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Mercruiser Thunderbolt IV Timming Pre ignition

D

Dean Schreiner

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"Replaced 5.0 Engine with 5.7,

"Replaced 5.0 Engine with 5.7, Intake valves tuliped, What should advanced timing be at 4000 RPM, Was at 39 degrees. OK? What should it be?"
 
"I'd think 36* MAX....

"I'd think 36* MAX......

32/ 34* otta do it...... Brand new motor,+ all....."
 
"Thanks Bondo. But what does i

"Thanks Bondo. But what does it mean when it says Module Advance 22 degrees, Total advance: 30 degrees? I want to make certain there is no Pre-Igniting. It has a 8 degree BTDC"
 
"The TBIV ignition module supp

"The TBIV ignition module supplies 22* advance, this combined with base ignition timing of 8* should make a total advance of 30*. 39* is too much for a stock motor and is asking for detonation on lake 87 octane."
 
"I've been apart of dyno t

"I've been apart of dyno testing of 400hp 5.7L marine engines, backing the timing down from 36* to 30* only resulted in the loss of 10hp and equal torque thru the powerband.

On my peronal 355 marine engine I am running 34* advance with no problems. 10-1 compression ratio with AFR aluminum heads on 89 octane with no detonation."
 
What do I do?
I set at 8 deg


What do I do?
I set at 8 degrees BTDC. Should I set At WIde open throttle At 34 degrees and forget the BTDC. What are my options? I have Induction advance timing light.
I did tulip the intakes on last engine with same Thunderbolt IV system.
 
"post model, and year of engin

"post model, and year of engine.timing curve should not be hard to look up. go from there."
 
"It's a power up job, 5.o

"It's a power up job, 5.o LX to a 5.7, using same componets. Module 805361T-3, Module Advance: 22*, Initial Timing 8* BTDC Total advance 30*
Curve says at 3400 RPM and above between 20.5* and 23.5* minus initial timing. So would tha mean ideal would be between 28.5 and 31.5 at above 3400 Rpm? How far off is safe.
Cam not dialed in.

Thanks"
 
"you are correct. add base tim

"you are correct. add base timing. on a new engine, keep the advance at spec. or below. 39 is too much. if you get detonation damage, no warranty! if base timing is on, either module is bad, or advance timing lite is wrong. (more likely) figure a way to mark the balancer, and see what you truely have at zero advance on the lite."
 
"Thanks Scott! But I'm not

"Thanks Scott! But I'm not 100% on what you are saying, Can you further explain?

Thanks"
 
figure curcumference of dampen

figure curcumference of dampener. divide by 360. thats one degree. make something up on paper if you like. can tape it on dampener. (it only needs to last a couple of minutes) check your timing with lite set at zero advance. see what you get.
 
"Thanks Scott. I thought thats

"Thanks Scott. I thought thats's what you ment. It was a Craftsman timing light, I exchganged it , it read differant, I don't trust them and will do check anyway, don't happen to know diameter or circumference of a small block Chevey Damper do you?

Thanks for taking the time to help everyone out!"
 
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