Engine Masters rod ratio test results

[David Redszus]

Do you own a distributor machine?

Yes, it has been modified to accept electronic distributors as well as points, centrifugal types. It has a the ability to fire 8 spark plugs which can be observed with a magnifier and a variable pressure chamber with primary and secondary traces visible on a scope.

How much actual experience do you have repairing distributors and using distributor machines to calibrate advance curves, hours, days, years, decades?

Over 45 years of restoring (never merely repairing), recurving advance curves, removing bounce and jitter at high rpms, and indexing the proper firing interval between cylinders.
Also graphing the advance curves so the distributor can be correctly installed in the engine.

Have you ever gathered timing information on a dyno in 500 or 1000 RPM steps through an engine's full RPM range to maximum engine speed, used a distributor machine to apply that information and confirmed the results on the dyno?

No. We gather engine data using high speed logging directly from the engine while it is on the race track. Data in rpm steps is bogus. A higher sampling rate will produce smooth data curves that can be fed into engine simulations.
Dyno tuning is only a beginning step toward track winning performance.

We sell and service engine management systems (MoTec), and perform the ignition and fuel mapping as well. Our history includes vintage high pressure fuel injection systems as well.

You present a good argument that a vintage mechanical distributor can be a more accurate ignition timing device than an ECU.

Forty to fifty years ago, even Formula One engines used mechanical distributors, (sometimes more than one), quite successfully. Then we went through a series of changes including: magnetic triggers, optical triggers, Hall Effect triggers, transistor switch boxes, CDI boxes, hybrid systems, individual coils per cylinder, etc. Did I mention knock retard system ignitions? While the management of the systems improved, not much has changed in the plug gap.

Whatever the device, if it misfires or does not have the proper interval and curve, it is not a performance part.

What do you consider a good vintage?

I will admit my bias. Since we have worked with Bosch for so many years and received so much technical assistance from them (still do), they are my vintage preference.
With regard to current technology, either the MoTec or factory systems with reprogramming, and linked to a quality
data logger is my choice (requirement).

[maxracesoftware]

Over 45 years of restoring (never merely repairing), recurving advance curves, removing bounce and jitter at high rpms, and indexing the proper firing interval between cylinders.
Also graphing the advance curves so the distributor can be correctly installed in the engine.

48 years
my Marquette Distributor Machine ( purchased 1972 ) ... made my own Spark Plug load bar w/adjustable Plug Gaps
what i did was experiment with 5 or so Distributors that would start missing at certain RPMs
adjusted Plug Gaps until Distributor Machine should same RPM as Race Car or Dyno
and its worked great all these years with that Gap ... and correlates within +- 100 RPMs on Dyno
this Pic in 1980's
still works in 2020 ... moved it into Dyno Engine Room years ago .

[David Redszus]

Over 45 years of restoring (never merely repairing), recurving advance curves, removing bounce and jitter at high rpms, and indexing the proper firing interval between cylinders.
Also graphing the advance curves so the distributor can be correctly installed in the engine.

48 years
my Marquette Distributor Machine ( purchased 1972 ) ... made my own Spark Plug load bar w/adjustable Plug Gaps
what i did was experiment with 5 or so Distributors that would start missing at certain RPMs
adjusted Plug Gaps until Distributor Machine should same RPM as Race Car or Dyno
and its worked great all these years with that Gap ... and correlates within +- 100 RPMs on Dyno
this Pic in 1980's
still works in 2020 ... moved it into Dyno Engine Room years ago .

Nice set up, looks somewhat similar to mine.

I have noticed a considerable difference in required firing voltage when firing plugs into a pressure
chamber compared to free air. As the pressure goes up, the voltage requirement does as well and the
spark duration diminishes until misfires occur.

Combining a scope with the distributor machine results in one of the most useful tools in the shop.

With a multi channel scope, various spark plug secondary wires can be tested as well. Some name brands
are not much (if at all) better than OEM wires.

Run the test bench with the shop lights turned off and watch the light show. All that is missing is a guitar.

[maxracesoftware]

Over 45 years of restoring (never merely repairing), recurving advance curves, removing bounce and jitter at high rpms, and indexing the proper firing interval between cylinders.
Also graphing the advance curves so the distributor can be correctly installed in the engine.

48 years
my Marquette Distributor Machine ( purchased 1972 ) ... made my own Spark Plug load bar w/adjustable Plug Gaps
what i did was experiment with 5 or so Distributors that would start missing at certain RPMs
adjusted Plug Gaps until Distributor Machine should same RPM as Race Car or Dyno
and its worked great all these years with that Gap ... and correlates within +- 100 RPMs on Dyno
this Pic in 1980's
still works in 2020 ... moved it into Dyno Engine Room years ago .

Nice set up, looks somewhat similar to mine.

I have noticed a considerable difference in required firing voltage when firing plugs into a pressure
chamber compared to free air. As the pressure goes up, the voltage requirement does as well and the
spark duration diminishes until misfires occur.

Combining a scope with the distributor machine results in one of the most useful tools in the shop.

With a multi channel scope, various spark plug secondary wires can be tested as well. Some name brands
are not much (if at all) better than OEM wires.

Run the test bench with the shop lights turned off and watch the light show. All that is missing is a guitar.

i also had the Marquette Oscilloscope hooked a few times with Distributor Machine as well as a few times on the Dyno
i wish i would have not sold the Marquette Oscilloscope to a friend

i also back-to-back old Champion Spark Plug checker w/Air pressure Psi -vs- what i was seeing on Dyno + Distributor Machine
played around with modififying Plug ground straps to J-style and J-style pointed end-shapes in 1970's
modified many Distributor single point-plates to for 32oz ? Accel dual-points
used clear distributor caps for more testing
really cool at nite to turn lights off in the Shop and spin a Distributor hooked up to my Spark Plug Load-Board
and watch + hear MSD fire multiple sparks at low to mid RPM then change to lesser multiple sparks at highr RPMs
could spin a Magneto to 9500 RPM , and normal distributors to 11,000 RPMs easily , optional higher HP electric motor
... also cool was smell of Ozone from MSD sparks

i'll Post a Pic of my Marquette Oscilloscope later today or tonite

[Tuner]

You guys are "bringing a tear to me one good eye." I have the same rigging and been doing the same spark gap and oscilloscope games since the early '70s. What a long strange trip it's been. First played with a couple of my father's friends' distributor machines in the 50s in grade school, used the same machines with purpose in high school, got serious with borrowed machines in the mid 60s and got my first machine in 1972, oscilloscope in '75 and still use a DM every few days, plan to tomorrow or Sunday.

Have you fired an ignition on your spark rack or a plug gap and blown on the gap with a shop air nozzle or your breath and watched the arc move out of the gap to the plug shell? If you use a rubber vacuum line to blow on the gap with your mouth, be aware the hose will conduct electricity. High resistance, but none the less a conductor with the moisture of your breath.

In this forum a few times I have mentioned high RPM advance curves and posted a recipe for HEI distributors to make a curve that advances about 1 degree per 1000 from 3000 to 8000 + . Have either of you calibrated distributors with high RPM curves such as this, HEI or otherwise?

Have you noticed it seems the "short rod" engines benefit more dramatically from the correct high RPM curve?

Mr. Redszus, amongst all the files and data logs you have accumulated in Motec and dyno results isn't there a means to ascertain a trend relating spark advance to this short vs. long rod issue?

[ClassAct]

You guys are "bringing a tear to me one good eye." I have the same rigging and been doing the same spark gap and oscilloscope games since the early '70s. What a long strange trip it's been. First played with a couple of my father's friends' distributor machines in the 50s in grade school, used the same machines with purpose in high school, got serious with borrowed machines in the mid 60s and got my first machine in 1972, oscilloscope in '75 and still use a DM every few days, plan to tomorrow or Sunday.

Have you fired an ignition on your spark rack or a plug gap and blown on the gap with a shop air nozzle or your breath and watched the arc move out of the gap to the plug shell? If you use a rubber vacuum line to blow on the gap with your mouth, be aware the hose will conduct electricity. High resistance, but none the less a conductor with the moisture of your breath.

In this forum a few times I have mentioned high RPM advance curves and posted a recipe for HEI distributors to make a curve that advances about 1 degree per 1000 from 3000 to 8000 + . Have either of you calibrated distributors with high RPM curves such as this, HEI or otherwise?

Have you noticed it seems the "short rod" engines benefit more dramatically from the correct high RPM curve?

Mr. Redszus, amongst all the files and data logs you have accumulated in Motec and dyno results isn't there a means to ascertain a trend relating spark advance to this short vs. long rod issue?

Exellent post Tuner, but I have some questions.

How do you change the gap on your spark rack.

And about paragraph two...do you know this as an old wives tale, or have you experienced being shocked while blowing on a runner hose to watch the spark moving across the gap?

TIA

[swampbuggy]

In a high performance engine, especially a high RPM/ race engine, the longer connecting rod has more points scored in the plus column than shorter rod setup. This is MPO. Now that the train is back on the tracks, LOL Mark H.

[treyrags]

The race engine builders I have seen are more concerned with getting the deck as low as possible to straighten out the intake track as much as they can. Whatever rod length that requires is what they end up with, within reason.

[Walter R. Malik]

The race engine builders I have seen are more concerned with getting the deck as low as possible to straighten out the intake track as much as they can. Whatever rod length that requires is what they end up with, within reason.

That sure is one reason ...
Back in the 90's when stock deck height was required for Trans Am racing, we used a 6.300" length rod with a 3" stroke in the 18 degree, 309 Chevys, simply to get the piston a lot lighter. That reciprocating weight was a whole lot more important than whatever the rod length needed to be.

[Little Mouse]

So what if sbc, you used a 3.00 stroke 6.50 length rod and 1.00 CH piston. 2.16 rod ratio
The piston would be light and with that short stroke and really long rod there would be little side loading on the rings and piston. Would it be dud performance wise compared to using a shorter rod, or no difference in a negative way. Howard's has a steel I beam rod 6.50 a bit heavy at 680 grams. Callies has a 6.30 rod 620 grams. These rods are in my affordable range $800.00 Howard's, $650.00 callies.

[Little Mouse]

Walter R. What type and size 18 degree head was used on the 309 cu.

[gmrocket]

You guys are "bringing a tear to me one good eye." I have the same rigging and been doing the same spark gap and oscilloscope games since the early '70s. What a long strange trip it's been. First played with a couple of my father's friends' distributor machines in the 50s in grade school, used the same machines with purpose in high school, got serious with borrowed machines in the mid 60s and got my first machine in 1972, oscilloscope in '75 and still use a DM every few days, plan to tomorrow or Sunday.

Have you fired an ignition on your spark rack or a plug gap and blown on the gap with a shop air nozzle or your breath and watched the arc move out of the gap to the plug shell? If you use a rubber vacuum line to blow on the gap with your mouth, be aware the hose will conduct electricity. High resistance, but none the less a conductor with the moisture of your breath.

In this forum a few times I have mentioned high RPM advance curves and posted a recipe for HEI distributors to make a curve that advances about 1 degree per 1000 from 3000 to 8000 + . Have either of you calibrated distributors with high RPM curves such as this, HEI or otherwise?

Have you noticed it seems the "short rod" engines benefit more dramatically from the correct high RPM curve?

Mr. Redszus, amongst all the files and data logs you have accumulated in Motec and dyno results isn't there a means to ascertain a trend relating spark advance to this short vs. long rod issue?

Your simply amazing...been at it since the 50’s

What do you think about high gear retard making a car run better?

[Walter R. Malik]

Walter R. What type and size 18 degree head was used on the 309 cu.

They were Chevrolet "BowTie" low port and high port heads depending upon what that team owner wanted. All those engines used the same Reed cam grind and Ryan Falconer steel, 1.6/1 rocker arms.
Of course, a lot of other teams had engines built elsewhere.

[ericjon262]

The key takeaway that I noticed, was that the short rod was more sensitive to changes in ignition timing than the longer rod, I attribute this in my mind to the shorter rod having less dwell at TDC, which to me implies that the engine with the longer rod will perform more consistently as outside parameters change IE: air temp, baro, humidity ect. I think I would prefer to run a longer rod due to that, but I'm not going to build my engine specifically around the connecting rod either.

[swampbuggy]

Tonight i was studying all the data that was gathered from analyzing a camshaft on a Cam Pro Plus. I started out looking at the lifter rise/valve lift at .050" and then increasingly in .050" steps (ie) .050--.100--.150--.200--.250 and up to max. lifter rise. I was looking at the degrees ATDC at which these lifter rise points occurred mainly to see where the valve lift number was at in the area of 70 to 80 degrees ATDC. As i was pondering this that and the other a thought came to mind. The engine with a longer con-rod set up has more degrees of piston dwell in the TDC area. So the piston starts down the hole a little bit later, but while the piston was not yet moving the camshaft was still turning opening the valve giving it "more" of a head start in relation to the piston compared to a shorter rod set up. Does this make sense ? Mark H.