Ac delco conversion

[Stingray1961]

Hi guys I changed over from my thunderbolt ignition to the ac delco kit from Michigan it says on the paper work -4 with manifolds that have 12 bolts and 2 with 8 bolt manifolds for initial timing mine is the 12 bolt one I had a heck of a time getting the distributor to line up at one I converted to this because my thunderbolt module was shot any of you guys have any suggestions on timing. I have been chasing my boat this year just lack of power rebuilt my carb now ignition 1993 4.3 mercruiser

 

[alldodge]

Carb model is set at 8 BTDC with the distributer in base timing mode

 

[Stingray1961]

Well I have tried up loading picture of Michigan motors and no it says -4 atdc with there set up stock with thunder bolt ignition is 8 degrees btdc

 

[Rick Stephens]

I have a carb'd 4.3 Vortec with the Delco EST and I set mine to 2 while in base.

 

[Stingray1961]

Yes mine is not vortec does your intake have 8 bolts mine has 12 which by there chart says -4

 

[Rick Stephens]

Yes mine is not vortec does your intake have 8 bolts mine has 12 which by there chart says -4

I took a pre-Vortec engine and put Vortec heads and a Performa intake on it. Vortec heads have 8 intake bolts.

 

[Stingray1961]

Nice I wonder why the difference between heads would change timing because according to Michigan motors mine is suppose to be -4 my boat been driving me crazy rebuilt carb then I lost spark so I put the ac delco kit in but it's still not running strong the only thing I have left to check is if my exhaust flappers are restricting my exhaust

 

[alldodge]

Only thing I can think of is MM using the atdc keeps less load on the motor and therefore no chance of preignition happening. Some day might want to talk to MM about it

 

[Stingray1961]

Rick when you changed heads and intake did you have to make any throttle cable mods or direct bolt in

 

[Rick Stephens]

I changed pretty much everything. I tossed the Rochester and went with a Edelbrock 1409. The reason for that was the Roc needed an adapter which made my motor too tall to fit under the doghouse. There was no difference in any case with the Mercruiser linkage. Even the throttle bracket worked with both carbs.