How's all that working out for you? I'll probably get a spacer and put it on when it warms up some outside and see how that does.

 

So far so good. I honestly don't have many miles on it (maybe 100) because my truck is perpetually on jackstands, most of that being self-inflicted. But I don't recall having a noticeable hot and cold start difference.

 

I'm with Dave on this one. Heat and modern fuels just don't go together very well. The fuel isn't really boiling away, just getting foamy. I've had a lot of experience with heat-related fuel problems on my '84 351W 2 bbl.

When you shut off a warm engine, underhood temperatures keep climbing for a little while. The hottest time is probably about 30-45 minutes after shutdown. That's when most problems are reported. If you shut off the engine while warm and then restart within a few minutes, the fuel is still relatively cool, so no issues. Sit for a few hours or more, and the fuel cools off enough. Even though some may have evaporated, there's still enough remaining in the float chamber for a quick start.

I had asked about the starter cranking speed. If the starter gets heat-soaked (often a problem with headers), that can cause slow cranking speed while hot. Also, the compression increases on a warm engine because the rings expand and seal better. If you have a marginal starter system (all components, not just the starter), it may not have enough oomph to overcome this increased load. When an engine is cold, compression is lower and this places less load on the starter system. Reduced compression sounds bad, but not always, especially for starting. Think of a kickstart motorcycle engine with a compression release, that lets your puny self spin the engine faster. That's why I was asking about starter cranking speed, to make sure we were troubleshooting the correct issue.

With my truck, when fighting with a hot restart, I've noticed the starter cranking speed actually increases after a few seconds. Seems kinda odd at first, but I believe this is caused by hot fuel bubbling/foaming out of the carb and getting into the cylinders. All this extra unburnt fuel washes the oil from the cylinder walls. No oil = reduced compression = less load on the starter = faster cranking speed. However, unlike the previous example of a compression release on a motorcycle, even though the engine is spinning more quickly, that hot foamy fuel is hard to ignite and might even foul the spark plugs. Therefore, the cranking time increases.

My truck had previously been giving me lots of grief due to hot fuel. This was more than just the nuisance of long cranking times for a hot restart. I've actually had the engine quit on me shortly after working hard, while just loafing along. My best guess was when using lots of fuel while the engine was working hard, the fuel stayed relatively cool passing through the carb. But when I throttled back, and fuel flow dropped way off, the fuel had enough time to absorb heat and turn foamy.

After being stranded several times, it was time for drastic measures. I made several changes to reduce heat reaching the carb. I'm pretty sure the primary culprit was the exhaust crossover passage inside the intake manifold, but I also made some other changes. Long-winded details of my travails here, post #6:

https://www.ford-trucks.com/forums/1...l#post16083555


My conversion to an electric fuel pump:

https://www.ford-trucks.com/forums/1...tallation.html


Some thoughts on fuel quality and octane:

https://www.ford-trucks.com/forums/1...g-and-you.html


Also, consider experimenting with different brands of fuel. (Per the link above, use the lowest octane) I've noticed a big difference in heat-resistance between brands. My truck is much better now after being modified, but my Jeep (unmodified '74 Chev V8) is still VERY sensitive to the brand of fuel. I'm very partial to Chevron, and it has worked best for me. On the other hand, I've had the most trouble with 76, even though it also considered a Top Tier fuel. Go figure, must be slight differences in the additive package. I'm not bashing any brand of fuel, just thinking some stuff is perhaps not optimized for ancient carbs.

 

I read a couple of really good articles about modern fuels and hot days. Ethanol has a lower boiling point than regular gas. I think you can go up a grade on the octane and that will help, or I think the general consensus was to add about a gallon of diesel per tank of corn squeezings. If I run across those articles again I'll link them.

 

MMO, 4oz per 10 gallons, good for what ails ya!

 

Yes want to add enough to raise the boiling point of the fuel.
EFI cars / trucks the whole system from tank / pump till after the injectors is under pressure and this will raise the boiling point just like the cooling system is under pressure to raise the boiling point of the coolant.

I got to say so far my little 300 six does not have any issues starting when hot but I also have not had it running during the summer but fingers crossed I will not.
Dave ----

 

Not so much anymore, it's just the opposite now with modern fuel:

https://www.ford-trucks.com/forums/1...g-and-you.html


The general gist is to use the lowest octane you can without causing knocking. Higher octane fuel typically has more ethanol, and less resistance to heat issues.

 

MMO? Diesel is cheaper.

 

And easier to put in.
The station I go to has the diesel pump as part of the gas pump just a different nozzle.
Pump in 1 gallon into each tank then fill the rest of the way with gas and done.
Dave ----

 

Yeah, mine keeps it around back, but it's a local station so it's still convenient. I think for the first little bit I'll drive twenty minutes for straight gas, and after I know she's running good I'll start mixing diesel with ethanol gas here in town.

 

I only have a single 18 gallon tank (bummer I know), are you saying I should put a gallon of diesel in it and fill the rest up with regular gas and that might help this issue?

 

I don't remember the exact ratio, but yeah. I'll see if I can find that other article now that I'm back home.

 

Before trying the diesel addition is there a fuel station that offers ethanol free gas? I use only ethanol free in all my small gas engines.

Also I was wondering how you were using the accelerator pedal when starting?

 

Well, I found it but it pretty much says just the opposite of what I've been saying. I need to sit and think awhile on why I've got in my head adding a bit of diesel is a good idea. https://www.militarytrader.com/mv-10...other-gas-woes

*edit*
looks like it was from this post, which recommends, or allows you can use a quart of diesel per tank. I feel like there is another article on it though, if I trip over it in my bookmarks I'll add a link for it as well.
https://www.ford-trucks.com/forums/1...l#post18109525

 

+1 on that.

For the moment, I’d hold off on mixing your own fuel blend, etc. Maybe try a different brand of fuel, as previously suggested, but I wouldn’t go much deeper than that for now.

With my truck, a big factor with a hot restart is how I position the gas pedal. I’ve found it works best if I slowly open the throttle about one third of the way. Definitely don’t pump the pedal, as that causes the accel pump to spray extra fuel (and/or foam) into the intake manifold, which makes things worse.

If the first start attempt fails, don’t release the gas pedal until after trying again. Otherwise, the accel pump sprays again, and you want to avoid that.