El Camino Central Forum banner

1 - 20 of 35 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Just installed anew 383 stroker 450 HP motor in my 70 elky. Left the stock radiator in. My problem is when I drive down the freeway the coolant bypasses the radiator cap and out the overflow hose. bought a new cap but didn't help. Any guesses?
 

·
Registered
Joined
·
372 Posts
Just installed anew 383 stroker 450 HP motor in my 70 elky. Left the stock radiator in. My problem is when I drive down the freeway the coolant bypasses the radiator cap and out the overflow hose. bought a new cap but didn't help. Any guesses?
Either the engine is overheating or you need a radiator cap with more psi. My '68 L79 327 has a 15 psi radiator cap and the only time any coolant goes out the overflow tube is after I cut the engine off and it sits for a while. It didn't come with an overflow tank so I had to add one.
 

·
Premium Member
Joined
·
864 Posts
Just installed anew 383 stroker 450 HP motor in my 70 elky. Left the stock radiator in. My problem is when I drive down the freeway the coolant bypasses the radiator cap and out the overflow hose. bought a new cap but didn't help. Any guesses?
Do you have the overflow tank hooked up?

Joe
 

·
Registered
Joined
·
12,533 Posts
welcome B
unless you have a Coolant Recovery Tank, and a 2way Recovery Cap,
the heat and pressure will push about~ 4-5 inches of coolant out of the radiator,,
ether on the ground or to a overflow or catch tank..
it will stay like that from then-on, unless you have leaks..
when you check the radiator cold, it should be down 4-5"..

and overflow tank and recovery tank/cap are not the same..
the recovery setup will put the coolant back in the radiator as it cools,,
when you check the radiator cold, it will be full...
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5
Do you have the overflow tank hooked up?

Joe
Thanks for your input my cap is also 15#. Like your 68 I have no recovery tank. Although at first I thought it was an overfill issue my problem is this pushes till the radiator is empty. Might the after market water pump be pushing to hard?
 

·
Registered
Joined
·
6 Posts
Discussion Starter #6
Thanks for your input my cap is also 15#. Like your 68 I have no recovery tank. Although at first I thought it was an overfill issue my problem is this pushes till the radiator is empty. Might the after market water pump be pushing to hard?
Forgot to mention this only seems to be happening at high rpms (freeway) not at idle in the garage.
 

·
Premium Member
Joined
·
864 Posts
Thanks for your input my cap is also 15#. Like your 68 I have no recovery tank. Although at first I thought it was an overfill issue my problem is this pushes till the radiator is empty. Might the after market water pump be pushing to hard?
Forgot to mention this only seems to be happening at high rpms (freeway) not at idle in the garage.
I would add an overflow/surge tank first as dieselhead described, if that doesn't fix the problem you have a leak somewhere else. If you do have a leak I would start at the freeze plug above the starter.

Joe
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
I would add an overflow/surge tank first as dieselhead described, if that doesn't fix the problem you have a leak somewhere else. If you do have a leak I would start at the freeze plug above the starter.

Joe
I dont understand why an overflow tank would cure this problem or why a freeze plug would create one,
 

·
Premium Member
Joined
·
864 Posts
I dont understand why an overflow tank would cure this problem or why a freeze plug would create one,
When your engine heats up the coolant expands and has to go somewhere. The pressure cap allows the expanding coolant a place to go. If it goes to the ground you loose coolant. If you have a recovery tank it goes there. When the engine cools down with a recovery tank it will suck the expanded coolant back into the radiator.

If your coolant is leaking from the block the most common leak is a freeze plug, and the most common of those is the one above the starter.

Joe
 

·
Registered
Joined
·
12,533 Posts
don't see how you could empty the radiator thru the cap/overflow,
unless your pushing out steam/water..

is this a newer block, roller cam / 1 piece seal
does the temp gauge fluctuate a lot ??

got pics of your setup ??
 

·
Premium Member
Joined
·
1,145 Posts
Is this a new build? First test drive? It could possibly be your thermostat not opening.
Hate to go extreme here but...by your description of all the coolant being pushed out it sounds like there's a leak between your combustion chamber somewhere and the water jacket. Make sure your head gaskets are on correctly.
 

·
Registered
Joined
·
1,323 Posts
Your engine is bigger than stock, probably needs a bigger radiator too. I needed a larger radiator when I replaced the 305 slug in my 84 with a 300HP crate engine.
 

·
Registered
Joined
·
1,323 Posts
Standard symptom for needing more radiator is the engine overheats at highway speed, but not around town. In contrast, overheating in town and cooling off at highway speed is generally the engine fan.
 

·
Registered
Joined
·
12,533 Posts
x2 or a missing spring in the lower hose..
didn't want to go there till we find out if the stock radiator is
a LS6 BBC 4row radiator,, or a 1row for a 160hp 307..

don't think he likes us anymore, hasn't been back in 5-6 days..
 

·
Registered
Joined
·
932 Posts
Just installed anew 383 stroker 450 HP motor in my 70 elky. Left the stock radiator in. My problem is when I drive down the freeway the coolant bypasses the radiator cap and out the overflow hose. bought a new cap but didn't help. Any guesses?
I agree with recovery tank and Rad cap , But if the funds are available a after market Radiator or one with more coolant rows may be the best.
just from old experience I had an old biscayne 230-6 ccyl , No AC,, 1 row,, swapped a 350 into it , Boil over on occasion found a Rad from a 69 Gran Prix , more row, had AC, solved the issue.
Hope this helped
 

·
Premium Member
Joined
·
205 Posts
How do you know the number of rows in a radiator by looking at it?
 

·
Registered
Joined
·
12,533 Posts
take the cap off the radiator, look at the end of the Core
you may need to lower the coolant a little to see them..

actually the number of rows doesn't mean a whole lot with out all the other info,
like the Tube width.. its basic-ly the thickness of the Core..

you can have a 1 row now days with 2+ inches thick tube,
or a 1row that looks like its smaller than a 1/2 inch..

in the olden days radiators were 1,2,3, or 4 row, with 1/2inch tubes..
1row was 4cylinder
2 was a V6
3 was a small block
4 was a big block
but radiators were bigger back then too..

but there are really cheap radiators out there now days,
some have big gaps between the tubes so the core looks thicker..
less tubes per inch in the vertical, less total number of tubes..
some have lower Cooling Fin's per inch count [less cooling]
some are very thin, some are glued together..
any way to cut cost, and make it look like your getting something your not..
 

·
Registered
Joined
·
6 Posts
Discussion Starter #20
x2 or a missing spring in the lower hose..
didn't want to go there till we find out if the stock radiator is
a LS6 BBC 4row radiator,, or a 1row for a 160hp 307..

don't think he likes us anymore, hasn't been back in 5-6 days..
Sorry I’ve been gone so long I didn’t know anybody was still out there helping me I appreciate your input the radiator I have is the stock radiator for a small block Chevy I don’t understand the spring in the lower hose comment I would love for this to be a radiator issue and not a head gasket issue I planOn doing a compression check and any leak down check to see if I can detect any small differences I hope desperately that this is the radiator issue thank you again for your input
 
1 - 20 of 35 Posts
Top