Vacuum advance and Distributor identification

[Pat Travellall]

Hello guys,
I am new on this forum
I just buy an '74 4wd IH Travelall 100 ( 392 ci engine with Holley quadrajet)
before to take full advantage of this Travelall, I'd be sure it is working properly
I start by checking all major mechanical components and I find that I need to replace the vacuum advance unit of my distributor
but I can not find the needed item for sale !?

I'm not sure if this is the right distributor for this engine ... And not sure of the distributor model or the vacum advance unit model )
I hope the fans and enthusiasts of the subject can help me a bit to sort it all
I search before on the ihc vehicle distributor identification ... And "I think" it is a "cast aluminium Holley distributor" with points ignition,
his body was sandblasted (remanufactured parts, I think) and I guess it is the reference : 427908-c91
and on the body of the "curved point" vacuum advance I found "677-7" indications !

I search on the ihparts website but I dont find any "curved point" vacuum advance unit for an points ignition distributor
I find only "curved point for electronic ignition" distributor !?
Someone just tell me if what I seek is correct? And if the part is still available somewhere ?
Or if I am wrong ?

And ... If this 677-7 indication on the vacuum unit signify 7* advance ?
I would also replace the points ignition by a pertronix module ... I found the 1481 reference ... I'm good ?

Any help is welcome ... I living in europe and this is an almost unknow model for all us'car fans here ...
Here are some pictures of my parts :

 

[ihpartsjeff]

You must be confused as we do have what you are looking for - remanufactured vacuum advance unit for IH engine w/ Holley or prestolite distributor - IH Parts America

Being that you are in belgium you will need to call or email us to place an order. Our phone number is 530-274-1795 or email us at sales@IHPartsAmerica.com

 

[Pat Travellall]

Hi Jeff, thanks for your reaction
I see these parts on your website
but I have chose from :
1# curved point,electronic ignition - 3* advance
2# curved point,electronic ignition - 5* advance
3# curved point,electronic ignition - 7* advance
4# vacuum advance - Holley straight point - 7* advance
5# prestolite distributor

and I "think" I need a vaccum advance for a Holley curved point !?
#1,2 or 3 are for electronic ignition !
And #4 are for straight point !
These two features are not offered together "not electronic & curved point" ? I am wrong? Or I misunderstands the description of what is advertised ?
Thanks in advance
pat

 

[ihpartsjeff]

Hi pat,

you are misunderstanding what you are reading. Yes you do have a Holley curved point distributor. The vacuum advance for the electronic ignition is the same for a curved point, hence the comma between the two. So that narrows you down to three choices ~ 3, 5 or 7 degree. On the arm of the vacuum advance should be a number stamped on it. That is the amount of degrees of advance that it is designed for. Please note that on occasion we will find an arm with no number on it.

 

[Pat Travellall]

Hi again Jeff ...
Thanks for these indication ...
I never imagined that this comma could mean "or" ...
I cleaned this vacumm unit before my first post on the forum
and I dont find any stamped indication on the arm of my vacuum unit ...
Just 677-7 on the body !? (see my pictures)
have you an idea of the significance of this 677-7 ?
Otherwise I really do not know which of the 3, I need to order ?

I also have to order service parts for this vehicle ...
But I still go around the vehicle to know all my needs for this ...
I would not fail to contact you to order all that parts

pat

 

[FDChappie]

Hi pat,

since this is a light truck, I would suggest you go with the 7 deg advance unit. You'll get better economy that way. The heavier trucks would not need as much advance.

If you have an adjustable timing light set your total advance so you have 32-34 deg total advance. This all assumes you have 87 octane regular gas there.

 

[RMScout]

To add to what chappie said it is a great idea to time and tune your engine for your particular conditions. As a general rule more advance helps with performance up until the point you get pre-ignition (pinging) or detonation. I don't know what your plans are for the truck, but gear ratio, heavy loads, hills, towing, engine tune, elevation, humidity, and heat all affect the amount of timing your engine can tolerate.

So as far as which vacuum can to use I would agree with chappie and go with the 5 or 7 degree unit depending on load and usage. If you get any pinging you'll just need to reduce the initial timing until it stops. Or use a higher octane fuel.

P.s. Regarding the octane rating many places in the world do not use the (r+m)/2 formula like the us so statements like "87 octane" can create confusion when talking with our friends in the old countries.