455 Engine camshaft

[Rich Kinas]

All, I was wondering if anyone has swapped to a roller cam (with roller lifters of course) and roller rockers and kept the original quadrajet? Any
performance improvements? Good, bad and ugly...? Thanks,

Rich
--
Rich Kinas
1976 Elaganza II
Orlando, FL

 

[Jim Hupy]

Why? Are you planning to rev the engine past 5000 RPM? That is where you
MIGHT see any benefit from rollers. The 455 is a torque monster, a stump
puller. It needs max torque at 1800 to 4200 rpm or so. It is pulling 12,500
pounds. Save your money and re-gear the final drive to 3:55 to 1, or 3:70
to 1. You will get WAAAYYY more bang for your monetary investment. But,
what the heck, it's your money, spend it how you see fit.
Jim Hupy
Salem, Oregon

On Thu, Nov 21, 2019, 2:49 PM Rich Kinas via Gmclist <

> All, I was wondering if anyone has swapped to a roller cam (with roller
> lifters of course) and roller rockers and kept the original quadrajet? Any
> performance improvements? Good, bad and ugly...? Thanks,
>
> Rich
> --
> Rich Kinas
> 1976 Elaganza II
> Orlando, FL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[john r. lebetski]

Roller cam setups came about for CAFE. Trying to squeak fractions of a mile per gallon more out of engines. They are largely successful but not
without problems. In fact I have never had a non roller cam fail. I have had a roller cam fail in a small block Chevy. And search all the problems
FCA is having in their "Hemi". Mostly roller needle bearings. If that little roller ever does not rotate the cam is done.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Jim Hupy]

I only have personal experience with roller tappet camshafts back to
1962-62 or so.
We ran an Iskendarian Super LaGuerra 565 camshaft in a Small Block
Chevrolet engine in a "C" gasser. It had an additional rev kit that
installed in the valley. Ed himself ground those cams for us.
The engine block was a C.O.P.O. piece from Chevrolet Racing Division.
It had a 327 sized bore, with 283 sized crankshaft journals and bores. It
displaced 302 cubic inches ready to race. Everything else was aftermarket,
but it had Stu Hilborn mechanical fuel injection, Vertex Magneto, etc.
Shift point was 9500 RPM. No, I did not stutter or misquote. Parham quick
change with 4:55 - 1 gearing. The all up weight was 2990 pounds. A 39 chev
coupe with 25% engine setback. Chev 4 speed, or a B & M HydroStick. Full
rollcage. A purpose built racecar. This was just before E.T Brackets. Run
whut ya brung. My last real racecar. I drove for other teams after that,
but nothing that I had ownership of.
Those cams would show critical wear after 25 or 30 passes. That is
forever in today's drag cars. But, 9500 rpms is extreme service. No one
that we raced against could achieve that, back then. But, that stuff does
wear out, like flat tappet stuff wears out. Just Saying.
Jim Hupy
Salem, Oregon

On Thu, Nov 21, 2019, 7:01 PM John R. Lebetski via Gmclist <

> Roller cam setups came about for CAFE. Trying to squeak fractions of a
> mile per gallon more out of engines. They are largely successful but not
> without problems. In fact I have never had a non roller cam fail. I have
> had a roller cam fail in a small block Chevy. And search all the problems
> FCA is having in their "Hemi". Mostly roller needle bearings. If that
> little roller ever does not rotate the cam is done.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[tmsnyder]

With the reduced zinc in modern oils, I would think there would be an advantage to using a roller cam instead of a flat tappet.
--
Todd Snyder, Buffalo NY
1976 Eleganza II

 

[john r. lebetski]

ZDDP is lower now in SN but oils have other EP chemistry today. I own many old GM muscle cars and never had a cam issue. It's all about intended RPM
range. That dictates spring pressures required. Given our working RPM range, the GMC Olds is one of the last candidates for high ZDDP oils. Remember
that ZDDP increases general friction in engines , but does act as an EP lube as an accidental secondary benefit. It was first added as an antioxidant
with the accidental discovery that it was an Extreme Pressure lube. Same as Viagra, which was a heart drug that failed clinical testing phase, but had
secondary effects.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[LarryW]

> ZDDP is lower now in SN but oils have other EP chemistry today. I own many old GM muscle cars and never had a cam issue. It's all about intended
> RPM range. That dictates spring pressures required. Given our working RPM range, the GMC Olds is one of the last candidates for high ZDDP oils.
> Remember that ZDDP increases general friction in engines , but does act as an EP lube as an accidental secondary benefit. It was first added as an
> antioxidant with the accidental discovery that it was an Extreme Pressure lube. Same as Viagra, which was a heart drug that failed clinical testing
> phase, but had secondary effects.

Really...and just how is it that you are so familiar with the side effects of Viagra????
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

 

[bill wevers]

I've seen some owners with high-load racing valve springs on their motorhome heads.
I would think that a stock valve spring would be sufficient and have less wear
on an engine that never sees 4000 RPM.

When I had my 455 rebuilt, the machinist measured the stock springs he removed.
And they still were in spec for pressure after 40 years.

I put in a mild cam with 440 lift, 256/260 duration, only slightly bigger than stock.
The torque maxes out below 3000 RPM, which is 65-70 MPH. I could probably use a
higher gear ratio. I have the power drive chain reduction.

If I slow down to 60, it makes a big difference in fuel economy.
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose

 

[john r. lebetski]

Larry, from doing audio for long long boring pharmaceutical company drug launches in hotel ballrooms. You get all the inside scoop if you listen.

--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[jim kanomata1]

What most of you have not experienced with roller cams is the distributor
gear.
if you use brass or phenolic gear, it will last about 1,000 miles befor it
will wear out.
You can get a Nitrided one if you can find one.
I did three and all went south when the gear fragments ot into the bearings
and I bought it.

On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

> Larry, from doing audio for long long boring pharmaceutical company drug
> launches in hotel ballrooms. You get all the inside scoop if you
> listen.
>
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> 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

 

[Rich Kinas]

I love the wisdom of the group here! I just like to be prepared, and in
this instance I was planning on what to possible do IF when I pull the
intake to put on the exhaust crossover blockoff plates, and so chip off all
the cookies that I am sure are going to be present I will pull the camshaft
cover (or whatever you call it, valley tray, something else?) and visually
inspect the camshaft lobes. And depending on what I find maybe have to make
some choices. Of course my wife does not like where this is
heading....Normally I would have snatched this motor out by now, but the
motor was running great and pulling it would make my wife frown.. So for
now unless the cam is shot I will just button the intake back up and press
on!. Oh something I saw this weekend at a swap meet in Moultrie GA, was in
the valley of an olds motor somebody installed screen mesh either brazed or
epoxied in place (very nice and neat) above the cam, I guess to catch any
cookies from dropping into the block. I thought this was interesting.
Anybody else ever seen this?

Rich

On Fri, Nov 22, 2019 at 11:22 PM Jim Kanomata via Gmclist <

> What most of you have not experienced with roller cams is the distributor
> gear.
> if you use brass or phenolic gear, it will last about 1,000 miles befor it
> will wear out.
> You can get a Nitrided one if you can find one.
> I did three and all went south when the gear fragments ot into the bearings
> and I bought it.
>
> On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

>
> > Larry, from doing audio for long long boring pharmaceutical company drug
> > launches in hotel ballrooms. You get all the inside scoop if you
> > listen.
> >
> > --
> > John Lebetski
> > Woodstock, IL
> > 77 Eleganza II
> >
> >
> > _______________________________________________
> > 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
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Rich Kinas]

Jim what makes this different between a flat tappet cam and a roller cam?

Sent from my iPhone

>
> What most of you have not experienced with roller cams is the distributor
> gear.
> if you use brass or phenolic gear, it will last about 1,000 miles befor it
> will wear out.
> You can get a Nitrided one if you can find one.
> I did three and all went south when the gear fragments ot into the bearings
> and I bought it.
>
> On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

>
>> Larry, from doing audio for long long boring pharmaceutical company drug
>> launches in hotel ballrooms. You get all the inside scoop if you
>> listen.
>>
>> --
>> John Lebetski
>> Woodstock, IL
>> 77 Eleganza II
>>
>>
>> _______________________________________________
>> 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
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[Jim Hupy]

Not a simple answer but, the factory camshafts are (for the most part, all)
made of cast metals. But, with the Oldsmobile engines starting with the
infamous 350 diesels, used a billet steel camshaft.
Most, if not all of the aftermarket camshaft grinders, when they
started to make high lift/long duration roller cams, prefer the steel
blanks over the cast ones, for a number of reasons, the major one being the
weldability of the steel over the castings.
But, that leaves the distributor gear harder than the hinges to the
gates of hell. Bronze distributor gears and steel cam gears are not
compatible, wear-wise.
Race engines don't live long enough for that to be a problem, but for
our uses in a motorhome over 10's of thousands of miles, it is a very real
concern.
The fix? Find and use a distributor gear that has compatible
characteristics with the steel cam blanks. There is a product, I know it as
"Mehinite", that has the right machinability and wear properties. You swap
the bronze gear for the special one, and wear comes into the acceptable
range.
Clear as mud, right?
Jim Hupy
Salem, Oregon

On Sat, Nov 23, 2019, 7:42 AM Richard Kinas via Gmclist <

> Jim what makes this different between a flat tappet cam and a roller cam?
>
> Sent from my iPhone
>
> > On Nov 22, 2019, at 11:21 PM, Jim Kanomata via Gmclist <

> >
> > What most of you have not experienced with roller cams is the distributor
> > gear.
> > if you use brass or phenolic gear, it will last about 1,000 miles befor
> it
> > will wear out.
> > You can get a Nitrided one if you can find one.
> > I did three and all went south when the gear fragments ot into the
> bearings
> > and I bought it.
> >
> > On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

> >
> >> Larry, from doing audio for long long boring pharmaceutical company drug
> >> launches in hotel ballrooms. You get all the inside scoop if you
> >> listen.
> >>
> >> --
> >> John Lebetski
> >> Woodstock, IL
> >> 77 Eleganza II
> >>
> >>
> >> _______________________________________________
> >> 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
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Rich Kinas]

Actually that makes a lot of sense. Thanks for the schooling! I love
learning about stuff like this...

Rich

On Sat, Nov 23, 2019 at 11:05 AM James Hupy via Gmclist <

> Not a simple answer but, the factory camshafts are (for the most part, all)
> made of cast metals. But, with the Oldsmobile engines starting with the
> infamous 350 diesels, used a billet steel camshaft.
> Most, if not all of the aftermarket camshaft grinders, when they
> started to make high lift/long duration roller cams, prefer the steel
> blanks over the cast ones, for a number of reasons, the major one being the
> weldability of the steel over the castings.
> But, that leaves the distributor gear harder than the hinges to the
> gates of hell. Bronze distributor gears and steel cam gears are not
> compatible, wear-wise.
> Race engines don't live long enough for that to be a problem, but for
> our uses in a motorhome over 10's of thousands of miles, it is a very real
> concern.
> The fix? Find and use a distributor gear that has compatible
> characteristics with the steel cam blanks. There is a product, I know it as
> "Mehinite", that has the right machinability and wear properties. You swap
> the bronze gear for the special one, and wear comes into the acceptable
> range.
> Clear as mud, right?
> Jim Hupy
> Salem, Oregon
>
> On Sat, Nov 23, 2019, 7:42 AM Richard Kinas via Gmclist <

>
> > Jim what makes this different between a flat tappet cam and a roller cam?
> >
> > Sent from my iPhone
> >
> > > On Nov 22, 2019, at 11:21 PM, Jim Kanomata via Gmclist <

> > >
> > > What most of you have not experienced with roller cams is the
> distributor
> > > gear.
> > > if you use brass or phenolic gear, it will last about 1,000 miles befor
> > it
> > > will wear out.
> > > You can get a Nitrided one if you can find one.
> > > I did three and all went south when the gear fragments ot into the
> > bearings
> > > and I bought it.
> > >
> > > On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

> > >
> > >> Larry, from doing audio for long long boring pharmaceutical company
> drug
> > >> launches in hotel ballrooms. You get all the inside scoop if you
> > >> listen.
> > >>
> > >> --
> > >> John Lebetski
> > >> Woodstock, IL
> > >> 77 Eleganza II
> > >>
> > >>
> > >> _______________________________________________
> > >> 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
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[jim kanomata1]

There are tons of people that have no idea about this, including the engine
builders.
Most will sellyou a roller am without addressing the distributor gear. When
you do, they will tell you to usse the brass/bronze gear or a phenolic one
as the work on race engine as they run for short distances and does not
wear that much.

On Sat, Nov 23, 2019 at 8:13 AM Rich Kinas via Gmclist <

> Actually that makes a lot of sense. Thanks for the schooling! I love
> learning about stuff like this...
>
> Rich
>
> On Sat, Nov 23, 2019 at 11:05 AM James Hupy via Gmclist <

>
> > Not a simple answer but, the factory camshafts are (for the most part,
> all)
> > made of cast metals. But, with the Oldsmobile engines starting with the
> > infamous 350 diesels, used a billet steel camshaft.
> > Most, if not all of the aftermarket camshaft grinders, when they
> > started to make high lift/long duration roller cams, prefer the steel
> > blanks over the cast ones, for a number of reasons, the major one being
> the
> > weldability of the steel over the castings.
> > But, that leaves the distributor gear harder than the hinges to the
> > gates of hell. Bronze distributor gears and steel cam gears are not
> > compatible, wear-wise.
> > Race engines don't live long enough for that to be a problem, but
> for
> > our uses in a motorhome over 10's of thousands of miles, it is a very
> real
> > concern.
> > The fix? Find and use a distributor gear that has compatible
> > characteristics with the steel cam blanks. There is a product, I know it
> as
> > "Mehinite", that has the right machinability and wear properties. You
> swap
> > the bronze gear for the special one, and wear comes into the acceptable
> > range.
> > Clear as mud, right?
> > Jim Hupy
> > Salem, Oregon
> >
> > On Sat, Nov 23, 2019, 7:42 AM Richard Kinas via Gmclist <

> >
> > > Jim what makes this different between a flat tappet cam and a roller
> cam?
> > >
> > > Sent from my iPhone
> > >
> > > > On Nov 22, 2019, at 11:21 PM, Jim Kanomata via Gmclist <

> > > >
> > > > What most of you have not experienced with roller cams is the
> > distributor
> > > > gear.
> > > > if you use brass or phenolic gear, it will last about 1,000 miles
> befor
> > > it
> > > > will wear out.
> > > > You can get a Nitrided one if you can find one.
> > > > I did three and all went south when the gear fragments ot into the
> > > bearings
> > > > and I bought it.
> > > >
> > > > On Fri, Nov 22, 2019 at 5:10 PM John R. Lebetski via Gmclist <

> > > >
> > > >> Larry, from doing audio for long long boring pharmaceutical company
> > drug
> > > >> launches in hotel ballrooms. You get all the inside scoop if you
> > > >> listen.
> > > >>
> > > >> --
> > > >> John Lebetski
> > > >> Woodstock, IL
> > > >> 77 Eleganza II
> > > >>
> > > >>
> > > >> _______________________________________________
> > > >> 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
> > > > _______________________________________________
> > > > GMCnet mailing list
> > > > Unsubscribe or Change List Options:
> > > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> 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

 

[Mike Perez]

Crane Cam makes a roller cam with a pressed on iron gear that is designed to use a stock distributor gear. I have it.

In my opinion, there is little downside to hydraulic roller cams other than cost so long as you either use a cam with the pressed on iron gear, or you
can find the melonite gear. They are very difficult to find. The melonite gear from Straub Technologies has a part number of 205-5147 if you are
looking.

Honestly, this is an apples to oranges comparison. You can't just look at cam specs for a hydraulic roller cam and compare them directly to a flat
tappet cam. They perform totally differently. The hydraulic roller cam lobes will be more rounded vs a flat tappet cam. This means that the valve
is being held open for longer at the same total lift. Because of the increased tappet velocity of the hydraulic roller lifter plus the longer time the
valve is open gives you more power at the given amount of lift; or more power under the curve.

Because of this, you can't just compare a cam profile from a flat tappet vs a hydraulic roller just by intake and exhaust duration.

Also, keep in mind that because of the Toronado intake, only hydraulic lifters with the scalloped tops will clear the intake.

Pros: Less friction, more power, good for modern oils, better fuel economy (probably won't notice on a GMC)
Cons: $$$$$$

By the time you buy the cam, lifters, distributor gear (if needed), pushrods, valve springs, etc...., you start getting into a decent chunk of change.


Side note: Yes, the 455 is a stump puller type engine. Yes, the peak torque is down low which is good for a heavy vehicle. With that said, having a
little extra RPM available with our limited transmission gears is not a bad thing.

 

[Jim Hupy]

Cam profiles are different between flat tappet grinds and rollers, because
they can be. The abruptness of the take-up ramps can only be so steep due
to 2 factors. One is extreme wear on the parts, and the other is a
phenomenon known as as rebound. The parts all come under extreme load and
resist those forces by "rebounding". This, when you add secondary harmonics
from the springs, leads to a condition known as valve float. The valves are
still open when the pistons get there. Not good, not good at all.
How do they combat this? Lighter components, (titanium, etc) is one
way. Stiffer valve springs, roller tipped rockers, etc. is another. Lots of
tricks here.
Then, comes the next generation of cam designs. ROLLERS. Everyone
knows that rolling friction is far less than sliding friction. But,
everything is a trade off. Roller tappets are much heavier than flat
tappets, particularly in non hydraulic applications. Need stronger springs
to keep the roller stuff in intimate contact. Increases wear, creates more
heat. So, part of what you gained with rollers is partly lost in practice.
We could debate this forever, and it's kinda fun to do it, for me at
least.
But, experts will agree that at lower rpms, there is no advantage to
roller cams.
Jim Hupy
Salem, Oregon

On Sun, Nov 24, 2019, 6:42 AM Mike Perez via Gmclist <

> Crane Cam makes a roller cam with a pressed on iron gear that is designed
> to use a stock distributor gear. I have it.
>
> In my opinion, there is little downside to hydraulic roller cams other
> than cost so long as you either use a cam with the pressed on iron gear, or
> you
> can find the melonite gear. They are very difficult to find. The
> melonite gear from Straub Technologies has a part number of 205-5147 if you
> are
> looking.
>
> Honestly, this is an apples to oranges comparison. You can't just look at
> cam specs for a hydraulic roller cam and compare them directly to a flat
> tappet cam. They perform totally differently. The hydraulic roller cam
> lobes will be more rounded vs a flat tappet cam. This means that the valve
> is being held open for longer at the same total lift. Because of the
> increased tappet velocity of the hydraulic roller lifter plus the longer
> time the
> valve is open gives you more power at the given amount of lift; or more
> power under the curve.
>
> Because of this, you can't just compare a cam profile from a flat tappet
> vs a hydraulic roller just by intake and exhaust duration.
>
> Also, keep in mind that because of the Toronado intake, only hydraulic
> lifters with the scalloped tops will clear the intake.
>
> Pros: Less friction, more power, good for modern oils, better fuel
> economy (probably won't notice on a GMC)
> Cons: $$$$$$
>
> By the time you buy the cam, lifters, distributor gear (if needed),
> pushrods, valve springs, etc...., you start getting into a decent chunk of
> change.
>
>
> Side note: Yes, the 455 is a stump puller type engine. Yes, the peak
> torque is down low which is good for a heavy vehicle. With that said,
> having a
> little extra RPM available with our limited transmission gears is not a
> bad thing.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Irish Rogue]

Jom Hupy:
Nice explanation Sir!
Thank You,
Mike/The Corvair a holic

Sent from my iPhone

>
> Cam profiles are different between flat tappet grinds and rollers, because
> they can be. The abruptness of the take-up ramps can only be so steep due
> to 2 factors. One is extreme wear on the parts, and the other is a
> phenomenon known as as rebound. The parts all come under extreme load and
> resist those forces by "rebounding". This, when you add secondary harmonics
> from the springs, leads to a condition known as valve float. The valves are
> still open when the pistons get there. Not good, not good at all.
> How do they combat this? Lighter components, (titanium, etc) is one
> way. Stiffer valve springs, roller tipped rockers, etc. is another. Lots of
> tricks here.
> Then, comes the next generation of cam designs. ROLLERS. Everyone
> knows that rolling friction is far less than sliding friction. But,
> everything is a trade off. Roller tappets are much heavier than flat
> tappets, particularly in non hydraulic applications. Need stronger springs
> to keep the roller stuff in intimate contact. Increases wear, creates more
> heat. So, part of what you gained with rollers is partly lost in practice.
> We could debate this forever, and it's kinda fun to do it, for me at
> least.
> But, experts will agree that at lower rpms, there is no advantage to
> roller cams.
> Jim Hupy
> Salem, Oregon
>
> On Sun, Nov 24, 2019, 6:42 AM Mike Perez via Gmclist <

>
>> Crane Cam makes a roller cam with a pressed on iron gear that is designed
>> to use a stock distributor gear. I have it.
>>
>> In my opinion, there is little downside to hydraulic roller cams other
>> than cost so long as you either use a cam with the pressed on iron gear, or
>> you
>> can find the melonite gear. They are very difficult to find. The
>> melonite gear from Straub Technologies has a part number of 205-5147 if you
>> are
>> looking.
>>
>> Honestly, this is an apples to oranges comparison. You can't just look at
>> cam specs for a hydraulic roller cam and compare them directly to a flat
>> tappet cam. They perform totally differently. The hydraulic roller cam
>> lobes will be more rounded vs a flat tappet cam. This means that the valve
>> is being held open for longer at the same total lift. Because of the
>> increased tappet velocity of the hydraulic roller lifter plus the longer
>> time the
>> valve is open gives you more power at the given amount of lift; or more
>> power under the curve.
>>
>> Because of this, you can't just compare a cam profile from a flat tappet
>> vs a hydraulic roller just by intake and exhaust duration.
>>
>> Also, keep in mind that because of the Toronado intake, only hydraulic
>> lifters with the scalloped tops will clear the intake.
>>
>> Pros: Less friction, more power, good for modern oils, better fuel
>> economy (probably won't notice on a GMC)
>> Cons: $$$$$$
>>
>> By the time you buy the cam, lifters, distributor gear (if needed),
>> pushrods, valve springs, etc...., you start getting into a decent chunk of
>> change.
>>
>>
>> Side note: Yes, the 455 is a stump puller type engine. Yes, the peak
>> torque is down low which is good for a heavy vehicle. With that said,
>> having a
>> little extra RPM available with our limited transmission gears is not a
>> bad thing.
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
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[Rich Kinas]

Mike,

You stated "Also, keep in mind that because of the Toronado intake, only
hydraulic lifters with the scalloped tops will clear the intake." Well for
me that kind of puts the nail in coffin if the roller lifters with their
locking bar would interfere with the intake. Is this what you mean?

Rich

On Sun, Nov 24, 2019 at 2:15 PM Mike Kelley via Gmclist <

> Jom Hupy:
> Nice explanation Sir!
> Thank You,
> Mike/The Corvair a holic
>
> Sent from my iPhone
>
> > On Nov 24, 2019, at 12:39 PM, James Hupy via Gmclist <

> >
> > Cam profiles are different between flat tappet grinds and rollers,
> because
> > they can be. The abruptness of the take-up ramps can only be so steep due
> > to 2 factors. One is extreme wear on the parts, and the other is a
> > phenomenon known as as rebound. The parts all come under extreme load and
> > resist those forces by "rebounding". This, when you add secondary
> harmonics
> > from the springs, leads to a condition known as valve float. The valves
> are
> > still open when the pistons get there. Not good, not good at all.
> > How do they combat this? Lighter components, (titanium, etc) is one
> > way. Stiffer valve springs, roller tipped rockers, etc. is another. Lots
> of
> > tricks here.
> > Then, comes the next generation of cam designs. ROLLERS. Everyone
> > knows that rolling friction is far less than sliding friction. But,
> > everything is a trade off. Roller tappets are much heavier than flat
> > tappets, particularly in non hydraulic applications. Need stronger
> springs
> > to keep the roller stuff in intimate contact. Increases wear, creates
> more
> > heat. So, part of what you gained with rollers is partly lost in
> practice.
> > We could debate this forever, and it's kinda fun to do it, for me at
> > least.
> > But, experts will agree that at lower rpms, there is no advantage to
> > roller cams.
> > Jim Hupy
> > Salem, Oregon
> >
> > On Sun, Nov 24, 2019, 6:42 AM Mike Perez via Gmclist <

> >
> >> Crane Cam makes a roller cam with a pressed on iron gear that is
> designed
> >> to use a stock distributor gear. I have it.
> >>
> >> In my opinion, there is little downside to hydraulic roller cams other
> >> than cost so long as you either use a cam with the pressed on iron
> gear, or
> >> you
> >> can find the melonite gear. They are very difficult to find. The
> >> melonite gear from Straub Technologies has a part number of 205-5147 if
> you
> >> are
> >> looking.
> >>
> >> Honestly, this is an apples to oranges comparison. You can't just look
> at
> >> cam specs for a hydraulic roller cam and compare them directly to a flat
> >> tappet cam. They perform totally differently. The hydraulic roller
> cam
> >> lobes will be more rounded vs a flat tappet cam. This means that the
> valve
> >> is being held open for longer at the same total lift. Because of the
> >> increased tappet velocity of the hydraulic roller lifter plus the longer
> >> time the
> >> valve is open gives you more power at the given amount of lift; or more
> >> power under the curve.
> >>
> >> Because of this, you can't just compare a cam profile from a flat tappet
> >> vs a hydraulic roller just by intake and exhaust duration.
> >>
> >> Also, keep in mind that because of the Toronado intake, only hydraulic
> >> lifters with the scalloped tops will clear the intake.
> >>
> >> Pros: Less friction, more power, good for modern oils, better fuel
> >> economy (probably won't notice on a GMC)
> >> Cons: $$$$$$
> >>
> >> By the time you buy the cam, lifters, distributor gear (if needed),
> >> pushrods, valve springs, etc...., you start getting into a decent chunk
> of
> >> change.
> >>
> >>
> >> Side note: Yes, the 455 is a stump puller type engine. Yes, the peak
> >> torque is down low which is good for a heavy vehicle. With that said,
> >> having a
> >> little extra RPM available with our limited transmission gears is not a
> >> bad thing.
> >>
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >>
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[johnny]

Hupy, I be;ieve that motor was the Can - AM engine fitted to Camaros (Think COPO order Z280) which didn't make quite the power of the Ford tunnel
port motors, but the Camaro stuck better and often won even with less power. If memory server, '68 Sebring Mark Donahue had the Camaro and George
Folmar had the mustang. They'd hit the back straight and Folmar would put the motor on him and pass easily. Comes the crooked and the reverse -
Donahue would blow past at about the second turn and keep gaining through the crooked.

--johnny
\
--
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