72-2 set up, ho wdo you go about this?

Cheeze · Post by **Cheeze** » Sun Mar 14, 2010 5:17 pm

Evening guys, just a quick question about this 72-2 set ups, i am having a problem with space on my lower pully and being close to my chassis leg.

So how would i go about building a 72-2 and what do i need?

cheers

NITROPIXIE · Post by **NITROPIXIE** » Mon Mar 15, 2010 4:12 pm

Hey Cheeze

Basically a 72-2 setup works off the camshaft instead of the crankshaft. As the camshaft rotates at half the speed of the crank then we use a 72-2 setup, or really a 36-1-36-1 setup. As you have probably seen the pictures in the forum, such as dean924's i believe, you will need this type of triggerwheel. The problem lies with how big you make the triggerwheel as if it is too small then the teeth will be tiny and the vr sensor wont pick them up.Basically your teeth will be half the size on a 72-2 trigger wheel than a that of a 36-1 of the same diameter.

Have a look on the forum and get in contact with the guys who have done it previously if you would like some further detail.

Dean924s · Post by **Dean924s** » Mon May 24, 2010 9:46 pm

Search my posts. I did it on my 924s and it works great!!!! If you have any questions ask away.

Funky Diver · Post by **Funky Diver** » Wed Jun 09, 2010 8:18 am

Apologies for the newb question, however is this the same reason for using the 72-2 ratio on a dizzy also, or would that application be better suited to 36-1?

I've just ordered my kit and am a LONG way off making final decisions about placement of the timing wheel, but I'd like it to be as discreet as possible, so cam shaft sproket was one Option that I'm investigating.

Dean924s · Post by **Dean924s** » Wed Jun 09, 2010 12:59 pm

Yes If you drive it off the distributor (or inclose it in the housing it will also require a 72-2.

Funky Diver · Post by **Funky Diver** » Wed Jun 09, 2010 2:50 pm

Sweet, thanks Dean. My initial idea was to use the stock dizzy cap with the Ford VR sensor mounted in one of the HT LEad hubs pointing downwards onto a drilled/sprocketed wheel fit on the dizzy shaft. Cut off the unused dizzy hubs, fill with epoxy, sand, seal and paint black. But, like I say... I am a LOOOOOOOOONG way off even getting close to that yet. Arm chair mechanicing is great fun

Dean924s · Post by **Dean924s** » Thu Jun 10, 2010 12:27 am

Just start collecting parts. Ebay or the local pic and pull is your friend!!! Makes the $$$$ aspect of it better as well. Get a box and put things in to it and then take them out when you have a moment and start planning measuring fabricating etc. A little bit here and a little bit there and the next thing you know you have all the parts. The next thing you know you will have a complete "kit" in a box for your car that can be installed a just a couple hours. This is how I did mine. For that matter I approach most car related projects of this type in this manor. It allows for fabrication and what not while the car is still running. I have another box that I keep all the original unmodified parts I take off so I can go back to stock if I have to / want to.

Welcome to the obsession!!!

Cheeze · Post by **Cheeze** » Wed Jun 30, 2010 5:35 am

Very late reply on this guys, the main problem i have is what sensors do i use and where can i find them?

I have heard of using a rx7 sensor is this right? if so its not really a car we have laying about in scrap yards up here lol.

And having a look over google, a 72-2 wheel doesn't seen the easiest to find

Dean924s · Post by **Dean924s** » Wed Jun 30, 2010 3:50 pm

Wheels are available from McMaster-Carr (where I got them) But you have to remove the teeth. I have a couple sensors and trigger wheels lying around from my build. Where you at? There is a RX7 in my local P7P that has the sensors in it. I also got a bunch off eBay really cheep. You get two per crank angel sensor. Now that I think of it I bet I have 4-5 around as I think I have a couple of the crank angel sensors lying around.

You should go read up my thread on the build of my set up for my 924s. I has answers as well as where to get the entire setup for a 72-2 setup.

http://www.mcmaster.com/#spur-gears/=7rb0wj

I ended up ordering direct from the local supplier of the gears as not everything they sell is in McMaster-Carr. Again I posted all this information in my build thread.

See this >>> http://www.autosportlabs.org/viewtopic.php?t=2026

From that thread

My original gear (1/4" wide) I got through McMaster Carr on line:
http://www.mcmaster.com/
Part Number: 6325K67
Steel Plain Bore 14-1/2 Deg Spur Gear 24 Pitch
72 Teeth
3" Pitch Diameter
1/2" Bore
Catalog page 1039

I still think that this may have been ok since when I changed over to the 3/8" wide one I found a loose connection in the VR sensor wiring. However I am now using a 3/8" wide wheel that is a bit larger in diameter and I had to remove the hub from it to bring it closer to the face of the cam gear cover so the sensor would line up properly and allow for a good solid mounting of the sensor directly to the cover.

Anyway to get the new gears I went to the martin website (google is your friend) and looked at there catalog and found what I wanted. I then called them directly and they steared me to there local branch (listed below) Craig smith was very helpful!! However you can not purchased directly form them you will have to go through a retailer. Craig was very helpful in finding a local company that I could purchase from. I called them and placed the order and they shipped it to my door. I would bet that there is one local to you as there was with me.

Here is the info I have for my local sources.

Craig Smith
Martin Sprocket and Gear
357 Fortune Blvd.
Milford, Ma 01757
Phone: 1-508-634-3990
Fax: 1-508-634-3998
e-mail: <mailto:[email protected]>:
Web: www.martinsprocket.com

The local retailer is:

MOTION INDUSTRIES INC
11 CABOT ROAD
WOBURN, MA 01801
Phone: 7813765850
Fax: 7813765908

The details for the second gear that I ordered that was 3/8" thick/wide was are as follows

1.0 MARTIN S2072 14 3/8 SPUR GEAR
1-2 DAYS/UPS
Item No..........: 00372887

Patriq · Post by **Patriq** » Mon Aug 02, 2010 8:12 am

Hi !

I used a 72-2 on my rebuilt dizzy. Reason were difficulties mounting a trigger wheel on the pulley, and NO where to mount the sensor.

It works like a charm, and I can also fine tune position of trigger en relation to TDC. (I know one can do that with software to now....)

Search in the "powered by" thread for my 1970 Alfa Romeo Junior Zagato.

A user 'Alexander' helped me alot with my installation. He also has a converted dizzy on his installation. He also helped me source a RX-7 sensor, which is the only sensor I've had working with the small teeth on such a trigger wheel.

Just ask me if you need more advice. Good luck !

Dean924s · Post by **Dean924s** » Mon Aug 02, 2010 1:42 pm

I may have a couple extra sensors as well. (I would have to fish through the box's from moving)