Rad hose blows off
- Thread starter 91A-77B
- Start date
Mart
Well-known member
Again, 4lbs is a good compromise. Remember the original system ran at 0 lbs (atmospheric) While the outright pressure will probably not burst an original radiator, the cycling between cold 0lbs and hot 18lbs will fatigue the radiator. I had to do some repairs to my 40 radiator and make sure the 4lb cap really was 4lbs.
Mart.
Mart.
glennpm
Well-known member
With this high a pressure, the separation force, blowing off the hose is 45.33 lb.
With a 4psi cap, 9.6lb.
KiWinUS
Well-known member
Re-read posts #2, 14, 24 and 25.
You need a zero to 4 pound max cap.
As to finding one, you will need to take the cap you have to a radiator shop or Auto Parts store.
What makes you feel you need a higher boiling point? 50/50 antifreeze will give you
higher boiling point.
glennpm
Well-known member
1.3 = 18.85, or 19 rounded off.
"A standard 50/50 mixture of antifreeze (ethylene glycol) and water has a boiling point of approximately 223°F to 227°F (106°C to 108°C) at atmospheric pressure.
The addition of pressure significantly increases this threshold. In a typical vehicle cooling system with a 15 PSI pressure cap, the boiling point rises by roughly 45°F, resulting in a total boiling point of approximately 265°F to 270°F (129°C to 132°C).
Key factors influencing the boiling point include:
Pressure Cap Rating: Each pound per square inch (PSI) added to the system raises the boiling point by approximately 3°F.
Mixture Ratio: While 50/50 is standard, higher concentrations of glycol (e.g., 60/40) can raise the boiling point further, though pure antifreeze is less effective at heat transfer and has a higher freezing point than the optimal mix.
Altitude: Boiling points decrease at higher altitudes due to lower atmospheric pressure (approximately 2°F decrease per 1,000 feet of elevation)."
OK. Switched to plastic hose, Tried Indian Head, let it set overnight to grip. Put aircraft-style clamp on in the morning. Tightened it, fired up engine, off she blew. Head is Navarro, identical to its mate on the other side, which never blows, even without Indian Head. So problem is clearly with head casting. Out-of-round casting outlet, maybe with wobbles. Regardless, the solution is to remove head and have machinist buddy, who is genius with all the equipment to back him up, do his magic. Lesson to be learned: Just because it is a famous name brand, the name on the head (Navarro) doesn't mean he did the casting. Sand shifts and castings are affected. If you're still with me in a couple of weeks, I'll have pulled the head, had the machining done, and be back to getting her on the road. Hopefully before January 31.
19Fordy
Well-known member
Before you start machining the hose outlet on the head measure it with a vernier caliper to see if it truly out of round. If it is, you could apply a layer of JB Weld on the low spots
to make the OD uniform. Lot easier than machining and you won't reduce the OD of the outlet. While you're at it check the other head also.
to make the OD uniform. Lot easier than machining and you won't reduce the OD of the outlet. While you're at it check the other head also.
tubman
Well-known member
I agree with he measuring part. One thing I haven't seen here is some actual numbers on the head spigots. I also agree that removal and machining would be premature,
I don't know what the correct diameter should be for the top hose. I have an engine here with Offenhauser heads. The outlets measure 48 millimeters left, and 50 millimeters right. Forgive the metric measurements, I am a machinist and fractions make no sense. 1 3/4" is 44.5mm 2" is 50.8mm 1 7/8" is about 47.5mm. I never had any problems with the Offy heads using the one piece hoses for '48 car.
glennpm
Well-known member
Totally agree with this approach.
Did you get 5psi thermostats? The ones you have now are crazy high.
No luck. Cleaned surfaces. applied Indian Head, allowed to become sticky, slid hose onto head, left overnight, clamped with spring-type premium clamp next morning. 11 lb. cap from NAPA. Hose blew off after about 3 minutes of running. Remembered that there was minor leakage when stock '37 rad with no pressure cap was used. Off will come head, expert machinist I know will make neck perfectly round, non-tapered, and hopefully ridge around upper neck. Still open to ideas, opinions. Head coming off Monday. I appreciate any input. Thanks
The Navarro heads are vintage, probably 1950's - 60's. A tad past warranty period. I opened them to 76cc's to help flow for blower. The 11 lb. cap raises boiling point by 33 degrees (thanks glennpm) to 245. I'm OK with that. I'm going to carefully measure the outer circumference of the neck both for out-of-roundness and taper top-to-bottom before taking final step of machining.
Excuse the repeat report above; didn't realize my posts are in 2 series.
Excuse the repeat report above; didn't realize my posts are in 2 series.