vacume secondaires

S

swamper2

Well-known member
had a guy tell me i should only use mech. carb.on airboat mtrs. says I will have trouble dwn. the road. I put weakest spring in the vac. pot and seems to work well for 10 yrs. (406sbc.) any thoughts would be appreciated.
 
I think he's refering to the diapham getting a hole under rough environment conditions. If you find that the vacumm isnt opening it should be replaced. if it has never opened than you could replace with a different spring. single plane intakes don't produce alot of vacumm especially at higher rpm when you need the 4 barrels opened.
 
thats a great intake as far as vacuum and torque are concrened. remember that vacuum also works your power valve and they are both interchangable. They power valve will work with part throttle and the accelerator pump for imediate acceleration. And an engine will pull vacumm acording to the load your asking it to do. Also in the picture are vacuum advanced distributors which pull vacuum from the carb so an intake which builds vacumm better like a dual plan and a smaller carb will which builds vacumm faster will all take thier toll on the ultimate tune up.
 
More important is correctly sizing the carb to your engine and jetting it correctly. Most people over carb their engines. Each engine is different. One may be good with two barrels open most of the time. Another may need all four to breath right. Try a few different combinations. Your driving style will also affect this. Generally you can use a larger carb with vacuum. Machanical needs to sized just right.
 
thanx for all the good info, like I say the motor has been workin fine, I'm turnin a 78 sensenick 3 bld on the 3 mark w/ a 2.09 stinger on a 16 alumitech and do dry with no problem, in the process of upgradeing to a 80 r and 2.38 soon.
 
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