Hello,
First of all, I apologize for making another carburetor thread. I know that this subject has already been widely covered on this site. I am looking for advice selecting between two specific carburetors.
I have two Holley Ultra Double Pumpers in the 650cfm and 750cfm flavors. Part numbers 076650bk and 076750bk.
The 650 has 63 main jets and 73 secondary jets.
The 750 has 73 main jets and 80 secondary jets.
The 750 has down leg boosters and the 650 has the standard ones shown in the picture.
I would like to return one of the two and keep the other for use on my car. My car is a replica Lola T70 on a steel tube chassis and weighs around 2300 lbs. It has a Cleveland engine that was built by Hall Pantera in the 1990’s but I do not know the specs. For what it is worth, I have looked into the cylinders with a bore scope and the pistons are flat with valve reliefs cut in the them. The engine seems to be fairly mild, nothing too hot. At some point I would like to upgrade the cam. The engine had a 600cfm vacuum secondary on it that was in need of a rebuild and I thought it would be best to upgrade to something bigger rather than rebuild.
I am leaning towards keeping the 750 but I am unsure if this is correct, as I have read that some here say it will be too rich in a mild engine and that I will loose low end drivability.
I know that with the limited information I have provided it is difficult to determine what is best but I do appreciate any advice.
Thank you
