" hey GRUMPYVETTE??
I have a '69 c10 2wd auto with a 327.It has double hump heads,victor junior intake,longtube headers,k & n filter,larger than stock cam.(in when I bought it,do not know size)(It has a noticeable idle).It has a single feed holley 600.It feels like it is being held back and needs a bigger carb.Any suggestions?
I bought a rebuilt holley 4777 650 double pumper,and after looking at recommendations on holleys website,I should have gotten vacuum secondary??Thought about a 670 street avenger carb with vac sec. and elect. choke.This truck is a daily short distance to work and weekend driver"
the 600 cfm carb is easily able to supply a 327 sbc displacement,(assuming its tuned correctly and opening fully of course) the 650cfm might give a very small increase but the one factor that sticks out in the parts list you posted is the vic jr intake, a rpm air gap will almost always prove to be superior in similar combos.
one reason the vacuum secondaries carb is suggested is that the 327 can,t even use the full 600 cfm untill the rpms build up past about 6000rpm, so the vacuum secondaries carb acts like a smaller carb under most conditions and only supplies the necessary flow rates(yes thats a tunable feature in most of the holley vacuum secondaries carbs)
http://www.4secondsflat.com/Carb_CFM_Calculator.html
if your running a hydraulic cam , and stock valve springs youll rarely see rpm levels above about 6300rpm
if the spark plugs look good and it runs correctly theres not much to be gained with the larger carb, if youve got it and it won,t cost you to test swap go right ahead and try, but I think the main factor here is the single plane intake design and its restriction of low and mid rpm cylinder fill effeciency vs the slightly superior high rpm potential of the current intake design, a potential thats mostly not useable because I suspect the engines cam, and drive train limits you to under 6300rpm most of the time, where the dual plane should prove to be a better match, especially with an auto trans that shifts well below that rpm band.
I have a '69 c10 2wd auto with a 327.It has double hump heads,victor junior intake,longtube headers,k & n filter,larger than stock cam.(in when I bought it,do not know size)(It has a noticeable idle).It has a single feed holley 600.It feels like it is being held back and needs a bigger carb.Any suggestions?
I bought a rebuilt holley 4777 650 double pumper,and after looking at recommendations on holleys website,I should have gotten vacuum secondary??Thought about a 670 street avenger carb with vac sec. and elect. choke.This truck is a daily short distance to work and weekend driver"
the 600 cfm carb is easily able to supply a 327 sbc displacement,(assuming its tuned correctly and opening fully of course) the 650cfm might give a very small increase but the one factor that sticks out in the parts list you posted is the vic jr intake, a rpm air gap will almost always prove to be superior in similar combos.
one reason the vacuum secondaries carb is suggested is that the 327 can,t even use the full 600 cfm untill the rpms build up past about 6000rpm, so the vacuum secondaries carb acts like a smaller carb under most conditions and only supplies the necessary flow rates(yes thats a tunable feature in most of the holley vacuum secondaries carbs)
http://www.4secondsflat.com/Carb_CFM_Calculator.html
if your running a hydraulic cam , and stock valve springs youll rarely see rpm levels above about 6300rpm
if the spark plugs look good and it runs correctly theres not much to be gained with the larger carb, if youve got it and it won,t cost you to test swap go right ahead and try, but I think the main factor here is the single plane intake design and its restriction of low and mid rpm cylinder fill effeciency vs the slightly superior high rpm potential of the current intake design, a potential thats mostly not useable because I suspect the engines cam, and drive train limits you to under 6300rpm most of the time, where the dual plane should prove to be a better match, especially with an auto trans that shifts well below that rpm band.