deepockets

just want to here your input on timing. 632 14-1 comp big cheif, twin carbs. c-16 gas. my builder says that the big motors don't like to much timing, so he put it at 33. every other bbc. engine i've ever run has been 36-38 degrees. why do you think i should run less leed on the new engine. thanks

demented

I ran into the same thing on the same motor and head combo.Only difference is that I am running alcohol injection. My base timing is 32 degrees. It is all relataive to the combustion chamber shape and head configuration. My 632 with conventional heads needed 36 degrees to run right but the different heads required less. You will actually make more power if you need to use less ingintion lead.

thedude

A Big Chief style cylinder head has a "rolled" valve angle which minimizes the combustion chamber volume which in turn allows a very small dome to dispurse volume to achieve maximum compression. The shallow chamber combined with the minimal dome and velocity of the ports allow for an effencient combustion. On a real good 11 degree Big Chief with 2X4 carbs, I have went as little as 29.5 degrees. It depends on what the head is, but if this is an 18-14 degree style big chief I would never exceed 32-33 degrees.