# 1965 new 389 wont idle, overheating, low vacuum



## torpedo51 (Sep 8, 2009)

I just had my 389 rebuilt by a trustworthy machine shop. I have date matching intake manifold, tri-power, and block. All was installed just today, including new fuel pump, lines, etc. Fuel spray good, spark correct and set to -14deg. Oil pressure good.

I've backed out the idle screws on the center carb. It wont seem to idle unless I move the choke cam to full ON position. It seems to be sitting at about 900 rpm. When I blip the throttle, the choke falls back to zero, and the car dies.

I put a vac gauge on the manifold which reads exactly 2" when the car is idling (with the choke on at 900 rpm).

I don't see any vac ports unplugged or leaking. I used new gaskets on the manifold and carbs. Whats the deal?


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## BearGFR (Aug 25, 2008)

torpedo51 said:


> spark correct and set to -14deg.


Hoping I'm just misunderstanding here... but just to make sure, that's not MINUS 14 degrees (as in 14 degrees retarded) is it? (if it is, that's a big contributor to your problem if not all of it)

Also, coould you please tell us more about the valve train? (which cam, lifters, rockers, --- how were they installed and adjusted, etc.)

Trying to get a starting reference point...

Bear


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## ALKYGTO (Mar 29, 2010)

+1 ont the rocker arm adjustment. Lifters probably not pumped up and the valves are'nt closing all the way. Do a compression test to tell for sure.


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## geeteeohguy (Feb 2, 2008)

If it's pulling 2" of vacuum at idle, it shouldn't be running. Verify TDC with the distributor, and set the initial timing at 6 degrees BTDC (+6). It sounds like you have the initial timing set about 20 degrees retarded. Do the basics (timing) before tearing into the engine, please.


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## torpedo51 (Sep 8, 2009)

I've got some improvement.

The rocker nuts were compressed all the way down - I backed them off, took out the slack, and added a half turn. The build (cams, rockers, etc.) is essentially stock.

The timing was ATDC. All my experience comes from VW manual where BTDC is referred to as a negative value. Anyway, I've set it to +6, and it runs so well that it starts perfectly and the idle is very, very high.

The problem is that its still overheating so fast that I don't have time to dial it back. I've got the two idle screws all the way in minus a full turn, so maybe I need to back out the throttle screw?


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## BearGFR (Aug 25, 2008)

Saw your other post about the "mystery parts" ---- make sure that you DO have both those metal tubes and seals installed inside your timing cover, the seals between the ends of the tubes and the back side of the pump plate. If those are missing, you won't have any coolant circulation and yes, it will overheat in a heartbeat. Also search for other threads on this forum about "water pump plate clearance" and similar terms that will tell you how to properly adjust how the plate fits the back of the water pump. 

Yes, slow the idle down using the speed screw on the carb. If you're not positive those tubes are present behind your water pump though, I recommend you stop now and tear it down to make sure before proceeding.

Here's an example of what the tubes look like:









Bear


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## jmt455 (Mar 26, 2012)

^X2.
Same thing happened on my 455. The builder was not very familiar with Pontiac engines.
There is no coolant circulation through the block & heads without those water pump sleeves.


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## torpedo51 (Sep 8, 2009)

My timing cover (1966 p/n 9783130) doesn't have the tubes. It has one cast tube, but the rubber sleeve doesn't appear to fit nicely between the plate and the cover here. Do you have an exploded parts diagram for my timing cover?


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## facn8me (Jul 30, 2011)

Just how fast is this thing overheating? Sure you don't have a bad gauge?


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## torpedo51 (Sep 8, 2009)

Boiling coolant starts to spew from the overflow tube.


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## BearGFR (Aug 25, 2008)

Wow... then make sure your pump plate clearance is right and that you don't have a thermostat that's stuck shut. 

Bear


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## torpedo51 (Sep 8, 2009)

Ok, so after dialing in the carbs correctly (tri-power), readjusting the valves again while hot, it stopped overheating. I had already checked the plate clearance, and its good to know that I didn't have any *extra* parts that I should have used. Today is the first day I've driven the car since I bought it - 7 years ago. Awesome! Thanks for all the help!


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## geeteeohguy (Feb 2, 2008)

Torpedo, your 389 DOES NOT use the tubes and seals with the water pump and timing cover. Only later engines used this....'69 and up, pretty much. If it's spewing out of the overflow instantly, you may have cylinder pressure in your cooling system from a leaking head gasket, etc. The upper radiator hose should be soft, and no pressure should build up in the system for at least a few minutes after initial start-up.


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## facn8me (Jul 30, 2011)

I think he has a sticky T-stat or a weak radiator cap...


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