Question for the carb guys !!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**tkeduk8r** · 12-22-2002, 03:10 AM

what are the correct jet and metering rod sizes for a Rochester MV single barrel carb.... Ive got a 106 jet and a .073 rod... my prolem is only bout 13 mpg with the straight six (250) and 3.73 gear with 3 on tree... it runs and idles mint with 22 in/hg vaccuum... i looked up figures in my haynes and got .080 for the rod and 95 on the jet... something doesnt make sense... it also is a hard starter, both before and after the rebuild on the carb AND when i take the airhorn off the carb after sitting a night the fuel bowl is dry... any xperiences??? this is puzzling me.... thanks in advance for the help...
--mike

**tkeduk8r** · 12-22-2002, 03:13 AM

oh and ive also got good even compresion across all cylinders and uses little if any oil... just been on two rod trips with it in last few months and have logged over 5000 mi... and no fuel leaks i can see...
--mike

**tkeduk8r** · 12-23-2002, 01:06 PM

nobody out there has a clue.. i cant believe that.... ttt
--mike

**COBALT** · 12-23-2002, 06:20 PM

...not a lot of people have a monojet, or have the numbers in their heads. I had problems when I was working on my 2GV.

What did the rebuild kit tell you for the specifications? My specs came with the kit, and it was only a matter of making sure they matched.

Aside from that the fact that your bowl dries up at night tells me you have a gasket that isn't sealing under the airhorn. Have you checked for vaccuum leaks when the engine is running?

**tkeduk8r** · 12-24-2002, 12:37 AM

yup.. checked for vac leaks and im good to go... i get steady 22 hg on the gauge with out any vibration and ive disconneted each vac source and plugeged to try to systemativcally eliminate and leaking legs...i put the jet and metering rod in out of the rebuild kit, but according to a spec inthe haynes i should have a .080 and the rod out of the kit is a .073... and i cant find a spec for the jet but there is quite a bit of slop when the rod is placed in the jet... i ordered another carb kit with teh carb part number off of it (last time i just used the model and make of p/u and rochester mv for manual trans) to double check myself... and your right the only places it could leak would be the jet, the small oriface next to the jet or the gasket, but i havnt noticed any leaks at all... any other suggestions????
--mike

12-22-2002, 03:10 AM	#1
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	Question for the carb guys !!! what are the correct jet and metering rod sizes for a Rochester MV single barrel carb.... Ive got a 106 jet and a .073 rod... my prolem is only bout 13 mpg with the straight six (250) and 3.73 gear with 3 on tree... it runs and idles mint with 22 in/hg vaccuum... i looked up figures in my haynes and got .080 for the rod and 95 on the jet... something doesnt make sense... it also is a hard starter, both before and after the rebuild on the carb AND when i take the airhorn off the carb after sitting a night the fuel bowl is dry... any xperiences??? this is puzzling me.... thanks in advance for the help... --mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

12-22-2002, 03:13 AM	#2
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	oh and ive also got good even compresion across all cylinders and uses little if any oil... just been on two rod trips with it in last few months and have logged over 5000 mi... and no fuel leaks i can see... --mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

12-23-2002, 01:06 PM	#3
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	nobody out there has a clue.. i cant believe that.... ttt --mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

12-23-2002, 06:20 PM	#4
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	...not a lot of people have a monojet, or have the numbers in their heads. I had problems when I was working on my 2GV. What did the rebuild kit tell you for the specifications? My specs came with the kit, and it was only a matter of making sure they matched. Aside from that the fact that your bowl dries up at night tells me you have a gasket that isn't sealing under the airhorn. Have you checked for vaccuum leaks when the engine is running? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

12-24-2002, 12:37 AM	#5
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	yup.. checked for vac leaks and im good to go... i get steady 22 hg on the gauge with out any vibration and ive disconneted each vac source and plugeged to try to systemativcally eliminate and leaking legs...i put the jet and metering rod in out of the rebuild kit, but according to a spec inthe haynes i should have a .080 and the rod out of the kit is a .073... and i cant find a spec for the jet but there is quite a bit of slop when the rod is placed in the jet... i ordered another carb kit with teh carb part number off of it (last time i just used the model and make of p/u and rochester mv for manual trans) to double check myself... and your right the only places it could leak would be the jet, the small oriface next to the jet or the gasket, but i havnt noticed any leaks at all... any other suggestions???? --mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's Last edited by tkeduk8r; 12-24-2002 at 12:39 AM.



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