Keep blowing heater cores in Cuda???

[wjohnson]

I've built a 70 Cuda with a 6.1 third generation motor. I've gone through 3 heater cores in a very short period of time--there's too much pressure in the cores and they're "bulging" and blowing all over the place.

Any help out there????

Thanks!

[RacerHog]

Sounds like to much system pressure... 16lbs or more?

[te.ringer]

does the engine have a by pass hose like the small blocks use ? or just the fancy thermostst with by pass built in under it.try a 10lb cap thats what we use on all the heavy duty trucks,its possible all the coolant exiting the motor when cold is going through the core until thermostat opens.go luck with this after 45 years working on everything with a engine this is a first(with the swelling) some late models have a return line going to the resivore to reduce pressure and remove air from system