To any of you current and former V8 conversion owners, I would appreciate your advice.

I’m nearing the end game of my coolant system overhaul (1965 Chevrolet stock, carbureted 283 in.³ V8) and I spoke with Don, the veteran at Renegade Hybrids, the other day for quite some time.

Don said he has done V8conversions on 914’s for 40 years.

He suggested two things for my current project:

1.) Cut two or three 1/8 inch holes into a 160° thermostat . I prefer to go with the OEM 180 and I’m wondering if I should cut one, two or three holes in it - my veteran Ford tech neighbor thought perhaps I should cut one ( he’s going to help me pressure test the system and then pull a vacuum to fill it if the radiator doesn’t leak after I removed those 30 year old hoses ).

2.) Burp the coolant system with the car nose down. Part of the reengineering/overhaul here is that I am adding Moroso expansion tank/coolant tank next to the engine as high as I can get it. The engine is actually nose down a bit so the Ford tech thinks that with the vacuum system we should be able to get every bit of air out of it but if we nose it down then maybe steam pockets or air will stay in the back of the heads since they are already higher than the front when the car is level on the ground.

Any thoughts/suggestions/experiences regarding the above?

Thank you all!

I would not drill any holes in the thermostat...as it defeats the purpose. A good thermostat should have a little jiggle valve in it, which is all you should need.

I'd get one of these or rig up something similar to get the "head" significantly higher than any other part of the system. https://www.amazon.com/Thorstone-Radiator-A...47741&psc=1

I've done lots of SBC swaps (never in a 914), but I've had the best luck removing the thermostat housing and filling through there....squeezing the accessible hoses to burp the system as you go then a final top-off to about level with the gasket surface before installing the T-stat and housing, then hook up the hoses, install the funnel, and fill' er up about an inch from the top....then go fondle the hoses some more, and fire it up.

If you're running an electric water pump, remove the rad cap and hot wire the pump. Run it and keep topping up until the coolant settles at the correct level. Works great on my LS build.
If you're not, get hold of one of the vacuum coolant fill kits. I've used those, too, and they work quite well.
Best of luck.

On my 350 SBC conversion I use a modified Dedenbear expansion tank with no thermostat. The electric water pump and fans run by a Davies Craig digital controller. During warm up the controller senses the temperature in the expansion tank and pulses the water pump on/off until it gets to operating temp then it runs the pump 100% duty cycle and controls the fans as needed. Initial fill up is easy. I bypass the controller to run the EWP full on while filling and have a bleeder screw at top of radiator until all air is purged. Also I open the heater valve so the pump can circulate through the heater core. I’ll raise the rear of the car up a bit to help bleed any air out of the lines under the car but I don’t think it’s really necessary. The expansion tank is already highest point in the system.
Guy

Renegade is located in hot Las Vegas Use their system and have no worries. I went through 3 water pumps 3 radiators and 3 different fan combinations trying not to pay for the Ron Davis radiator and fans that Renegade supplies with their kit. After all the trial and error I purchased that system and used it on a a 355 small block a 427 small block a honda v6 and know a 2.4 gm ecotec and engine runs cooler than a cucumber. LOL Measure 3 or 4 times and do it once.

My memory is sketchy on the subject but I think the suggestion for drilling holes in the thermostat may have more to do with reducing cavitation on the mechanical water pump than getting air out of it. The original SBC wp has in internal bypass that the renegade setup does not. I drilled 2-3 small holes in my thermostat when I was running that setup.

I also sometimes would raise the rear of the car when adding fluid, but settled on checking and topping off the overflow tank as my routine for getting air out. After 3-4 heat cycles it should be free.

Thanks, Gents.

No electric water pump.

@FL000 I believe you are correct about cavitation. These Rod Simpson (and Renegade) conversions run a Mopar big block waterpump in a housing that is quite different than said pump was engineered for. Don (at Renegade) said that the car should not be revved past 3000 rpm until the thermostat has opened up. Otherwise, he said, he has seen the mopar impellers break off fins from cavitation. . .he’s seen as many as 6 out of 8 break off and get lodged in the system.

With this setup I’ll go with the 3 holes since there is no internal bypass.

@FL000 , did you run an expansion tank in the rear?

This old conversion had an old round style Corvette expansion tank (Harrison - now DeWitts) in the front which makes no sense since it should be the highest point in the system which would be in the rear near the engine and above the thermostat housing .

I also plan on putting a three-quarter inch bleeder at a point just past the thermostat housing (still in the engine bay near the firewall -i.e. before the radiator) that I can keep lower than the expansion tank. When I want to bleed it I have enough slack to raise it up higher than the expansion tank and open the valve .

Based upon the system used in (modern) GT 40’s, I will not be routing a small line for overflow from the radiator because it would have to go down to the rocker and back up - apparently the GT 40 guys suggested just blocking that small hose and using it to purge any air from the top of the radiator if necessary .

Any thoughts on that ?

Affirm, I run an expansion tank in the rear at the highest point.

Click to view attachment

Agree no need to run a small hose from radiator to overflow, however, I forgot to mention last night that a petcock bleeder in the top of the radiator makes it very easy to bleed air captured there. I also bleed this after each heat cycle (and when initially filling the system) the first few times.

Click to view attachment

Thank you, Sir!