PCV installation

[Rut]

I'm in the process of figuring out how to install a PCV on a 1275 to reduce the amount of oil coming out of the rear seal. The car has the Weber DGV/Pierce manifold and I can find no provision for a vacuum line. It may be right in front of me, but I can't locate it. Is it possible to replace the oil filler cap or modify one to accept a PCV and run the vacuum line to the intake manifold or carb? Has anyone done this and does it help? Any help with this project will be greatly appreciated.
Thanks, Rut

 

[Rut]

I spoke with Pierce Manifolds (manufacturer) and they said there was a boss underneath the mounting plate to drill and tap for a vacuum port. Does anyone have a suggestion regarding the size of this port and what size/type adapter would be best for the PCV on the valve cover? I would prefer to modify the oil filler cap vs the nice aluminum valve cover if possible. Would a PCV from a later Midget be the best choice?
Thanks, Rut

 

[Trevor Jessie]

Does the car have an oil separator on the front of the timing chain cover?

 

[Rut]

Yes, it does...attached to a brass fitting under the air filter. Hose is new and the oil filler cap is nonvented.

 

[Deleted member 8987]

Odd. All my experience with non-PCV-equiped vehicles includes either a vented oil fill cap or another vent high on the engine.

One thing you need to do once you get the PCV in, is to warm it up, find your UNI-SYN, start it, remove oil cap, insert UNI-SYN, and hand-rev the engine.
If you end up with pressure, the POSITIVE cranckcase ventilation valve is not able to handle the blowby.

 

[Spridget64SC]

1968 to 1974 Spridget 1275's used a connection from the front cannister to a PCV or "Gulp" valve supported from a bracket bolted to the manifold and connected to the twin carburetor bodies through a "Y" tube ahead of the throttle butterflies. Not sure about the 1967 arrangement. 68-74 also had a carbon cannister arrancement. This arrangment also collected crankcase gases from the valve cover. That is the "J" looking tube on the front of the valve cover ahead of the cap. Has a small < 1/8" hole in the end of the tube. Caps on all these 1275's were non-vented.

A good factory shop manual with show the 68-74 1275 emissions controls features.

The brass fitting on the underside of the Weber filter housing is to use the carb inlet negative pressure and the drawing force for the crank case fumes. A little cartridge type PCV valve could easily be inserted in the pipe between the filter housing and the cannister on the front of the engine.

Would not recommend any connection to the manifold for PCV purposes. Way too much vacuum at idle. Might end up looking like a 1950's DDT mosquito sprayer.

Find out why you are getting so much blow by. Might be something that requires correction. Leakdown test is best (pressurizes cylinder) or compression test.

HTH,
Mike Miller

 

[bigjones]

It has been my experience that simply hooking up to the air filter housing, in the hope of some sort of vacuum, has been useless in controlling oil leaks.

True, the obnoxious PCV gases may get eventually get burnt, but what is required IMHO is a definite vacuum.

Cheers!
(still leaking)

 

[Rut]

I'm not at a critical point with my car, but it is coming along and I will want to drive it...soon! Given the things I've found wrong so far and the fact that I have a new rear seal (the kind that won't leak!) in with the parts that came with the car, my guess is that there might be an old seal that's next to gone in there. Is there a relatively easy to check besides pulling the engine? I want to do it right, but I'm not a glutton for punishment.

 

[Deleted member 8987]

Me? I'd want to know what backpressure inside the crankcase I had before putting the new seal into place.

 

[Trevor Jessie]

There are not a lot of good reports regarding that aftermarket seal kit.

 

[Rut]

Thanks guys, how do I measure the crankcase pressure? Can I alter an oil filler cap with a gauge or is there somthing ready made I need to know about?
Thanks, Rut

 

[Trevor Jessie]

You can do something like this:
https://www.perr.com/tip3.html

It will let you know if any future changes you make are helping or hindering.

I believe that these engines work best with slight negative pressure. Others believe they should just be well vented to be near atmospheric pressure.

 

[Rut]

Being part of the medical trade does have its perks. I have a water column manometer and connected it to the oil filler cap per instructions and got 0 movement. I took the cap off and sealed the valve cover oil filler with plastic wrap and connected the tubing to that to make sure it was patent. I ran the car at idle, and up to about 4k and the manometer showed 0 movement...no pressure, no vacuum. Oil still pours out of the transmission and I need other ideas. I've checked the oil level and it's between the hi and lo mark. The engine is a rebuild with less than 1 hour on it and the builder may have not known about the fitting of the rear seal, I don't know. The PO had that done and I have all of the documentation, but was several years ago. There's no oil coming out of the engine, just the hole in the tranny.
Thanks again, Rut

 

[Trevor Jessie]

Check the crank case pressure on the front timing chain cover. If you are not seeing pressure there, then I'm guess the crank scroll cap is ill fitting, or the scroll on the crank itself is worn.

 

[Rut]

How would I go about that? Pull the hose off the separator and tee in a line?
Thanks

 

[Trevor Jessie]

don't worry about a T, just measure directly.

 

[Rut]

I took the hose to the separator off from the carb side and slipped an airtight adapter in and hooked it up to the manometer. No change regardless of rpm, reads 0. The connection under the air filter frame looks like it won't add any negative pressure or vacuum to the system since it's just filter media above the connection hole. I wish there was a vacuum port on the carb to try, but only a boss on the manifold for drilling. Pierce Manifolds said that I could drill and tap the boss without removing it from the car and that can't be correct. I would at least have to remove the carb and block the engine side if I do that to add a pcv. Thoughts?
Thanks again, Rut

 

[Gerard]

Because the amount of oil you are losing is excessive, even for an old engine, and from the results of your other tests, I'm beginning suspect one of two things (or a likely combination of both):

1. Little care or attention was given to the assembly of the half moon seal. This is a semi-circular cast iron piece at the back of the block and mates with the rear main cap and completes the function of the scroll seal.

2. Improper assembly of the oil pan seals.

If your engine was assembled with cork seals at the front and rear of the pan (around the front and rear main caps). Many amateur/inexperienced engine builders don't realize the cork gaskets lengths are "run wild" and either leave them too long, which leaves a gap for oil to escape; or the were trimmed flush, preventing a good seal. The end result is the same. Some gasket sets include formed neoprene seals which do not have the same problem. Unfortunately, there is no easy way to see what's in there short of dropping the pan. Another issue is if the pan bolt were over torqued, which distorts the flange on the pan.

If all else fails, I would drop the oil pan to examine the seals, but if it's the half moon seal that is the culprit, there's no choice but to pull the engine.

 

[Rut]

Gerard,
Thanks for the detailed reply. The shop that did the work in 2003 has a good reputation, but that doesn't mean they know a lot about this kind of car. I've emailed the po to find out if he has any ideas about the rebuild. If I need to pull the engine I would think that it's pretty straight forward. Do you think it would be worthwhile to drill and tap the boss on the manifold and connect the oil separator to it via a PCV? This would give me some negative pressure, but I don't know if it would correct anything. From what I understand, negative pressure in the crankcase is a good thing regardless. Also, the only oil I see at all is thru the transmission, not any on the oil pan.
Thanks, Rut

 

[Trevor Jessie]

If you plumb a PCV valve into the manifold, you would need some way of metering it so that it does pull too much vacuum and pull excessive amounts of oil fumes into the manifold. I do not have a good solution for this.