Dave Cunningham

Well, finally got my car out of the trailer to do some cruising to the places you guys suggested I go down here in SoCal. Thought I would put a few shakedown miles on it around town here in Hemet, as the motor was just put back together before I left BC. As usual the car started to get hot right away sitting at the horrendously long traffic lights down here, and as it got to about 220 it started running rough at idle, got it back to the Rv park, let it cool down for about 1/2 an hour, and tried to put it back in the trailer, could barely get it started, won't idle, missing like crazy at lower rpm, mananged to get it in there but something is definitely wrong. Any suggestions? When I took off and The car was cold to normal operating temp it was fine

Westlotorn

Dave, if it only hit 220 you did no damage at all. If it exceeded 240 you might have an issue. New Engine no miles on it and now you are in Hot Weather and Heavy Traffic.
I would get help right now and figure it out before attempting to drive again.
I think you need to start with the basics and decide what to do next.
The fact it won't run now can be as simple as moisture got in your distributor cap or as major as you lost a head gasket. I hope it is simple but I think it is time to put up the White flag ask for help and then move on. Maybe one of our knowledgeable forum members in S Cal can offer help.
The problem in S Cal is you don't figure out who is close by how far away they are, everything is measured in how long it takes to get there. I have had 10 mile drives take an hour and a half down there many times. I am 450 miles north of you but I hope someone is close or someone can direct you to a good reputable shop that can help.
Cooling Basics
Is the fluid circulating in the radiator?
Is the radiator full?
Has the radiator overflowed while running or does it overflow constantly?
Is your fan clutch engaging?
The engine is brand new. You may have an issue as simple as a loose hose clamp.
With the engine warm and the radiator and all hoses warm tighten the clamps. You will never get a good proper clamp force on a cold hose it must be warm to properly torque them. Warm hoses are soft and you get proper clamping force. Maybe one was loose and you drained down your fluid without knowing it.

babbah

Could be a fuel issue when it gets hot. check the carb for flooding. If good then check ignition.
Keep us posted.

SupremeDeluxe

I'm guessing you still have your distributor connected to ported vacuum, the factory configuration. This will cause that engine to idle at 200-210 even with a perfect cooling system.

How was the new engine broken-in? Everything runs hot while it runs-in.../

Viet Nam Vett

I have seen many with this problem.. and most of the time it turns out to be the above as Mr, Deluxe has stated. If your advance is re traded at idol you will run Hot. (Ported)

I have been called by my bud and solved his 435 Hp over heat Car simply buy going to UnPorted and adjusting the idol.

Of Course not let us rule out any of the coming and above suggestion items to check. But most of the time that is the problem.

You can thank the Gov-Ment for retarded spark so we don't poison our fellow country men.

Long Live The EPA....NOT

tbarb

I agree with post #4, if you are not sure how the distributor vacuum advance is connected get someone to take a look for you.

The retarded spark timing and extended low speed driving will reject combustion heat to the heads and then coolant. Temps rise in the block and engine compartment then the gasoline starts to boil and it's vapor pressure pushes out the carburetor venturi nozzles.

The engine runs rich etc. until it cools down. Ever boil water in a pot with the lid on, that's what happens in the carburetor bowl and if tri-power you have three pots on the stove.

These same problems can indicate a bad coil but more than likely it's fuel related. Do you have one of those reproduction ignition coils on the engine.

Frankie the Fink

Sounds like classic percolation and heat soak to me. All the above suggestions are good. An I/R temp gun shot at the fuel bowls when the issue occurs can help. Temps approaching 150* or thereabouts are bad news. Sometimes you can hear the fuel boiling after engine shut down or look down the carb throat and see fuel dribbling down on the throttle plates... That means you are essentially dealing with a flooded engine when this occurs.

I wouldn't rule out a bad coil either as tbarb suggests...I've had two go bad with similar symptoms...

DansYellow66

I'm with the others above on the ported advance - my BB's operating temperature dropped significantly when I made this very simple change. I suspect the bad idle is due to excess fuel perculating into the carb throats and flooding the engine. Your plugs are probably soaked. I would consider an oil change before putting too many miles on it. You might also consider adapting the GM or a Mr. Gasket heat baffle kit under the carb also to help shield it from engine heat. On another Holley equipped car I have, after a hot shutdown I could wait about 10 - 15 minutes and see fuel spitting out of the accelerator pump squirter due to the pump cover down underneath, absorbed heat directly off of the manifold and percolating the fuel.

tbarb

Dan,

If you have a umbrella check valve in that accelerator pump you can remove the cover and drill a small hole (.015)+- in the cavity and this should vent the vapor back the the float bowl so it will not push up and out of the squirter nozzle.

To the O/P, you can also experiment with lowering the float level approx three or four flats (1/2) turn or more to increase the spill distance between the fuel height in the bowl and the venturi nozzle.

Dave Cunningham

Ok , thanks so much for your replies, I ran across a great article by John Hinkley, while doing a search. I just came in from firing the car up this morning, gave it one pump and it fired instantly, but then died, started it again and it died, started once more and really gave it some throttle, pulled it out of the trailer, parked it , and it did continue to idle at about 800. Pulled off the ignition shield cover to check that nothing was grounding out on the coil or whatever, everything seems to be fine, and since it seems to be running alright, I would imagine the coil is ok. Unless it craps out when it gets hot, it is the TI coil supplied by TI specialties by the way.
Anyway, checked all the float levels , and they are bang on, maybe as someone suggested , I should lower them a couple of turns?
Checked the coolant level, it's right up there. Pulled a couple of plugs, they look a little on the black side to me, and one of them especially was quite wet ( see pic)
As for changing the vacuum source, my next question is where to pick up a full manifold vacuum port. The only thing I can see to use would be the plugged port for the power brakes. Any suggestions here would be appreciated.i really want to try. This vacuum thing, because I never had this issue with my 66 L72, and I bet it was using full manifold vacuum.

Dave Cunningham

Photo

Westlotorn

I see the problem, it is obvious: The spark plug says made in Japan! Should say made in USA!
Actually looking at the plugs they are very wet and black. Your combustion is to rich for sure. You may have a couple plugs fouled out adding to your start up issue.
This engine is new those plugs should read med gray or tan but not black, too rich or White too lean.
I think you are on to the solution. The vacuum advance may very well be your temp problem at idle and maybe the temp is causing the carb to flood.
Follow the advice given by fellow big block owners and hopefully enjoy your vacation.

tbarb

There should be a vacuum choke pull off on the center carburetor and you can Tee into that to provide the full manifold vacuum advance to the distributor. It may be necessary to check the vacuum specs on the vacuum advance control, you want the control to pull to it''s limit at approx 2" less that your engine idle vacuum. Can you recall where the initial timing is set now.

If by saying the floats are right on because the fuel drips out the check hole I think you would be safe to lower approx 3/4turn (clockwise) on all carburetors and try things out.

FWIW, make sure the A/F emulsion screws are set when the engine is good and warm so the plenum is up to the operating temperature. I can't see wet plugs but they look black, carbon on the spark plug is the product of un burned fuel.

If you are on vacation enjoy and don't get deep into the car until you get home.

SupremeDeluxe

Follow link, pictures of how mine is plumbed for full manifold vacuum to the distributor.

https://www.corvetteforum.com/forums...t-results.html

Dave Cunningham

Well here is where I am at, I took all your advise, as well a old school mechanic friend of mines as well.
- pulled all the plugs replaced them with a new set of AC Delcos
- got a fitting for the brake vacuum supply, and routed it to the distributor.
- dropped the float levels about half a turn.
- backed off the mixture about a third of a turn.

Fired it up and it ran perfectly, but I was surprised that the idle did not change, should it not have gone up?
Anyway took it out for a rip, still in the upper 80s here today. Went to the Napa store a couple of miles away, ran good, temp at about 190 to 200,
But by the time I got back it was up to 220 again, but at least still running perfectly. I think maybe as someone suggested the vacuum pot on the distributor, is not actuating, the one that is on there would be just a stock gm one. I wish I had read the post about Teeing into the choke , that would have been too easy. Both the choke and vacuum advance port seem to be at the same level. Maybe this carb was already supplying manifold vacuum?

Dave Cunningham

Side pic

SupremeDeluxe

Dave,

What plug did you use? I run R44XLS in mine, cannot tell much difference to the 45XLS plug. The 43 heat range seems too cold for street use in my experience.

Nick

tbarb

When you say backed off the mixture 1/3 turn if you are talking about the emulsion screws adjust them with a hot running engine. Adjust each side approx the same turns out to acheive the highest idle speed or highest vacuum. You may need to reset the idle during this adjustment.

Dave Cunningham

All I did was back off the mixture screw about a third of a turn when the motor was cold, I'm thinking it is electric fan time if I am going to have any fun with this car while I am down here.

Powershift

By "back off" a third of a turn I hope you actually turned the mixture screw clockwise and "in" towards its seat versus counterclockwise (and more open and rich setting). ???

Please clarify.

Larry