rsvert89

1997 Mercruiser 5.7 Alpha, was a 2bbl, non vortec heads. Standard ignition system. The new engine has Vortec heads, Howards Cams Roller cam, Edelbrock RPM Air Gap intake. Standard exhaust manifolds. The cam manufacturer said I want between 32-34 degrees of timing at 2500rpm. Going by the book, and the cover on my engine, it looks like base timing is 8 degrees btdc, and 22 degrees module advance, for a total of 30 degrees. Can I swap modules from a different engine to get to the 32-34 degree range? Anyone know of a particular engine that has that? Thank you in advance.

SB

iTrader: (1)

If you have Tbolt IV ignition, just set total degrees where you want it...and let base fall where it falls.

Do you have Tbolt IV or V ? What module # do you have ?

rsvert89

I am not sure of my part number. Looks like I have Thunderbolt V, and I believe it says v8-22 on the module

SB

iTrader: (1)

Tbolt V uses a mean best timing set up...using a knock sensor and tachometer......so very unconventional. It also has a special procedure to check base timing because of all of this. Do a search on it in google land to learn more...I'd have to write a small book to let you know all it's workings.

Tbolt IV is conventional...ie: doesn't adust for anuthing...just has an electronic advance.

rsvert89

I know mine does not have a knock sensor. I have timed it before and there was a sequence of grounding a wire to set base timing if I remember correctly. Is it hard to switch to thunderbolt iv? Would my distributor be ok, and just change module/sensor in the distributor? Thank you for the help.

SB

iTrader: (1)

I could be wrong, but I have not seen a Tbolt V without a knock sensor.

Here, go nuts:
http://www.boatfix.com/merc/Servmanl/16/16B4R2.PDF


Edit in: oh, you would have to swap the module harness to go from a V to a IV.

rsvert89

Found a module from a thunderbolt IV that is V8-24. Anyone know if the wiring is the same?

SB

iTrader: (1)

Look up , we posted at same time...lol.

Griff

From what I have read, Vortec heads do not like more than about 30* of timing.

Trash

I would characterize it as not that they don't like more than 30* of timing but rather they don't respond as much to timing over that amount. I would still target 32*.