Good engine destroyed. Yours could be next.

[Bob Dunahugh]

I got a call from someone today. That severally damaged a real good running 455. That I built for him 2 years ago. That engine is now trash. When the engine was going in. I pleaded with him to put a GM/Howel EFI system in. His response was. " My carb works great. It's been working to perfection. The carb was rebuilt last year. By someone that knows them well." I should keep my mouth shut on this. As I could go on for days. Over engines. On ways to extend your engines service life. But I'm just sick of this happening. I now know of 4 good engines destroyed in this manner. In the last few years. Engines are my thing. I could post a lot on engines. But it's best that I not. I push GM engines way past their design paramotors. And don't destroy them.

Sorry. I digress. That stock Q jet has always been considered to be one of the finest carbs ever built. As to controlling the air/fuel ratios. Over its entire operating range.
The general though. Is that the carb dumps an air/fuel mixture into an open chamber. That's in the intake manifold. Well. Not really. The Q jet that came on the GMC. Are really two carbs in one aluminum casting. Thus. The left carb feeds 2 cylinders on each side of the engine. The right side feeds the other remaining 4 cylinders.
The problem is that if one side of the carb goes lean. And starts burning up its 4 cylinders. You'll have absolutely no idea of the in pending destruction. Till it's just too late. With the GM/Howell system. The engine check light will come on. To let you know of any issues. Then tell you what's wrong.
Engine service life before the mid 80's was under 100,000 miles. Then in the late 80's. EFI came along. Then service life more than doubled. Yes. Other things that helped. But EFI was the BIGGY. If you wish to talk on this issue. Contact me direct. Not on the net. Or 319-521=4891 Cell.
Bob Dunahugh
78 Royale since 2003

 

[jim kanomata1]

Bob,
So what did the carb do that trashed the engine???

> I got a call from someone today. That severally damaged a real good
> running 455. That I built for him 2 years ago. That engine is now trash.
> When the engine was going in. I pleaded with him to put a GM/Howel EFI
> system in. His response was. " My carb works great. It's been working to
> perfection. The carb was rebuilt last year. By someone that knows them
> well." I should keep my mouth shut on this. As I could go on for days.
> Over engines. On ways to extend your engines service life. But I'm just
> sick of this happening. I now know of 4 good engines destroyed in this
> manner. In the last few years. Engines are my thing. I could post a lot on
> engines. But it's best that I not. I push GM engines way past their design
> paramotors. And don't destroy them.
>
> Sorry. I digress. That stock Q jet has always been considered to be
> one of the finest carbs ever built. As to controlling the air/fuel ratios.
> Over its entire operating range.
> The general though. Is that the carb dumps an air/fuel mixture into
> an open chamber. That's in the intake manifold. Well. Not really. The Q
> jet that came on the GMC. Are really two carbs in one aluminum casting.
> Thus. The left carb feeds 2 cylinders on each side of the engine. The right
> side feeds the other remaining 4 cylinders.
> The problem is that if one side of the carb goes lean. And starts
> burning up its 4 cylinders. You'll have absolutely no idea of the in
> pending destruction. Till it's just too late. With the GM/Howell system.
> The engine check light will come on. To let you know of any issues. Then
> tell you what's wrong.
> Engine service life before the mid 80's was under 100,000 miles. Then
> in the late 80's. EFI came along. Then service life more than doubled.
> Yes. Other things that helped. But EFI was the BIGGY. If you wish to talk
> on this issue. Contact me direct. Not on the net. Or 319-521=4891 Cell.
> Bob Dunahugh
> 78 Royale since 2003
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502

 

[Jim Hupy]

The stock GMC intake manifold is a split flow design. One side (a Primary
and Secondary) of a quadrajet carb feeds 2 cylinders on each side of the
engine, and the other side (Primary and Secondary) of the quadrajet feeds
the remaining 4 cylinders (2 on each side) of the 455.
So, in a perfect world where the quadrajet is working as the factory
designed it to do, all 8 cylinders receive a correct amount of air/fuel
mixture.
BUT, when the quadrajet is NOT working as designed, (like happens
when well intentioned but uninformed tweakers mess with jets and needles in
an attempt to improve their fuel economy, for example), it is easy for 4
cylinders to go very lean, and toast the whole engine.
Jim Hupy
Salem, Oregon

> Bob,
> So what did the carb do that trashed the engine???
>

>
> > I got a call from someone today. That severally damaged a real good
> > running 455. That I built for him 2 years ago. That engine is now trash.
> > When the engine was going in. I pleaded with him to put a GM/Howel EFI
> > system in. His response was. " My carb works great. It's been working to
> > perfection. The carb was rebuilt last year. By someone that knows them
> > well." I should keep my mouth shut on this. As I could go on for days.
> > Over engines. On ways to extend your engines service life. But I'm just
> > sick of this happening. I now know of 4 good engines destroyed in this
> > manner. In the last few years. Engines are my thing. I could post a lot
> on
> > engines. But it's best that I not. I push GM engines way past their
> design
> > paramotors. And don't destroy them.
> >
> > Sorry. I digress. That stock Q jet has always been considered to be
> > one of the finest carbs ever built. As to controlling the air/fuel
> ratios.
> > Over its entire operating range.
> > The general though. Is that the carb dumps an air/fuel mixture into
> > an open chamber. That's in the intake manifold. Well. Not really. The Q
> > jet that came on the GMC. Are really two carbs in one aluminum casting.
> > Thus. The left carb feeds 2 cylinders on each side of the engine. The
> right
> > side feeds the other remaining 4 cylinders.
> > The problem is that if one side of the carb goes lean. And starts
> > burning up its 4 cylinders. You'll have absolutely no idea of the in
> > pending destruction. Till it's just too late. With the GM/Howell system.
> > The engine check light will come on. To let you know of any issues. Then
> > tell you what's wrong.
> > Engine service life before the mid 80's was under 100,000 miles. Then
> > in the late 80's. EFI came along. Then service life more than doubled.
> > Yes. Other things that helped. But EFI was the BIGGY. If you wish to
> talk
> > on this issue. Contact me direct. Not on the net. Or 319-521=4891 Cell.
> > Bob Dunahugh
> > 78 Royale since 2003
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[zandr milewski]

So, given that failure mode, does the Howell have two O2 sensors, one
per bank?

> The stock GMC intake manifold is a split flow design. One side (a Primary
> and Secondary) of a quadrajet carb feeds 2 cylinders on each side of the
> engine, and the other side (Primary and Secondary) of the quadrajet feeds
> the remaining 4 cylinders (2 on each side) of the 455.
> So, in a perfect world where the quadrajet is working as the factory
> designed it to do, all 8 cylinders receive a correct amount of air/fuel
> mixture.
> BUT, when the quadrajet is NOT working as designed, (like happens
> when well intentioned but uninformed tweakers mess with jets and needles in
> an attempt to improve their fuel economy, for example), it is easy for 4
> cylinders to go very lean, and toast the whole engine.
> Jim Hupy
> Salem, Oregon
>
>

>
>> Bob,
>> So what did the carb do that trashed the engine???
>>

>>
>>> I got a call from someone today. That severally damaged a real good
>>> running 455. That I built for him 2 years ago. That engine is now trash.
>>> When the engine was going in. I pleaded with him to put a GM/Howel EFI
>>> system in. His response was. " My carb works great. It's been working to
>>> perfection. The carb was rebuilt last year. By someone that knows them
>>> well." I should keep my mouth shut on this. As I could go on for days.
>>> Over engines. On ways to extend your engines service life. But I'm just
>>> sick of this happening. I now know of 4 good engines destroyed in this
>>> manner. In the last few years. Engines are my thing. I could post a lot
>> on
>>> engines. But it's best that I not. I push GM engines way past their
>> design
>>> paramotors. And don't destroy them.
>>>
>>> Sorry. I digress. That stock Q jet has always been considered to be
>>> one of the finest carbs ever built. As to controlling the air/fuel
>> ratios.
>>> Over its entire operating range.
>>> The general though. Is that the carb dumps an air/fuel mixture into
>>> an open chamber. That's in the intake manifold. Well. Not really. The Q
>>> jet that came on the GMC. Are really two carbs in one aluminum casting.
>>> Thus. The left carb feeds 2 cylinders on each side of the engine. The
>> right
>>> side feeds the other remaining 4 cylinders.
>>> The problem is that if one side of the carb goes lean. And starts
>>> burning up its 4 cylinders. You'll have absolutely no idea of the in
>>> pending destruction. Till it's just too late. With the GM/Howell system.
>>> The engine check light will come on. To let you know of any issues. Then
>>> tell you what's wrong.
>>> Engine service life before the mid 80's was under 100,000 miles. Then
>>> in the late 80's. EFI came along. Then service life more than doubled.
>>> Yes. Other things that helped. But EFI was the BIGGY. If you wish to
>> talk
>>> on this issue. Contact me direct. Not on the net. Or 319-521=4891 Cell.
>>> Bob Dunahugh
>>> 78 Royale since 2003
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>>
>>
>>
>> --
>> Jim Kanomata
>> Applied/GMC, Newark,CA
>> jimk
>> http://www.gmcrvparts.com
>> 1-800-752-7502
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[Jim Hupy]

The Howell comes with one 02 Sensor. But it also comes with the EBL that
opens up a whole new world of tuning possibilities. While nothing is the
Ideal setup, and the intake manifold has a block off plate to allow the 2
barrel Howell throttle body to adapt to the quadrajet 4 barrel intake
manifold is not ideal either.
A whole new plenum type manifold that only had to flow air, with
individual port injectors would seem at first glance to be the real "Cats
Meow" for fuel injection. But, if one or more injectors fail to meter
correctly, they can and do cook individual cylinders. There is plenty of
examples of that happening, too.
As is often said "Taint nuthin' perfect". Same is true with any
mechanical device. STUFF HAPPENS.
Jim Hupy
Salem, Oregon

> So, given that failure mode, does the Howell have two O2 sensors, one
> per bank?
>

> > The stock GMC intake manifold is a split flow design. One side (a Primary
> > and Secondary) of a quadrajet carb feeds 2 cylinders on each side of the
> > engine, and the other side (Primary and Secondary) of the quadrajet feeds
> > the remaining 4 cylinders (2 on each side) of the 455.
> > So, in a perfect world where the quadrajet is working as the
> factory
> > designed it to do, all 8 cylinders receive a correct amount of air/fuel
> > mixture.
> > BUT, when the quadrajet is NOT working as designed, (like happens
> > when well intentioned but uninformed tweakers mess with jets and needles
> in
> > an attempt to improve their fuel economy, for example), it is easy for 4
> > cylinders to go very lean, and toast the whole engine.
> > Jim Hupy
> > Salem, Oregon
> >
> >

> >
> >> Bob,
> >> So what did the carb do that trashed the engine???
> >>
> >> On Sat, May 8, 2021 at 7:44 AM Bob Dunahugh

> >>
> >>> I got a call from someone today. That severally damaged a real good
> >>> running 455. That I built for him 2 years ago. That engine is now
> trash.
> >>> When the engine was going in. I pleaded with him to put a GM/Howel EFI
> >>> system in. His response was. " My carb works great. It's been working
> to
> >>> perfection. The carb was rebuilt last year. By someone that knows them
> >>> well." I should keep my mouth shut on this. As I could go on for days.
> >>> Over engines. On ways to extend your engines service life. But I'm just
> >>> sick of this happening. I now know of 4 good engines destroyed in this
> >>> manner. In the last few years. Engines are my thing. I could post a
> lot
> >> on
> >>> engines. But it's best that I not. I push GM engines way past their
> >> design
> >>> paramotors. And don't destroy them.
> >>>
> >>> Sorry. I digress. That stock Q jet has always been considered
> to be
> >>> one of the finest carbs ever built. As to controlling the air/fuel
> >> ratios.
> >>> Over its entire operating range.
> >>> The general though. Is that the carb dumps an air/fuel mixture
> into
> >>> an open chamber. That's in the intake manifold. Well. Not really.
> The Q
> >>> jet that came on the GMC. Are really two carbs in one aluminum casting.
> >>> Thus. The left carb feeds 2 cylinders on each side of the engine. The
> >> right
> >>> side feeds the other remaining 4 cylinders.
> >>> The problem is that if one side of the carb goes lean. And starts
> >>> burning up its 4 cylinders. You'll have absolutely no idea of the in
> >>> pending destruction. Till it's just too late. With the GM/Howell
> system.
> >>> The engine check light will come on. To let you know of any issues.
> Then
> >>> tell you what's wrong.
> >>> Engine service life before the mid 80's was under 100,000 miles.
> Then
> >>> in the late 80's. EFI came along. Then service life more than doubled.
> >>> Yes. Other things that helped. But EFI was the BIGGY. If you wish to
> >> talk
> >>> on this issue. Contact me direct. Not on the net. Or 319-521=4891 Cell.
> >>> Bob Dunahugh
> >>> 78 Royale since 2003
> >>>
> >>> _______________________________________________
> >>> GMCnet mailing list
> >>> Unsubscribe or Change List Options:
> >>>
> >>
> >>
> >> --
> >> Jim Kanomata
> >> Applied/GMC, Newark,CA
> >> jimk
> >> http://www.gmcrvparts.com
> >> 1-800-752-7502
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >>
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[78gmcroyale]

I'm one of the unfortunate ones who lost a great rebuilt 403 after only 5,0=
00 miles.=C2=A0 Q-Jet which was rebuilt by an expert several years earlier =
malfunctioned, took the A/F ratio to 19!=C2=A0 Burned a huge hole in #8 pis=
ton.=C2=A0 I had another engine rebuilt and decided to have it dyno'd, that=
's when they discovered the bad carb.=C2=A0 If I wouldn't have had it dyno'=
d, I'd have put the carb on the new engine and probably smoked another one.=
=C2=A0 Instead I put on a Holley Sniper Quadrajet EFI system along with the=
matching Holley Hyperspark Distributor/Ignition system.=C2=A0 =C2=A0Engine=
runs absolutely awesome.=C2=A0Sent from my U.S.Cellular=C2=A9 Smartphone=
-------- Original message --------From: Bob Dunahugh Date: 5/8/21 9:44 AM (GMT-06:00) To: gmclist Subject:=
[GMCnet] Good engine destroyed. Yours could be next. =C2=A0=C2=A0 I got a =
call from someone today. That severally damaged a real good running 455.=
=C2=A0 That I built for him 2 years ago. That engine is now trash. When the=
engine was going in. I pleaded with him to put a GM/Howel EFI system in. H=
is response was. " My carb works great. It's been working to perfection. Th=
e carb was rebuilt last year. By someone that knows them well." I should ke=
ep my mouth shut on this.=C2=A0 As I could go on for days. Over engines. On=
ways to extend your engines service life. But I'm just sick of this happen=
ing. I now know of 4 good engines destroyed in this manner.=C2=A0 In the la=
st few years. Engines are my thing. I could post a lot on engines. But it's=
best that I not. I push GM engines way past their design paramotors. And d=
on't destroy them.=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Sorry. I digress. That sto=
ck Q jet has always been considered to be one of the finest carbs ever buil=
t. As to controlling the air/fuel ratios. Over its entire operating range.=
=C2=A0=C2=A0=C2=A0=C2=A0 The general though. Is that the carb dumps an air/=
fuel mixture into an open chamber. That's in the intake manifold.=C2=A0 Wel=
l. Not really.=C2=A0 The Q jet that came on the GMC. Are really two carbs i=
n one aluminum casting. Thus. The left carb feeds 2 cylinders on each side =
of the engine. The right side feeds the other remaining 4 cylinders.=C2=
=A0 The problem is that if one side of the carb goes lean. And starts burni=
ng up its 4 cylinders. You'll have absolutely no idea of the in pending des=
truction. Till it's just too late. With the GM/Howell system. The engine ch=
eck light will come on. To let you know of any issues. Then tell you what's=
wrong.=C2=A0=C2=A0 Engine service life before the mid 80's was under 100,0=
00 miles. Then in the late 80's. EFI came along.=C2=A0 Then service life mo=
re than doubled. Yes. Other things that helped.=C2=A0 But EFI was the BIGGY=
.=C2=A0 If you wish to talk on this issue. Contact me direct. Not on the ne=
t. Or 319-521 4891 Cell.Bob Dunahugh78 Royale since 2003_________________=
______________________________GMCnet mailing listUnsubscribe or Change List=
Options:

 

[trevor pordage]

My throttle body system has one O2 sensor on the left hand side. I assume from the info above that each injector feeds 2 cylinders on each side so
therefore we only need to monitor the O2 on one bank to gauge the ratio of fuel.
--
Trevor
Brisbane Australia
Siesta Koala 76 Edgemont (old Bobby Moores)
71 Cadillac Eldo Convert
58 Cadillac Eldorado Brougham Project

 

[johnny]

My coach has an Atomic MSD fitted (It was a California coach), and has 2 O2 sensors. Left bank feeds the MSD, right bank feeds gauge. It has many
modes, I leave in in ratio mode. If I ever saw it go over 15 - 1 or so, I'd find out why (It hasn't).

--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