400 SBC Overheating

[monte]

I have a mate that bought a so called crate engine from the USA ,its a 350 chev and he fitted in his 34 Tudor ,still give him shit about that anyway it was getting hot all the time so after checking everything he could think of he decided to remove the heads ,some of the head bolts were pretty loose and one head gasket was stuffed ,he replaced gasket ,tightened the heads down and all was good ,I told him I would be concerned about the rest of the engine and he should quickly replace it with a Cleveland ,he still has the chev in there and its going fine but is building a 34 roadster for his wife and a lovely Windsor in it ,good luck with it mate

[32V8]

This is what I would do to address the same problem.
1/ Check that you have the correct water pump fitted. ie, a serpentine pump will not work with a v belt system as they are designed to run in the opposite direction.
2/ Get the car onto a freeway where you have a long non stop run. Travel at 100 kph and watch the temp, if it slowly gets hot I would suspect a partially blocked radiator. If so remove tanks and clean out ie. rod out the radiator properly, back flushing is a waste of time, replace radiator and insert a sock in top radiator hose to catch any crap coming from the engine. If it stays at normal temp on the freeway its not the radiator. You have to do this first to eliminate a blocked radiator.
3/ If it gets hot when you turn off the freeway and start, stop start driving, its an air flow problem. Check thermo fans, shroud, quality and cooling capacity of radiator. ie design of radiator. My mate has an A model with a 347 Windsor in it and always had overheating problems, it had a well known Aussie radiator fitted and it was was too small to keep the engine cool. Replaced now with a locally made radiator of larger capacity and no overheating dramas now.
Im an old fella and started my driving life with flat heads so over heating was a way of life for me. It took a while to work it out but this is my method and I haven't changed it over the years.
You must eliminate the possibility of a partially blocked radiator first, or you will never solve the problem.
Good luck old Son!!

[1934cv]

A long shot - did you replace the head gasket? From memory, the 400s had a funky gasket setup with steam holes.

Cheers,
Harv

Thanks Harv I have the radiator at the repair shop getting the leak fixed, and I called into my mechanics workshop who did my original engine check and timing he is now suspecting a head gasket leak so when I get the radiator back I will drive it to his workshop and he has some way of checking to see if it is the head gasket? I have a spare set of head gaskets for the 400.

[1934cv]

Does this have a points type ignition or an electronic ignition? What type of advance? If vacuum advance is it ported or manifold vacuum? does this overheat while cruising or at idle?

It has a points ignition and the vacuum advance is connected to just below the carby on the manifold. Today I had it at a fast idle and still went to 100C. Phil

Totally foreign motor to me mate. BUT - as with anything, the basics.

Block is spotless inside? totally?

All hoses are run where they need to be? (can delete later once you know all is OK) set it up as factory first before fiddling.

water pump spins the right way? (think some marine engines were reversed for twin motor boats)

all pulleys are all good for right diameter?

thermostat has been checked in a jug of boiling water? (can you see it work? + thermometer in pyrex jug)

valve timing is correct?

IGN timing is as close as you can get it? vacuum advance in good nick, adv. weights & springs on the dizzy shaft all good, etc.

The rest of the system (heater core & radiator) up to the task and CLEAN?

What fans you have? flex fans are like flyscreens on a submarine.

Shroud?

Radiator cap is good? how many PSI is it rated to?

Electric thermo's? if so, is the set point OK? Are they push or pull fans? not spinning the wrong way?


this is the stuff I'd be looking at on whatever engine it is before I'd dig any deeper. I know some things were answered but you need to guarantee the block's innards are clean as a doctor's needle before going any further I'd reckon. Even water on first start is OK when checking for leaks.... once you know it's all good, then go stick the coolant in after a flush.

Cheers, Mudgy

Thanks Mudgy to answer your questions all the thermostats (71deg, 87deg were both new) the pulleys appear to be the originals for this engine as well as the water pump, I haven't check the vac advance, the radiator is new with size 460mm x 460mm x 100mm fine core. I have used a 4 blade fan, 2 x 10" electric fan and a 6 blade flexi fan from my 34 Chev Sedan in my avatar which has been on the road for 40 years now running a 307 Chev and powerglide and which I drove around Australia in 1983. I have the electric fans behind the radiator and they are pulling. When I fill the cooling system it takes 12 litres of water to fill so this may rule out blockages in the engine. Phil

[34 tub]

Hi 34cv
That radiator seems to be an odd size for a 34 Chev, usually taller than width and no more than 50mm thick.
Using a 100mm thick fine core will greatly restrict the air flow through the core and what air is flowing through
would be at the radiator temp at the mid way point therefore providing no further cooling effect, modern
radiators are quite thin and have large air flow capacities and utilise a good quality coolant.
Not unusual to see a Commie VT onwards V8 radiator mounted upright in an 34 Chev or Ford grill shell.

Thanks David

[Harv]

A long shot - did you replace the head gasket? From memory, the 400s had a funky gasket setup with steam holes.

Cheers,
Harv

Thanks Harv I have the radiator at the repair shop getting the leak fixed, and I called into my mechanics workshop who did my original engine check and timing he is now suspecting a head gasket leak so when I get the radiator back I will drive it to his workshop and he has some way of checking to see if it is the head gasket? I have a spare set of head gaskets for the 400.

If he is suspecting a blown head gasket, he might check for radiator bubbles (as Chop Shop suggested), or could pressure test the cooling system, or could have a fancy gauge to detect carbon monoxide in the radiator.

The link below gives a better background on the 400 Chev steam holes. Good info to understand (and check both the gaskets and heads when the heads are off). Not a bad idea to check your spare gaskets for the holes too. Many blokes reckon the 400 is just another small block, and mix-and-match 307/350/327 heads and gaskets... sometimes with bad results.

https://www.enginelabs.com/news/steam-h ... ll-blocks/

Cheers,
Harv

[T1916]

I had a Hino 100mm thick core in my 28 Dodge with a 20" thermos fan. The fan could not pull enough air through the core. Replaced with a 60mm core and put the original 6 bladed fan back on the 360ci. Runs fine now and twice as much air blowing out the bonnet side louvres. It could be the same with your radiator.


Cheers GT.

[Sudsy]

[/quote] the vacuum advance is connected to just below the carby on the manifold. [/quote]

The vaccuum advance should be connected to the base of the carby not to the manifold. As mentioned about the head gaskets the 400 had a steam hole between the 2 middle cylinders as they are siamesed. If they accidently used a normal SBC head gasket that could be causing your problem. Also if the cam timing is wrong can cause overheating.

[1934cv]

A long shot - did you replace the head gasket? From memory, the 400s had a funky gasket setup with steam holes.

Cheers,
Harv

Thanks Harv I have the radiator at the repair shop getting the leak fixed, and I called into my mechanics workshop who did my original engine check and timing he is now suspecting a head gasket leak so when I get the radiator back I will drive it to his workshop and he has some way of checking to see if it is the head gasket? I have a spare set of head gaskets for the 400.

If he is suspecting a blown head gasket, he might check for radiator bubbles (as Chop Shop suggested), or could pressure test the cooling system, or could have a fancy gauge to detect carbon monoxide in the radiator.

The link below gives a better background on the 400 Chev steam holes. Good info to understand (and check both the gaskets and heads when the heads are off). Not a bad idea to check your spare gaskets for the holes too. Many blokes reckon the 400 is just another small block, and mix-and-match 307/350/327 heads and gaskets... sometimes with bad results.

https://www.enginelabs.com/news/steam-h ... ll-blocks/

Cheers,
Harv

Hi Harv, Having repaired the radiator and had my mechanic do a carbon monoxide test and the liquid changed colour to indicate there is carbon monoxide in the cooling system so we believe it is a blown head gasket so next plan is to take off the heads and check. 1934CV

[Harv]

Good news - that helps narrow the problem down. Let us know how you go once the heads are off.

Cheers,
Harv

[1934cv]

Good news - that helps narrow the problem down. Let us know how you go once the heads are off.

Cheers,
Harv

Hi Harv Now for an update heads are off and my mechanic took a look and it appears that it was leaking under the head gasket to the block so I have the heads at a local machine shop to be planed I hope to have them back next week then put it back together and see and hope this works? Phil

[Harv]

One step closer. It's amazing how even a small head gasket leak can make a huge overheating issue.

Watch out for the steam holes/gasket issue when you screw the heads back on.

Cheers,
Harv

[FRANK BASILE]

One step closer. It's amazing how even a small head gasket leak can make a huge overheating issue.

Watch out for the steam holes/gasket issue when you screw the heads back on.

Cheers,
Harv

Good reminder for him. I remember back in the 90,s our son doing his apprenticeship with an independent Jag workshop picked up a smoky series 1 with a Chev "350". When we went to tear it down we found it was actually a 400 with one badly damaged bore. We replaced the block with a 350 and I do recall when messing with this that we were told the existing 400 heads would go on the 350 block, but 350 heads could not go on a 400 block.

[Sudsy]

[/quote]

Good reminder for him. I remember back in the 90,s our son doing his apprenticeship with an independent Jag workshop picked up a smoky series 1 with a Chev "350". When we went to tear it down we found it was actually a 400 with one badly damaged bore. We replaced the block with a 350 and I do recall when messing with this that we were told the existing 400 heads would go on the 350 block, but 350 heads could not go on a 400 block.[/quote


Frank you only have to drill the steam holes in the middle and 400 head will be the same as other SBC's

[FRANK BASILE]

Thanks Bob. You mention "drilling the steam holes" . This applies to 400 heads being used on the 350 block? . We got told that one could not use 350 heads on a 400 block. But the other way around was okay. We did end up just replacing the 400 block with a 350 and using the heads that were on the original stuffed 400 block. The other difference from memory was the balancer, something to do with 400 crank and balancer being a matched pair ? . Long time ago now.