• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

351w overheated, blew radiator cap off.

lhinterman

Newbie
Joined
Mar 25, 2020
Messages
34
I drove up a mountain to about 10,000 feet and the 351w overheated to the point it blew the radiator cap off. I was towed.

The heads are removed and the head gasket's (both of them) were melted and let water into the block. The heads are not cracked, the block is not cracked on the surface, the engine paint was burnt, and the valves looked ok.

I am having a shop put new head gaskets on and will try to start it this week.
What else should I be looking for?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
Pull the radiator inspect the core. If it was blown that hard the cores may be expanded, collapsing the fins.
 

Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,875
check the main and rod bearings too. I would suspect the whole assembly while its out. is this a well used engine or a brandy new one?
 

Timmy390

Bronco Guru
Joined
Jan 1, 2011
Messages
5,609
Loc.
Conway, AR
I drove up a mountain to about 10,000 feet and the 351w overheated to the point it blew the radiator cap off. I was towed.

The heads are removed and the head gasket's (both of them) were melted and let water into the block. The heads are not cracked, the block is not cracked on the surface, the engine paint was burnt, and the valves looked ok.

I am having a shop put new head gaskets on and will try to start it this week.
What else should I be looking for?

If it got that hot it needs a total going through. Heads magnafluxed and pressure tested. The block needs to be check too as well as bearings heck everything.

I would not trust anything at this point.

Tim
 
OP
OP
lhinterman

lhinterman

Newbie
Joined
Mar 25, 2020
Messages
34
Good advice! New engine 1500 miles roller cam and rockers. The shop has taken the engine apart. The intake valves are bad, the rings are burnt and stuck. The pistons, crank, block and rods are ok.
I will have them check the radiator.
 
OP
OP
lhinterman

lhinterman

Newbie
Joined
Mar 25, 2020
Messages
34
No I didn't loose all the coolant before the cap blew.
The engine tear down is complete. Bad rings, some valves, spark plugs, some hoses, and gaskets. The radiator is ok.
The shop replaced them all, the engine is back in and running. The sniper EFI broke and we can't reprogram it. A new module is coming from Holly.
I will update you later.`
 

Jambi

Contributor
Jr. Member
Joined
Aug 3, 2012
Messages
101
Out of curiosity, what radiator were you using? I'm building up a 351W right now and I'm a little concerned about keeping it cool, particularly after reading about your experience.
 
OP
OP
lhinterman

lhinterman

Newbie
Joined
Mar 25, 2020
Messages
34
Sorry it took me so long to get back to you. I just got the results from overheating.

I have a 2 core aluminum radiator with two 850cfi fans, and there is no way that is good enough for a 400HP 351w.

I would suggest that you look for a larger radiator. I contacted TBP this morning to get the dimensions on their Tri-flo 4 core radiator to see if it will fit without modification.

I have a chevy 454ci in my 57 truck and I have had heating problems for a long time. It gets hot in the summer. I put a 3 core alum from am radiator with two 10" fans in it and it still gets hot in the summer. I still don't try to drive in a parade or I would be towed home. I use a shroud in both trucks.
 

bamabaja

Contributor
Sr. Member
Joined
Mar 25, 2012
Messages
723
Loc.
The Shoals
Please share your thoughts on the Toms radiator fitting with the 351. That’s coming up on my install. Thanks
 

blubuckaroo

Grease Monkey
Joined
Jun 11, 2007
Messages
11,795
Loc.
Ridgefield WA
WOW! I've never heard of a cap blowing off. I would have thought it would have just relieved the pressure like it's suppose to.
You must have really good hoses.
Did it damage the fill neck on the radiator?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
If you blow a head gasket bad enough it is possible to pump so much cylinder pressure into the cooling system so fast that the cap can't vent out that 3/8" overflow hose. That is why I started with checking the cores on the radiator. They have been known to swell and collapse the fins. The radiator will hold more water, but you won't get airflow.
 

Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,875
Sorry it took me so long to get back to you. I just got the results from overheating.

I have a 2 core aluminum radiator with two 850cfi fans, and there is no way that is good enough for a 400HP 351w.

I would suggest that you look for a larger radiator. I contacted TBP this morning to get the dimensions on their Tri-flo 4 core radiator to see if it will fit without modification.

I have a chevy 454ci in my 57 truck and I have had heating problems for a long time. It gets hot in the summer. I put a 3 core alum from am radiator with two 10" fans in it and it still gets hot in the summer. I still don't try to drive in a parade or I would be towed home. I use a shroud in both trucks.

Have you tried driving them with the hoods off? do they still over heat with the hood off?
 

68ford

Bronco Guru
Joined
Dec 26, 2004
Messages
2,710
Sorry it took me so long to get back to you. I just got the results from overheating.

I have a 2 core aluminum radiator with two 850cfi fans, and there is no way that is good enough for a 400HP 351w.

I would suggest that you look for a larger radiator. I contacted TBP this morning to get the dimensions on their Tri-flo 4 core radiator to see if it will fit without modification.

I have a chevy 454ci in my 57 truck and I have had heating problems for a long time. It gets hot in the summer. I put a 3 core alum from am radiator with two 10" fans in it and it still gets hot in the summer. I still don't try to drive in a parade or I would be towed home. I use a shroud in both trucks.

I run 2 14in high cfm spal fans on a much larger than normal EB radiator. You need at least 3500cfm for a small block. Ford taurus fan is about that and the only single fan that does a good enough job. For you. If block I would say 2 16in fans are needed and equally as large of radiator.
 
Top