Spark Plug, Compression, Gearing, and Power Feedback

[Hardway]

I have been gathering some baseline info in an effort to find out why my 240z feels to be lacking power.  It runs good, idles smooth, but just does not have any "plant you in the seat power" in any gear.  Below are the specs along with some pictures of the spark plugs I pulled.  I have not checked the timing and I know how important it is, just didn't want to put the used plugs back in to do so as I plan to install some new ones.

L28 N42 Block #184718  Was told it was bored out to 2.9L but have no way to validate this.

1973 E88 head with stock cam in good shape and properly adjusted valve train.

Triple Dellorto DHLA40 carbs, rebuilt, and appear to running a bit rich based on the plugs

Mallory Uni-Lite distributor with electronic breakerless conversion, MSD Blaster 2 coil, Taylor Sprial-Pro wires, AutoLite #64 spark plugs below gapped around .044

Stock cast iron manifold

Compression: #1 150, #2 151, #3 150, #4 151, #5 151, #6 150  I think this looks really good!

Based on my setup I believe I should get a set of NGK B6ES-11 or BR6ES-11 spark plugs.  Do I need resistor plugs or not? 

The transmission is a 280zx Turbo 5-speed unit in great shape.  Diff is a 3.54 with a Precision LSD.  Am I losing power due to my gearing?

Once I get new spark plugs installed I will check my timing and post my numbers.  Any feedback or ideas is greatly appreciated.

[Patcon]

Is it me or do the plugs look oily, especially near the washers?

[Zed Head]

You won't lose power due to gearing, just acceleration from a dead stop or very low speed.  

One thing that jumps out in your list is a cylinder head designed for 2.4 liters on a 2.9 liter engine.  That's going to choke air flow and limit the potential.  Another might be the exhaust system, after the manifold.  Muffler and pre-muffler.  They can choke power also.

Finally, maybe inconsequential, but I don't think that Mallory Unilite is designed for .044" gap.  Might be getting some missing while under power.  Especially if you still are using the ballast resistor.

Patcon has replied while I was writing but I'm going to post anyway.

[rcb280z]

6 minutes ago, Patcon said:

Is it me or do the plugs look oily, especially near the washers?

They look really oily. 

Hardway, you burning thru oil faster than normal?

[Hardway]

I knew I would get some good questions and feedback!  Yes, the threads are oily as the valve cover gasket is weak.  The whole passenger side of the engine is grimy.  A new gasket is going on as well as cleaning up the engine some.  I don't know about oil burn as I have not driven the car enough to tell.  The oil level has not changed since I did it in September and that has been with a few 40 mile round trips to cars and coffee at 80mph and there is no smoke of any kind based on my personal experience and those that have driven behind me.

Interesting observation on the head Zed.  If I were to replace it, what would you suggest?  Possibly a '75 - '76 N42?

On the exhaust side, I know the manifold is not ideal but my series-1 car has an all stock exhaust and felt like it had more grunt.  This car just has a Dynomax muffler fed via 2.5" exhaust with no resonator. 

So the gap may be too much for the Uni-Lite?  Does this mean I should run spark plugs designed for a smaller gap?

[Zed Head]

I think that the E88 is the head that people sometimes put the bigger valves in.  So that's an unknown.  But you definitely need the flow to match the displacement.  Fresh air is the limiting factor for power.

I was trying to point out that the manifold is just the start of the exhaust system.  The two mufflers after it and the pipes can hinder exhaust flow.  John Coffey often posted about how the exhaust system after the manifold was the most significant improvement for performance.  It's the first modification for power.  And the 240Z system is smaller, I believe, in diameter,at certain points, than the 280Z system.  And your engine is bigger than a 280Z's.

From what little I know about the Unilite system, yes, .044" is to big. It was one of the first electronic systems but not a "high energy" system.  Probably about like a 1976 factory electronic ignition system, which is at 0.28 to 0.031".  Even the later Nissan systems spec. at 0.039 to 0.043" gap.

The second two are easy to get into, take a measurement on the pipes, check the ignition system part numbers and ballast.  The head will be harder to figure out.

[EuroDat]

An E88 73 head could be an early L26 or the last of the L24 where they started with the emmision chambers. The E88 up to around mid 72 are the most desirable of the E88. The E88 on the L26 had the larger exhaust valve and emmision chambers.

Too many unknowns in the head to say if it is causing you grief. Do you have any info on what is done to the head?

[madkaw]

Got to have timing involved in this conversation- period

[Mike W]

Jeff - Sounds like a very interesting problem and I hope that I can get involved and help you get to the bottom of this.  A couple of thoughts.

First, before you start changing anything I would get a baseline on your timing.  As you know I also run triples (Webers, not Dellortos) and I have found that they seem to like a lot of advance at idle.  If it were me, I would get a baseline on where your timing sits at idle and also understand at what RPM you are "all in".  This way at least you know where you sit.  In my setup, and admittedly they all tend to be a little different based on engine and ignition configuration, I run about 12 degrees advance at idle and am all in at around 3200 RPM with an advance of about 32 degrees.  The Unilite has the capability of changing your advance curve but the process to do it is tedious and trial and error at best (ask me how I know).  This was one of the main reasons I went with the 123 Ignition dizzy.  Regardless, getting this information I believe is critical to understanding where to really look for the problem.

I also run an E88 head and it was one of the last ones used I believe prior to the intro of the 280.  Mine came with the larger exhaust valves and I recently upgraded the head to larger intakes as well.  So I do believe that the E88 is capable of producing good power and so even though that might be a limiting factor, to me it doesn't feel like that should be the first place to start looking.  Admittedly I also run with a stage 3 Isky cam and I know that has definitely helped on the power side.

Finally, I am not really understanding the relationship between spark plug gap and the unilite output.  When I had the unilite installed I also ran with an MSD ignition box so we are not comparing apples to apples, but in my mind the dizzy is providing a trigger to the coil and it is the job of the coil to provide a high voltage output to the plugs.  As long as the dizzy has the ability to drive a low resistance coil, it should be the capability of the coil that determines plug gap, not the dizzy itself.  Perhaps I have this wrong and I might be missing something, but I'm having a hard time wrapping my head around this one.  Maybe someone can straighten me out if I'm out of line here.

Hope some of this helps.  Let me know if you want to hook up and spend some time on this.  I'd be happy to try and help out.

Mike.

[Hardway]

Thank you for all the feedback guys.  I am going to go pick up a set of spark plugs over my lunch hour and install this evening so I can determine where my timing is.  Regarding the plug selection, should I go with set of NGK B6ES-11 or BR6ES-11 spark plugs.  Do I need resistor plugs or not? 

The coil is a MSD Blaster 2 so I believe it should handle the higher gap.  However, running the plugs with a more conservative gap might be a good place to start.  I will see what the plugs recommended gap is and start there.

I will have more to add to this story later today.  Stay tuned!

[Chickenman]

MIke W. With inductive electronic ignitions, the ignition Module has a HUGE influence on how strong the spark energy is. Early trignition boxes like the 1975 and 1976 models flowed very little current. In the order of 2 Amps maximum.  That's no better than a stock points system. Spark plug gap on the 1975 and 1976 models is factory recommended .030" to .032". In 1977 and 1978 models, the Trignition box was updated and is much more powerful. With those model years the recommended gap is .042" 

The Unilite is an early generation model and also does not have much Spark energy. So you need to run a smaller gap. 

 

Add in an exteranl MSD or other CDI box, and the picture is entirely different. 

[Mike W]

Chickenman. Thanks for that explanation.  Makes sense.  I love this forum.  I learn something new every day.

Jeff - FWIW, I run resistor plugs.

Mike.