Royale Iowa
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Re: [GMCnet] Comp Cam Break In [message #238995 is a reply to message #238956] Thu, 06 February 2014 15:42 Go to previous messageGo to next message
mikethebike is currently offline  mikethebike   United States
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JohnL455 wrote on Thu, 06 February 2014 09:15

While on the rotation theme, was Olds one of the first to advertise valve rotators? Blurry memory but thought it was about the time of lead free fuel to help prevent valve burning. If so was it the lifter that rotated the valve and how so? Do our 455 403 have this?



All valves will rotate. Back in the 1950's when AMOCO pushed lead free gas all kinds of stories circulated about how bad it was for your engine but tests proved that below 4000 rpm it didn't matter if you ran lead free or not. How often did you run above 4000 in your 1957 Buick or your 455 cid GMC/MH? Now, if you were sporting around in a Power-Pack or Fuelie Chevy with a 6500 rpm power peak......different story.

I was talking to Carl Harr about this and he mentioned a GM product called EOS which is an additive package for new engine run-in but can also prevent flat tappet cam failure. A friend is having his 1966 GTO off-frame $$$$$$$'d and his engine builder built Ward Burtons 2002 Daytona 500 winning engine. I'll talk to Ken and find out which oil he recommends be run in the GTO. It is a specialty oil loaded with the ZDDP additive package.
Re: [GMCnet] Comp Cam Break In [message #238997 is a reply to message #238930] Thu, 06 February 2014 15:50 Go to previous message
mikethebike is currently offline  mikethebike   United States
Messages: 331
Registered: January 2014
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Senior Member
Matt Colie wrote on Wed, 05 February 2014 20:08

Kosier wrote on Wed, 05 February 2014 20:15

Rob,

Yes, cam lobes are ground on a taper on a flat tappet cam. They are flat on a roller tappet cam for obvious reasons.
I have no proof, but I assume it is to keep the cam pushed to the rear against the thrust face on the front of the block.
On the roller cam, you have to use a thrust button to keep the cam located
Also, just realized that if the lobe didn't have a taper to match the lifter, the lifter would ride on the very center and
not rotate. Amazing the things you never consider until someone else broaches the subject.

Gary Kosier

Gary,

The flat tappet cam specifications that I have seen have a taper of 1~2°. That and the 5~15' radius of the cam follower are to make the followers rotate. If they stop rotating, they wear very badly and fast. The axial thrust from this is pretty small. I have spun a flat tappet cam in a bare block with valve gear. It will snap from dwell to the next dwell even on a V-8 but it does not push out.

Prior to modern CCMs it was a real bear to measure and confirm either of these values. The OEs had special gages, but when you are measuring Brand C or F for a report to Brand G, it was often interesting.

Matt


I agree 100% with the follower rotation statement. As far as cam walk...the SBC are famous for it and every speed shop in the world sells a kit to stop it whereas the SBF utilized a cam design that prevented it. But I have doubts as how critical it is in an engine that never sees more than what....4500.....and how often does that happen?

If I ever go into the Olds I'm converting it to a roller. Regardless of cost.

CRANE part number 809611

[Updated on: Thu, 06 February 2014 15:56]

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