Author Topic: 1972 chevy c30  (Read 3845 times)

Offline jbh7052

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1972 chevy c30
« on: August 07, 2018, 06:35:12 PM »
Hey Mr. Ruggles!  Want to start with saying thanks for your help in the past. You, your kit and your book helped me fine tune a quad for a small block chevy in my jeep! Still running great! Now, I just purchased a standard kit from you and it will go on a stock 350 in a 1972 c30. Gear ratio is 4:10 and tire size is 235-85-16. I have a 1992 700R4 tranny. Any advice on initial setup of the carb? 7042210

Offline Cliff Ruggles

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Re: 1972 chevy c30
« Reply #1 on: August 08, 2018, 03:35:28 AM »
Set the float to factory specs, and make sure the power piston hanger arms are level and exactly even.  They used an APT system in the baseplate in that model so very important that the metering rods aren't hanging in the jets are different heights.

The 700-R4 will require a TV cable hook up.  Not sure if there is enough material far enough from center on that carb to make it happen.  You may need to add a piece to the linkage for correct geometry/operation of the cable......Cliff

Offline jbh7052

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Re: 1972 chevy c30
« Reply #2 on: August 08, 2018, 07:27:53 PM »
Thanks for the input sir! I have the tv system in place already before the carb rebuild. I will check everything you mentioned and am thankful for your advice. I will get it rebuilt this weekend and post results.

Offline jbh7052

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Re: 1972 chevy c30
« Reply #3 on: August 11, 2018, 06:04:53 AM »
I have the carb apart now and soaking in cleaner.  To gain access to the apt do I just take out the aluminum  plug in the base plate?

Offline 77cruiser

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Re: 1972 chevy c30
« Reply #4 on: August 11, 2018, 06:19:57 AM »
Yes. Then you may have to use some heat to get the screw to turn.
Jim

Offline jbh7052

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Re: 1972 chevy c30
« Reply #5 on: August 11, 2018, 08:02:47 AM »
Thanks 77cruiser!

Offline jbh7052

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Re: 1972 chevy c30
« Reply #6 on: August 16, 2018, 07:02:00 AM »
Got the Transmission done and back in the 72! Carb rebuilt with cliffs kit. Started and idled first thing! However I was unable to get the APT screw to break loose....maybe I am a little chicken to get mean with it. Anyway, after discovering the throttle cable was a 1 1/2 in short of full travel and got the tv cable adjusted for good line pressure to the fresh 700R4 I am on the road. Again this is a stock 350 in a 1972 C-30 with 4:10 gears so it aint no race car! truck weighs 5,500lbs so she is a little beefy! Seams to be a little sluggish for in town driving but it cruises at 70mph with minimal throttle! Timing is set to 8 deg before TDC with HEI dist and a vacuum advance attached to ported vacuum source front right of carb just above throttle plates. Do I understand Cliffs book correctly that the APT only helps with part throttle or cruise applications? The gas mileage in town  is hideous which I believe the APT will help with correct or will it only help with the steady throttle position?

Offline Cliff Ruggles

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Re: 1972 chevy c30
« Reply #7 on: August 16, 2018, 09:33:23 AM »
With a C-30 truck and 4.10 gears I wouldn't expect great fuel economy in the city for stop and start driving.  It still should be decent when everything is tuned correctly.

I owned a 1970 GMC 3/4 ton truck many years ago with a stock 350 and 4.10 gears.  I ran 7.50-16" tires on it.  The engine was rebuilt back to stock with a GM 350/300hp camshaft.  It did pretty good for fuel economy for what it was.  Averaged around 11-12mpg's and a little better at 14-15mpg's on the highway cruising around 65-70mph........Cliff

Offline jbh7052

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Re: 1972 chevy c30
« Reply #8 on: August 17, 2018, 04:15:16 AM »
Well sounds like I am not far off then! Thanks for the advice and another great rebuild! It has a little hot start issue. I am gonna bump the float down a little off the factory setting  and see if it improves. Thanks again!

Offline Cliff Ruggles

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Re: 1972 chevy c30
« Reply #9 on: August 17, 2018, 05:19:15 AM »
I'd set the float at 1/4" and look elsewhere for the hot start issues......Cliff

Offline jbh7052

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Re: 1972 chevy c30
« Reply #10 on: August 19, 2018, 10:29:09 AM »
Pulling the airborne off today and setting  the float level to 1/4.  Does a spacer help enough with heat transfer to help alleviate some of the hot start symptoms? If so what height? Anything other than a thin plate will render the divorced choke useless right?

Offline 77cruiser

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Re: 1972 chevy c30
« Reply #11 on: August 19, 2018, 02:26:43 PM »
It would help if it was plastic or wood. What is the fuel pressure?
Jim

Offline jbh7052

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Re: 1972 chevy c30
« Reply #12 on: August 19, 2018, 06:55:47 PM »
Not sure on fuel pressure. Factory style AC Delco pump. I will get a gauge and check that as well. Thanks for the help!

Offline Cliff Ruggles

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Re: 1972 chevy c30
« Reply #13 on: August 20, 2018, 03:46:48 AM »
The factory 1/4" thick gasket is plenty of insulation from the heat of the intake.  Spacers make using the divorced choke a lesson in humility and I doubt if that's what the issue is anyhow.

Did you pressure test the casting during the rebuild to make sure the bottom plugs aren't leaking?....Cliff

Offline jbh7052

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Re: 1972 chevy c30
« Reply #14 on: August 22, 2018, 11:25:57 AM »
No sir I did not pressure test. However I marine tex the locations illustrated in your book. Sorry for the delay in my response...came down with strep and didn't feel like wrenchen on it. I set the float to just over 1/4 in from top of casting and plan on checking fuel pressure this week. Funny thing is my other quadrjet that you helped me build for specifically for my jeep has the same hot start. I must  be doing the same thing wrong twice 🤔 Both are great starting and great running carbs. I will post what I find after fuel pressure test.