LT-1 Replacement Carb Suggestion

[GaryH]

It won't do it if it's not completely warmed up, Eric. It has to be driven at least 5-10 miles first. When it's cold it runs great. The hotter the weather the worse it is. I took it out this morning to let a friend drive it and it ran great. It's chilly today and we didn't go far though. The only thing that seems a little odd is, in order to set the float level I have to have the needle/seat screwed down so far that the adjusting nut is barely catching the top of it. It was like that prior to the rebuild also. Are there different length needle/seats? The floats seem fine and they are not full of fuel. I'm pretty certian it's a carb issue. I'll ask around my car club and see if anyone has a carb I can borrow to see if that fixes it though. Let me know your thoughts on the needle/seat height.

[VintageMusclecar]

When you went through the carb, what brand of a kit did you use? Did you replace the floats? If so, are they brass, plastic, or nitrophyl?

On a Holley needle & seat, usually 2-3 threads showing above the float bowl will put the fuel level at or just below the sight plug.

Keep me posted.

[GaryH]

It was a Holley kit for the 3310. I purchased two 8.5 power valves and the blue bowl gaskets separately. I matched all the holes in the new gaskets with the old ones and they all appeared to be correct. I did not replace the floats. They are brass and appear original. I'm lucky if there is more than a thread or two sticking above the bowl on the needle & seat. You have me thinking I should pop this back apart and double check things on the floats and try some different needle and seats....

[VintageMusclecar]

Gary;

For no more than what they cost, go get a new pair of HOLLEY .110" needle & seats (stay away from the generic rebuilder jobs, esp. the Borg-Warner styles!) and a pair of new brass floats. When you re-assemble the float bowls, baseline the floats by inverting the bowl and running the floats down until the top of the float is at the bottom of the float hinge screws. That usually gets them very close.

Make sure the floats operate freely and don't stick or have any tight spots. Sometimes you might have to gently "tweak" the float hanger "ears" to get everything to set just right.

Also, while you've got it apart, check the metering block surfaces on the main body of the carb and see if they've ever been machined flat.

Keep me posted.
Eric

[GaryH]

Eric, I just got done pulling the carb. I took out the 8.5's and installed a 6.5 in the front and a 7.5 in back. That's the only ones I had laying around. I studied the floats and they look great. The hangers are square and do not appear to have ever been bent for any reason. I reassembled and reset the floats. Something is definitely amiss there. I have to crank the needle down almost to the point that it's flush with the top of the carb in order to set it correctly. That's both front and rear. I took it out for a ride and it's better. It likes the 6.5 in the front. I have better response and it pulls better at light to medium throttle. For the first time since I've had the car it had a consistent idle every time I came to a stop. Skies were threatening so I didn't go far but it is improved. I'll pick up a set of needle and seats tomorrow and see if they are any different. If not, I'll take it back apart and replace the floats and adjust as you suggested. With your help maybe I can get this squared away Thanks for taking some time out on this Easter Sunday and helping!

[VintageMusclecar]

Gary;

I'd still replace the needles & seats as well as the floats just to eliminate them as a possible cause. If you can't find them locally for a decent price, let me know.

Glad to help.

Eric

[GaryH]

The project is complete Eric. I installed the floats and needle & seats this morning. I took it out for a quick ride and it seems fine. I will know better after I can put some miles on it on a warm day. I don't know what the deal was with the floats. They were the same weight as the new ones and had the same hinge angle but now my needle & seat height is correct. Looking at it before I took it apart, the float drop had to be way off. They were both screwed down to almost the bottom of the bowl.