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389 cuts out when cruising

3K views 8 replies 5 participants last post by  jeff will 
#1 ·
Hello Guys,

I just joined the forum and look forward to getting involved with the forum. but I do have a problem with my 389 that I really need some feed back on. I recently installed a 1960 389 tri power in my ----yes a 1940 Hudson Hot rod I know some of you purest may not appreciate that fact but its a long story I'll leave for later.
First the specs about the Engine as I said it decoded as a 1960 block with 1964 heads and a set of 1959 tri-power carbs.
The engine was professionally rebuilt by a very experience builder as were the carbs as well. The cam is not stock but is considered mild.its bolted to a turbo 350 trans using a Wilcap adaptor plate assembly
My problem or problems
The motor starts and runs fairly well (but does seem to be a little rough) but as it warms up and we start to take it down the road it will all of a sudden shut down.
What we have done so far to trouble shoot
We are using 93 octane fuel, at first the front carb was loading up with fuel so we added a fuel regulator
the fuel pump is now regulated at about 3.5-- 4 psi
the timing is set at about 6 degrees btdc
the distributor is a HEI with external coil
when we took off the top of the carbs after a short run we notice the fuel in the center carb bowl was bubbling.
we did notice on one of our short runs that when it shut down at about 2000 rpms, while coasting it would start back up but when we put the hammer down it would start to stall and shut down again.
Another set up is that we have the distributor installed with the vacuum advance on the passenger side of the engine----- during some of my research I noticed that the vacuum advance on early 389 appears to be on the drivers side of the engine----- one mechanic said that this does not cause the shut down as long as we time it with the number one plug and that we're running an HEI dist.

Does any one in the forum have a clue about our shut down problem??:frown3:
 
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#2 ·
Jeff...Hudson sounds really cool!....lots going on here, now of course you know much of this, but just to start...you know that the Pontiac Dist spins counter clockwise...unlike a Chevy.....it must be indexed correctly to the number one and spinning in the right direction...

Make sure your plug wires and firing order are lined up accordingly..

As that would cause rough running and a stall, because it would be so out of time..

Next are the Centrifigal weights inside Dist working? With car off and cap off do they turn freely by hand? They should if they were stuck and not responding to rpm increase you would get no additional spark..

Is Vacumn can in Dist working does it move on Vacumn? Test it....

At the carb...a lean condition can stall and a rich condition can stall

They often happen just when you press the pedal, does it happen then? You may have to reset the mixture on carb from beginning...you know 1 1/2 turns out etc.....also is this cut out on a warm or cold engine? If it is a cold engine I would be looking at the choke system and the fast idle speed screw as well....set them to factory specs.....

If warm then reset mixture...a weak coil, a shorting plug, a loose rotor, or a cracked distributor cap could also cause such problems. Timing could be advanced a little, try it a 10 BTDC and see if it is any better...

Is your Vacumn to Dist to full manifold Vacumn or ported? Pull the hose off the Dist can and put your finger on it at idle...if you have Vacumn it is full..if you don't it is ported.....ported will only give you six at idle not much....so you need to see what is up in that dizzy....

Hang in there you will get it car sounds awesome!:smile3:
 
#5 ·
Jeff...just double check....your dizzy does not ONLY have to be pointing at the number one plug.......

The number one cylinder must be at TDC on the compression stroke.....

It can easily be missed or thought you had it right....make sure...

TDC on compression number one, rotor points at #1 , firing order correct and dizzy spins counter clock wise....if all that is correct than move on to other stuff....
 
#6 ·
To add, I would maybe hook up a timing light and either put in the dash were you can reach it or tape the trigger down and put it some were you can see it to see if it's losing spark. If it is then put a test light on the + side of the coil to see if it's losing power. If it's losing spark but not power you might have a weak coil or coil wire.
 
#7 ·
"The motor starts and runs fairly well (but does seem to be a little rough) but as it warms up and we start to take it down the road it will all of a sudden shut down."
I had a bad vacuum leak on my '67 400. Of course I can't tell what you're vacuum set up is, but it's worth a check. In the front of my manifold there is a nipple to which vacuum hoses connected. The nipple was loose in the block (it was just pressed in). I couldn't hear it. When I would start the car, it would run a little rough but when I got out on the road it would try to cut out. I could feather the gas to keep it running but it was no bueno. A friend came over and listened to the engine. He said "I don't know what else is wrong, but you need to fix that vacuum leak first." A little JB Weld plugged the leak and all was well in the village. Too much rock & roll and too many planes rides has destroyed my mid-range hearing. Recently I though I needed a tuneup. Seems a vacuum splice to work the a/c dashpot came off. Tiny hose but enough to run rough. Put it back on (tighter this time) and rough running went away. Good luck.
 
#8 ·
OK, here are my thoughts, however wrong they could be, but it kinda sounds more like carb/fuel problems.


You stated "at first the front carb was loading up with fuel so we added a fuel regulator."

By "loading up with fuel" I assume you mean the carb is flooding over out the top. If you are using a factory fuel pump, and not an electric fuel pump that replaces the factory pump, you should not require a fuel pressure regulator. The needle and seat should be doing their job unless they are incorrect OR the float setting is too high. I have had the experience where some of the viton rubber tips on the needle have a more blunt end versus a nice taper to it and the blunt type ends don't seem to seal as well and will cause flooding. I don't know if this is due to the manufacturer of the kit or not, but these two items need to be considered.

Next, "when we took off the top of the carbs after a short run we notice the fuel in the center carb bowl was bubbling."

If the fuel was bubbling, it sounds like percolation or excessive heat from the manifold/engine or even underhood temperatures are being passed to the carb and causing the fuel to boil (I have read that the 93 octane gas gets its octane from additional quantities of ethanol, so this might cause the gas to bubble/boil more easily?). Your first option may be a set of phenolic insulators that keep heat down. Click here: 1959-1966 End Carb Throttlebases- Please Read the Full Description Prior To Ordering- Also the Service We Offer for Your Throttlebases | Pontiac Tripower You may also want to read these tips as there are some good ones on carbs that could apply as well: THE CARBURETOR SHOP / Troubleshooting

If the engine has a mild cam, it will run a little rougher, but keep in mind that you may have to play around with the timing a little which means setting to the factory spec at the crank might not be optimum. If the timing is retard too much, the engine will heat up quickly & run hot. This will increase your exhaust temperatures and you have an exhaust crossover on the intake that goes under the center carb. Could be throwing extra heat under the carb, causing percolation of the fuel. So, you might want to try advancing the distributor timing a few degrees and see if any differences in running or engine temp. If you get ANY engine pinging under acceleration, your timing is too advanced and needs to be backed off. Engine pinging/detonation will damage your engine.


"but when we put the hammer down it would start to stall and shut down again."

Are you running a large enough fuel line from the tank to the fuel pump? Do you have the correct steel lines on your carbs, not a fuel block with rubber hoses?

It could be an ignition problem, but ........I'd be looking at the carbs/fuel system from what I have read. :thumbsup:
 
#9 ·
Hey Pontiac Jim,

Your correct the front Carb was flooding out the top of the carb, we have a fuel pump from AMES but I was told that these carbs cannot handle very much pressure so with the regulator we set the pressure at 3.5 as recommended by the rebuilder. yes the we have a correct set of factory fuel lines not a fuel block. however the line from the fuel tank is rubber. I did notice the rubber tips on the needle are relatively flat, when we took them apart to check for blockage we notice a very small amount of crud (black speck) on the top of the red rubber tip, we assumed this was keeping the tips from sealing

Thanks for the tips on the fuel/carb idea, I too have been reading up on the phenolic insulators also, does any one have these on their engine, and do they really work?

Thanks again for your advise

Hot Rod Hudson Jeff
 
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