Picture of 72 LT-1 vacuum hose routing?

[Gary S.]

I am in the midst of running down a vacuum leak that is driving me crazy and I need a photo or schematic of the vacuum hoses for the AIR system on a 1972 LT-1. I have the AIM schematic for the TCS system which is very basic and easy to understand but I am still looking there for the AIM system. I thought I would ask here before digging deeper into the AIM.

I took the hoses off in order to facilitate my valve adjustment and now the car dies when I pull the vacuum hose off of the distributor and before I can get it plugged. That suggests to me that I have a vacuum leak in the areas described. Fwiw, I am running full time vacuum (distributor to nipple on base of the carb) with the appropriate distributor vacuum advance (information that was supplied by Duke a couple of years ago - thank you). In this set up the TCS is sitting there and not functioning.

These last few days have been one of those "fix it until it is broken" kind of times.

Thank you as always.

Gary

[Gary S.]

Re: Picture of 72 LT-1 vacuum hose routing?

It took a bit of searching but I pieced together the vacuum set up. Why this isn't on a single page I don't know.

This is what is currently set up:
1. 4 way "T" with full time vacuum coming from front of the base of carb, one line to diverter valve (AIR), one line to choke, one to Distributor bypassing TCS completely
2. vapor hoses are untouched with larger hose on left nipple on right side of carb, smaller hose on right nipple.

Is there anything wrong with this setup - if so, I can't find it.

Here are my issues:
1. the car starts with difficulty and idles poorly with everything hooked up.
2. As soon as I pull the vacuum line off of the distributor in order to plug it the car dies. So I can't do a proper timing procedure because of this.

To my limited knowledge this has to be a vacuum leak or I have made a fundamental and simple mistake. I have tested the small filter and the three port check valve, checked the PCV valve and all is good.

I am frustrated here. Any help?

Gary

[Larry M.]

Re: Picture of 72 LT-1 vacuum hose routing?

Gary,

I can't help you with your stalling problem, and you may already have routed your vacuum hoses correctly, but as a reference, see these photos from Dobbins' 2nd edition Fact Book. For the sake of argument, let's assume the hoses shown are correctly installed (with the exception of the missing AIR pump).

Larry

[Larry M.]

Re: Picture of 72 LT-1 vacuum hose routing?

Now that I look a little further, page 135 of the 5th edition TIMJG has a clearer photo.

[Gary S.]

Re: Picture of 72 LT-1 vacuum hose routing?

Larry,

Thanks for the photos - they do help. And yes, the TIMJG has good photos even if they're a bit dark. The Dobbins photos are good even if the AIR sytrm has been removed and the hose to the vacuum tank is missing.

I haven't found the vacuum leak - it must be small since I'm only getting 11 inches of vacuum whereas I was getting 14+ a year or two ago. Time to retest (3rd time) each hose and item that accepts vacuum to see where it might be going.

Thanks again

[Ed H.]

[Gary S.]

Re: Picture of 72 LT-1 vacuum hose routing?

Ed,
Thank you for the additional information. Duke had commented earlier when i asked about the Williams/Hinckley method and suggested that idle mixture would need to be adjusted. I must have missed the part, or more likely not understood, about reduced vacuum. Honestly, I bet I spent 3 hours chasing a vacuum leak as well as testing every hose and associated mechanism for vacuum issues. The car is running now and relatively decently once the idle mixture was properly adjusted. One of the issues I had was an incorrect starting point for the mixture setting. It was far too rich and I finally got it working. In addition, the timing was off a bit and I had to set it by ear before I could put a timing light on it. Some more fiddling with spring tune up and I will be on the road .

Thank you for the post.