venting

RICKG · Post by **RICKG** » Sat Sep 15, 2012 10:01 am

http://www.cj3a.info/sibling/cjv35u/v1.jpg
on the link above item 4 is described as "metered".
i believe this means that the fittings are of the restricted type
with aprox .040 orifices, am i correct? btw there are many other great
drawings that i am referring to while building my vent system..

Post by **wesk** » Sat Sep 15, 2012 10:11 pm

I believe metered in that context refers to controlling the amount of vacuum available at the PCV valve which has a restriced pair of orifices and a check valve.

The 0.040 restricted fitting is the one at the wiper "T" that feeds the distributor vent system.

BobW · Post by **BobW** » Sun Sep 16, 2012 6:36 pm

Everyone is correct.

Item 1 is metered crankcase vacuum, it is "metered" by the PCV valve.

Item 4 is metered distributor vacuum, it is "metered" by the orifice fitting in the wiper tee.

Rick, do you have a CJV35?

oilleaker1 · Post by **oilleaker1** » Mon Sep 17, 2012 12:16 am

So, item 4 "T" sucks on the distributor which gets it's air supply in the crossover tube. I just put a 1/8 inch flare T there. If it doesn't have a .040 hole, what happens? John ( does the M38A1 have a metered fitting also like this?)

evanso1975 · Post by **evanso1975** » Mon Sep 17, 2012 1:11 am

You can fabricate that 0.040" fitting using a standard male connector:
http://www.cj3a.info/sibling/m38vent/vent3.htm

Owen.

oilleaker1 · Post by **oilleaker1** » Mon Sep 17, 2012 5:52 am

Thanks Owen! I had a similar modification in mind, but getting the other T would be a simple change out. The ball check fitting was a mystery also and you answered that too! The question still remains: What happens if you don't install the T restriction? Wipers work like crap????? John

RICKG · Post by **RICKG** » Mon Sep 17, 2012 9:14 am

BobW wrote:Rick, do you have a CJV35?

No, i have M-38 MC51986, eng MC74754. Tom M indicated to me
once that it was on the tail end of a 102 unit production run
starting with MC51887 and ending with MC51989. This run
utilized the closed style vent system according to Tom. I'll
model my vent sys after this drawing if you agree..
http://www.cj3a.info/sibling/m38vent/ventq.jpg
Thx for sharing your knowledge of the various vent systems
with the group, Bob..

Post by **wesk** » Mon Sep 17, 2012 9:31 am

John,
The wiper "T" gets the resticted orifice in all M38's on the port of the "T" that goes to the distributor. The distributor venting system and the PCV valve are considered calibrated vacuum losses. This means the engineer took their use of vacuum into consideration when the carb metering schedule was developed. When you increase the amount of vacuum loss at either of these restrictions it causes an upset in carb metering resulting in overly lean mixtures.

Rick,

102 unit production run
starting with MC51887 and ending with MC51989

That was a pilot run with the newer engine, late starter and late vent system. It is announced in the PS Magazine articles Ryan posted.

RICKG · Post by **RICKG** » Mon Sep 17, 2012 10:04 am

http://www.cj3a.info/sibling/m38vent/ventq.jpg

Wes, would you agree that im building my vent system to
the right drawing?

oilleaker1 · Post by **oilleaker1** » Mon Sep 17, 2012 12:37 pm

This is a great thread! Thanks all. Now , did the M38A1 also have the orifice and at what location? I'm going back to it now and take a look. John

evanso1975 · Post by **evanso1975** » Mon Sep 17, 2012 1:00 pm

Check this vent parts list for the M38:
http://www.cj3a.info/sibling/m38vent/vent4.htm

If you look about 1/3 of the way down that list, the special fitting is part number 7348568. Now, page 87 of the G758 ORD 9 shows that same part number. So the M38A1 had the same fitting, apparently on the distributor vent line to the tee fitting. Seems logical so far.

This is my best guess for the location:
If you look at the diagram on page 70 of the ORD 9, then I would say that the special fitting is on the end of line EE that goes into the wiper tee fitting DD.

Hopefully, other members more clued up on the M38A1 vent system than me can confirm the location.

Owen.

Post by **wesk** » Mon Sep 17, 2012 4:34 pm

Yes the A1 also had that distributor plumbing and restricted fitting in the same wiper "T".

oilleaker1 · Post by **oilleaker1** » Mon Sep 17, 2012 5:57 pm

OK, thanks much. John

Post by **wesk** » Mon Sep 17, 2012 9:18 pm

Rick,

Yes I would agree the late vent system is correct for your M38 if going with a factory resto.