I read that someone else experienced this.
This is something that I've noticed on a few engines over the years.
I thought it was the choke so I removed the choke plate - No improvement.
I thought I was imagining it but I clocked it and It's definitely quicker / more responsive at part throttle before the engine reaches operating temp.
I thought it was the heat riser heating the charge - I blocked the riser - No improvement
I bought an Air Gap intake and I'm about to install that
Anyone else have something to add?

Thanks

 

Check your timing -- my '91 RS would run great when cold, but idled rough and would stall at stop lights when warmed up. Ended up replacing just about everything on the car before I figured that out.

Also it would help to know the year and engine/fuel delivery system of your car.

 

Typically speaking, an engine will perform best with hot oil and cool coolant flowing through it. Inlet air temperatures is also a big contributing factor. As the engine bay warms up it will tend to increase the temperature of the air it's providing the engine via heat soak, etc.. This is especially noticeable with open air filters under the hood without a fresh air source. As the air heats, the molecule density decreases, which ultimately means less oxygen.

I personally run a 180 degree thermostat and a custom fan controller to keep the engine a bit cooler. I don't think I ever go above 185-190 degrees now. 30 degrees can be a big difference, performance wise.

 

I have CAI
It's a carbed 350
I'll do some checking to see whether everything is working OK

 

There's a good chance it's hot fuel.

The block-mounted pump gets REAL HOT from being bolted to the block. Especially when someone has "improved" the fuel system by "cleaning up the engine bay" or putting in a "high performance" fuel pump like "all the fast cars" have, and eliminated the return line.

Make sure the return is hooked up properly and put 2 gaskets under the fuel pump. Maybe even, make yourself a thicker one out of bulk gasket material to go under the blockoff plate, too. Or even,

https://www.summitracing.com/parts/ctr-85-000/overview/

Put it on underneath the plate with a thin schmear of sealer, as if it's a gasket; not, instead of the plate.

 

It's cool where I live and the air is dense. It rarely reaches 70 here.
My CAI is working
I should maybe check my thermostat and my gauge.
It would be odd that both the stat and gauge would be off and the engine is overheating, but it wouldn't be the first time that there have been 2 things that were out at the same time.

 

None of what you mentioned really has any impact on the potential problem.

Make sure your fuel return is working, and try insulating the body of the fuel pump from block heat.

Might also be a good idea to verify that the carb fuel bowl level stays the same at full temp.

 

What kind of CAI setup do you have? Picture?

 

Thanks for that advice
I'd be inclined to try that out, except that what I'm experiencing takes place after less than 15 min of driving, maybe even 10 min
I'll check it out though and see if the FP is hot

 

So it runs better when it has a bit of choke..... Do you need larger main jets in the carb?

 

I'm going to change the heads soon cause I got some higher CR heads.
When I do that mod, I'm going to do some serious jetting work on the carb
It's possibly running rich, cause when it's cold it seems to be best

 

Closing the choke slightly richens the mixture.

If it runs better by doing that, it's too lean to begin with.

Start by checking the fuel level in the bowl. Don't mess with the jets and other calibration parts until you sort out whatever is wrong with the function of the system. It is a total waste of time to pretend to calibrate a fornicated carb.

I still suspect a heat related fuel issue.