thunderbolt 4 mod

[Stingray312]

I'm looking for a thunderbolt 4 igm mod/amp(15248t01) for my 1988 7.4l bravo 330hp. I'm currantly using a mod from a 1983 7.4 trs 330 hp on my starb engine but the timing drops to 2 deg atdc when shifting from idle into gear.once rpms come up above 800 rpm timing returns to 8 deg btdc. any help?

 

[wca_tim]

Re: thunderbolt 4 mod

I'm looking for a thunderbolt 4 igm mod/amp(15248t01) for my 1988 7.4l bravo 330hp. I'm currantly using a mod from a 1983 7.4 trs 330 hp on my starb engine but the timing drops to 2 deg atdc when shifting from idle into gear.once rpms come up above 800 rpm timing returns to 8 deg btdc. any help?

How do you know it is dropping???

 

[Stingray312]

Re: thunderbolt 4 mod

I put a timing light on the engine while its rpm dropped and saw the timing had dropped to 2 deg atdc.as soon as rpm are advanced to about 800 the timimg jumps back to base timing. 8 deg as was initiallly set. i was told the TRS mod may see the lower rpm's and thinks the engine is cranking and retards timing to help ease starting

 

[jtybt]

Re: thunderbolt 4 mod

There's usually a # on it saying something like V8-22 or V8-24 or V8-HP

 

[Stingray312]

Re: thunderbolt 4 mod

both the mod from the TRS and the bad one i took off the engine(had a crank no start condition) are stamped V824,which should be for a V8 with a total of 24 deg of advance above the base of 8 deg. total of 32 deg at wot

 

[jtybt]

Re: thunderbolt 4 mod

You can get them on Ebay for about $100....but test them. Some aren't any good.



Oh Yeah! The advance curve for most TB IV modules advance into the mid 3000 and some into the 4000 RPM range.


You might have to register to see the chart

http://www.offshoreonly.com/forums/...uiser-ignition-module-question-ign-curves.jpg

 

[Stingray312]

Re: thunderbolt 4 mod

thanks, I'll start checking ebay. new ones seem to be around $325 to $375 w/o a harness to up grade from older box mod to the newer plastic plug in mod....oh well ,the price of boating