2 newbie questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72DCT · 11-17-2006, 01:47 AM

To all seasoned owners,

Sorry in advance for the elementary questions but... I just got my dream, 72 Super, 350, two-tone and I was wondering:
1) what should the RPMs read when traveling at HWY speed (65-75mph)? I have been told about 2500. Does that sound right?
2) If the truck sits outside without starting for a day or two it takes a minute for the engine to turn over for the first time, after that it starts right up. I have been told "350s are just fussy." --not by the seller, I'm not that green.

The engine has 22,000 miles on the rebuild and about 55,000 prior to that. Thanks and more silly questions to follow as I find out what I don't know.

72 DCT

crazyred · 11-17-2006, 02:24 AM

First off BIG WELCOME from the north and you have come to the right place for help.
As for my help well im still too green to give you a good answer !!!
But for my truck i put a fillter in with a little check ball inside to stop the fuel in the carb from running back to the tank. It seem to work for me day to day. But if i let the truck sit for a week well im back to hard starting

Bad71chev406sbc · 11-17-2006, 02:39 AM

1) Rpms all depend on......what trans?? What gear ratio?? What tire size?? My chevy, with a 4spd manual, 3.73s, and 275/60r15s....60 mph(at least that's what my speedo said) was about 3000rpm.

2) Every old chevy i've owned, has done this. After a couple days of sitting, nice long hard crank to start. this happens when the fuel decides to head back to the tank, plus...this also happens when the carburator's float bowl(where the fuel is before it actually enters your engine) gets dry....the fuel evaporates. But.....that choke should help out, feed some fuel back in the system. I like to keep a jumper-pak in the truck with me at all times. Nice when the truck is being stubborn. Another cause of this problem is proper engine timing. too far advance, was my problem.

Werewolf · 11-17-2006, 07:12 AM

Rochester carbs sometimes develop leaks in the fuel wells under the jets. Generally, though, that would lead to hard starting when the truck is warm because too much fuel is getting into the engine. If the leak is minor, after a day or two, it would empty the float bowl and cause the truck to take a bit to start.

You could also check the choke operation when the truck is cold, make sure it closes. In any event, you should have to pump the truck once to the floor to prime the engine and set the choke every time you start it cold.

And yes, RPMs depend on rear gears and transmission. I had a '67 C20 with 4.56 factory rear gears, and despite having a new TH-700 in the truck, complete with lockup converter kit, the truck still turned 3k at 50mph. Pushed 5k at 80. That poor 283.

**Already Gone** · 11-17-2006, 10:44 AM

Quote:

Originally Posted by 72DCT

To all seasoned owners,

Sorry in advance for the elementary questions but... I just got my dream, 72 Super, 350, two-tone and I was wondering:
1) what should the RPMs read when traveling at HWY speed (65-75mph)? I have been told about 2500. Does that sound right?
2) If the truck sits outside without starting for a day or two it takes a minute for the engine to turn over for the first time, after that it starts right up. I have been told "350s are just fussy." --not by the seller, I'm not that green.

The engine has 22,000 miles on the rebuild and about 55,000 prior to that. Thanks and more silly questions to follow as I find out what I don't know.

72 DCT

Welcome to the board and remember no question is stupid. I see lots of threads where veteran board members (including myself) have learned somthing new. Does your truck have the factory tach or an add-on one? It would nice to see some pics of your truck too. On your question about the Highway RPMS I'd need a little more info like is the trans automatic or manual and what rear end ratio you have as well as tire size.. Asuuming you are running a 3 speed automatic and have 3:73 rear gears( like most of these trucks came with) your rpms at 60MPH should be around 2900RPMs..

krue · 11-17-2006, 02:46 PM

Welcome to the board from South Mississippi!

72DCT · 11-17-2006, 03:14 PM

Thanks for the quick responses. I'll try to attached some photos next time. The answers to some of your questions that will help answer my RPM question... 3 speed, auto trans, factory tac, tire size 235/75/15. I do not know the rear gear ratio. How do I find it? Thanks again.

72DCT · 11-17-2006, 03:22 PM

here are some photos

**Already Gone** · 11-17-2006, 03:36 PM

Nice truck, in fact great looking truck with Cheyenne Package and Factory A/C with the factory tach. Someone will correct me if I'm wrong but I do believe the standard rear end ration for your truck is 3:73 and if its different it will show on the data label on the inside of the glove compartment door. If your ratio is 3:73 you should be turning around 2900 at 60MPH with the 235/75R15 tires.

72DCT · 11-18-2006, 09:45 PM

Thanks. I did more research and you are correct. It is 3:73.
DCT 72

Longhorn Man · 11-19-2006, 12:57 AM

actually, it should be 3.07 onless otherwise optioned.
Small block and auto got a 3.07 on 1/2 tons standard.

Texasdeere · 11-19-2006, 01:24 AM

Wow! That is a great find! Beautiful original looking truck.

Rick Mills · 11-19-2006, 01:35 AM

Nice truck. Welcome to the board from Colorado.

11-17-2006, 01:47 AM	#1
72DCT Registered User Join Date: Nov 2006 Location: OK Posts: 4	2 newbie questions To all seasoned owners, Sorry in advance for the elementary questions but... I just got my dream, 72 Super, 350, two-tone and I was wondering: 1) what should the RPMs read when traveling at HWY speed (65-75mph)? I have been told about 2500. Does that sound right? 2) If the truck sits outside without starting for a day or two it takes a minute for the engine to turn over for the first time, after that it starts right up. I have been told "350s are just fussy." --not by the seller, I'm not that green. The engine has 22,000 miles on the rebuild and about 55,000 prior to that. Thanks and more silly questions to follow as I find out what I don't know. 72 DCT

11-17-2006, 02:24 AM	#2
crazyred yeeha Join Date: Sep 2005 Location: Sherwood Park & Fort McMurray, Alberta Posts: 72	Re: 2 newbie questions First off BIG WELCOME from the north and you have come to the right place for help. As for my help well im still too green to give you a good answer !!! But for my truck i put a fillter in with a little check ball inside to stop the fuel in the carb from running back to the tank. It seem to work for me day to day. But if i let the truck sit for a week well im back to hard starting __________________ 1969 GMC 910 97% rust free 2002 olds Alero 1986 New Yorker 4dr ... the new DD...My POS car... dude its got a turbo!!! Don't drink and drive, you might spill something!!! Daryl Kuchmak

11-17-2006, 02:39 AM	#3
Bad71chev406sbc Registered User Join Date: Nov 2006 Location: Boring, Oregon Posts: 162	Re: 2 newbie questions 1) Rpms all depend on......what trans?? What gear ratio?? What tire size?? My chevy, with a 4spd manual, 3.73s, and 275/60r15s....60 mph(at least that's what my speedo said) was about 3000rpm. 2) Every old chevy i've owned, has done this. After a couple days of sitting, nice long hard crank to start. this happens when the fuel decides to head back to the tank, plus...this also happens when the carburator's float bowl(where the fuel is before it actually enters your engine) gets dry....the fuel evaporates. But.....that choke should help out, feed some fuel back in the system. I like to keep a jumper-pak in the truck with me at all times. Nice when the truck is being stubborn. Another cause of this problem is proper engine timing. too far advance, was my problem. __________________ '71 SNB, 406sbc, TH350 w/ Transpak & Starshifter, 12bolt w/ 3.73s, 2" Early Classic front coils, 2.5" Flowmaster Super 40's

11-17-2006, 07:12 AM	#4
Werewolf Woof? Join Date: Jun 2005 Location: Raleigh, NC Posts: 276	Re: 2 newbie questions Rochester carbs sometimes develop leaks in the fuel wells under the jets. Generally, though, that would lead to hard starting when the truck is warm because too much fuel is getting into the engine. If the leak is minor, after a day or two, it would empty the float bowl and cause the truck to take a bit to start. You could also check the choke operation when the truck is cold, make sure it closes. In any event, you should have to pump the truck once to the floor to prime the engine and set the choke every time you start it cold. And yes, RPMs depend on rear gears and transmission. I had a '67 C20 with 4.56 factory rear gears, and despite having a new TH-700 in the truck, complete with lockup converter kit, the truck still turned 3k at 50mph. Pushed 5k at 80. That poor 283. __________________ 1968 LWB CST BB 2004 Avalanche Z71 LT3. 2003 S-10 ZR2 (hers). 1997 Astro 1992 Caprice wagon, 500k stock miles. Nursing wounds after a bad wreck. 1997 Saturn - need gas mileage from something! Last edited by Werewolf; 11-17-2006 at 07:13 AM.

11-17-2006, 02:46 PM	#6
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: 2 newbie questions Welcome to the board from South Mississippi! __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

11-17-2006, 03:14 PM	#7
72DCT Registered User Join Date: Nov 2006 Location: OK Posts: 4	Re: 2 newbie questions Thanks for the quick responses. I'll try to attached some photos next time. The answers to some of your questions that will help answer my RPM question... 3 speed, auto trans, factory tac, tire size 235/75/15. I do not know the rear gear ratio. How do I find it? Thanks again. Last edited by 72DCT; 11-17-2006 at 03:16 PM. Reason: photos didn't attach

11-17-2006, 03:22 PM	#8
72DCT Registered User Join Date: Nov 2006 Location: OK Posts: 4	Re: 2 newbie questions here are some photos Attached Images

11-17-2006, 03:36 PM	#9
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,119	Re: 2 newbie questions Nice truck, in fact great looking truck with Cheyenne Package and Factory A/C with the factory tach. Someone will correct me if I'm wrong but I do believe the standard rear end ration for your truck is 3:73 and if its different it will show on the data label on the inside of the glove compartment door. If your ratio is 3:73 you should be turning around 2900 at 60MPH with the 235/75R15 tires. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

11-18-2006, 09:45 PM	#10
72DCT Registered User Join Date: Nov 2006 Location: OK Posts: 4	Re: 2 newbie questions Thanks. I did more research and you are correct. It is 3:73. DCT 72

11-19-2006, 12:57 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 2 newbie questions actually, it should be 3.07 onless otherwise optioned. Small block and auto got a 3.07 on 1/2 tons standard.

11-19-2006, 01:24 AM	#12
Texasdeere Registered User Join Date: Sep 2006 Location: League City, Texas Posts: 732	Re: 2 newbie questions Wow! That is a great find! Beautiful original looking truck.

11-19-2006, 01:35 AM	#13
Rick Mills Senior Member Join Date: Dec 2003 Location: Colorado Posts: 351	Re: 2 newbie questions Nice truck. Welcome to the board from Colorado. __________________ The Fastor Pastor '68 swb, 447 BBC/ 6-71 Weiand, Dual 950 Bigs Carbs/ 2 1/2" Header tubes - 4" collectors/ M-21 4speed: '70 swb; TH-400 - bagged & shaved. Looking for new engine or parts. Wife - Original {A Real Classic!}



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