Twin Cam Dyno Results

[surfguitar58]

Dyno run after change to electronic ignition         (2/18)...4th gear:  96.70 rwhp and  95.14 lbs torque

Forgive me for being a little out of touch on some automotive basics, but how does electronic ignition get us 6 more rear wheel HP? Is this a programmable set-up like JB mentioned in an earlier post? I have an un-installed Pertronix kit that came with the car. If I can get 5% more HP just by installing it, I will definitely move installing it up the priority list!

Tom

[TCS4605R]

After I installed a Lumenition system on my TCS I notified that shining a timing light on the flywheel timing marks showed a very thin fine line while the stock point/condenser showed wide blurred line.  I imagine the HP gain was due to very accurate spark timing.

Tom
74 TCS - 4605R

[BDA]

Five percent is more than I would have expected. The condition of the points and condensor, the dwell setting, as well as the ability of the spring to keep the points follower in contact with the dizzy cam could play against a point/condensor system. If the coil was changed with the Pertronix ignition, that could affect the power also.

My motor was built with an Allison optical ignition that worked great till it didn't. I think the light failed since it was from long before LEDs. In Luminition does not use LEDs, I would advise swapping it with a Pertronix.

Those are nice numbers and you should be proud of the improvement you made, literarymadness! Good job!

[literarymadness]

It is a Pertronix  III.  Most guys installed the II (~don't know if that makes a difference but it is hotter than the II) .  All I did was Dyno the car at the same place before (and usually at 10:00 a.m. to keep the outside temperature the same) and after each change and show you the printouts.  My guess for the drastic increase is that the original distributor was a little warn-out so the electronic ignition simply gave the motor what it was missing plus maybe one or two extra hp.  Like I said wanted to be more scientific and look at dyno numbers only and not guess on horsepower. That is why I was asking other members to post their dynos...to compare.  Dyno machine have a certain margin of error but if you use the exact same dyno everytime, it should be accurate in terms of relativity to a particular vehicle.

[literarymadness]

Thanks BDA!!! and yes I went with a hotter 50,000 coil. The Pertronix is the D7190609 with rev limiter.

[Kendo]

Since motorcycle carbs were mentioned, I have been eyeing http://www.v-performance.com/products/air_fuel.html for after I repaint my car. They show some Lotus installs. No affiliation, of course.

Ken

[surfguitar58]

Since motorcycle carbs were mentioned, I have been eyeing http://www.v-performance.com/products/air_fuel.html for after I repaint my car. They show some Lotus installs. No affiliation, of course.

Ken

Very interesting Kendo. The Elan twin cam the show has some funky adapters between carbs and Stromberg manifold. Worth looking into.
t

[Grumblebuns]

Looking closer at the Elan photo on the VPD website, it appars that the Mikunis are bolted directly to the head with their adapter eliminating the emissions manifold with the internal balance tubes. Be curious to hear how the Stromberg twin cam motor runs with out without balancing out the intake pulses. I was cautioned many years ago not to bolt the Strombergs directly to the head for this reason.

Does the difference in type of carburetor make a difference in not needing a balance system? The Mikunis are flat slides, I believe while the Strombergs are CD type.

Joji Tokumoto
Fallbrook, Ca 

[Bainford]

A big thanks for the link to Vintage Performance. Those Mikuni conversion kits are quite intriguing, and no need to seek out a Weber head.

[Pfreen]

Here is my two cents worth on the subject of carbs.  The motorcycle carbs may or may not work great as delivered and may require a lot of calibration/ jetting.  So, it could be a hassle.  If you have an engine dyno, it fairly easy. I am sure the losses in the carbs would be less than the Strombergs so if done right, you will probably  gain some horsepower.

As for the balance tube, I have twin SU carbs with no standard bypass butterflies and balance tube.  It was like that when I bought it in 1986.  I installed a balance tube by drilling out the front vacuum boss all the way through to the back runner, but not through the back vacuum boss.  I then jb welded a 1/2” hard copper tube between the two runners.  I then went through the ports and ground the pipe flush with the inside of the front and back runners.  I has been in the head for 30 years and never loosened or leaked.

If it were me, and I wanted to improve on stock carbs, I would install a fuel injection system like this on https://www.classicfuelinjection.co.uk/ that appears to be SU carbs.  That way, you have just throttle plates, injectors, controller and O2 sensor.  You can adjust it until it is perfect with a laptop computer or maybe even an ipad.  The engine will start immediately, idle and pull like crazy.

I have not done this because I am happy with performance as is.

[jbcollier]

The flat-slide carbs have no butterflies, main or secondary venturis, no accel pump nozzles.  At WOT there is just a thin needle (round) and an emulsion tube nozzle in the carb bore.  That's it, that's all.  Have gander down an Weber/Dell sometime.  There's a lot of stuff in the way of airflow.  If I had a Stromberg TC head, I would fit flat-slides.

[2766R]

I know this is an older thread but feel like it's the right place.  I finally got around to making a mount for my i-Phone so I could use the Perf-Expert app to get some sort of idea/base line of performance, specifically HP and Torque at the wheel.  The motor is stock appearing with headers and fabricated air box with a cone filter.  It still retains CB ignition; Pertonix III to be installed eventually.  Internally it is built up with a steel billet crank, I believe JE pistons, .040 over(recent rebuild), and hot street cams from many years ago.  Cams and crank were installed in the early '80's, probably sourced by the shop from Dave Bean.  These results will need to be confirmed with a couple of more runs and eventually a real chassis dyno.  The real reason I'm posting is to have others see if I've done my due diligence with spec entry and whether the results seem reasonable. 
Thanks! Gerry

[Pfreen]

Gerry,

I also used this app.  I think your cda number of the frontal area but does not include the flow coefficient.

I used a cda of 4.57 ft^2  .  This came from this source https://www.automobile-catalog.com/auta_details1.php.

The frontal area sited in this is close to your number total number.  I am rooting for me to be wrong since my torque and hp calc will be higher. 

A big  frontal area number will increase the torque and horsepower calculation from acceleration.

[2766R]

Gerry,

I also used this app.  I think your cda number of the frontal area but does not include the flow coefficient.

I used a cda of 4.57 ft^2  .  This came from this source https://www.automobile-catalog.com/auta_details1.php.

The frontal area sited in this is close to your number total number.  I am rooting for me to be wrong since my torque and hp calc will be higher. 

A big  frontal area number will increase the torque and horsepower calculation from acceleration.

You, sir, are absolutely correct; I had entered just the raw frontal area without considering Cd!  Using your Cda of 4.57 ft^2, the recalculated results are posted here.  This is exactly why peer review is so important; others will catch when one has erred.  Now I feel the results are pretty much what should be expected.  Thanks!

[Pfreen]

I was playing around with the program and found another issue with your input data.
The curb weight the program wants includes a full tank of gas (about 96 pounds).  I weighed my car and it weighed 1679 lbs with a full tank of gas.  It is a bit heavier than stock since it has ac.

Also, I entered additional weight as 215 lbs since I weigh 205 lbs and I take some tools with me.  I would assume you don't weigh 110 pounds.  Anyway, any increase in weight will increase your hp numbers.

I will post my results soon. 

I will say your rpm red line is impressive.  I only take mine to 6750 RPM, but it only has the stock crank.