The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Q-Jet conversion

Hard Luck · 10-12-2009, 04:20 PM

If you step in it and the thing wants to die, it's too much fuel. With Q-jets that can be very likely because those secondarys are so large, look at rear rods and jets sizing. Also, it came off of a 318 so the vacuum signal is a bit different. Always recheck the float setting, could be too much fuel in the bowls leaking into the venturis. You would be supprised how many cars are over-carbed and run ok but once you dial it in right it is like you did a performance cam upgrade.

What we do not know is the size of the engine, any mods to it, and the size of the carb.

Always pull a used carb apart if it has been run. Even if you just put in a gasket kit. It may have been gone through but if there is junk in the there and it gets in between the rods and jets, same problem. Gum and varnish build up if it has been sitting for a while and don't nessesarly come off from running it.

I got a truck with a NEW carb on it. He had put it on two years ago and only put about 500-1000 miles on the truck since then. I dialed it all in but was having intermittent problems but decent drivablity. I pulled it apart to find out that some junk from the old tanks and lines had passed the filter and got everywhere. A $17 gasket kit, some cleaner, compressed air, and a few hours, and I was back in business ready to move on to the next project! Even though it was new, once it has been run, you need to check it out.

10-12-2009, 04:20 PM	#13
Hard Luck I've got grease on my mind. Join Date: Sep 2007 Location: Oly, Wa Posts: 481	Re: Q-Jet conversion If you step in it and the thing wants to die, it's too much fuel. With Q-jets that can be very likely because those secondarys are so large, look at rear rods and jets sizing. Also, it came off of a 318 so the vacuum signal is a bit different. Always recheck the float setting, could be too much fuel in the bowls leaking into the venturis. You would be supprised how many cars are over-carbed and run ok but once you dial it in right it is like you did a performance cam upgrade. What we do not know is the size of the engine, any mods to it, and the size of the carb. Always pull a used carb apart if it has been run. Even if you just put in a gasket kit. It may have been gone through but if there is junk in the there and it gets in between the rods and jets, same problem. Gum and varnish build up if it has been sitting for a while and don't nessesarly come off from running it. I got a truck with a NEW carb on it. He had put it on two years ago and only put about 500-1000 miles on the truck since then. I dialed it all in but was having intermittent problems but decent drivablity. I pulled it apart to find out that some junk from the old tanks and lines had passed the filter and got everywhere. A $17 gasket kit, some cleaner, compressed air, and a few hours, and I was back in business ready to move on to the next project! Even though it was new, once it has been run, you need to check it out.