i have interesting situation
 

me and my dad are putting together a 1977 nova RS with a olds 455 motor. when we start the engine and run it for any length of time, as soon as you kill the motor antifreeze begins shooting out of the overflow and the radiator is full of suds bubbles! we don't think there's a thermostat in it. theres no oil/antifreeze mixing and we checked the intake with spray and found no leaks. we are completely stumped!!!! also, we can't get the idle below 1500 rpm and the idle screw is all the way out. the engine won't even die when we tighten the mixture screws all the way in, it actually speeds up! we found every vacuum leak we can and plugged them all off. we found 4 ports that were open and we plugged them but it only brought it down 300 rpm from the previous idle of 1800rpm. HELPPPPPPPP!!!!

As for the coolant problem:

You sure you have the coolant mixed right? Could just be that there's not enough antifreeze. I know the water neck on SBC and BBC motors is always a problem source...make sure it's tight and not damaged. Maybe you got some kind of chemical in the mix. You could drain and replace the coolant if you haven't done that in awhile.

As for the idle problem:

It could be that either the screw is stripped or maybe it's the wrong screw entirely and not making contact. What size carb are you using...it could be too big. Also check to make sure the throttle cable and/or cam are not sticking.

This could be a ton of things so i'm just throwing out ideas.

How about the intake...hold old is the gasket? Even the slightest pinhole could cause a high idle like that.

I think most likely the problem is with the carb. If it's an old carb maybe you simply need a rebuild. Make sure the butterfly(s) is/are sealing in their seats when the throttle is at idle.

If they are seating correctly, then that means the problem is somewhere between the carb and heads. So then concentrate on the intake. A gasket change is pretty simple on that motor, so it might be worth it if the gasket is not too new. It would at least eliminate a major possible problem source.

If none of this works, check your plugs for residue and see if maybe you are running too rich. It's unlikely that a fuel problem would cause this sort of behavior, but not impossible.

Since I don't know how old this motor is or what kind of new parts are in it, it's hard to say. But if the gaskets haven't been done in awhile, that would be a great place to start. Especially at the intake.

i'm not sure on the size of the carb, but it don't look big enough to be to much for the 455. it has no choke and no fast idle on it and it's a holley but thats all i know cause i don't have it here to look at. i don't see how chemicals could mske it puke all the fluid out of the radiator. the engine was back flushed before we put on the radiator and all that. it doesn't mstter if it just runs for 5 seconds it will blow the antifreeze out of the overflow at a pretty damn good pressure and the radiator is filled with foam.

i'm not sure on the size of the carb, but it don't look big enough to be to much for the 455. it has no choke and no fast idle on it and it's a holley but thats all i know cause i don't have it here to look at. i don't see how chemicals could mske it puke all the fluid out of the radiator. the engine was back flushed before we put on the radiator and all that. it doesn't mstter if it just runs for 5 seconds it will blow the antifreeze out of the overflow at a pretty damn good pressure and the radiator is filled with foam when you shut off the engine.

Well... I've had enough scotch for the night.

Cracked head?

Incorrect headgasket (or improperly installed).

Was the engine running in the previous car? Was it opened up before it was installed?

Make sure the water pump is getting water from the BOTTOM of the radiator. Sometimes with motor swaps things like that get overlooked. :)

And make sure the bottom hose has a spring inside it to keep it from collapsing. With a big motor the suction from the water pump is very strong.

You might check out the carburator gasket to see if it's the right one, that it fits both the carb, and the manifold.

it was running fine before we pulled it from the donor, no water problems but the idle was still screwed up i think.i think the carb just needs rebuilt

i'll have to check on the carb gasket but i doubt it. the bottom hose does have a spring in it, i checked that. how would the water rotation get changed??

You sure you have the right water pump pulley?

Some engines have different flow paths, when I swapped a 351 into where a 300 was, the hoses were switched, in relationtionship to the radiator, and I was trying to pull water from the top of the radiator. :eek:

Valid point, however the gen I and II SBCs and BBCs all have the same coolant flow. It's the gen III's and IV's that are reversed.

this is an olds 455 engine. i'm not a pro on olds versus chevy coolant flow so this could be the case since we put an olds engine where there was a chevy. i just always thought you couldn't screw that kind of stuff up. top hose and thermostat to top connector on radiator, bottom hose from water pump to bottom of radiator.

also, when the radiator cap is off while it's running theres a jet of coolant flowing towards the pass. side of the car where the bottom hose is located so i kinda figure it's right but i'll look into it more. if you guys know something about sbc vs. bbo coolant flow let me know. thanx

If it still blows water after only a short few minutes, it sounds like you have a blockage somewhere - like a gasket blocking a water passage? Also, double check for a thermostat.

Just a thought. Hard to trouble shoot without being there..... I agree the idle problem is the carb - rebuild it.

Harry