Question For GMCTD

[Alaska Aviator]

I built a manometer to test my CDR - the results were:

2" WC at idle (700 rpm)

5" WC at 2000 rpm and same at about 2500 rpm

My question is that the vacuum at idle is about twice or more than I've seen recomended - is my CDR still operating within design parameters?

TIA

AA
:D

[gmctd]

Vacuum level depends on restriction in intake path - air filter, ducting, etc.
Dirty air filter will increase vacuum.

CDR is a vacuum regulator, fully closed at ~4" wc
in the 6.2 with single-tube CDR mounted on the passenger side valve cover.

I'd say, since your readings are 1" higher than normal, check the air filter and such.

Your CDR is functioning correctly.

[Alaska Aviator]

I should have mentioned that mine is the type installed above the heater pipe off the crossover - dumping back into the oil fill tube.

It is not installed on the valve cover - is there an advantage to the valve cover installed version?

AA
:D

[gmctd]

The disadvantage is in replacing the passenger-side valve cover - the pipes need to be disconnected from the injectors and raised for clearance to R&R.

GM switched for simplicity and convenience - CDR in the valve cover, one tube to the intake manifold.
That system was used to the end of 6.5L production

If you plan to keep the truck, the extra work would also give indication of engine condition, by cleanliness of valve train on that head.

[Alaska Aviator]

My right side valve cover has the hole in it for the CDR - I think it is a 91 Mr Goodwrench motor (it was installed before I got the Suburban)

I guess since it is working correctly I'll leave it alone - I'm a firm believer in "if it ain't broke, don't fix it!" however, if the valve cover position is preferred, I don't mind upgrading as I am in the process of restoring the whole rig.

AA
:D