fasteddy

I have 2 7040250 carbs. One is rebuilt and recolored and the other is a nice core. I am planning on getting the recolored one set up to QB specs with the right jets and rods. I am restoring a 1970 Rallye 350 4 speed car.

I noticed that the two carbs have different vacuum ports on the back. One has two individual ports of different sizes and the other has a single port coming out with a t on it.

Is one of these not correct?

I would like to use the recolored one which has the T. I don't know if the top plate is original to the carb though?

Also, there are two different idle mixture screws. One is just a hex head and the other also has some knurling on it. Which one is right for a 1970?

Thanks!

Pat

shiftbyear

Are the date codes both for 1970, one may have been a service replacement.

fasteddy

Good call. The one with the T is 3259 and the other one is 1122. The second one with the two separate ports must be a service replacement carb.

joe_padavano

I would have sworn the two straight ports were the correct configuration, but the CSM clearly shows that the "T" fitting is correct. The straight port on the "T" connects to the hot air feed line to the choke stove in the crossover, and the side port connects to the vent line on the TCS solenoid. I think this was a last minute retrofit to accommodate the TCS in 1970. Later carbs (like a 7042250) have the two straight ports. That would be consistent with the thought that it is a later service carb.

fasteddy

Thanks for the confirmation Joe. I also would have sworn that the two ports was correct.

The good news is that I can use the carb that was rebuilt and recolored.

What about the idle mixture screws though? Which ones should a 1970 have? I have a 7042251 and a 7040250 with the knurling, but the 69 built 7040250 does not have that. It is also possible that when it was rebuilt they put new ones in.

Thanks!

Pat

olds 307 and 403

I would think the top mixture screw is right, I have never seen the hex head on Qjet's.