Not Your Average Overheat Question

[mosel70]

Really good replies, thanks to everyone.,

I only have one water pump, a FlowKooler.
https://www.summitracing.com/parts/BRA-1671
I took the front 1100 CFM pusher fan off. Now only 1300 Mishimoto twin puller fans (2600 CFM total) on. Carb mix screws 1 1/2 turns out, it came new out of the box at 2 1/2 turns out. Edelbrock said that's about right. No vacuum leaks anywhere. It starts bleeding coolant from rad to overflow tank when super hot. 19lb rad cap. Electric choke working fine.

So, my son-in-law came over and got me to stop wanting 800 RPM at idle just because it feels smoother. He said I've got to live with the slight rumble from that cam. Now it idles at about 1200 in park, and 550 in gear at a stop. Still too much of a drop and not sure why.

Motor nearly overheats at a stop but much better than deep red on the gauge needle.

I've ordered two of Derale's 2100 CFM 14" fans (4200 total)
https://www.summitracing.com/parts/DER-18214
with their 16795 PWM Fan Controller
https://www.summitracing.com/parts/der-16795
They should fit my Mishimoto fan shroud perfectly and give me a tight seal.

I'll let you know if it fixes the overheat. I don't like it when guys ask for help, get lots of answers, but never tell you what actually worked. You, too? Ha!

[geezer#99]

Originally Posted by mosel70

Really good replies, thanks to everyone.,

Now it idles at about 1200 in park, and 550 in gear at a stop. Still too much of a drop and not sure why.



a!

It does that because of a lack of enough initial timing to idle at 750 in park and 600 in gear.
To compensate at present you likely have the curb idle screwed in enough to let it idle like it does.
Two problems arise from that. Retarded timing makes it run hot. Increased primary throttle opening has it idling on the power circuit.

A test to check for too much throttle opening is to screw in either mixture screw and see if it quits.

What's your timing curve like?
How much initial?
How much mechanical?

[Andy4639]

2500 bare min on cfm fan for a big block! 2 fans @4200 means they both have to be on all the time. One fan is only 2100 CFM This isn't enough to keep the BB cool!

The turns on the carb are starting points not the rule. The idle in park you need to adjust them to the max vacuum period! No question about it. It's the only way to do it. 2 turns maybe right for your setup but until you do the adjustment trust me it needs to be checked. Check out their video on it.

Cooling. Rule of thumb!

1,250 CFM for a 4-cylinder
2,000 CFM for a 6-cylinder
2,500 CFM for a 8-cylinder
Note: Big horse power means big fans!

You Tube

[mosel70]

Thanks for last two replies today.

I just turned the mixture screws in all the way one at a time from 1 1/2 turns and it decreased RPM from 850 to 550 but did not stall engine.

I can't check timing right now because when I installed a new water pump I also installed a new harmonic balancer and adjustable timing pointer. So I need to find TDC again to get the pointer right and will then check timing again.
https://www.summitracing.com/parts/SUM-164700 (timing pointer)

One thing of note is my vacuum advance is connected to port (passenger) vacuum on my Edelbrock 750 carb.

Thanks again!