my 318 motor runs cold..!!

[claybill]

i have asked this question last fall..tried and considered things, then put the car away for the winter..started it up last week and attacking some of the old problems.. what happens is..

i have a 318 auto in my 41 coupe. with a new holley 600 performer carb set to proper standards.

it takes forever to warm up..like 20 miles.! (180 thermo). when going around corners it coughs and bucks, needing a choke.

I checked acc pump and it is spitting gas in FOR SURE.!

i wonder what else might have this effect at low speeds..

GLASPAK mufflers, ex. pipe size, carb metering/jets, air cleaner, acc pump too little/too much, a diff thermostat....any of these things might effect the coughing at low speeds when you step on the accelerator pedal..

is it the carb? and which jets..?

bill

[greg g]

what do the plugs look like, do you have hot air to the carb?? What are you running for a radiator? Maybe try blocking some of it off for a test. Is your t stat working properly? Where is your timing at??

Over the course of my experience, I have seen many street rods/hotrods, or other cars with modified engines to be over carbe'd, usually leading to poor idles, driveability problems, and rich running at anything but WOT. I am a bit concerned about this on my Studebaker. The carb I picked up for it is a carter AFB 4bbl from a 327 Chevy. Since my engien is only a 259, I might be in that boat.

Hopefully the dual exhaust will take a bit of the slack but who knows.

I think the carb is around a 600 Cfm deal, probably should be around 500 for "best" results.

Edited March 20, 2011 by greg g

[Alshere59]

For the long wrm up I would look at the thermastat. Sounds like its not sealed or stuck open half way. If its going around corners only when it coughs etc. I would say the float. So only at low speed? Assuming it does this warm or cold.

What was the last thing you worked on before this started last fall?

Edited March 20, 2011 by Alshere59

[claybill]

this was a new install motor&carb..coughing performance from day 1. at medium and up throttle it is very responsive..idle is also smooth & steady.

carb was set to 318 specs.(total install was done by very capable mechanic, )

not a 'corner' problem, other than in town i go slower around them.!!!

bill

can an air cleaner be too big.?

[greg g]

to much air is only a problem after the thottle butterflies as in a vacuum leak.

[RobertKB]

Time to put the flattie back in!

[claybill]

OH!..thanks a lot robert.!

ha,

bill

[John Reddie]

I have found that on the 318 engines, the intake manifold has a passage that goes from the left bank to the right bank. This provides carburetor heat from the exhaust manifold heat riser. This passage over time gets blocked with carbon and very little or no heat for the carb base is the result. This too can produce hesitation like you describe. It can also prevent the choke from opening properly. In order to correct it, the intake manifold is removed and the passage cleaned out.

John R

[claybill]

john..sounds like my situation...however a major undertaking. i will check thermostat first. then attack the manifold..IS THERE no way to clean that via the carb base.?/????

bill

[greg g]

Bill, there were several other external tests suggested you could do before tearing the manifold apart, did you dismiss them??? Did you look at the plugs, did you try blocking some of the radiator, did you see how your acc pump was set, an it be ajusted for more or less movement. A blocked intake passage while having some effect on driveability has absolutely no bearing on operating coolant temp.

You need to find out the why's of the operating temp before addressing the drivability issues it may be causing.

As stated, you are preposing the driveability problems are because of low operating temps, so it only makes sense to get your op temps where you need them before daling with the symptoms. Supposed you pulled you manifold, rooted out the suspect passage, put it back together and then on restart you find the same low temp situation, time and money wasted.

What is the actual coolant temp after a 20 mile run??? Does your car have an electric fan, when doe it come on, shut off? Do you know the accuracy of your temperture gauge???

There is a path to follow that doesn't require removal of major components, I would take that road first.

[Dodgeb4ya]

It usually takes quite a few miles to plug up the intake manifold heat riser passage. Is there even a heat riser on the exhaust manifold to direct the heat up through the passage? To check the crossover passage if you do have a properly operating heat riser, start the engine up and run it at a fast idle and after 2-4 minutes you should be able to feel the intake get warm at the base of the carb. If it stays cold and the carb base feels really cold and there is iceing at the carb base you have no heat to the base of the carb.

A lot of the 318/360's used a 2" flex heat tube off the exhaust manifold to supply hot air into the air cleaner and this helped cold drivability with these cold blooded engines.

This was a common problem here in the cold damp winter time here in the Northwest.

When cold you need heat under or into the carb until the engine is warm. Summer time should not be so bad.

[greg g]

But again this has no bearing on the coolant temp he says is his root situation.

[Dodgeb4ya]

But again this has no bearing on the coolant temp he says is his root situation.

Just posting some more info as the heat riser passage issue was mentioned. Might be of help to others.

[claybill]

i will buy an infrared heat sensor this week. i will check the thermo also this week. i will check the radiator coolant with the infrared tool....

thanks for the help.

[Niel Hoback]

Your first post says it takes 20 minutes to warm up. That means your thermostat is not closing. Change it and the stumbling and bucking caused by a cold engine will likely go away.