Distributor Springs Advice

I'd look at one of the vacuum reading charts on line to see if you find a description of your twitch and what the variation is between the high and low readings.

By the way, speaking of my manifold, while I was looking around under the hood, I noticed something interesting, or concerning actually. On one of the runners of the manifold directly under the carb, I noticed that there appeared to be a crack on a sharp edge. I am not sure if its just paint separating, or if its actually a crack, and possibly a vacuum leak. You guys ever seen anything like this on your engines? If it is a crack, it looks like a little epoxy mix (I forget the name of the famous stuff) may plug it up. I couldn't feel any suction when I put my finger over it with engine running.

It might be less trouble overall to just take the carburetor off then do things on the workbench especially if you have a metal fuel line.

Getting that sprung to get it off and back on can be "not a lot of fun" especially if you cross thread the fittings.

If you have the non stick reusable gaskets in there now, it should come apart easily.

You have to watch out for the O rings on the accelerator pump transfer tube that goes between the metering block and the body and also the O rings on the transfer tube between the primary and secondary bowls. (Older carburetors don't have the accelerator pump transfer tube, their body and metering block and the gasket between them are different with a drilled passage instead of the tube)

Having a carburetor kit on hand is always a good thing in case you run into problems.

Also if it's on the bench, getting the accelerator pump linkage together right is easier.

But..............it can be done on the boat.

Something I learned from a chef who also worked on carburetors, if you spray the gaskets with some PAM or whatever your favorite cooking spray is before assembly, they.ll come off easier the next time. Even the non stick gaskets like a shot of PAM

davidg wrote: I assume the only way to change the dwell is to change the points gap, correct? If so, to increase the dwell, do you decrease or increase the point gap? Other than the idle screw, the only other way to adjust it I could see was two very small screws (one on each side of the carb metering plate).   I assume one, or both, or to adjust the idle circuit.

Reducing the gap will increase the dwell

The 2 screws each feed the idle circuit for their associated primary venturis. They both get adjusted together Shoot for best vacuum idling in gear

1 1/2 turns out is the "usual" starting point and turning out richens the idle mix on your marine 4160

The idle circuits could also need cleaning. Best way is to remove the primary metering block and then soaking and blowing out the passages with air.

An ultrasonic cleaner works good for the soaking if you happen to have one

Field Report #2......Success!

Points Cleaning: Not wanting to make too many changes at one time so I could tell what actually fixed things, I left the NAPA spring in the dizzy. As Mark suggested above, I dragged a piece of an ACE Hardware brown paper bag through the points to clean them. I learned this trick late in life (as in last week) when the boat wouldn't start. I had sprayed PB Blaster on the timing advance weights. Apparently some got on the points and it wouldn't start. My marina guy grabs a piece of an ACE paper bag, drags it through the points a couple of time, and wallah......it fired right up. The PB Blaster and points apparently don't work and play well together.

Points Gap: Yesterday, I inadvertently took the points off the dizzy plate, and screwed up the adjustment. Re-gapped them today to .018".

Timing: I confirmed I was at 10 BTC. Also watched the timing mark go up toward 25ish or so at 3,000 rpm. So, the advance is working properly.

Result: Headed out from the dock to open waters, and brought the rpm's up to 2500 or so. No stumbling, no missing. Ran like a pup!   

Dwell: I checked the dwell once everything else was pretty much dialed in. The spec calls for 29-33. I was at 25. I assume the only way to change the dwell is to change the points gap, correct? If so, to increase the dwell, do you decrease or increase the point gap?

Hillman #119 Spring: I wanted to see if the boat would even run with the NAPA spring, and it did. I am not sure it's optimal, but, I feel a lot better today, than I did yesterday at this time. Next time up, I would like to throw the #119 in to see if I can feel a difference. I will say that with the NAPA spring, the acceleration is okay. It certainly wasn't a rocket sled. Hopefully the lighter spring will put a little hitch in the giddy-up.

Overall, I am pretty satisfied with how its running now. I sure do appreciate all the input and advice you guys gave. However, I am still a little concerned with the quality of the idle. Tends to range from 600 in gear at idle, to 1100 in neutral.. So, I am going to research the finer points of tuning the 4160 carb. Other than the idle screw, the only other way to adjust it I could see was two very small screws (one on each side of the carb metering plate).   I assume one, or both, or to adjust the idle circuit.

Thanks Ken! I may go back up today and continue working on it to try and dial it in.

My manual on page 9 looks completely different than the reference guide from this site. It does not have all the info regarding the different distributors, and timing difference.   

As it relates to my idle, when I drop it in to gear, it seems like it drops down quite a bit. I will try to get specifics numbers, but, it seems like around 300-400 rpm.

Gonna take the dwell meter with me today to put that in the mix to see how close I am using .018 as the gap on the points.

I was just reading my original CC manual that came with my boat. It say that the idle should be 600 rpm in gear. I have been setting my timing with the boat in neutral, and the rpms are probably closer to 900/1000. Should I be setting the timing with the boat in gear at 600 rpm?

Also, point gap spec is .018" (I had been using .017"....probably not a big deal), and the dwell spec is 29-32. The timing spec is 6 degrees, but, it seems like everyone is using 10, as am I.

I’m sure you realize this can all be done on the trailer?

Initial Field Report: Mixed Results!

The Good: The NAPA spring for "my distributor" my marine guy got me did help the timing to work. The timing was advancing at higher RPM's like it was supposed to. Got close to the 25ish BTDC mark when revving at mid throttle, based on what I could guesstimate under bad conditions.

The Bad: Got everything buttoned up. Idle seemed fine. Gave it some gas to get underway, and it was running real rough (seemed like it was missing). Made sure all the plug wires were attached, and tried again. Same thing.

The Ugly: Trying to work on a boat in 90 deg. heat, 110% humidity, blistering sun, and 2'-3' swells.

The Springs: Top is the NAPA. Bottom is the Hillman #119. Only tried the NAPA today.

Anyone know why the boat would suddenly start to run very rough with a new spring in and the distributor advance "working"? I may have inadvertently changed the point gap, but, I think I had it very close. Maybe the condenser is bad?? But the distributor is "fixed" and it now runs rough. Go figure!?!

I'll need to keep tinkering with it to figure it out. May throw the Hillman spring on, and/or go back to no small spring at all and see what happens. It ran perfect with no spring.

Compare the Napa springs to the # 119. Tell us how they compare in length (overall), number of full coils and diameter. If you have a spring fish weighing scale, pull just hard enough to cause the coils to open up slightly and tell us the weight for each spring.

KENO wrote: You won't find any numbers or graphs from PCM showing the curve, but I might know a backyard hack who'd have some numbers to compare with yours

Speaking of numbers, for whoever cares, here's what I came up with for the PCM heavy spring and a Hillman #119 installed in a clip down cap distributor.

RPM            advance

500             0 plus initial

1000           4 plus initial

1500           12 plus initial

2000           16 plus initial

2500           18 plus initial

3000           22 plus initial

3500           24 plus initial

4000           24 plus initial won't go any higher because of the slot length in the advance plate (also referred to as the stop plate at times) limiting the advance.

Now these were with my tach which may read different than your tach and my eyeballs which aren't your eyeballs but they give you an idea of the timing curve with the springs mentioned above.

Some people may like it, some may not, but I think it's pretty good keeping in mind that with the heavy spring you don't reach full advance till about 3500 to 4000 rpm as it originally came from the factory.

The engine runs good with this setup

With the screw down cap the advance plate is different (shorter slots) and the max advance will be less if you start with the same initial timing.

andrewmarani wrote: i'm probably diving too deep in the weeds

I've been in those same weeds and that's how I eventually found the Hillman #119

I have quite a collection of springs for other brand distributors and none of those really came close to the original.

If the springs are weak you will bring the timing in early which can cause performance issues, pinging and maybe detonation.   If the spring is rusted it is weak and your timing will come in early. If you have a Speed Shop locally they usually have a selection of springs to choose from. Summit Racing shows many available on line or check the hardware store selection. If the new spring is too strong it will delay your advance and make the engine sluggish.

andrewmarani wrote: Nope, not spending $17 to ship two springs that I could mail for 75 cents. I will buy the #119 springs and see how they compare.

Probably a good move

I'd been using one of the Hillmans for about 300 hours before I decided it was time to post here about it.

Kinda like acceptance testing to be sure I was happy with it.

Nope, not spending $17 to ship two springs that I could mail for 75 cents. I will buy the #119 springs and see how they compare.