1970 Tiara with Toronado FWD Question about power train

The secondaries on your carburetor may not be opening . Rebending the throttle linkage may cure this problem if it exists. With the choke full open
look in the carburetor with the gas pedal to the floor are the secondaries open you will need to open the rear throttle plate to see the rear
butterflies. Engine off of course. Also your distributor advance may need to be recurved or cleaned and the weights lubed also it should be set at
about 10 dog initial . If you are interested in a lower final drive gearing call Jim k at applied he supplies various gear ratios for your rig.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Any and all of the previous suggestions need to be checked. Also, did you manually shift down to second @ 45 mph? The throttle linkage under the dash
could be bent not allowing full throttle.
The stock differential ratio is 307:1. There are various other ratios available that can increase performance on the climbs and the flats.
--
Patti & Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
77 Palm Beach - Parts Coach
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.
 
Compression alone doesn't dictate the health of the motor. Ignition makes a huge difference in how it runs as well as fuel (carb) or lack of same as
in restricted fuel supply which could be any number of things. You also could have a gear ratio that's not RV friendly such as a 2.73. You'll just
have to do a bit of research to figure it out. Good luck, Hal
--
1977 Royale 101348,

1977 Royale 101586, Diesel powered,

1975 Eleganza II, 101230,

1974 Eagle Bus 45',w/slideout,

Rio Rancho, NM
 
> I have a 1970 Ultravan Tiara. It uses the same Toronado drive train that the GMC motorhomes use. My mechanic tells me the engine is in good
> shape. The low cylinder shows 145 and the high cylinder shows 154 in a recent compression check. My rig weighs 8,000 lbs which is heavy for a
> Tiara. They were delivered at 6,500 lbs.
>
> I understand the 23 foot GMC motor home weighs 10,000 lbs and the 26 footer 12,000 lbs give or take a few lbs.
>
> I recently crawled over the Cascades on Washington Hwy 20 east and was routinely down to 20 mph with the vacuum gauge in the deep red. If my rig
> weighed 12,000 lbs I am pretty sure I would still be on the other side of the Cascades.
>
> Can anyone give me some recommendations or some threads to pull on improving my rigs climbing performance? (I don't have a problem doing 70 on
> the flat but usually keep it at 65 or below).
>
> Regards,
>
> Rick Daley

Rick,

The Ultravans that I have seen that were 455 were all fit with power directly removed from a Toronado. Most of the standard package had a 2.73 final
drive, but the 3.07 (what was shipped in TZE) was from the trailer tow package, and it was wrong for the TZE that day. There are better available
now.

We have a 9460# 23' coach, and we crossed the Big Horn (the GPS reported 9200msl) on the way to Yellowstone with out any real issues. I expect any
naturally aspirated engine to have not put out full power over 8000MSL.

I fully agree that you may not be getting the secondaries open. When we open ours, the racket is unmistakable. If the carburetor is still the stock
Rochester, then the secondaries are mechanical link. You can have someone step on the throttle and see if they do open fully. (The actual throttle,
not the air valve.) If not, fix that before you do anything else.

If you ever have to do engine work, we have people that can provide some important guidance.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
downshifting and keeping a little more rpm's.

I would believe you have some performance issue with your engine. making sure carb is working properly is one thing, the next is to make sure the
distributor is working properly. 20MPH is pretty slow.

the motorhomes have a ratio of 3.07 for stock coaches. Many drop to a lower gear ratio for the best in mountain climbing, and towing. But there are
plenty of 3.07 GMC motorhome gears that people climb mountians doing 40MPH in 2nd gear.


--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jim Kanomata in Newark, CA has replacement final drive units as low as
4.10:1.

https://www.gmcrvparts.com/category-s/149.htm

Applied GMC -
38424 Cedar Blvd Newark, CA 94560
Phone: 800-752-7502
Email: mail

RonC

On Mon, 01 Jul 2019 12:09:54 -0600 Matt Colie via Gmclist

> > I have a 1970 Ultravan Tiara. It uses the same Toronado drive
> train that the GMC motorhomes use. My mechanic tells me the engine
> is in good
> > shape. The low cylinder shows 145 and the high cylinder shows 154
> in a recent compression check. My rig weighs 8,000 lbs which is
> heavy for a
> > Tiara. They were delivered at 6,500 lbs.
> >
> > I understand the 23 foot GMC motor home weighs 10,000 lbs and the
> 26 footer 12,000 lbs give or take a few lbs.
> >
> > I recently crawled over the Cascades on Washington Hwy 20 east and
> was routinely down to 20 mph with the vacuum gauge in the deep red.
> If my rig
> > weighed 12,000 lbs I am pretty sure I would still be on the other
> side of the Cascades.
> >
> > Can anyone give me some recommendations or some threads to pull on
> improving my rigs climbing performance? (I don't have a problem
> doing 70 on
> > the flat but usually keep it at 65 or below).
> >
> > Regards,
> >
> > Rick Daley
>
> Rick,
>
> The Ultravans that I have seen that were 455 were all fit with power
> directly removed from a Toronado. Most of the standard package had
> a 2.73 final
> drive, but the 3.07 (what was shipped in TZE) was from the trailer
> tow package, and it was wrong for the TZE that day. There are
> better available
> now.
>
> We have a 9460# 23' coach, and we crossed the Big Horn (the GPS
> reported 9200msl) on the way to Yellowstone with out any real
> issues. I expect any
> naturally aspirated engine to have not put out full power over
> 8000MSL.
>
> I fully agree that you may not be getting the secondaries open.
> When we open ours, the racket is unmistakable. If the carburetor is
> still the stock
> Rochester, then the secondaries are mechanical link. You can have
> someone step on the throttle and see if they do open fully. (The
> actual throttle,
> not the air valve.) If not, fix that before you do anything else.
>
> If you ever have to do engine work, we have people that can provide
> some important guidance.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

Ron & Linda Clark
North Plains, ORYGUN
1978 Eleganza II
 
> What is the most common gear ratio found on the GMC Motorhome? Is it something other than what the Toronado came with?

Rick,

The common ratio in a Toronado was 2.73. There was a towing package that included a 3.07. That is even wrong for my 23' at 9460. If I can get to
it, I will change mine to a 3.55. JimK sells as high as 4.10.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Before I went off looking at different differential ratios, etc. I would be checking things like carb back barrels not opening or vacuum or mechanical
advance not working.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Thanks Matt. Frequently when I put the pedal to the floor going up a steep slope at a slow speed, I get a back fire. I suspect that is abnormal
> for a Rochester. As to whether the secondaries open, I don't know but there doesn't seem to be any significant increase in noise - except for the
> backfire.
>
> I am on my way to Yellowstone. I have been there before in this rig - came in from the east and left out the west side. I had no idea at the
> time that the elevation was nearly 8,000 feet. I weigh an additional 1,500 lbs now but I don't think that means anything more than I will be moving
> even slower than before.

Rick,

The backfire is not normal. You should be able to pull that. Given the year and driveline, the timing would be a definite question. It should do
that if we did.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Pull the distributor cap and check the advance weights and springs. Also,
vacuum hoses to the vacuum advance on the distributor.
Jim Hupy
Salem, Oregon

On Tue, Jul 2, 2019, 5:27 PM Matt Colie via Gmclist
wrote:

> > Thanks Matt. Frequently when I put the pedal to the floor going up a
> steep slope at a slow speed, I get a back fire. I suspect that is abnormal
> > for a Rochester. As to whether the secondaries open, I don't know but
> there doesn't seem to be any significant increase in noise - except for the
> > backfire.
> >
> > I am on my way to Yellowstone. I have been there before in this rig -
> came in from the east and left out the west side. I had no idea at the
> > time that the elevation was nearly 8,000 feet. I weigh an additional
> 1,500 lbs now but I don't think that means anything more than I will be
> moving
> > even slower than before.
>
> Rick,
>
> The backfire is not normal. You should be able to pull that. Given the
> year and driveline, the timing would be a definite question. It should do
> that if we did.
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
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