Issues at idle

[Dave Neptune]

Timing mark

Jim, your mark will be where you mount the pointer. First you need to find TDC and then put the mark on the pulley. From there you need to mark the increments you desire for checking
Personally I think it is a waste of time, although a cool idea. Setting the timing via the "power timing" is what I got paid to do when doing power timing on a rear wheel dyno. I would only use the timing light to see where the timing wound up after setting it via power. This is the best way to set timing in a static load application like a boat, because the prop is the same load that the dyno would be. We all have differant hulls and props and the tweaking to get it right is what power timing is.
If I want to check or modify the advance curve I would use a distributor machine to get what I wanted to try and then power time it!

I'm ready for some grief on this post so have at it!

Dave Neptune

[thatch]

"Two Different Worlds, We Live In Two Different,etc,etc

Dave
While power tuning the timing certainly will result in the highest power output of these engines, I have chosen to go with close to the factory recommended advance numbers. In doing so I have an engine that, despite being pretty high on the mileage scale, will start on a dime, idle smoothly at 500 rpms and produce almost zero blowby, (without the use of a pcv valve). Establishing an accurate top dead center mark on an A4 is a little difficult while using the flywheel pin, so I chose the method that you have probably used a gazillion times and just used a dial indicator down the #1 plug hole. In the case of a Catalina 30, with it's distributor side access door, using an accurate mark on the accessory drive pulley just makes sense. My timing setting?, 2 degrees btdc at idle. Another mark, 5/8" ahead of the tdc mark, gives me the 17 degree mechanical advance check position.
Tom Thatcher

[Dave Neptune]

Advance?

Tom, do you have access to a distributor machine? Do you also have the "plot" of the adv curve. I am not saying that it is better to power time especially since it does require a bit of experience to develope that particular touch, it sure did for me. I do think it is far more difficult for a novice to find TDC and plot the degrees properly though. I wonder if there is any conversion numbers (timing plot) for our new fuels. Most of the fuel avalable today is designed for higher compression albeit with a lower octane rating . My guess is that the curve could be sped up a bit because of better fuel today than when the engine was designed.
Have you checked by power timing to see if it is any different than your setting at idle setting of 2 degrees? Mine too will idle all day (did so recently) at 600 however I do have blow by and low compression in two holes.
I seem to remember Tom at Indigo saying something about curving the distributor and I didn't get any numbers. However I did get his spring kit to change the advance a bit and correct for removing the drag of the points on the advance mechanism. The old dist machine I have available won't hook to an electronic ignition though.
I have your book at work and haven't explored it much yet, perhaps the curve is plotted in it.

Wish list could be a "degree wheel" sticker for the accy pulley. That would be nice.

Dave Neptune

[thatch]

"The poor man's distributor machine"

Dave,
In the past, as I'm sure you have done, is to use a degree wheel and a timing light to observe the the timing through the relavent rpm range of whatever engine that we're trying to build a smooth advance curve for . In the case of our A4's there should be 0 degrees at idle (700 rpm) and 17 degrees of mechanical advance that should all be in by 1800 rpm's, according to Robert Hess's factory notes. By doing a little math concerning the
3-3/4" accessory drive pulley, I came up with 5/8" as a pretty good distance between the tdc and full advance marks. I feel that the factory timing is probably fairly conservative so I went ahead and bumped it up about 2 degrees. As far as an actual curve goes, I have not bothered to watch what is happening from idle to my target rpm of 2000 but, I do know that it's all in at cruising speed. Since I don't spend much time at half throttle, I don't see it as being too important..... My concern in setting the timing using the
"power tuning method" is that, I feel it is very difficult for the average guy to do it correctly. An engine tuned for maximum power is an engine that is on the ragged edge of detonation. I also feel that some of our "excessive blowby" cases are the result of excessive ignition advance. I knew that this conversation was far from being over.
Tom

[Dave Neptune]

Info

Tom, I absolutely agree about experience being required to set the timing
statically under load. Good equipment like a dyno and or a good ear and tach. That is why I always set to max and then back it off a tick for an easy running smooth engine. My concern is that it would probably be more difficult for most to actually find TDC without an indicator and the skill to actually find TDC then.
I would love to see timing marks for our beasties especially for those of us that tinker. The 5/8" you refer to is around the outside diameter of the pulley I asume. Is it actually 5/8 or was that the closest fraction to your decimal figure? I think that with the modern fuels (yes even E-10) and an electronic ignition that t bit faster curve would be advantagis. One thing does suprise me though and that is a total of 17 (34) degrees. For a 3500 RPM rated engine with 6.5:1 compression that seems a bit short. My guess would be around 38~40 total, even at 2400 RPM's. I'm curious to find out if 2 or even 4degrees makes an improvement for you.
Did the max at 1800 come from Universal or Hess. For the most part I don't trust Hess's numbers on to many things that aren't copied from the manufacturer. A lot of his stuff for the A-4 is actually from the old fords regarding the carbs and plug recomendations. Yeh it is the same carb but for a different application altogether and a larger displacement.
I checked with Zenith and they have a few set ups for the same carb, they just don't have what went to what unless you have an original carb part number. My ole friend who works on A-4's says he has come across many different jetting sequences when doing the carbs. They all work just not as well as the correct one. I have seen thre in the late model carb myself.

Dave Neptune

[thatch]

"Hess info"

Dave,
I have 9 pages of A4 info from Robert Hess which appear to be re-prints from actual universal manuals. The info includes engine numbers concerning manufacturing dates, bearing, piston, valve and tuning information that seems to all be correct as far as I can see. The 5/8" distance between my tdc and the 17 degree advance mark on the outer lip of the accessory drive is actually .556" by my math, which is actually closer to 9/16" (sorry). My attempts at establishing accurate timing marks for our A4's come from virtually all of the other gas engines that I have worked on over the years. They all have had the timing "locked down" at the factory (in the case of lawnmoyer engines) or are supplied with accurate marks, pointers and timing information. When the A4 was designed around 1950, most auto engines had similar compression ratios and timing numbers. This produced an engine that ran smoothly but that was a little bit lazy compared to todays quick accelerating, high revving motors. I have found, at least in my case, that by keeping this "lazy" state of tune I have an engine that shows almost no blowby (yes, advancing ignition timing does increase blowby) and which will idle down lower allowing me to ease into the slip a little slower. I realize that I could tune for more power but I seem to be able to reach hull speed without having to do so.
Tom

[Dave Neptune]

Tune time

Thanx Tom, I hadn't tried my trig skills for a while! While sitting in the slip for a while except fopr a few whale watching excursions I will have some time. I'm going to dig out an indicator and generate a plot on the drive to see where I'm at for kicks.
I have seen 38 plus on more than a few under 8:1 load duty engines. If I remember right I set up a Ford Flathead hot rodder's dist. for 38 degrees and he wqas camed up a bit. I had to notch it out a bit and he was quite happy. I don't remember where he set it in though!!!
I'll let you know what I find out when I get it done. I'm most interested in being sure4 it is full advance at 1800.
Most of Hess's stuff is OK I just don't like the way his carb stuff accumilated.

Thanx for the info.
Dave Neptune

[thatch]

"Close to Agreeing"

Dave,
My timing is set at 2 degrees btdc at idle at the accessory drive so when you add the 17 in the distributor, I am actually runing a total of 38 crankshaft degrees or, in other words, right about where you think I should be. The running qualities are so good at this setting, I doubt that I will be doing much more testing. As I see it now, the best thing that we could be doing is to figure out an easy way to install easilly readable marks on either the accessory drive or the flywheel. Different boats seem to present different challenges in this regard.
Tom

[roadnsky]

Gents-
FWIW, after listening to you two for most of the weekend,
I've decided to go back to a "baseline" TDC timing to get some 'numbers' to compare to my previous 'power timed' setting.
If there are enough differences to bother, I'll post 'em here.

Otherwise, I'll lay low and wait for you guys to serve-n-volley some more.

[thatch]

"My distributor thank's you"

Jerry, Thank's for offering to help sort this thing out. If there is an area of speculation that should have been sorted out long ago it is in the area of the A4's ignition system. We have burning out coils and overloaded modules and no real timing numbers that we can trace back to the manufacture. It's amazing that these things run at all. Maybe we should all go to diesel. On second thought......
Tom

[jpian0923]

Seems like we need to get Neil in on this discussion if coils and timing are in play?

[Dave Neptune]

More input good

Jerry, thanx for the offer of your numbers. That would be most helpful. I am going to fabricte something for my beastie along the lines of Tom's set up. I'm going to look for a protracter around the diameter of the drive pulley unless someone knows the diameter, that will save a trip. My access is from the top so seeing the acc'y drive is just a bit of a hassle. It sits rather close and somewhat undre the sole of the boat. I think I will be able to see it OK.

Tom, no worries, I'll call but probably not today. I am laying a good friend to rest and spending time with his family today.

Dave Neptune

[sastanley]

dial indicator

Hi Dave & Tom & Jerry,

I took Dave's advice and 'power timed' my engine this summer, and then backed it off 'just a tick' so I wasn't 'blowing anything up'. It seems to be OK, but why not do it properly? Since I have good access to the side like Tom, I really like the accessory drive timing mark approach.

So, for those of us that have been thinking about this but haven't done it yet..which type of dial indicator would be most appropriate to pick up for checking the piston position for accurate TDC? There are simple ones, and magnetic ones and clamp on ones, etc..which one works for this application?

Also, just to make sure I am not screwing up acronyms, BTDC is BEFORE Top Dead Center, correct?

[roadnsky]

Also, just to make sure I am not screwing up acronyms, BTDC is BEFORE Top Dead Center, correct?

Correct Kemo Sabe.

[edwardc]

Is a dial indicator really necessary, or is it overkill for this application? I mean, how accurately can you mark or read TDC on the pulley anyway?

I'm thinking that a skinny wood craft dowel may be enough. Just slip it thru the #1 spark plug hole and let it set on top of the piston. Then watch/feel it go up and down as you wiggle the crank until you find TDC.