guys my old 70 gmc will cut off - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70' GMC · 07-08-2007, 10:07 PM

the carb was running rich and now I think its not gettin enough gas it is a holly 4 barrel kinda old though but it has been built not to long ago. I used to be able to melt the tires

COULD YA HELP ME OUT

mnunn454 · 07-09-2007, 06:26 AM

I'd start by checking all fuel filters, fuel pressure, check vacuum lines and do a vacuum gauge test. Then I'd check the fuel float levels in the carb bowls.

If you find nothing suspicious, take your carb model number to the speed shop and get a couple of bowl and metering body gaskets and maybe a few o-rings (if required). Then pull both the bowls for inspection. Check the needle and seat in particular to verify it's operating as it should, looking for debris and sediment, corrosion, etc. Ensure they swing freely. Verify the power valve isn't blown. While checking the needle and seats, make sure there's no fuel inside either of the floats.

That should get you started. Tell us what you find.

70' GMC · 07-09-2007, 09:12 AM

Would it be easier to put a new holly or edelbrock 4 barrel on it to save some time and money?

mnunn454 · 07-09-2007, 02:44 PM

Quote:

Originally Posted by 70' GMC

Would it be easier to put a new holly or edelbrock 4 barrel on it to save some time and money?

Easier? Yes.
Save Time? Yes.
Save Money? No. The gaskets and maybe a needle/seat would cost less than $50. Heck, you might even get a whole Holley rebuild kit for that amount.

Since time "is" money, I usually use $15 per hour (give or take) as a yardstick to evaluate these kind of decisions.

Assuming the old one isn't "worn-out", if a new carb costs $400 after taxes, and a kit is $50, then you'd have to spend $350 in labor (23 hours) rebuilding/adjusting it before it'll make sense to replace it. This also assumes you're mechanically inclined. If not then you're probably be better off replacing it and paying the $400.

RedZ71 · 07-09-2007, 04:18 PM

just as a qualifier... i consider myself a mechanical novice (i can read and follow directions), and i was able to rebuild my qjet and get the truck to start on the first try.

ive got a little bit of mechanical experience under my belt (ive never done anything deeper than sparkplugs on the engine, but i have changed a fuel pump and rebuilt the front driveshaft on my Z71. if you have any basic mechanical skills, you can probably do the rebuild kit yourself (tho you might have to have a knowledgeable friend help you tune it back again).

07-08-2007, 10:07 PM	#1
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	guys my old 70 gmc will cut off the carb was running rich and now I think its not gettin enough gas it is a holly 4 barrel kinda old though but it has been built not to long ago. I used to be able to melt the tires COULD YA HELP ME OUT __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

07-09-2007, 06:26 AM	#2
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: guys my old 70 gmc will cut off I'd start by checking all fuel filters, fuel pressure, check vacuum lines and do a vacuum gauge test. Then I'd check the fuel float levels in the carb bowls. If you find nothing suspicious, take your carb model number to the speed shop and get a couple of bowl and metering body gaskets and maybe a few o-rings (if required). Then pull both the bowls for inspection. Check the needle and seat in particular to verify it's operating as it should, looking for debris and sediment, corrosion, etc. Ensure they swing freely. Verify the power valve isn't blown. While checking the needle and seats, make sure there's no fuel inside either of the floats. That should get you started. Tell us what you find. __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe

07-09-2007, 09:12 AM	#3
70' GMC HERE.......Somewhere Join Date: Oct 2006 Location: Birmingham AL Posts: 2,488	Re: guys my old 70 gmc will cut off Would it be easier to put a new holly or edelbrock 4 barrel on it to save some time and money? __________________ Current rides: 2013 Hyundai elantra gt DD 1995 camaro my first crush lmao Was: 1970 with a 350 4barrel and 288 horses Classics make it possible!

07-09-2007, 04:18 PM	#5
RedZ71 Junior Member Join Date: Jan 2007 Location: Dallas, TX Posts: 246	Re: guys my old 70 gmc will cut off just as a qualifier... i consider myself a mechanical novice (i can read and follow directions), and i was able to rebuild my qjet and get the truck to start on the first try. ive got a little bit of mechanical experience under my belt (ive never done anything deeper than sparkplugs on the engine, but i have changed a fuel pump and rebuilt the front driveshaft on my Z71. if you have any basic mechanical skills, you can probably do the rebuild kit yourself (tho you might have to have a knowledgeable friend help you tune it back again). __________________ Jonathan 2001 ECSB Silverado Z71 1971 LB C10 Custom www.z71silverado.com



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