Looking for Opinions on Aluminum Heads

[Carl Stouffer]

As discussed in a previous thread, I have a J head on the left side of my 455 and a K head on the right. The K head evidently has a couple of burned
exhaust valves Which came to light during a leak down test. The left J head is in much better shape.

I know the J head is the preferred head for our application, and Bob Dunahugh has offered to get one to me to replace the K head, but I have always
been intrigued by the aluminum heads that are available for the Olds engines. I have actually seen a few coaches with them on their engines, and it
makes sense to have the more efficient combustion chamber shape, the better heat dissipation, and the weight savings of the aluminum heads.

I contacted Jim Bounds, and his opinion is that we need the low compression smog heads (J) for our engines to develop the low end power we need the
most. I just wanted to get more opinions on this so I can make an informed decision on this before starting on the project.

What do you guys think of aluminum heads, pro or con, and why?

Thanks
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[robert mueller]

Carl,

I did a bit of Googling and found that the flow through the ports on the Edelbrock heads is higher than stock for high RPM engines.
Larger ports means lower velocity and in a GMC I don't think that's good.

IIRC Dennis Sexton has a set on one of his GMC's so hopefully he will comment.

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Carl Stouffer
Sent: Sunday, July 30, 2017 9:18 AM
To: gmclist
Subject: [GMCnet] Looking for Opinions on Aluminum Heads

As discussed in a previous thread, I have a J head on the left side of my 455 and a K head on the right. The K head evidently has a
couple of burned exhaust valves which came to light during a leak down test. The left J head is in much better shape.

I know the J head is the preferred head for our application, and Bob Dunahugh has offered to get one to me to replace the K head,
but I have always been intrigued by the aluminum heads that are available for the Olds engines. I have actually seen a few coaches
with them on their engines, and it makes sense to have the more efficient combustion chamber shape, the better heat dissipation, and
the weight savings of the aluminum heads.

I contacted Jim Bounds, and his opinion is that we need the low compression smog heads (J) for our engines to develop the low end
power we need the most. I just wanted to get more opinions on this so I can make an informed decision on this before starting on
the project.

What do you guys think of aluminum heads, pro or con, and why?

Thanks
--
Carl

 

[dennis sexton]

Carl

I installed edelbrock aluminum heads back in '07 but sold the coach before driving it enough miles under varied conditions to give a measured or
quantitative reply. I would not hesitate to install them again. But there have been others since - one of the more recent is Loffen.

I had two cracked heads and at the time no ready source for good J heads nor a quality machine shop. I was interested in trying the aluminum heads and
there was not going to be a better or less expensive time to do so.

I have part numbers and prices for most everything I did if it would be of help.

At the time I also built up a carburetor to match using some of Ciiff Ruggles suggestions . Jetting, power spring, pull over enrichment and such.

I can give you more details and I have some photos on the site - but my info would be dated to '07.

Dennis



> Carl,
>
> I did a bit of Googling and found that the flow through the ports on the Edelbrock heads is higher than stock for high RPM engines.
> Larger ports means lower velocity and in a GMC I don't think that's good.
>
> IIRC Dennis Sexton has a set on one of his GMC's so hopefully he will comment.
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of Carl Stouffer
> Sent: Sunday, July 30, 2017 9:18 AM
> To: gmclist
> Subject: [GMCnet] Looking for Opinions on Aluminum Heads
>
> As discussed in a previous thread, I have a J head on the left side of my 455 and a K head on the right. The K head evidently has a
> couple of burned exhaust valves which came to light during a leak down test. The left J head is in much better shape.
>
> I know the J head is the preferred head for our application, and Bob Dunahugh has offered to get one to me to replace the K head,
> but I have always been intrigued by the aluminum heads that are available for the Olds engines. I have actually seen a few coaches
> with them on their engines, and it makes sense to have the more efficient combustion chamber shape, the better heat dissipation, and
> the weight savings of the aluminum heads.
>
> I contacted Jim Bounds, and his opinion is that we need the low compression smog heads (J) for our engines to develop the low end
> power we need the most. I just wanted to get more opinions on this so I can make an informed decision on this before starting on
> the project.
>
> What do you guys think of aluminum heads, pro or con, and why?
>
> Thanks
> --
> Carl
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Dennis S
73 Painted Desert 230
Memphis TN Metro

 

[LarryW]

The late GREAT Bob Drews had issues with the cast heads. So, now this is second hand information and just what I remember from our conversations.
After unsuccessfully trying to install hardened seats in several sets of cast heads he finally broke down and got a set of Mondello aluminum heads and
installed them. He was running a throttle body injection with EBL software. IIRC the first thing he noticed was the somewhat significant changes he
had to make in both spark and fuel tables. (more spark and richer fuel). He also noticed better power throughout the RPM ranges that he ran in his
GMC. He attributed these changes to better flow in these aluminum heads. Aside from these changes, he saw no down side (other than price) to using
those heads.

With this in mind, If you change to the aluminum heads, be aware that you may have to make some changes to both spark (in fuel tables on EFI, or
distributor changes in non EFI) and in fuel.(Either in the fuel tables or by re-jetting in the case of a Carburator.) Just my take on this.
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

 

[Jim Hupy]

The Edelbrock performer series heads are similar to the flow
characteristics of the Oldsmobile Ka heads used on the W-30 Cutlass and
442 HP. Their intended use is for an rpm range a bit higher than we
normally see with our motorhomes, but they are low enough compression
ratio, with improved squish area, that they will work. If you have
exhausted your supply of good G and J iron heads, the Edelbrock Aluminum
heads are an option. We really don't have a need for high rates of cubic
feet per minute in our coaches. We need good port to manifold matching, as
well as blocked exhaust crossovers. Valve sizes are more than adequate for
our uses. Remember, flow velocity is greater in smaller ports, and a
matched setup will always outperform a larger mismatched one.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> The late GREAT Bob Drews had issues with the cast heads. So, now this is
> second hand information and just what I remember from our conversations.
> After unsuccessfully trying to install hardened seats in several sets of
> cast heads he finally broke down and got a set of Mondello aluminum heads
> and
> installed them. He was running a throttle body injection with EBL
> software. IIRC the first thing he noticed was the somewhat significant
> changes he
> had to make in both spark and fuel tables. (more spark and richer fuel).
> He also noticed better power throughout the RPM ranges that he ran in his
> GMC. He attributed these changes to better flow in these aluminum heads.
> Aside from these changes, he saw no down side (other than price) to using
> those heads.
>
> With this in mind, If you change to the aluminum heads, be aware that you
> may have to make some changes to both spark (in fuel tables on EFI, or
> distributor changes in non EFI) and in fuel.(Either in the fuel tables or
> by re-jetting in the case of a Carburator.) Just my take on this.
> --
> Larry
> 78 Royale w/500 Caddy
> Menomonie, WI.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[jim kanomata1]

Jim,
So many people miss the boat when it comes to utilizing accessory to
improve performance.
Most high performance accessory does little at RPM below 3400.
I remember when I was in college, I helped a friend install a 3/4 cam in
his truck. It ran great at high RPM but did nothing at 3,000, actually ran
worse.
Aluminum heads are great, but for long term use on a coach it has some draw
backs as the Aluminum expands and contracts a different rate and thus
creates some issues prematurely.

> The Edelbrock performer series heads are similar to the flow
> characteristics of the Oldsmobile Ka heads used on the W-30 Cutlass and
> 442 HP. Their intended use is for an rpm range a bit higher than we
> normally see with our motorhomes, but they are low enough compression
> ratio, with improved squish area, that they will work. If you have
> exhausted your supply of good G and J iron heads, the Edelbrock Aluminum
> heads are an option. We really don't have a need for high rates of cubic
> feet per minute in our coaches. We need good port to manifold matching, as
> well as blocked exhaust crossovers. Valve sizes are more than adequate for
> our uses. Remember, flow velocity is greater in smaller ports, and a
> matched setup will always outperform a larger mismatched one.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>
> > The late GREAT Bob Drews had issues with the cast heads. So, now this is
> > second hand information and just what I remember from our conversations.
> > After unsuccessfully trying to install hardened seats in several sets of
> > cast heads he finally broke down and got a set of Mondello aluminum heads
> > and
> > installed them. He was running a throttle body injection with EBL
> > software. IIRC the first thing he noticed was the somewhat significant
> > changes he
> > had to make in both spark and fuel tables. (more spark and richer fuel).
> > He also noticed better power throughout the RPM ranges that he ran in his
> > GMC. He attributed these changes to better flow in these aluminum heads.
> > Aside from these changes, he saw no down side (other than price) to using
> > those heads.
> >
> > With this in mind, If you change to the aluminum heads, be aware that you
> > may have to make some changes to both spark (in fuel tables on EFI, or
> > distributor changes in non EFI) and in fuel.(Either in the fuel tables or
> > by re-jetting in the case of a Carburator.) Just my take on this.
> > --
> > Larry
> > 78 Royale w/500 Caddy
> > Menomonie, WI.
> >
> > _______________________________________________
> > 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.appliedgmc.com
1-800-752-7502

 

[Jim Hupy]

Yes, I agree that bi-metallic corrosion is a problem with aluminum heads,
and getting them to hold head gaskets with their different expansion
co-efficient vs cast iron, plus their reduced fastener torque are all
problems that cast iron heads do not have. But, as our supply of suitable
iron cores dwindle, it is perhaps something to think about. Me personally,
I much prefer cast iron.
Finding a good automotive machinist with some grey hair and a lengthy
career of successfully fixing burned out valve seats and cracked cast iron
is a tall order for some parts of the country. If you know one, it is good
to keep him in your speed dial, and remember him on Christmas, too.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> Jim,
> So many people miss the boat when it comes to utilizing accessory to
> improve performance.
> Most high performance accessory does little at RPM below 3400.
> I remember when I was in college, I helped a friend install a 3/4 cam in
> his truck. It ran great at high RPM but did nothing at 3,000, actually ran
> worse.
> Aluminum heads are great, but for long term use on a coach it has some draw
> backs as the Aluminum expands and contracts a different rate and thus
> creates some issues prematurely.
>

>
> > The Edelbrock performer series heads are similar to the flow
> > characteristics of the Oldsmobile Ka heads used on the W-30 Cutlass and
> > 442 HP. Their intended use is for an rpm range a bit higher than we
> > normally see with our motorhomes, but they are low enough compression
> > ratio, with improved squish area, that they will work. If you have
> > exhausted your supply of good G and J iron heads, the Edelbrock Aluminum
> > heads are an option. We really don't have a need for high rates of cubic
> > feet per minute in our coaches. We need good port to manifold matching,
> as
> > well as blocked exhaust crossovers. Valve sizes are more than adequate
> for
> > our uses. Remember, flow velocity is greater in smaller ports, and a
> > matched setup will always outperform a larger mismatched one.
> > Jim Hupy
> > Salem, Or
> > 78 GMC ROYALE 403
> >

> >
> > > The late GREAT Bob Drews had issues with the cast heads. So, now this
> is
> > > second hand information and just what I remember from our
> conversations.
> > > After unsuccessfully trying to install hardened seats in several sets
> of
> > > cast heads he finally broke down and got a set of Mondello aluminum
> heads
> > > and
> > > installed them. He was running a throttle body injection with EBL
> > > software. IIRC the first thing he noticed was the somewhat significant
> > > changes he
> > > had to make in both spark and fuel tables. (more spark and richer
> fuel).
> > > He also noticed better power throughout the RPM ranges that he ran in
> his
> > > GMC. He attributed these changes to better flow in these aluminum
> heads.
> > > Aside from these changes, he saw no down side (other than price) to
> using
> > > those heads.
> > >
> > > With this in mind, If you change to the aluminum heads, be aware that
> you
> > > may have to make some changes to both spark (in fuel tables on EFI, or
> > > distributor changes in non EFI) and in fuel.(Either in the fuel tables
> or
> > > by re-jetting in the case of a Carburator.) Just my take on this.
> > > --
> > > Larry
> > > 78 Royale w/500 Caddy
> > > Menomonie, WI.
> > >
> > > _______________________________________________
> > > 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.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Carl Stouffer]

There are literally millions of cast steel block/aluminum head engines coming from the OEMs, The Chevy LS truck engine comes to mind, and the Buick
300 had aluminum heads clear back in 1964. I have one of those LS engines in a truck with 194,000 miles on it and the only repair that it has ever
needed was an O-ring on the oil pick-up. Evidently the head gasket issues have been resolved. I already have an aluminum (Gary Rockwell) intake
manifold mated to the cast heads. I think that is a minor issue.

I DO have a good head guy and Olds specific machine shop here in Tucson, Larry's Engine and Machine, who specializes in boat 455 engines so I could go
either way if need be. By the time I get another J head here and recondition the one I have, I will be getting up there in $$$. Albeit not as much
as a set of These heads:

http://www.ebay.com/itm/Speedmaster-PCE281-2152-Oldsmobile-400-425-455-Aluminum-Cylinder-Heads-188cc-7-/311859190878?_trksid=p2385738.m2548.l4275

My mechanic" son, admittedly a high performance guy, is extolling the Virtues of aluminum heads, so I'm trying to get enough information to make an
intelligent decision. If Bob Drews and Dennis Sexton had good luck with them, that is a positive. The main negative seems to be increased runner
velocity, potentially hurting the low end, but the 455 is a stump puller in whatever form.

Continued discussion would be helpful.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[Jim Hupy]

Carl, it helps to remember the Vega, and the early Cadillac Northstar, and
the 1.8 liter G.M. 4 cylinder engines. They served as test beds for the
L.S. and other successful engines to follow. I worked on quite a few of
those things, most of the time coolant in the oil problems as well as
combustion sealing.
Some very bright people burned a bunch of midnight oil to cure those
things.
The Olds 455 and particularly the 403 are not ideal candidates for
retrofitting with aluminum heads due to their head bolt placement and water
jacket proximity to the cylinder bores. I am not saying that it CAN'T BE
DONE SUCCESSFULLY, just that very careful selection of gaskets and sealants
is necessary, as well as the finish on the top of the block. Keeping a very
close eye on coolant change intervals and probably some Blackstone oil
analysis on a regular basis won't hurt, either. Not trying to talk you out
of it, just maintain a healthy skepticism. Ultimately, it's your money and
your choice.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> There are literally millions of cast steel block/aluminum head engines
> coming from the OEMs, The Chevy LS truck engine comes to mind, and the
> Buick
> 300 had aluminum heads clear back in 1964. I have one of those LS engines
> in a truck with 194,000 miles on it and the only repair that it has ever
> needed was an O-ring on the oil pick-up. Evidently the head gasket issues
> have been resolved. I already have an aluminum (Gary Rockwell) intake
> manifold mated to the cast heads. I think that is a minor issue.
>
> I DO have a good head guy and Olds specific machine shop here in Tucson,
> Larry's Engine and Machine, who specializes in boat 455 engines so I could
> go
> either way if need be. By the time I get another J head here and
> recondition the one I have, I will be getting up there in $$$. Albeit not
> as much
> as a set of These heads:
>
> http://www.ebay.com/itm/Speedmaster-PCE281-2152-Oldsmobile-400-425-455-
> Aluminum-Cylinder-Heads-188cc-7-/311859190878?_trksid=p2385738.m2548.l4275
>
> My mechanic" son, admittedly a high performance guy, is extolling the
> Virtues of aluminum heads, so I'm trying to get enough information to make
> an
> intelligent decision. If Bob Drews and Dennis Sexton had good luck with
> them, that is a positive. The main negative seems to be increased runner
> velocity, potentially hurting the low end, but the 455 is a stump puller
> in whatever form.
>
> Continued discussion would be helpful.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[dennis sexton]

Carl

Consider discussing gaskets and sealants with Edelbrock tech - they had specific recommendations (at one time).

And review what rockers and push rods you may need. Rockers may also dictate the need for taller valve covers to provide clearance.

At the time (2007) Edelbrock considered the motorhome an excellent application for the heads.

Dennis

> There are literally millions of cast steel block/aluminum head engines coming from the OEMs, The Chevy LS truck engine comes to mind, and the
> Buick 300 had aluminum heads clear back in 1964. I have one of those LS engines in a truck with 194,000 miles on it and the only repair that it has
> ever needed was an O-ring on the oil pick-up. Evidently the head gasket issues have been resolved. I already have an aluminum (Gary Rockwell)
> intake manifold mated to the cast heads. I think that is a minor issue.
>
> I DO have a good head guy and Olds specific machine shop here in Tucson, Larry's Engine and Machine, who specializes in boat 455 engines so I
> could go either way if need be. By the time I get another J head here and recondition the one I have, I will be getting up there in $$$. Albeit
> not as much as a set of These heads:
>
> http://www.ebay.com/itm/Speedmaster-PCE281-2152-Oldsmobile-400-425-455-Aluminum-Cylinder-Heads-188cc-7-/311859190878?_trksid=p2385738.m2548.l4275
>
> My mechanic" son, admittedly a high performance guy, is extolling the Virtues of aluminum heads, so I'm trying to get enough information to make
> an intelligent decision. If Bob Drews and Dennis Sexton had good luck with them, that is a positive. The main negative seems to be increased
> runner velocity, potentially hurting the low end, but the 455 is a stump puller in whatever form.
>
> Continued discussion would be helpful.

--
Dennis S
73 Painted Desert 230
Memphis TN Metro

 

[robert mueller]

Carl,

It seems that the general consensus is the aluminum heads will work OK. When I read the installation instructions it noted that you
had to match the ports in the head to the manifold.

New thought: since the heads are designed for a higher RPM range than we normally run I wonder if installing a Cloyes cam gear
advanced 4? would help with the low RPM torque?

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces] On Behalf Of Carl Stouffer
Sent: Monday, July 31, 2017 3:42 AM
To: gmclist
Subject: Re: [GMCnet] Looking for Opinions on Aluminum Heads

There are literally millions of cast steel block/aluminum head engines coming from the OEMs, The Chevy LS truck engine comes to
mind, and the Buickb300 had aluminum heads clear back in 1964. I have one of those LS engines in a truck with 194,000 miles on it
and the only repair that it has ever needed was an O-ring on the oil pick-up. Evidently the head gasket issues have been resolved.
I already have an aluminum (Gary Rockwell) intake manifold mated to the cast heads. I think that is a minor issue.

I DO have a good head guy and Olds specific machine shop here in Tucson, Larry's Engine and Machine, who specializes in boat 455
engines so I could go either way if need be. By the time I get another J head here and recondition the one I have, I will be
getting up there in $$$. Albeit not as much as a set of These heads:

http://www.ebay.com/itm/Speedmaster-PCE281-2152-Oldsmobile-400-425-455-Aluminum-Cylinder-Heads-188cc-7-/311859190878?_trksid=p238573
8.m2548.l4275

My mechanic" son, admittedly a high performance guy, is extolling the Virtues of aluminum heads, so I'm trying to get enough
information to make an intelligent decision. If Bob Drews and Dennis Sexton had good luck with them, that is a positive. The main
negative seems to be increased runner velocity, potentially hurting the low end, but the 455 is a stump puller in whatever form.

Continued discussion would be helpful.
--
Carl Stouffer

 

[dennis sexton]

Rob

You might also look at the lift and duration of the CompCam RV cam. I did not replace my stock cam but reasoned that the increased intake valve size
would move the stock cam closer to the new grind - at the time it was the grind Arch and Drew Koba were working with.
The exhaust ports on the edelbrock heads are considerably smaller than stick which also influences exhaust flow rate and was tested to show
improvements across all rpm ranges.

Dennis

> Carl,
>
> It seems that the general consensus is the aluminum heads will work OK. When I read the installation instructions it noted that you
> had to match the ports in the head to the manifold.
>
> New thought: since the heads are designed for a higher RPM range than we normally run I wonder if installing a Cloyes cam gear
> advanced 4? would help with the low RPM torque?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
> USA '77 Kingsley - TZE 267V100808
>
>
> -----Original Message-----
> From: Gmclist [mailto:gmclist-bounces] On Behalf Of Carl Stouffer
> Sent: Monday, July 31, 2017 3:42 AM
> To: gmclist
> Subject: Re: [GMCnet] Looking for Opinions on Aluminum Heads
>
> There are literally millions of cast steel block/aluminum head engines coming from the OEMs, The Chevy LS truck engine comes to
> mind, and the Buickb300 had aluminum heads clear back in 1964. I have one of those LS engines in a truck with 194,000 miles on it
> and the only repair that it has ever needed was an O-ring on the oil pick-up. Evidently the head gasket issues have been resolved.
> I already have an aluminum (Gary Rockwell) intake manifold mated to the cast heads. I think that is a minor issue.
>
> I DO have a good head guy and Olds specific machine shop here in Tucson, Larry's Engine and Machine, who specializes in boat 455
> engines so I could go either way if need be. By the time I get another J head here and recondition the one I have, I will be
> getting up there in $$$. Albeit not as much as a set of These heads:
>
> http://www.ebay.com/itm/Speedmaster-PCE281-2152-Oldsmobile-400-425-455-Aluminum-Cylinder-Heads-188cc-7-/311859190878?_trksid=p238573
> 8.m2548.l4275
>
> My mechanic" son, admittedly a high performance guy, is extolling the Virtues of aluminum heads, so I'm trying to get enough
> information to make an intelligent decision. If Bob Drews and Dennis Sexton had good luck with them, that is a positive. The main
> negative seems to be increased runner velocity, potentially hurting the low end, but the 455 is a stump puller in whatever form.
>
> Continued discussion would be helpful.
> --
> Carl Stouffer
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Dennis S
73 Painted Desert 230
Memphis TN Metro

 

[CGeils]

Aluminum heads can be a benefit or a detriment depending on how the rest of the engine is built. All else being equal (chamber, port etc) the only
benefit to aluminum is the weight savings and relative availability. Aluminum dissipates heat of combustion faster so the head will be less knock
sensitive but also suffer about a 3% torque loss relative to cast iron. You should crank in a little more spark advance or build the engine with 1
additional point of compression to offset this loss when switching to aluminum.
With that said the aftermarket heads are subtly different in chamber shape and porting than our OE heads. The chamber shape will provide a slightly
faster burn resulting in a little less knock sensitivity, but the porting will be designed for a little higher rpm than is ideal for our application.
Keep the compression up to gain some torque back. You should be able to run 10:1 with aluminum heads vs 9:1 with a similar cast iron for the same
knock sensitivity. Cam selection is critical here. With an aluminum head and 10:1 CR I'd spec a cam with .450 lift and no more than about 215-220
degrees duration @ .050" lift. FYI 8:1 compression and a lot of duration is a formula for a bad running engine (torque loss all around). The other
downside to aluminum heads is less resistance to warpage. If you get the coolant much above 240F you will lose a head gasket due to head warpage.
Oldsmobiles are sensitive to cooling issues already so cooling system integrity is even more critical. The above combo should suffer little torque
loss but provide improved mid range (2500-4500) for passing and grade climbing power. I'd think this combo would work particularly well for those of
you running 3:42 or 3:70 final drives. Your results and opinions may very but this is how I intend to build my 403 within a few years.
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Chris Geils - Twin Cities
1978 26' Kingsley w/ very few mods; Headers, Progressive Dynamics 9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, 50k mi