Thunderbolt IV to Mallory

J

jhilton

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Nov 23, 2008
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I want the change from Thunderbolt ignition to the mallory but I cant see were you would hook up the shift interupt switch. 1989 with alpha drive. Has anyone done this conversion yet?
 
Don S

Don S

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Re: Thunderbolt IV to Mallory

Why in the heck would you want to do that? The Thunderbolt IV is a much better ignition system.
 
Bondo

Bondo

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Re: Thunderbolt IV to Mallory

Ayuh,.... Why,... The T-Bolt IV is about the Best marine igntion system there Is....
You're going Backwards....
 
J

jhilton

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Messages
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Re: Thunderbolt IV to Mallory

I have blown my motor 3 times in a year and a half. They say it is the timing. the last time I rebuilt it i set it at 0 initial and 32 total. Blew in 15 minutes. I think the thing has gone bad.
 
Don S

Don S

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Re: Thunderbolt IV to Mallory

Why would you set a Thunderbolt IV to 0? and on what? That in itself will not blow an engine in 15 minutes. You have other issues.
 
H

HT32BSX115

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Re: Thunderbolt IV to Mallory

Bond-o said:
Ayuh,.... Why,... The T-Bolt IV is about the Best marine igntion system there Is....
You're going Backwards....
Click to expand...

Yeah....agreed..... Only my Thunderbolt V is "better"!

I would fix the TB-IV as opposed to buying the Mallory.....
 
J

jhilton

Seaman
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Re: Thunderbolt IV to Mallory

are you saying that a tb IV can not go bad. I have rebuilt this motor for the last time. If it doesnt work this time Im sinking it.
Please answer the original question also.
 
Don S

Don S

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Re: Thunderbolt IV to Mallory

Please answer the original question also.
Click to expand...

Kind of hard to do without knowing what engine you have and what Mallory distributor you have.

Yes, the TB4 distributors can go bad, but if you have spark, and advance, then it's working.
 
Bt Doctur

Bt Doctur

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Re: Thunderbolt IV to Mallory

Just WHO are they? Can you describe whats been blowing up in the motor.
holes in pistons:detonation
very poor fuel quality, too much ethanol(dry gas)
a run lean condition from a intake leak, bad carb
excessive rpm
what parts are breaking?
 
J

jhilton

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Re: Thunderbolt IV to Mallory

chunks are coming off the top of pistons, and the top ring is tight on the bad pistons indicating detonation. I have a 350 with 9-1 compression on 89 octane gas with 32 degrees of total timing. The last time it came appart it was at 3200 rpm. time befor was 3600, and the first time was 4100.
 
J

jhilton

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Re: Thunderbolt IV to Mallory

I did not answer all of the q's . New carb,new everything and i mean everything exept the TB4.
 
S

searay3

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Re: Thunderbolt IV to Mallory

Yup, sounds like detonation. I have seen the tb4 go bad, but the engine could barely stay running. With what little info is given, my bet is the timing procedure being used is wrong or it's being 'power timed'. Both can cause severe detonation as would too low octane fuel. Get the proper manual for your engine/drive and follow it. Engine been modified for street power on a boat? That don't work well either...
 
J

jhilton

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Re: Thunderbolt IV to Mallory

What is power timed? I only know of one way to set the timing with a light. I've checked the balancer for tdc before and after the motor came apart, been on everytime. This motor is going together with 8.4-1 compression, and forged pistons.


Nobody has answered the original question, There is probably alot of people that would like to know the answer.:)
 
Don S

Don S

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Re: Thunderbolt IV to Mallory

Nobody has answered the original question, There is probably alot of people that would like to know the answer.
Click to expand...

NOBODY can answer, because we don't know what you have. Read reply #8
 
J

jhilton

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Messages
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Re: Thunderbolt IV to Mallory

1989 350 mercuiser With 1987 TB4 off of a my buddys boat, I dont have a new distributor yet, I wont buy one untill I know if it will work. My buddy got a MSD marine kit and it would not work, He bought there shift interupt switch and the head guy at MSD told him he must be the first one to ever buy because he didnt know how to wire it up either. ( the shift interupt switch)
 
Bt Doctur

Bt Doctur

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Re: Thunderbolt IV to Mallory

"Power Timing" :The art of turning the dist. while underway at max rpm to allow the most advance ,allowing the most power with the fuel being used at the time(octane rating). Puts the motor on the "Ragged Edge" of blowing itself apart.Depending on the particular advance weights ,spring rate, how much the holes and stops have been modified ,alters the max advance offered by a MECHANICAL DIST. Electronic ones have a "Hall Effect" device that allows a set degree of advance.TB`s spark or they don`t.
I`d "degree" the cam to make sure you can timing is ok,and verify the timing mark on the damper is TDC #1 .You must remember that marine engines run under "constant load" not like a car.
 
J

jhilton

Seaman
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Nov 23, 2008
Messages
66
Re: Thunderbolt IV to Mallory

I have degree the cam and checked balancer everytime.
 
J

jhilton

Seaman
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Nov 23, 2008
Messages
66
Re: Thunderbolt IV to Mallory

Ok, The tb4 was bad. The box had the correct curv in it but it would not stop adding timming. The timing was on par and i did not check it beyond the 3200 rpms. So when the rpms went above that it just kept advancing with the rpms until it would blow. So to eveyone who thinks they cant go bad i have one. This is the story of my life. Im the only one in the world that it has happend to. The machin shop was right the first time, Im just a slow learner. Thanks for all of the info and help.:)
 
K

krisnowicki

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Messages
1,172
Re: Thunderbolt IV to Mallory

yep..... I had one go bad. I got a good used one on ebay for 90..... are you saying would it not stop advancing? how far would it go ? what was your base 8 deg btdc?
 
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