46 Chevy vacuum assist shift - 01/05/15 07:51 PM
Hi. My 46 coupe has the vacuum assist shifting & it worked just fine with the original 216 engine. Smooth as could be.
But I just completed an engine swap with a 1957 235 engine that I had a complete rebuild with 0.060 bore & flat top pistons, new valves with hard seats etc, dual Clifford heated intake with 2 two barrell Webber 34-36 carbs, Langdon HEI, new 264 grind cam, lifters, springs & other assorted goodies & although I have enough manifold vacuum for the vacuum advance to work & the engine runs great the vacuum shift barely allows me to shift. It is very sluggish.
Cannot find my vacuum guage but from memory that hotter grind cam should be what is the culprid on a loss of vacuum???
I don't think adding a canister will help because that will not increase the inches of vacuum, only the avalible volume of that lower vacuum??
If so I think my options are to either use a dual diaphram fuel pump (I have one) and run a line from it to the shift assist OR to order the shift link that bypasses the vacuum shift assembly entirely. I will be ordering some other items from Chevs of the 40's this week anyway.
So my question is from your experience which of these options would be in my best interest? Or other options? I have the 3 on the tree & this coupe will never be raced. Building it as my daily driver & for cruises, tours & shows.
Any advice appreiated. Thanks, Jimmie
But I just completed an engine swap with a 1957 235 engine that I had a complete rebuild with 0.060 bore & flat top pistons, new valves with hard seats etc, dual Clifford heated intake with 2 two barrell Webber 34-36 carbs, Langdon HEI, new 264 grind cam, lifters, springs & other assorted goodies & although I have enough manifold vacuum for the vacuum advance to work & the engine runs great the vacuum shift barely allows me to shift. It is very sluggish.
Cannot find my vacuum guage but from memory that hotter grind cam should be what is the culprid on a loss of vacuum???
I don't think adding a canister will help because that will not increase the inches of vacuum, only the avalible volume of that lower vacuum??
If so I think my options are to either use a dual diaphram fuel pump (I have one) and run a line from it to the shift assist OR to order the shift link that bypasses the vacuum shift assembly entirely. I will be ordering some other items from Chevs of the 40's this week anyway.
So my question is from your experience which of these options would be in my best interest? Or other options? I have the 3 on the tree & this coupe will never be raced. Building it as my daily driver & for cruises, tours & shows.
Any advice appreiated. Thanks, Jimmie