Ignition kits for 1990 345LE - 454

[willhenshall]

Hi everyone - when I owned this motorhome for the first time for 5 years in the late 90s, I put an MSD ignition kit in, at the same time I added Banks Power headers and rebuilt the carbs with custom jets. Which made a huge difference to the power of the motor. I recently bought the coach back from the same guy I sold it to, he only put 18k miles on it in 18 years. So today it's only got 64,000 miles on the clock and is still in terrific physical condition. I drove it home to Los Angeles from Austin TX a couple of weeks ago, had a shop in Austin replace all the belts, hoses, new radiator, all tires, etc etc and she drove home no prob, but started to misfire towards the end of the 1600 miles back. The ignition is the original MSD kit that I put in, but it's now 20 years old, and everything is looking pretty corroded (the coach was not driven much over the past few years). So it's time to replace and start fresh. Does anyone have a lead on what is a good kit that will fit? Do any of the performance 454 big block kits such as this fit? My plan is to keep this coach for the next 40 years, so I want to install systems that are gonna run the test of time https://www.jegs.com/i/MSD/121/85551K/10002/-1 - your thoughts/feedback and advice gratefully appreciated!

[dadstoy]

Hello Will. I usually get a tooth or two knocked out by a few every time I add my opinion on this one, but here goes. With all the research I have done and reading through the performance books written by those in the know and those that actually dyno motors to back up what they say, I believe there is rarely an advantage to using high performance parts on our motor home engines that don't see RPMs much above 3000-3500.



It is my understanding that the GM HEI ignition is about the best there is for this generation of motors. The HEI ignition produces very adequate spark and timing for motors turning RPMs to about 6000. Higher RPMs, higher horsepower and higher compression engines do require hotter spark above these RPMs. But, since your motor home engine probably will never see anything above 3500-4000 RPMs and with it's low compression, anything other then stock equipment probably won't show any advantage.



Personally if I didn't live in Calif myself, I would put that $758 towards one of those $2500 EFI systems, not necessarily for better fuel economy because it would probably never pay for itself, but for better starting and driveability.



Stock OEM parts are easier to come by as well when you are broken down on the side of the road.


Anyway, something to think about.

[bkahler]

Originally Posted by dadstoy

Hello Will. I usually get a tooth or two knocked out by a few every time I add my opinion on this one, but here goes. With all the research I have done and reading through the performance books written by those in the know and those that actually dyno motors to back up what they say, I believe there is rarely an advantage to using high performance parts on our motor home engines that don't see RPMs much above 3000-3500.

It is my understanding that the GM HEI ignition is about the best there is for this generation of motors. The HEI ignition produces very adequate spark and timing for motors turning RPMs to about 6000. Higher RPMs, higher horsepower and higher compression engines do require hotter spark above these RPMs. But, since your motor home engine probably will never see anything above 3500-4000 RPMs and with it's low compression, anything other then stock equipment probably won't show any advantage.

Personally if I didn't live in Calif myself, I would put that $758 towards one of those $2500 EFI systems, not necessarily for better fuel economy because it would probably never pay for itself, but for better starting and driveability.

Stock OEM parts are easier to come by as well when you are broken down on the side of the road.

Anyway, something to think about.

Dean, I totally agree with your assessment about the OEM ignition. At less than 5,000 or 6,000 rpm you're not going to really gain much if anything. As far as reliability I'd rather have GM OEM reliability and ease of finding spares anywhere in the country. Finding spares for some aftermarket marvel while on the road can leave you stranded. Just my $0.02

Brad

[PeterH-350LE]

Interesting how, whoever installed your MSD, just left the original ignition module floating around inside of the distributor. Backward compatibility in case of trouble?
Before I would spent all that money on some fancy MSD, especially with Deans and Brads feedback, I would spend a 100 bucks and go back to original to see if it fixes your backfiring, acd556A and ACD1906 i believe.
Remember when we talked about the backfire on your trip back and I suggested to get an ignition module, since it is so readily available, little did I know you had a MSD system that bypassed the stock ignition module.
And I totally agree with keeping it simple and use parts that are available (or even better have a spare on board that is known to work.)

[bibbs]

$0.02 more! Stick with OEM

[GWallace]

One more comment to add about the GM HEI ignition module. As I was reviving my 1977 Argosy several years ago, I ran into a series of issues with replacement ignition modules. I purchased a replacement module from OReilly in the $30 price range (Made in China). The module failed as I was driving and I had to replace it so got the “Heavy Duty” imported version $35. It failed by intermittently turning off and then back on creating backfiring that ripped my new mufflers open. I then discovered that for reliability, I purchased a “US” made module from NAPA ($45 - $55). The GM branded modules are also apparently the higher reliability modules. In the future I will be very selective on which module I purchase. The module that I purchased 4 years ago from NAPA has not missed a beat.

[willhenshall]

Thanks for feedback , thoughts, advice from you guys. Much appreciated!