Tuning problems - L18/L16SSS hybrid with SU's

[Un4Scene]

I bought this car a couple of months ago to be my new DD and project car. It's been doing an acceptable job of both, but I've been having trouble getting it tuned to a level that I'm happy with. Any advice would be appreciated.

When I bought the car, it came with an L18 installed, and a damaged L16 block and head on the side. All the parts (carbs, dizzy, ignition, etc...) we're swapped from the L16 on to the L18. I was told that the L16 was the original, but after a fair bit of research it appears to be a true SSS motor (so, NOT the original motor). I have the SSS dizzy and SU's installed on the L18, and the L16 has a peanut head with the appropriate valve and port sizes for an SSS. I don't know where the L18 came from, or which head is on it, but I was told by the PO that it is also a peanut head.

After buying it, I drove it about 2,000 miles to get it home (Vancouver, WA to Omaha, NE), and it ran pretty damn well the whole time. It had more power than I expected on the highway, and it averaged about 34mpg. It wasn't perfect though - It sat around 4,100rpm @ 70mph (I have a factory tach), it absolutely refused to rev over about 5,000rpm, it stumbled badly under light-throttle from 2,000-3,300rpm, and it ran hot enough to keep the temp guage in the top 10% of it's range for almost the entire distance. Those issues prompted me to try to re-tune it once it was safely in my garage.

First attempt: The first time I looked at it, the crank timing was advanced way beyond the marks (the adjustment was maxed), and the dizzy was fairly centered in the marks. After setting the dwell to about 52 (with a dwell-tach), I used a timing light to adjust the crank timing back to about 11-deg - the factory spec for a stock L16. With these settings it ran much better at high-rpm (easily rev'ing up to 6,500rpm), it ran much cooler (temp guage centered), and at 70mph the rpm's were down to about 3,800, but it was stumbling terribly up to about 2,700rpm causing it to foul the plugs with unburned fuel.

Second attempt: I did the full tuning workup on the dual-SU's with a Unisyn guage - Matched and balanced at both idle and high RPM, adjusted the idle speed, repeated the process, etc... Initially, the motor ran quite well after this, though with noticably less-power than it had before. It still stumbled a bit at low rpm, but it was very minor. Then it got wierd. After a couple of weeks of driving, I noticed that it seemed to be running richer and richer without me changing anything. By the time I had a chance to try again,
it was spitting fuel out the exhaust, fouling all the plugs, dieseling when I shut it off, and my mpg had dropped to about 20.

Third attempt: I adjusted the mixture from scratch this time - starting at 2 turns out, and checking the (new) spark plugs and exhaust for unburned fuel. I also made sure the dashpots were full of ATF. This fixed the rich mixture, and it was running pretty good. A week later it was showing signs of an over-rich mixture again, without me having made any changes. I already had the Pertronix bits on order, so I waited to check it out until I had those to install, so I could do it all at once. Based on my experience, I think there's a lot of truth in the old adage that 90% of carburetor problems are caused by the ignition system, and I wanted to minimize this possibility.

Fourth attempt: I installed the Pertronix Ignitor (replacing the points), Pertronix 8mm wires, and I replaced the original coil and ballast with a 3.0ohm Pertronix coil. The ballast was measuring at 1.9ohms, so I knew that was going bad, and it just seemed wise to upgrade a 41-year old coil. Between my research and some advice from a Pertronix tech, I chose a 3.0ohm coil so I could eliminate the ballast and simplify the system (the stock system uses a 1.5ohm coil and a 1.5ohm ballast for a total of 3.0ohms resistance). [ Note: It's probably irrelevant, but I did check the dwell with the Pertronix bits, and found that the Ignitor sits at about 45-deg, which is about 3 below the minimum factory spec, and that's with it maxed out. I'm not sure why this is, but with a more powerful coil, I don't think it should cause a problem. ] When I was ordering the Pertronix bits, I discovered that the dizzy is the SSS model. After doing some research on the differences (and not finding much info), I finally figured out that I was gonna have to get creative with the timing, rather than rely on stock spec's. This time I hooked up the dwell-tach (which doubles as a regular tachometer), the timing light, the remote starter, and started over from scratch with the tuning. The steps I used were:
- Adjusted the crank timing to the point that it had the highest idle speed - this ended up being way past the timing marks, with the adjustment almost maxed
- Adjusted the dizzy to the highest idle speed - the first mark on the advance side
- Verified dashpot fluid level
- Adjusted the mixture based on plug appearance and exhaust (it was slightly rich again)
- Set the idle speed to about 850rpm on the external tach. I also noticed that this is reading as about 450rpm on the OE tach.
- Matched the carb balance at idle
- Matched the carb balance at 3,000rpm
- Set the idle speed to 850rpm again (on the external tach)
- Matched carb balance at idle
- Matched carb balance at 3,000rpm

With this tune it ran smoother than it ever has at idle/low-rpm, and at all RPM's with no load on it. When I drove to work the first time, I found that the tach is down to about 3,300rpm at 70. However, it was also running very hot again, it's stumbling very badly above 2,700rpm, and it wouldn't rev higher than about 3,800rpm. [ Note: At this point, I'm not sure which tach is correct. I find it hard to believe that I've managed a 1,000rpm difference @70mph with nothing but engine tuning adjustments. On the other hand, the motor does sound like it's running at a significantly lower RPM at any given road-speed than it has in the past. ]

Currently: I've been making some minor adjustments here and there to try to improve the running condition. I thought it might have started running so hot because it was detonating (even though I wasn't hearing it), so I added a bit more fuel to the mix. This didn't seem to improve anything, and may have actually made the stumbling worse so I set the mixture back to where it was. Then I thought the RPM's might be limited due to not-enough timing, so I advanced it a bit more. This also didn't seem to help anything. Next I tried retarding the timing a bit. This made a huge difference - it's still stumbling a lot, but now it will rev to at least 4,800 under load (I haven't had a chance to go any faster yet).

SO! Finally, this is where I'm at now:

-I still have some bad stumbling above ~2,700rpm, but only under light/lift throttle. At WOT there is no stumbling at all, at any RPM.

-There's also the issue of the mixture getting richer all on it's own... The only thing I can think of that could cause this is leaking/burning fluid from the dashpots, but that doesn't appear to be happening. Otherwise, I haven't the slightest idea.

-Engine temps are still very high on the guage. Though I haven't verified it's accuracy, the guage seems to reflect cooler temps with poorer running, and higher temps with smoother running - which makes sense.

-And finally, everything I know about L-series motors indicates that they like a lot of advance, but apparently this particular combination of parts likes a lot of advance at low-rpm, and considerably less at high-rpm... which doesn't really make sense to me. My best guess is that this has something to do with the different advance curve of the SSS distributor, but I'm still not really sure how to set this up in an optimal configuration.

If anyone has any insight or suggestions on how to improve this tune, I'd be greatly appreciative! Thanks in advance (pun intended).

~Laken

[James]

Nice post - you could give a class on how to ask for help on this forum. It usually takes about two weeks to get the amount of information you have provided in one post!

Your timing is way maxed out in my opinion - dangerous for your engine. At Idle it should be somewhere between 10-16 deg BTDC. The marks on the pedestal are essentially meaningless without having a baseline. There are two adjustment screws that can allow for adjustment (one on the bottom as well) that can change things.

I think 90% of your issues are timing. Since you have changed everything (granted over a series of well placed efforts), its hard to know.

I wouldn't mess with the carbs until you get the timing right. If thats a true SSS engine and distributor (single point is one indicator) - the mech advance is set up so that the initial advance at idle (what you set with the timing light) should be at 16 deg BTDC. Set this, and then use the carbs to get the idle about right. These engines will seem to like a lot of initial timing, but given what the distributor adds, it will be way too much.

[James]

One other thing to add. If you take the cam (thing that drives the points) off (there is a screw in the middle of it) your distributor, on the base of the cam are two ears that control the amount the weights in the distributor are able to advance the timing. There will be a number stamped on this piece. Take that number, multiply by two, and subtract from 36. That should get you in the ballpark of where your initial timing should be set. If its a stock dizzy - it should have a 13 stamped on it - which would put you at 10 deg. BTDC which is stock.

In re-reading your posts. Wondering if you have something loose in the intake causing a vac leak. might be worth a thorough go through with all of the nuts, bolts on all of the manifolds and carb mounts.

One question for you: There seems to be a large swing in your cooling - which may or may not be dependent on tune. Is your thermostat known good? How is radiator? Once my cooling system was in good shape, I could never get that much of a swing, even with stuff way out of tune.......

Looks like a nice car BTW.

[James]

Re-read your other post. Is the SSS dizzy on the L-18? If so, try setting it to 16 deg BTDC to start.
What is the head casting on the L-18?
FYI - a lot of used engines came from Japan - a lot of them SSS models, and got installed in these cars over the years. You could check the block number and compare on the ID plate to see if the block is original. (previous owner could have upgraded all of the parts on the original block).

[Un4Scene]

Nice post - you could give a class on how to ask for help on this forum. It usually takes about two weeks to get the amount of information you have provided in one post!

Thanks. This isn't my first forum, and I'm usually the one answering questions, rather than asking. Also, I've been working on cars for almost 20 years, with about 8 of that as a professional mechanic, so I have a pretty good grasp on what info is necessary.

Your timing is way maxed out in my opinion - dangerous for your engine. At Idle it should be somewhere between 10-16 deg BTDC. The marks on the pedestal are essentially meaningless without having a baseline. There are two adjustment screws that can allow for adjustment (one on the bottom as well) that can change things.

I think 90% of your issues are timing. Since you have changed everything (granted over a series of well placed efforts), its hard to know.

I wouldn't mess with the carbs until you get the timing right. If thats a true SSS engine and distributor (single point is one indicator) - the mech advance is set up so that the initial advance at idle (what you set with the timing light) should be at 16 deg BTDC. Set this, and then use the carbs to get the idle about right. These engines will seem to like a lot of initial timing, but given what the distributor adds, it will be way too much.

Thanks for the advice!

I don't know where the L18 block/head that's installed came from, and I don't have a manual/specs for it. Also, I'm not sure how much (if any) difference there was between the various years and models that came with the L18, or even whether this one has stock internals... I don't really know what I'm dealing with at all here.

It has 5 timing marks total - I'm assuming the first is for TDC, but I don't know the interval of the other marks. That makes it a bit difficult to set it to a specific advance. That aside, I don't know how well the stock timing would work when combined with a non-stock dizzy and intake system, and an unknown cam. That's why I tried setting it at the point where it had the highest idle speed. I'm guessing that the SSS dizzy has more initial timing built-in and/or a steeper advance curve - so steep that it's getting too much advance at high-rpm. I hate the fact that I've had to resort to experimenting/testing different settings, but I don't see what other choice I have. That's why I was asking for advice... hoping that someone else might have some experience with this particular combination of parts, or some insight in to what kind of numbers I'm working with here. Now that I've discovered that it has too much intial advance, I'll be dialing it back some when I get a chance... I'm just not sure how to determine where exactly I should set it at.

I agree completely about only messing with one sub-system at a time, but I had to re-tune the carbs to lean out the mixture. It's kinda difficult to tell how timing and ignition changes affect the motor when all the plugs are getting severely fouled with unburned fuel. I think I've got the mixture dialed in fairly well now, but I still haven't figured out what's been causing it to change over time, and that worries me. Hopefully I've got it set well enough now that I can determine how the timing is affecting the efficiency of the burn in the cylinders.

[Un4Scene]

Apparently you can type a lot faster than me!

The L18 block/head is in the car, but with all the other bits from the L16. Both heads have A87 casting numbers, but I know that really doesn't help much since A87 was used on both open and closed heads, and with various differnet valve and port sizes. I actually measured the valves and ports on the L16 head to verify that it matches the SSS specs, but I haven't had the head off of the L18 to check it out.

The plate in the dizzy is marked with "11" (indicating 14-deg initial timing). That, and the part number from the dizzy housing, match the info I've found for a SSS.

~Laken

[Un4Scene]

Oh - I didn't know there was a block ID number... Could you tell me where to find it at? It's not really relevant to the rest of this, but It'd be good to know if this is the original block!

~Laken

[Un4Scene]

Sorry - trying to do too many things at once...

I haven't verified that the thermostat or temp. sensor are accurate. I figured if it's been working for about 3,000 miles, including an 1,800 mile road trip, and it's never over-heated, then it's working well enough. I was planning on doing a full flush of the cooling system and replacing the hoses and thermostat, but I've been spending all my wrenching time on tuning instead.

I'm fairly certain that vacuum pressure/leaking is not an issue. I checked the vacuum pressure with a guage: measuring it at the line for the vacuum advance it's setting right around 5.50 at idle, which is about perfect based on the info I've found. As a side note, I have checked the cylinder compression too, and it actually tested far better than I expected. The spec for a stock L16 is around 170 psi with a variance of <20%, and mine measured at 174, 160, 170, and 175, for cylinders 1 through 4, respectively, for a variance of <10%. I'm not sure what the spec is for this L18, but that should certainly be good enough.

~Laken

[datzenmike]

- It sat around 4,100rpm @ 70mph (I have a factory tach)

I used a timing light to adjust the crank timing back to about 11-deg - the factory spec for a stock L16. With these settings it ran much better at high-rpm (easily rev'ing up to 6,500rpm), it ran much cooler (temp guage centered), and at 70mph the rpm's were down to about 3,800,

How would setting the timing reduce the revs form 4,100 down to 3,800 RPM @70????

[Un4Scene]

- It sat around 4,100rpm @ 70mph (I have a factory tach)

I used a timing light to adjust the crank timing back to about 11-deg - the factory spec for a stock L16. With these settings it ran much better at high-rpm (easily rev'ing up to 6,500rpm), it ran much cooler (temp guage centered), and at 70mph the rpm's were down to about 3,800,

How would setting the timing reduce the revs form 4,100 down to 3,800 RPM @70????

I'm not entirely certain. If you read on through the whole post, you'll see that, as it sits now, it hits 70mph at a reported 3,300rpm on the tach. So far I've seen a total varaince of about 1,000rpm @ 70mph. This has me a little puzzled as well. I could understand a slight variance based on how much power the motor is putting to the wheels, but everything is still connected through mechanical linkages and parts. The biggest change occurred after installing the new ignition coil - I'm wondering if this might have something to do with the tach display, since the tach is reading off the coil. I also noted in there that the OE tach is showing a different reading at idle than an external tach. I have no explanation for these discrepancies. /shrug

~Laken

[James]

On the side of the block, right under the head, there is a number behind the "L-16" mark.

The timing will be essentially the same whether you are using a Pertronix or stock. Head, valves cam etc will allow for a small difference in initial timing, but most L series engines like to live somewhere around 34-36 total advance. Depending on cam etc. more initial advance may be worthwhile - but you will have to limit the mechanical advance accordingly (shorten the slots) to keep the total advance in the happy range. You are right - different curve on the SSS.

I only mention the vac leak as it could give you some of the symptoms you mention.

SO - you have a pointer on the timing cover, and marks on the pulley.

They are at 5 degree increments, but its been so long since I had one (later models have a singular mark on the pulley, and degree marks mounted on the timing cover) I can't really speak to it. I do think there may be a 5 deg ATDC on the other side of the TDC mark (someone else will chime in).

I would take the time to set TDC - and see what mark you are dealing with - then paint that with a bigger line or different color. If you pull the valve cover - there is (if a decent or stock cam gear) a mark on the thrust plate that aligns with a mark on the gear which should get you close enough to TDC to see which mark.

[Un4Scene]

Ok, this is making more sense to me now. I forgot to consider the timing from the mechanical advance when I was thinking this through. So, esentially:
- Setting the timing on the crank is effective at all rpm's and all vacuum conditions. That's a given.
- The additional advance provided mechanically is to ensure adequate timing for low-vacuum conditions (low-rpm and WOT).
- The additional advance provided by vacuum is to ensure adequate timing under mid-high vacuum conditions (high-rpm, and lift/light-mid throttle)

So by adjusting the crank timing for maximum efficiency at idle, I ended up with WAY too much timing once both of the other sources of timing-advance kicked in. Got it.

Sorry, I guess I should've clarified about the timing marks - mine does have a pointer, with marks on the pulley. The mark in the most retarded position is significantly larger than the others, so I'm assuming that's TDC (I'm not in a position to tear the engine down to verify this). I guess I'll try adjusting it as if each mark is 5-deg more advanced and see how that turns out. I'll start with 14, as suggested by the number on the dizzy. Hopefully that'll get it close enough that I can fine-tune the adjustment on the dizzy itself. ...I just had a thought - I don't think I centered the dizzy before I set the crank timing the last time. That would certainly throw everything off...

I also thought that a lack of vacuum pressure may be part of the problem - that's why I tested it and checked my cylinder pressures.

Hopefully that'll address the majority of the tuning issues that I'm having. I'll update this post with the results. Thanks for the help!

~Laken

[Un4Scene]

Ok, so the first thing I did was take it for a drive to get it up to normal operating temp's, as I think tuning it cold may have been part of the problem when I tuned it last time. As it has been lately, the temp guage settled around 90% of the way across the sweep. After that, I checked the number on the dizzy, just to make sure, and it actually says 11-5. I'm assuming that means 11.5 which means intial timing of 15-deg. Then I centered the dizzy and checked the crank timing. If the timing marks on the crank are at 5-deg intervals, I'd estimate that it was set to around 30-deg of advance. I changed it to about 15-deg's. I also checked the condition of the plugs again, just to make sure that the mixture I'm running is burning well, and it does appear to be. No fouling on the plugs - just a nice light brown color. Then I took it for a test drive. The results are mixed...

- The first thing I noticed is that the temp guage is reading back in the center area again - around 60% on the highway. I'm quite happy about that part, because it was worrying me that it was running so hot. I can now confirm that my engine temps are directly related to the timing - the more advanced it is, the hotter it runs. The fact that it was running good or poorly after previous tunes was irrelevant - it was the just the timing changes that I made that were affecting this. I'll clarify how I figured this out below.

- It also seems to be running very smooth and strong at low-rpm's. It feels as powerful at low-rpm as it ever has, and it seems to be running just about perfectly till I get on the highway...

- In third gear it wouldn't rev over ~4,200rpm, and it started misfiring and stumbling badly around 3,500. In fourth gear it wouldn't rev over about 3,800, and it started misfiring around 3,100. The tach is now showing that I'm hitting 70 at ~3,100 (another decrease). [Note: At this point, I'm guessing that the OE tach is reading significantly lower than the actual engine speed, but it should still be useful for measuring comparative changes] Starting at about 60mph in third gear, and about 68 in fourth gear, the power starts dropping off drastically. This happens about the same time that it starts misfiring horribly. I have no doubt that the misfiring and the loss of power are directly related.

- After driving for a bit, I pulled over and advanced the dizzy timing by 2 marks. Once I started driving again I noticed that the temp guage was running hotter - about 70%, once it settled on the highway. The misfiring didn't get any worse or better, but it moved up the RPM range by about 200 rev's.

- I pulled over and adjusted the timing again - this time to the second mark on the retarded side of the center line. This time the temp guage settled around 50%, and the misifiring moved down in the RPM range - about 150rpm below where it was when the dizzy was centered.

With this new information, I'm guessing that the misfiring is unrelated to the timing (regardless, I don't think I want to advance the timing much more than it is now 'cause I don't want the motor running that hot). However, I don't really have any idea what could be causing it... When I got the car two months ago, it had a slight stumble under part-throttle from ~2,200 to 3,000rpm, but it was nowhere near this bad. It only seems to happen when the engine is under load, and the heavier the load is, the worse it gets. I'm not really sure how to interpret that. Is it just running out of breath? Bad mixture at high-RPM? Valve float? Lash adjustment? Any other ideas? I'm open to suggestions!

~Laken

[Un4Scene]

After reading through all this again, I realized that I made a couple of mistakes. First, the intial timing indicated by the dizzy should be 13-deg, not 15. That shouldn't be that big of a deal since it's well with in the range of adustability on the dizzy.

More importantly, I suppose I need to check my temp sensor out to make sure it's sending an accurate reading to the guage. It's certainly possible that it's reading lower than it should. If that's the case, then I may be judging a good operating temperature with incorrect information. Maybe it should be running with the guage almost pegged, and the guage is just giving me an incorrect reading. If that were true then I would feel much better about running the timing with more advance.

These mistakes still wouldn't explain the misfiring though, since it was misfiring just as badly when the advance was set about 15-deg higher...

~Laken

[Un4Scene]

I've been digging for answers all night, and I think I may have found something in this thread:

http://www.the510realm.com/viewtopic.php?f=30&t=22285

The problem discussed sounds awfully similar to what I'm experiencing, though mine doesn't seem as severe. I guess it's time to dig in to the SU's a bit more and check out the floats and levels.

...unless anyone has a better suggestion?

~Laken