Ignition conversion question
 

Hey fellas, need some advice....

I have new twin 502's moderately built, nothign special; 502's w/ TBS blowers making about 5 lbs of boost. When we did these last year we put the old TBIV ignitions on.

I bought MSD boxes, brackets, distributors, all the goods to upgrade the system... is this pretty much a direct swap? Any special concerns or anything I need to be aware of? CP Performance hooked me up with all the stuff, just wondering if there are any gotchas I need to be aware of. thanks!

There's no advantage to using the mechanical advance MSD distributors. The ones I've seen tend to rust badly inside and their sensors fail. Return them, use the Tbolt IV distributor, and Tbolt IV V6 modules. It will have a shorter advance curve, about 14 degrees, allowing for more initial advance.
Now after running that combo, see if you have plug fowling problems with extended idling. If so, you can add the MSD boxes to the Tbolt setup. Be sure to wire the MSD box with a big wire as close to the alternator/battery as you can. They have a habit of failing frequently and have been told it's due to low voltage at the box,

I appreciate that info. I already have a problem with fouled plugs from idling, and have had a lot of ignition issues last summer after the rebuilds. we checked the runout on the distributors and have realized they are kind of wearing out, I figured the MSD set up would be good. I actually bought the Hardin dist's becasue they pretty much were the same and a little bit cheaper.

Not sure about the Hardin distributors, but the Tbolts have the advantage of parts availability at the lake.
Were you running the V6 module when you had fowling problems? What was your inital and total advance?
BTW, I think I recognize your boat, have you been running it at the lake long?

I do have the V6 modules, wound up replacing them last year chasing down a problem and it turned out to not be them....
I hear ya on the parts availibility.... Total advance I think is like 30 but will need to double check... not sure on initial...

I have had about 3 years now... we run all up and down the channel from about the 1-21

Well, sounds like you need the MSDs. What's the spark advance curve on your new distributors? I'm guessing you know SC motors like a lot of initial advance. The MSD distributor uses bushings on the advance stop pins, like an old GM. If that's the case on the Hardins, use big bushings (short curve), light springs (earlier advance), and set your total advance at 30 again.
The MSD site has pretty good instructions online.

The MSD's work poorly in marine apps, like said before rust up bad inside....I ran mallory unilite before, easier to adj curve, and you want very little advance about 10-15 deg is it, then about 26-28 total, gives you more initial and will help clean the idle up and help your plug issue...Rob

I have twin 496's I built recently. There pretty stout engines and planned to you the tb1V ignition also. I like these for the simplicity as well as the low failure rate. I didn't realize you could use the msd box with that ignition. Any other real benefits to running these boxes? Also what one is the correct one for this. Seems like so many now a days,

thanks,

Well, now that Crane is up and running (i think?) again, I'd recommend avoiding anything MSD and putting the HI-6M boxes in. They hook up to the TB IV and allow you to select which curve you want on the fly.

Just my 2 cents but I thought I'd throw it out there!

Looks like the ticket. Other nice features with these are the rev limiter as well as the different advance curves. Sounds like you can use your existing module or use one of the several curves the box offers. I wonder if anyone can churp in here in regards to the performance upgrade with this or if the hotter spark ultimately helps more at just idle. HP gains?
http://www.cpperformance.com/detail.aspx?ID=9474

what about DUI ? Simple .....

http://www.performancedistributors.com/marinedui.htm

I'm running a couple of those on NA motors. They are simple and work great (20 years, no problem), but they dont offer the multiple spark that keeps your SC motor plugs clean at idle. Not sure how easy it would be to hook up an MSD box with it.

MSD has pretty good instructions on their site. See link. The Tbolt IV V6 module with MSD works pretty well on SC motors, I would just suggest buying a spare MSD box.
http://www.msdignition.com/instructi...pdf?terms=6460

I wonder how much different the internals and coil are on the dui's than that of the numerous ones you see on ebay for under 65.00.

They're basically a copy of GMs HEI. My understanding is that pretty much all the parts are interchangabe. Gotta love parts availability with that.
The difference, "USCG approved". In terms of price, not much different from an OEM GM distributor. I've pretty much given up on buying chinese repro stuff for my 68 corvette, boat or anything else that can leave me stranded.

you have a lot of input from a lot of people,this is how i do it,and have had no problems for many years.i use msd distributor,and lock it out,blower motors like the timing even at idle.they idle much cleaner this way,i never have fouled plugs,even after long perids of idling.also,30 degreese total is not enough timing,that will make your EGT,S sky high,thats really tough on the exhaust valves.you need 32 at a minimum,i run 34 on my 540,s. at 30 degreese,you are giving up 40 hp or more.on a na asperated engine,i like the merc distributors, with the v6 modules.:coolcowboy:

Has anyone used the Mallory three wire distributor/ignition systems that have the ignition system contained in the distributor? They still use the seperate coil and seem to work well. We put them on my Step-dad's '83 377 Scarab. It started up fast, R'ed higher, and ran a TON better with the new distributors.


http://www.summitracing.com/parts/MAA-3748201

I ran the Unilite back in the day, BIG trouble with the advance mechanisim. Unless of course they have improved it.

the mallory 3 wire is the unilite, ran one with my blower motor and in a few others worked great..no issues...also running a DUI in my 509 simple works great, harder to taylor the advance over the mallory..Rob

I think you tell DUI what advance you need and they set it up ..m

Somewhere around 2002 my cousin built a pair of NA 461cid engines which had the Merc Thunderbolt distributors that he took to Tom Earhart's dyno. These were very mildly cammed engines with FLAT tappet hydraulics w/8.6 comp ratio that made 461hp @5100rpm.

I was using the Crane HI-M6 ignition boxes on my own 565cid engines and I had a spare box so, I brought it along to try it for my cousin's dyno test engine---we were able to hook it up without any problems that I can remember to his Merc Tb distributors and saw NO HELP/NO GAIN.

I always have used the the Crane HI-M6 intion boxes on my NA 565's with MSD billet distributors and never did a BEFORE & AFTER/BACK TO BACK comparison test to see if there was any performance difference on my engines, but we had to hook up a relay to retard my advance only while the key was being turned during start-up of my engines. I have used the same Crane ignition boxes now for about the last 10 years or so, and one was even blasted with high pressure water and is still working today. So, they are very reliable in my experience with them vs the horror stories I hear about the MSD ignition boxes. I still have my spare Crane HI-M6 box that I have never used.

I have used an MSD billet distributor and Crane Hi-M6 box in conjunction with an MSD Crank Trigger system. I use the Crank Trigger system to avoid the plagues of the MSD distributors that quickly become rusted and create all kinds of grief and trouble I have had to find out shortly after I bought my AT in 2001.

Of course as someone has already mentioned, one of the things I like about an ignition box (be it an MSD or a Crane) is that they produce a multiple spark at idle speeds to keep the plugs from fowling during long idling periods.

Also, my engine builder likes the MSD ignition box as he has had no problems with them---this is because he always wires them directly to the battery as "rdoactive" has described in POST #2.