I have a problem with our 1975 Eleganza II that I hope the group can shed some light on. What kind of MPG would be considered normal? My first trip in a GMC, in 1977, from Los Angeles to Los Vegas and back, I got 10.1 MPG. That was with the stock engine, transmission, and the 3.07 gearing. It was very slow going back up the grade out of Los Vegas, but other than that, it was fine.
The 1975 Eleganza II has given us about 8.2 MPG on the last two rallies. We don't tow anything, we pack relatively lightly, I drive slowly.
----- Original Message -----
From: "James Hupy"
To: "gmclist"
Sent: Monday, June 26, 2017 8:01:32 AM
Subject: Re: [GMCnet] I have a quiet fan that runs when needed.
There is such a HUGE DIFFERENCE in performance of individual clutches with
the SAME PART NUMBER MADE BY THE SAME MANUFACTURER, that I don't know how
reliable any comparison data is. I personally have replaced between 20 and
50 clutches over the last few years, and they all work just a bit
differently relative to cut in temperature, cut out temperature and lock up
percentages. Some roar, some, not so much. The coil springs that open and
close the viscous fluid valve inside the clutches are a sensitive and
delicate item. No two are exactly alike. When you alter the air flow over
them, you change the game completely. When you change 3 or 4 things at
once, all bets are off. I wish you well with your modifications. But I
don't hold out much hope based on the poor quality of fan clutches these
days. This is not being critical of your work at all. Only the production
parts involved.
If there exists a manually engaged clutch that will predictably drive
the fan at the correct CFM to quickly reduce coolant temps, and it could be
engaged and disengaged accurately, I would be very supportive of it.
But, nothing ticks me off more than fighting one of the current
clutches into place, only to have it not work as advertised. I always keep
at least 2 of them on hand. P.I.T.A.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
> Interesting. I'd be interested in this. I just redid the radiator and
> added a large transmission cooler to the front. According to the Digipanel,
> that
> combination is saving me 10-20 degrees, but it must have an ancillary
> effect on air flow, as my fan clutch is coming on significantly more than
> before. It really drives home the point that the fan clutch just isn't
> measuring what needs to be measured, as the fluid temps are better but
> clearly
> the air temp in the region of the fan clutch sensor is up.
> --
> Thanks,
> Jeremy Knezek
> 1976 Glenbrook
> Birmingham, AL
>
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The 1975 Eleganza II has given us about 8.2 MPG on the last two rallies. We don't tow anything, we pack relatively lightly, I drive slowly.
----- Original Message -----
From: "James Hupy"
To: "gmclist"
Sent: Monday, June 26, 2017 8:01:32 AM
Subject: Re: [GMCnet] I have a quiet fan that runs when needed.
There is such a HUGE DIFFERENCE in performance of individual clutches with
the SAME PART NUMBER MADE BY THE SAME MANUFACTURER, that I don't know how
reliable any comparison data is. I personally have replaced between 20 and
50 clutches over the last few years, and they all work just a bit
differently relative to cut in temperature, cut out temperature and lock up
percentages. Some roar, some, not so much. The coil springs that open and
close the viscous fluid valve inside the clutches are a sensitive and
delicate item. No two are exactly alike. When you alter the air flow over
them, you change the game completely. When you change 3 or 4 things at
once, all bets are off. I wish you well with your modifications. But I
don't hold out much hope based on the poor quality of fan clutches these
days. This is not being critical of your work at all. Only the production
parts involved.
If there exists a manually engaged clutch that will predictably drive
the fan at the correct CFM to quickly reduce coolant temps, and it could be
engaged and disengaged accurately, I would be very supportive of it.
But, nothing ticks me off more than fighting one of the current
clutches into place, only to have it not work as advertised. I always keep
at least 2 of them on hand. P.I.T.A.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
> Interesting. I'd be interested in this. I just redid the radiator and
> added a large transmission cooler to the front. According to the Digipanel,
> that
> combination is saving me 10-20 degrees, but it must have an ancillary
> effect on air flow, as my fan clutch is coming on significantly more than
> before. It really drives home the point that the fan clutch just isn't
> measuring what needs to be measured, as the fluid temps are better but
> clearly
> the air temp in the region of the fan clutch sensor is up.
> --
> Thanks,
> Jeremy Knezek
> 1976 Glenbrook
> Birmingham, AL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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