Hi Folks,

I'm having a bit of a problem getting a 225 started when the motor is hot.
i.e. Say I've been driving it a while and then the car is parked for between 10 and 30 minutes.
It is almost impossible to get the car started unless I have the gas pedal completely to the floor. It usually takes more than one attempt to get it going.
I am guessing that this is due from heat soak... i.e. the motor and intake manifold are so hot that the fuel doesn't get down to the cylinders as it should.

The question is, what can I do about it?
Or is there some other problem going on here?

Another clue, though I am not sure it is related, is that when the motor gets hot after a long drive, it doesn't idle well. It is nice and smooth when it has not been driven far, but after a longer drive, it is rougher.

It occurred to me that the heat riser could have something to do with this. It isn't frozen in place or anything like that, though.

Thanks.

Hi there. What year and model is the vehicle that's giving you the hot-start/hot-idle problem? Which carburetor does it have? Is it all stock under the hood, or have there been modifications? Any underhood repairs or parts replacements? And, where do you live? You're right that heat soak is causing the problem, but with answers to these questions there may be additional, more specific causes that can be suggested. The heat riser valve definitely needs not to be stuck in the heat-on position, but you say yours isn't stuck, so that shouldn't be the problem. One good way to reduce the effect of heat soak on hot starting and idling is the fuel line mod.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

<<Hi there. What year and model is the vehicle that's giving you the hot-start/hot-idle problem? Which carburetor does it have? Is it all stock under the hood, or have there been modifications? Any underhood repairs or parts replacements? And, where do you live? You're right that heat soak is causing the problem, but with answers to these questions there may be additional, more specific causes that can be suggested. The heat riser valve definitely needs not to be stuck in the heat-on position, but you say yours isn't stuck, so that shouldn't be the problem. One good way to reduce the effect of heat soak on hot starting and idling is the fuel line mod.>>

Sorry I should have thought to include that info.
This is a 225 in a 73 Scamp. It has the Holley 1920 carburetor and the engine has not been modified in any way. I live in NJ. It has been hot recently but not really as bad as it could be in the summer.

This only happens after I have driven the car for a while, especially on the highway. If the car then sits a short time, it's OK, but if it's more than 10 minutes, it is hard to get it going again.

<<Hi there. What year and model is the vehicle that's giving you the hot-start/hot-idle problem? Which carburetor does it have? Is it all stock under the hood, or have there been modifications? Any underhood repairs or parts replacements? And, where do you live? You're right that heat soak is causing the problem, but with answers to these questions there may be additional, more specific causes that can be suggested. The heat riser valve definitely needs not to be stuck in the heat-on position, but you say yours isn't stuck, so that shouldn't be the problem. One good way to reduce the effect of heat soak on hot starting and idling is the fuel line mod.>>

Sorry I should have thought to include that info.
This is a 225 in a 73 Scamp. It has the Holley 1920 carburetor and the engine has not been modified in any way. I live in NJ. It has been hot recently but not really as bad as it could be in the summer.

This only happens after I have driven the car for a while, especially on the highway. If the car then sits a short time, it's OK, but if it's more than 10 minutes, it is hard to get it going again.

OK, well, the '71-'73 1920 carburetor is prone to hot-start problems, and the '73s tended to have extra-hot engine compartments, and NJ gasoline can tend to aggravate hot-start problems. So, here's a checklist of things to do:

Make sure the carburetor has the correct 3/8" thick base gasket.

Make sure the carburetor's float hasn't become fuel-soaked.

Install a new inlet needle and seat in the carb.

Do the Fuel line mod.

Make sure the PCV valve is correct (replace with a good quality new one)

Purchase from the dealer and install a carburetor heat shield p/n 5214 558 (it's also nice if you can get the heat shield extension 4105 070, but this is showing NLA. Perhaps your dealer is friendly enough to look and see if anyone's still got one). When you install this heat shield, check the bottom of the carburetor carefully to make sure you won't be blocking off any vacuum passages. Drill/cut as necessary.

Make sure your thermostatic air cleaner is working correctly so as to duct cold air to the carburetor when the engine's warm.

Install a 180° thermostat; my preference is Stant SuperStat #45358

Install a set of NGK #ZFR5N spark plugs (stock number 3459) gapped to 0.040". Remember to remove the metal ring washers before you install the spark plugs.

Install a NAPA Echlin long-tip rotor # MO-3000.

The carburetor/fuel line related measures will probably solve most of the problem, but be advised '73 was the first year for electronic ignition, and many of the early ECUs and pickups didn't work very well when they got quite hot. You can get good quality ECUs on today's market if you shop around, but you may want to look into the HEI upgrade instead.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

All very good advice. Thanks!

What is the purpose of removing the ring washers from the spark plugs?

The heat shield you mention... is it like the ones they put on slant 6s in 1980 and 81, white in color, covering the entire intake and exhaust manifolds?

The '63-'74 heads are designed specifically not to use spark plug ring washers. Using the washers with these heads moves the spark plugs' electrodes out of the optimal position and causes the plugs to run hot. This used to be common knowledge when there were scads of slant-6s on the roads, but it no longer is. Using the suggested NGK plugs (which have a special extended-projected tip) without ring washers will improve ignition of less-than-perfect mixtures, which will get you started faster and should improve idling even if there's some flooding.
That's it exactly.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'm very glad to know that I'm not supposed to be using the washers on the spark plugs. I did not know this!

I have always had 75 and later slant 6s which used different plugs. This is the first one I had that had spark plug tubes.

Do you think using the washers could cause gas mileage to decrease? I am getting about 21 mpg on the highway (at about 60 mph), and I think it should be better than that. I have checked everything I can think of... timing, valve adjustment, no vacuum leaks, etc.

As for gas mileage, I was thinking my front brakes might be dragging a bit, but I don't know what is normal. If I turn the front wheels by hand, they turn around 2 or 2 1/2 times and then stop. Removing the caliper lets them turn more freely. I am not sure what to think... the calipers aren't that old. Maybe some slight drag is normal.

Oh, possibly a little, but not significantly.
21mpg @ 60mph in a Dart like yours is actually quite good. You can probably increase it a little with the ignition system tweaks I mentioned previously, and it'll go up when you stop burning up so much extra gas every time you start it up hot, but your mileage does not sound abnormally low at all.
Perfect, no problem here. Remember, with disc brakes, some slight drag is normal.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.