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View Full Version : Distributor Replacement - 84 S&S 351w


markismm
03-22-2012, 05:52 PM
A long time ago, we replaced our Prestolite Points system with the electronic conversion kit. It worked flawlessly for years. The only thing we had to do is replace the electronic control module one time. During the last two seasons we have noticed that we are having a difficult time maintaining a consistent idle. The idle is smooth, but the rpm sometimes stays too high as if we had too much timing at idle rpm range.

We began looking at the distributor and noticed that the advance curve springs in the distributor seemed worn out. They certainly feel like they had stretched and were allowing play in the reluctor. In either event, our high idle problem was most apparent when we had been into the throttle and suddenly slowed down. The idle would remain high usually until the engine was shut off and restarted. We have concluded that this was due to the springs allowing the advance weights to sling out too much as a result of their being worn out.

After much searching, I could not find the exact advance springs that were from the factory for the Prestolite distributor. I tried other aftermarket brands but could never reproduce the same advance curve.

We finally decided to replace our old distributor with a new one altogether. See the pics below. We decided to go with the Pertronix Billet Marine Plug and Play distributor. I know Mallory is a tried and true brand, but there is really very little information out there on Mallory's Marine products specs.

Here is the motor with the old distributor...

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-33-04_825.jpg

Removal...

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-42-56_669.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-43-50_389.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-47-00_474.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-47-23_917.jpg

The old distrib...

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_14-26-42_902.jpg

markismm
03-22-2012, 05:55 PM
The new distrib and coil...

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-31-32_138.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-31-40_694.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_13-47-00_474.jpg

Comparison...

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_14-27-06_62.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_14-28-12_383.jpg

Installation

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_14-44-30_652.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_15-00-44_776.jpg

http://i9.photobucket.com/albums/a60/amndbrk1/2012-03-17_15-10-04_808.jpg

Now I am just looking forward to firing her up and seeing how well she runs now. I will report back with test results.

learjet2230
03-22-2012, 06:28 PM
Nice lookin twirly gig! What do those run if you dont mind me asking.

thatsmrmastercraft
03-22-2012, 06:39 PM
You will be very happy with the results, aside from just looking pretty.:cool:

ted shred
03-22-2012, 08:47 PM
I am looking at doing the same to my 83 PS. At the end of the season it was getting way to much advance. I found the large spring to have no effect at all any more. have had no luck finding new springs, so I think I will go the same route. The new one looks much more heavy duty.

TNPIG
03-22-2012, 08:51 PM
Man I wish I had the mechanical know how of some on here. I have an 84 s&s and I would have a lot more peace of mind if I did...

thatsmrmastercraft
03-22-2012, 10:14 PM
Man I wish I had the mechanical know how of some on here. I have an 84 s&s and I would have a lot more peace of mind if I did...

Not a difficult job to replace the dist. Certainly a job a local mechanic can handle - doesn't have to be a marine shop. Shouldn't cost much if you find the right guy.

markismm
03-22-2012, 10:35 PM
the new distrib ran me $276 on ebay, free shipping and .06 ohm 45000 volt flamethrower coil included. you can certainly tell it is a quality product. looks fantastic to me. going to get her brought back into service and fired up for the first time this weekend. the removal and install is super simple. the biggest thing is just ensuring you are sitting at top dead center on the number one cylinder and knowing your firing order (which is stamped on most engines or anyone on her can pretty much tell you) when you drop the new one in ensuring to point the rotor at the number one plug. the rest is firing her up and setting the timing right with a timing light. this whole replacement can be done in an hour.

TNPIG
03-22-2012, 11:24 PM
All of the rebuild threads on here of the classic stars and stripes are amazing for me to read through. I've learned a lot by going through those threads from start to finish. When I got my 84 S&S last year, all I knew about was wanting to ski. I didn't know a thing about it n the mechanical side. But hey, now I'm doing all the basic stuff myself like oil/tranny fluid, impeller change,etc. baby steps lol

03geetee
03-23-2012, 12:06 AM
Looks great man nice work!

JTR

thatsmrmastercraft
03-23-2012, 12:35 AM
All of the rebuild threads on here of the classic stars and stripes are amazing for me to read through. I've learned a lot by going through those threads from start to finish. When I got my 84 S&S last year, all I knew about was wanting to ski. I didn't know a thing about it n the mechanical side. But hey, now I'm doing all the basic stuff myself like oil/tranny fluid, impeller change,etc. baby steps lol

Many of us, including myself, came to this site with very little inboard knowledge. Fortunately this forum is full of people who have learned a lot and are willing to share the knowledge learned along the way. Keep plugging away and pouring through the site, and don't hesitate to ask questions. Soon enough you will be the guy with the answers.:toast:

markismm
03-26-2012, 10:14 PM
Fired her up for the first time with the new distributor and coil this weekend. The boat fired up immediately. One pump of the gas and vrrrroooommm. I was shocked too given that it was the first time I fired her up since winterizing. I love it when things work properly. The timing was off by only about 4 degrees. I took her from 8 degrees to 12 degrees and she settled right in to a nice smooth idle. Every time we rev'd her up in the drive way, she would settle right back down to about 750 rpms. I cant wait to put her in the water and see how well she runs out.

thatsmrmastercraft
03-26-2012, 11:08 PM
Nice. Good spotting on the dist. to be that close. I love the first start after doing some major work.

ProStar Slalom
03-27-2012, 10:31 AM
Fired her up for the first time with the new distributor and coil this weekend. The boat fired up immediately. One pump of the gas and vrrrroooommm. I was shocked too given that it was the first time I fired her up since winterizing. I love it when things work properly. The timing was off by only about 4 degrees. I took her from 8 degrees to 12 degrees and she settled right in to a nice smooth idle. Every time we rev'd her up in the drive way, she would settle right back down to about 750 rpms. I cant wait to put her in the water and see how well she runs out.


Is 12 degrees the spec timing, or just where it's running best for you? I thought specs were somewhere around 6-8? Thanks...staying old school on our '84 for now and it's time for new points this year.

markismm
03-28-2012, 02:57 PM
I've read that with a completely stock motor that timing in the 6-8 range is appropriate. But this motor has gt-40 heads, an Edelbrock performer intake and upgraded ignition system. With the components on the motor and our carburetor settings, it runs best with an advance of about 12 degrees. This is on regular 87 octane fuel. We have played with the timing quite a bit and are getting the best performance out of the motor at 12. Super smooth and no pinging.

thatsmrmastercraft
03-28-2012, 06:03 PM
I've read that with a completely stock motor that timing in the 6-8 range is appropriate. But this motor has gt-40 heads, an Edelbrock performer intake and upgraded ignition system. With the components on the motor and our carburetor settings, it runs best with an advance of about 12 degrees. This is on regular 87 octane fuel. We have played with the timing quite a bit and are getting the best performance out of the motor at 12. Super smooth and no pinging.

Sounds like you are right on the money.

barefoot
03-28-2012, 10:51 PM
Damn Son...that a good looking engine!

DH9441
08-01-2012, 05:13 PM
How does it not catch on fire when it throws all those flames?

sxerob
08-13-2012, 05:46 PM
How does it not catch on fire when it throws all those flames?

Heyyooooo!

First off, that engine looks fantastic! Gives me hope for my 84 S&S. I am looking in to the GT-40s and the Edelbrock Intake.

However, I am pretty sure I blew out either my coil or Dist this last week (I'm not getting spark) and I have been having a high idle issue as well. Did you test, or know how to test these components before you replaced them?

Cloaked
08-13-2012, 05:56 PM
........................

markismm
08-25-2012, 12:56 AM
sxerob. i responded to you pm. sorry it took me so long. i do not know how to test an ecm to see if it is good. i replaced that last when i had some ignition problems with my boat on the old converted distributor. i would start by replacing coil (because its cheap), then replace wires, cap, button and finally ecm. However, as I stated in my pm to you, it is almost as cheap to simply upgrade to a pertronix billet marine distirbutor as it is to replace all of those parts. i would recommend this upgrade. mine has worked flawlessly. hope this answers your question

sxerob
08-25-2012, 01:22 AM
Hey man. Thanks it does help. Actually, I was able to trace down the coil as my culprit. Even though it was a new Flamethrower that the PO had put on along with the ECM, it wasn't giving spark. Changed that and boom. All good.

I do still think that my dist has an issue. We're you referring to the little black "button" that is on the underside of the dist cap? Mines pretty worn and doesn't seem to be retracting.

markismm
08-27-2012, 02:05 PM
Glad you figured out the issue. Not too sure which "little black button" you are referring to? Is it part of the cap or rotor? The parts that was worn out in my old distrib which had been converted to electronic ignition were the timing advance springs. Both had some slop in them and as a result I was unable to properly set the idle. Everytime I set it, it would change once the engine had been revved up. I ended up having to set the idle too low to compensate for the change which caused other problems. In either event, I tried to use some advance springs from other kits, but I could not get the right advance curve. So I just replaced the distrib which has been great.

sbuell
08-27-2012, 02:15 PM
I do think I understand what you are refering to with the "little black button". I fought ignition issues a few years ago that sound similar. Tried two different ecms and a couple of coils along with plugs, wires, timing and most anything else I could think of. Finally tried a new distributor cap. When it arrived I realized just how worn down my center "little black button" was. New cap and all was well.

sxerob
08-27-2012, 02:24 PM
Yea... I didnt know how to accurately describe it with out the worlds longest run on sentence.

It the inside of the cap. When you turn it over, bottom center (which would be the top when installed) has a little "button" about 1/4" in diameter that is spring loaded. Seems like it would touch the top of the rotor when installed. Does that make sense?

Mine looks like its not sitting in the proper place as you can see the wear from where it should be sitting.

I'll try to take a picture of it tonight to make it more clear.

markismm
08-28-2012, 02:47 PM
Okay. Fully understand what you are referring to now with that description. Its been a while since I looked at mine. How long has it been since you replaced the cap and rotor. If it has been more than two or three seasons, probably time to just go ahead and replace unless everything seems to be working fine.