If you have a thermostat you should be OK. But Cavitation can also be before the pump if there is air there. I will post a picture of how they did away with the question of that with a petcock put in the $400 pump . The cavitation I am talking about is created when the motor is at idle.
If the water flows from the motor with no restriction at all. The free flow does not allow the pump to pressurize the coolant in the block. With out pressure in the block by the coolant running out as fast as it enters. It causes air pockets and bubbles to form at the top of the block and in the head. this makes more heat up there and causes the temp to rise while idling if your sender is still in the coolant.
I have an electric pump which is always at max flow it is not hindered by RPMs so a 1 inch works fine for me . If a manual pump is used you may need a smaller hole than a 1" at idle. do to the fact your water pressure going in is less.
That is why they sell three different 1" 3/4" AND 5/8". We made our own in 1/16 increments.No motor is the same . it depends on the Pump flow , and the cylinder wall thickness and the coolant passages. also type of head
The idea is to keep the air bubbles comming out of the pump from cavitating in the top of the block or heads We checked this with a infa-red temp. gauge. While idling we checked the head and block temp and compared it to the bottom of the cylinder. If there is an air cavity the reading will be much greater than the bottom. This will distort the cylinder and can cause damage. The best way we found is to run the smallest you can without it running hot at RPM's. The more pressure you can create without effecting the the high RPM cooling the better you are.
Pressure in most blocks could be up to 22# very hard to measure before the stat. That has nothing to do with the cap PSI .because the bottom hose is pulling coolant lowering the pressure in the rad. The idea is to use pressure to keep the top of the cylinders and the head full at idle with a manual pump . If the water flows out of the block without resistance it will cavitate. This is a common problem. and the cause of most detonation . The factory thermostat is designed for a standard cyl. wall thickness . Good race cars are tested and restricted accordingly.
You may be good but it doesn't hurt to check. Take your stat out and try a 3/4". See if it still runs hot at idle. and the same as it did at rpm's as with the stat. You can go smaller if it still runs cool at RPM's. As soon as you see it is raising the temp at RPM's your to small. go back to the next size bigger.
That is the reason we made are own with 1/16 increments. He wanted it perfect for the street. In a NASCAR they only worry about the temp at RPMs. A one inch hose is good . Tony Hirschman showed me this, He builds Modified NASCAR's and is on Kyle bush's team. His son Matt is the East coast champion. in Modified NASCAR . That is where they designed my cooling system for my NASCAR truck motor in my street car at the time. Kyle bush is amazed at what Tony does . I idled around with 12 1/2 -1 all day. on pump gas. I could take the car to 9000 on the street as long as it didn't load the motor at RPMs . and It didn't, It would turn the tires in drive. But on the track with slicks different story It needed race fuel.
The car never ran hot with this system when he did it. as long as the motor is full to the top at all rpm's you should be good. My son has built Nitro and methanol motors. diesel pullers. and big liquid bikes. He does work for Hirschman's on the Chassis in return for the fragola braided parts and help we get there. We walk out with what ever we might need . It saves the many trips and time if you have to buy what you think you may need one at a time.
Trust me I would not steer you wrong. My son and Tony play with whats new not what use to be. All you can do is try a re-stricter. It may be your problem. Only you can test it. Remember go smaller one size at a time. once you raise the temp at RPMs go back to the last size. Stats usually flow 1" some 3/4" as we have seen. There is logic to why they sell these restrictors. Once you have the right size take a ball and some sort of die and taper the re-strictor put the protruding side toward the hose. Good luck
View attachment 1715392122
