Suggestions on 400 Thermostat Housting/Neck

[dirtymac]

After reading through some of the documentation and threads about the unique thermostat on the 400 engines, I've decided to replace mine.  This is an item I think needs to be checked/replaced given the truck's age and questionable maintenance history.  I have the correct new thermostat.

The thermostat housing on my truck has two items screwed into it, possibly three, that I am unsure of how to handle.  One is clearly some kind of vacuum related bit.  The other has been broken off but after reading some threads, I believe this was also a vacuum related bit.  The third one I'm unsure of.  None of these bits are currently hooked up on my truck.  As a refresher, someone previously removed all of the SMOG equipment.

I was originally planning to replace the housing because I have had issues in the past with older ones leaking and the walls getting thin.  Since I'm not using these vacuum bits, should I worry about keeping them?  I'm not quite sure what they are for or if they might be useful in the future.  If I keep the old housing, or get a similar replacement, I could plug them.  I'm not sure of the repercussions of any of those options.

Here are some pics:

[Gary Lewis]

Will - If you aren't going to use those connections then I'd get a housing w/o them.  Or you can plug the openings.

Those things were used to control several things, like the vacuum to the vacuum advance unit, air injection pump, and even the EGR valve.  You can see how Dad's 351M was plumbed in the diagram below, and your 400 would have been quite similar.

We didn't use any of that after he took the smog equipment off, and the engine ran fine.  So if your engine doesn't have that equipment you could do w/o it as well.

[dirtymac]

I do have vacuum advance on the distributor but its plugged directly into the side of the carb.  I don't think anything else mentioned will ever get used.  She still idles a bit rough once she is warmed up.

We have researched a bit on rebuilding the cold-air intake but I'm not sure if it is worth the hassle.  The only thing left from that setup is the plastic bit wedged between the battery and radiator.  There may be some vacuum related pieces but I doubt they work.  Eventually, I'd like to get a new intake manifold and electronic throttle body but that might be a year or so down the road.

I found a Four Seasons brand replacement housing with the threaded openings for these vacuum bits.  If I crack ours open and its in rough shape, I could go that route and plug them until needed for something.

By the way, could you point me toward any pictures of Dad's engine compartment?  There are so many threads about your trucks I'm having a hard time finding some.

[ArdWrknTrk]

Will, can you show us a picture of the vacuum routing diagram on your truck?

[dirtymac]

As a matter of fact, I can.  I've been meaning to send this in because it is a bit different than some of those I have seen on here.  Our truck is factory non-catalyst.

[ArdWrknTrk]

Like anything over 8,500 gvw.

Thanks.  
It's easy to see the three VCV's that came attached to your water neck/thermostat housing.

[dirtymac]

So all three of those VCV's listed at the front of the vehicle would have been connected to the housing?  So I have one that is disconnected, one that is broken off and one that is either broken off or has been replaced with a plug.  Fantastic.

It's probably not important for this particular thread, but can you help me out with some of the abbreviations?  I looked through the Vacuum documentation on the forum and most of the abbreviations are there but I have a few I cannot decipher.  Those are:  VVA, LCV, VDV, SA-FY, TK, HICV.  Hopefully I didn't miss those in the documents.

[Gary Lewis]

A listing of the acronyms is available on the page at Documentation/Vacuum Systems/Vacuum Systems Acronyms.

[dirtymac]

I must be missing some of them then because I could not find the ones listed.

[ArdWrknTrk]

Let me see if I can help, will.

VVA Variable Vacuum
LCV Load Control Valve
VDV Vacuum Delay Valve
SA-FY ?? But looks like timed vacuum
TK Throttle Kicker
HICV High pressure cut-off valve

I'm unsure of the SA-FY, but if I spend a few minutes contemplating what it's ahead of, I will get it.

Hope this helps!  👍

[ArdWrknTrk]

On closer inspection, it looks like SA-FV

I'll have to look into that.
Even though my 87 diagram looks like someone threw up tri-colore spaghetti,  I don't have one of those.

[dirtymac]

Thanks Jim!  I don't expect I'll be needing any of those components but it helps a lot to know what they are as I run across them.  I've tried to keep everything I remove just in case.