400 SBC Overheating

[1934cv]

It has been awhile since I have posted to this forum, so I am open to suggestions to solve an overheating problem on my 1934 Chev Pick Up street rod.

I have been working on it for the last 4 years now have it together and can drive it but can only do about 5kms before the temperature reaches 100C. The engine is a 400 Small Block Chev 2 bolt mains all stock as far as I know as it was a crate motor from the US, still runs a 2 bbl carb and stock ram horns, according to the engine number and castings it was built between 71 - 74 it is connected to a 2 speed powerglide.

I have had the motor for 20 years sitting in my shed and it was a little frozen but was able to free up and inspected the bottom ends and bores were all OK. All I have done is replace the sump, timing gear and inlet gaskets. I have a custom made radiator to fit the stock 34 Chev grill and have tried using a single 4 blade fan, 2 10" electric rans and a 6 blade flexi fan. I have run it with a 71deg, 87deg and no thermostat.

I have had the local radiator guy high pressure clean the block and radiator with only minimal fine rust particles, he also suggested that the bonnet was restricting the hot air escaping from the engine bay so I now have 58 louvres punched in the bonnet top. I have removed the ERG pollution gear from the inlet manifold and plugged off the the water pump and inlet manifold heater connections. I have had the back plate off the water pump and the steel impeller looks in very good condition.

Yesterday a friend noticed that the harmonic balancer had a slight wobble when running and suggested that it may be affecting the timing and may cause the overheating when driving?

Open for suggestions to solve?

[chop_shop]

GDay,i'm no expert, but some thoughts...louvres in the boonet very cool, but seem a bit extreme, the hot will go somewhere (usually out under neath when moving) sitting idling might contribute but not convinced....
are you running a coolant mix ? when running with radiator cap off any airbubbles persisting after its warmed up ?
and when it hits 100c is that on the gauge (have you tried another gauge )or is it visually boiling and flowing out the radiator overflow ?
have you the right pulleys on the water pump, and i think there may be a reverse rotation chev water pump check you dont have that fitted unless running serpentine belt ....
i guess make sure those are correct, and then maybe look at ignition timing ?
could you loop the water pump to inlet manifold instead of blocking them off?
let us know how you get on....
cheers
Warren

[T1916]

Did you say "no thermostat ". Put one in, it does 2 things, allows engine to heat up and when open slows the flow of coolant allowing time for it to cool in the radiator.


Cheers GT.

[enjenjo]

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?

[FRANK BASILE]

As suggested check the ignition timing both at idle and for proper advance. Is it running lean? I have a 350 purchased back in the late 90,s . Had it sitting for a while, it is 74/75 build and was imported as a good runner. About 5 years ago I fired it up after fitting block huggers and an aftermarket alloy inlet manifold to dispense with the EGR and all the plumbing. It fired up and ran fine, but I noticed that the headers on the bank where the EGR was were starting to get really hot ,almost glowing. I shut it down. The engine is still sitting in the shed as a spare . I must get back to it at some stage . Your post reminded me of it. In my case it appears one bank is running lean. I was told that there are variations with inlet manifold gaskets.

[FRANK BASILE]

As suggested check the ignition timing both at idle and for proper advance. Is it running lean? I have a 350 purchased back in the late 90,s . Had it sitting for a while, it is 74/75 build and was imported as a good runner. About 5 years ago I fired it up after fitting block huggers and an aftermarket alloy inlet manifold to dispense with the EGR and all the plumbing. It fired up and ran fine, but I noticed that the headers on the bank where the EGR was were starting to get really hot ,almost glowing. I shut it down. The engine is still sitting in the shed as a spare . I must get back to it at some stage . Your post reminded me of it. In my case it appears one bank is running lean. I was told that there are variations with inlet manifold gaskets.

[1934cv]

GDay,i'm no expert, but some thoughts...louvres in the boonet very cool, but seem a bit extreme, the hot will go somewhere (usually out under neath when moving) sitting idling might contribute but not convinced....
are you running a coolant mix ? when running with radiator cap off any airbubbles persisting after its warmed up ?
and when it hits 100c is that on the gauge (have you tried another gauge )or is it visually boiling and flowing out the radiator overflow ?
have you the right pulleys on the water pump, and i think there may be a reverse rotation chev water pump check you dont have that fitted unless running serpentine belt ....
i guess make sure those are correct, and then maybe look at ignition timing ?
could you loop the water pump to inlet manifold instead of blocking them off?
let us know how you get on....
cheers
Warren

Thanks Warren To answer your questions. I am just using water at this time. No bubbles when the cap is off. When the gauge reaches 100C water flows from the overflow. I am using the stock pulleys with one V belt that came with the motor that lined up the the crank, water pump and alternator. Today looped the water pump to the inlet manifold and still the same, now worse as the radiator has now developed a small pressure leak. I am leaning towards I may have a dud engine. Phil

[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

[enjenjo]

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

Check the vacuum advance for function. I had one that would overheat in the length of a stop light. It was a defective vacuum advance. I had another one that had the cam timing off one tooth retarded that would do a similar thing. I had a third SBC that would overheat after pulling it out of long term storage that had the cooling system packed full of soy beans that swelled when wet and clogged the cooling system.

[FRANK BASILE]

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

Check the vacuum advance for function. I had one that would overheat in the length of a stop light. It was a defective vacuum advance. I had another one that had the cam timing off one tooth retarded that would do a similar thing. I had a third SBC that would overheat after pulling it out of long term storage that had the cooling system packed full of soy beans that swelled when wet and clogged the cooling system.

Here is another possibility. In the original post the timing gear was replaced. ............ May I ask how Soy beans ended up in a cooling system?

[enjenjo]

May I ask how Soy beans ended up in a cooling system?

Engine stored in the barn next to a field, varmints were storing loose beans in the engine. I didn't catch it. Add water and heat makes bean curd. It took a full day with a pressure washer to clean it out with partial disassembly.

[Harv]

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

Cheers,
Harv

[FRANK BASILE]

May I ask how Soy beans ended up in a cooling system?

Engine stored in the barn next to a field, varmints were storing loose beans in the engine. I didn't catch it. Add water and heat makes bean curd. It took a full day with a pressure washer to clean it out with partial disassembly.

Common problem over there Frank. The amount of nesting, what looked like acorn casings and rodent remains I recovered from imported vehicles was staggering, they crawl into every possible place. The 66 Mustang Convertible had a small bucket load of material in the plenum chamber , Removed both fenders and hooked the stuff out through the large drain holes on the upper cowl. They must have really pee'd on the drivers side, this caused rust around the fresh air inlet that I repaired.

[Mudgy]

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

[T1916]

Years ago I put a 307 and power-glide out of a HK brougham into a ford transit for a mate. Used the original radiator and the engine fan. Would run hot and nearly boil over. Customised the original fan shroud and fitted it. Engine never went over 80c after that. A shroud may make a big difference.


Cheers GT.