Flathead ignition

philrock

Member
I tried to put my new Arc 6620 flywheel on my (very old) Briggs flathead yesterday. The points cover prevented it from going on by about 1/4". I called Arc and they said I need a newer style ignition setup which eliminates points. They said get Briggs p/n 397358.

Is this correct? Is this all there is to it? Just bolt on this coil and remove the points, condenser, and points pushrod?
 
You may have to trim off the points cover boss, where the points and condenser cover mounting screw was too.As noted plug the hole where the breaker arm and plunger was, and loose the un-needed parts.The little points spring does make a good pull spring for a tillotson set up .
 
How about putting a Briggs PVL flywheel and coil on it.
It's a much better ignition system.
The PVL timing doesn't retard like the flat head and it has an aluminum flywheel.
 
I think he's got the arc flywheel already, Jimbo - but a good suggestion nonetheless.

Phil,
Pull the points cover off, pull the points, condenser & plunger. Take a short sheet metal screw or button head allen and thread down into the plunger hole (be certain that the end of the screw does NOT touch the crankshaft journal at all.) I like to put a small dab of silicone sealant on the threads as well. = Job done and you're ready to install your new flywheel and solid state ignition coil.



-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
28 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
The Briggs #397358 Coil comes with a little steel plug to press into the points plunger hole.

Fits nicely unless the hole has extreme wear.

I like to put a glob of JB Weld over top for extra security, but RTV will work just as well.

When ordering coil from supplier, make sure they check to see plug is still in there.

It should also include a B&S Logo timing key and a new kill switch wire.
 
Not to dredge up old topics, but...... How does one go about installing a B&S, PVL ignition on a flathead?
 
The flywheel has the same taper as the crank in the flat head so that's pretty simple. However the key ways are in different positions.
Some people just lap them together and then use red locktite on the taper.
I always put another key way in the correct place so if it ever comes loose you can just put a new key back in and your back in business, provided the crank or flywheel isn't damaged.
I don't do flat heads anymore but i have used the FH crank in an Animal for a stroker.
You are going to have to get the flywheel and coil in the right place and you should know how to use a piston stop and a degree wheel so you can be sure you have the timing right.
 
I've got a couple nieces that race Jr's and I am playing with motors more and more. Thanks for the input.
 
How about putting a Briggs PVL flywheel and coil on it.
It's a much better ignition system.
The PVL timing doesn't retard like the flat head and it has an aluminum flywheel.
Where would you set the timing on this, if it were open modified engine? Normally set it at 36 with 126 Dyno cam with 3hp flywheel and coil.
 
34-36* Is the recommended igntion timing .
Yes But if you change from a regular flathead coil to PVL and the timing does not retard?? How much effect would that have? I know from just putting a timing light on one if you set the static timing at 36 and rev it up to say 4500 then if retards down to about 33. My thought are set it lower with PVL. What have you experieced??Or anyone for that matter. I am going to put a PVL on an Open modified flathead turning around 9500.
 
I've not ran the pvl coil . Personally i would go 34* as you know it retards to 33* and thats a best i can get comprimise .
I did start the same conversion , depending on the block for the briggs flywheel you will need to clearance some on the block . I had the old point style .
Possibly need to fab a mount , simple enough .
 
Set it much more conservatively. The PVL will NOT retard as rpm increases. The flathead coils all do, and some more than others.
If you are seeing max HP (best power curve) with 33* timing using the stock coil, then set your PVL @33 on the bench.
 
Thanks Brian I am not sure where the best performance is. I have never check the timing at 8 to 10 thousand. 4500 is the most I want to rev it one the bench.
You probably have done it on a dyno. What are you thoughts???
.150 stroker, big valves intake ported to match carb. 80 over tilly 355 126 dyno cam.
 
Stroker engines move down the power curve in rpm. The bigger the stroke, the less you have to spin the engine up.

What makes me nervous is standing in front of the flywheel while I'm holding the timing light.
I've had a clone flywheel come apart (back in the days of stock flywheels) and I don't want any part of that again.
I'd set the ign. around 34* to start with and go from there.

Don't ever rev an engine without load -- you're simply testing the rod bolts. ;)
 
Hey guys, my coil slipped down and is rubbing the fly wheel. What do I space it at? Brian, it’s a motor you built a very long time ago.
 
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