Cinnabar 3.42 vs Caspro 3.55 or EFI?

[dave1]

>> I have the 3.07 and can spin the tires.
>> I don't think I need much more torque...
> ...But at 10,000' altitude nothing chirps. Also, when driving into a
>steady 50mph headwind (not uncommon hereabouts), at 5 - 6,000'
>altitude (what we consider flatlands), I'm either into the
>secondaries (~ 5 mpg) in third gear, or racing in second gear.
>Need something in between.

You may want to consider the Howell EFI system. It is closed loop and
altitude compensated so it adjusts the mixture based on driving conditions.
Also the TBI can pass a lot of air - noticeable increase in torque. But the
best part is how well the 455 starts and runs. Hot or cold, it starts right
up and runs flawlessly. When I started having carb problems I went back and
forth, trying to decide if the EFI was worth the $1200 cost. After running
it for a couple years I am very happy with the results. I would bet that it
would help a lot with altitude related performance problems. Something to
consider anyway...

Dave,
73 Sequoia

 

[bartz paul]

Dave:

Are you sure about "...the TBI can pass a lot of air - noticeable increase
in torque."??? Do you have any before and after torque data??

During the GMCMI Myrtle Beach Convention, Dick Paterson during one of his
seminar's, said, I believe, that the QuadraJet carburetor has a flow rate of
either 650 or 750 CFM. I understood him to say that during maximum
acceleration of our coach's, it only uses about 300 to 350 CFM flow. If
anyone else was at the seminar, do I have the right context???

Paul Bartz

From: Dave [mailtoGMDGM]
Sent: Wednesday, June 02, 1999 12:43 PM
Subject: Re: GMC: Cinnabar 3.42 vs Caspro 3.55 or EFI?

I have the 3.07 and can spin the tires. I don't think I need much more
torque. But at 10,000' altitude nothing chirps. Also, when driving into a
steady 50 mph headwind (not uncommon hereabouts), at 5 - 6,000' altitude
(what we consider flatlands), I'm either into the secondaries (~ 5 mpg) in
third gear, or racing in second gear. Need something in between.

You may want to consider the Howell EFI system. It is closed loop and
altitude compensated so it adjusts the mixture based on driving conditions.

Also the TBI can pass a lot of air - noticeable increase in torque. But the
best part is how well the 455 starts and runs. Hot or cold, it starts right
up and runs flawlessly. When I started having carb problems I went back and
forth, trying to decide if the EFI was worth the $1200 cost. After running
it for a couple years I am very happy with the results. I would bet that it
would help a lot with altitude related performance problems. Something to
consider anyway...

 

[dave1]

>Are you sure about "...the TBI can pass a lot of air - noticeable increase
>in torque."??? Do you have any before and after torque data??

Only my subjective observations. I don't have dyno data.

>...the QuadraJet carburetor has a flow rate of
>either 650 or 750 CFM. I understood him to say that during maximum
>acceleration of our coach's, it only uses about 300 to 350 CFM flow....

I would guess the difference is related to the fact that EFI keeps the
mixture right at all flow rates. My experience with carbs is that the
mixture is all over the map depending on temperature, altitude, load,
speed, throttle position etc.

Maybe a properly adjusted carb will perform as well as EFI. But it seems
that these carbs need a lot of attention to stay properly adjusted over
time. And changes in operating conditions (such as fuel and altitude) may
also require carb adjustments. The main thing I like about the EFI system
is that it is closed loop. It stays adjusted even as operating conditions
change.

Dave
73 Sequoia