Technical Slightly Hopped up 305 overheating...need some input.

The 305 in my 28 has consistent overheating issues, and it's frustrating the heck out of me. It's an early to mid 90s engine that someone put an Edelbrock hop up kit on (cam, intake, carb). It has a long water pump and no mechanical fan. I'm running two electric fans on the radiator, one on the front (around 2000cfm I believe?) that is pulling air in, and one on the backside (1k cfm?) that's pushing it on through and blowing into the bay. My coolant mix is pretty good.....4 of the 5 balls floated in the meter, so, what, good up to 240 degrees? Open hood sides, no shroud (I know, I know). I've worked with the dizzy and the air fuel mixture, albeit just based on the generic instructions that come with Edelbrock carbs (turning air till power loss, turning fuel till power loss). It will overheat idling and running...I can get about 10-15 minutes out of it on a CA day before it hits 220 and onward/upward till it boils. Looking for ideas or common experiences with this. I know there's a ton of things I could do, but I'd like to narrow down the most obvious/cheaper things first, and want to make sure I'm not off in left field.

 

305's are noted for cracking heads, any sign of compression getting in the rad? How about a thermostat, sticking? What radiator? And why no mechanical fan? Also, some Chevys had a reverse rotation water pump, are you sure yours turns the right way? Seems dumb, I know, but I've seen it happen a few times.

 

Bad thermostat, air in system, upper hose high than the radiator neck, to many fans only need a draw thru on the back side pulling air thru, blown head gasket, to much advance in timing

 

Ah yes, the radiator is one from Autorad, probably less than 5-10 years old at most, aluminum, and designed for SBC's. The thermostat is new, and pops at 190-195, I think? No mechanical fan for 2 reasons: 1) I've got little kids who, despite my best efforts, paw on my car.....I've seen other guys not run them, and I figured it would be fine...and my chi'rens get to keep their fingers and 2) No room at the moment because of the long water pump. I'd need to get the short pump, new hoses, a new alternator mount, etc...I'm trying to avoid that expense if I can. Is there a way to check the pump to see if it's rotating the correct way based on model, or how to see what model it is? What would be signs of compression getting in the radiator? Tons of questions in return.....I know XP

OH...and *no* signs of a blown head gasket from what I can see. Oil is fine, no leaks that I can see, etc.

 

First look at R Pope's second sentence in post 2.

Do you have the correct water pump for the belt system you are running? I think most if not all 90 and up GM V8's ran a serpentine belt system with a reverse rotation water pump. If the engine has the original pump on it or a replacement pump for a 90's 305 and you switched to V belts that would be the issue. The pump absolutely has to match the belt system you are running.

If that isn't the case and the engine runs right at what the thermostat is set at on the highway but heats up when you get in slow traffic or at an idle you have an airflow problem. One thing I have seen and been guilty of is having an electric fan bracket that blocks as much air as it allows though. Another thing is these cutsie "I want it to look like a race car" sheet metal grill inserts with a pattern of holes drilled in them that block a large percentage of air.

The other thing could be restrictions in the cooling system or an air lock in the cooling system due to something like the high loop in the upper hose that someone mentioned.

 

Guilty of the sheet metal insert, but the holes are huge!!! Lol. Here's a pic of the engine before I finished ***embling the car, the belt is a V belt and still runs the way shown. So I have it spinning backwards in that configuration?

 

The engine should have a stamped pad on the front of the block just under the left head which will
have the numbers to tell you what the original application was.- Look it up and find out if it was a
reverse location pump or not. Also check for collapsed hoses, many need the spring inside when
under pressure.

 

Maybe whoever ***embled the motor installed the cam too far advanced, or it's timed too far advanced; that will cause things to run hot. I broke a centrifugal advance spring in the distributor of a 327 once, and that caused it to overheat. If those things are OK, maybe some "water wetter" will help. It could also be circulating the coolant too fast to pull the heat effectively. I am Butch/56sedandelivery.

 

Take the front fan off. Drive up to speed of highway like 55-up for a bit. If the temps are good go home let idle. If it THEN overheats it is airflow issue. A pair of puller's or one very large puller fan should do the job. Adding a shroud will help. And for those in need when it gets TOO hot or TOO warm you use TWO O's. Spell fascist? Hell no, that would be TOO easy.

 

Drop the thermostat to a 160. Remove the front fan. Teach the children to stay back from the open engine compartment. simple fix should be change to short pump and run mechanical fan. Not a sure thing if you have other issues.

 

I would take the sheet metal insert off and the front fan off. MAKE SURE that the water pump is NOT reverse rotation. Install a 160 thermostat....All of this was already mentioned and easy to do.--- I would take the 190 thermostat and cut the center out, by cutting the two uprights off that hold the guts of the thermostat, leaving just what looks like a washer left, and just install the washer back in the housing. Then take the upper radiator hose off at the neck of the radiator and fill the system from the hose till water comes out the upper neck of the radiator, Install the hose and top off. That way the water won't have any air in it. I had this setup on a 31 coupe, That car would idle or run hard all day and run 170 to 200 with a SMALL radiator and one electric fan.

 

Some good stuff here.

The 2 fans is most certainly causing you air flow problems.
The math is backwards. You are pushing 2000 at the radiator and pulling 1000 from the radiator. - that's not going to add up to 3000. actually I'd be supprised if it totaled 1000 getting thru the radiator sitting still. Depending on the restrictor up front and shrouds you might only be getting 1000 heading down the road.

The pump rotation is another really good question. It's not that the pump will pump backwards, it's that the impeller is not catching water to pump because its spinning the opposit way.

 

My vote it with everyone else. Yank the pump and check the impeller direction. Buy a standard one off the shelf and compare the direction of the blades. I would personally leave the thermostat temp alone but use a new one. Then when filling it toss in a bottle of REDLINE water wetter. I'm amazed how well the stuff works. I use it in everything I own just for insurance. Many race tracks won allow antifreeze in the radiators so they run straight water and water wetter. It does the trick nicely.

 

Another thing on coolant.
Adding antifreeze enhances the ability to retain heat. Yes it increased the boiling point by a few degrees but it severely hampers the ability to shed heat. A 50/50 mix protects to -58f but reduces the cooling capacity by over 30%.

So, if you were in the artic, you certainly would want the freeze protection and retaining heat in the coolant would be a big plus.
However-
In the desert you'd get at least a 30% increase in efficacy out of your cooling system just by dumping the 50/50 mix and running straight water.
The problem -
You'll have no corrosion protection or lubrication with just water. So a 25/75 mix is more than enough in places where it doesn't cold snap to -58

 

yep, opposing fans not helping anything. not having shroud not helping - you know so, just get one. run a "big mouth" thermostat by Robert Shaw, etc. with lower than 195 that have now. what type radiator cap-rating of how many lbs? have overflow recovery tank? hoses have wire inside? have hose running from intake manifold to water pump - if not, install.

 

Yanked the thermostat this morning, old bolt snapped off in the intake....woohoo! I drilled it just enough to pull the threads out and it's all good again. Not a good harbinger of things to come, though...me thinks. I forgot that I went through this same thing on my 50 Chevy....obviously I didn't learn my lesson. I'm going to try the thermostat option along with removing the front fan and see how it does, next step is the short pump/mechanical fan combo.

But the black painted front of the radiator is so...so...FUGLY! lol....feels like mah private parts are all out there and exposed! I'm going to see how the 160 thermostat does I think. by cutting off the arms on the 190 (bottom with the spring or top with the arch?) what does that do, exactly? Going to refill per your advice, and remove the front fan.

Pulling the front fan, will check on the pump.

I'll see if I can find Redline here locally.

I'll redo the mix to that spec and see how it fares.

Cap is 16lb, I think? I'll double check. Yes, overflow recovery "tank". It's actually a puke tank that I keep partially filled for when it draws back up, in case I've lost any. Only that I've seen I've lost is when it gets too hot and seeps a bit from the cap. The top hose has wire, bottom does not. I haven't observed any collapsing in the bottom once I got it topped off.

 

No mechanical fan for 2 reasons: 1) I've got little kids who, despite my best efforts, paw on my car.....I've seen other guys not run them, and I figured it would be fine...and my chi'rens get to keep their fingers

No offense. I love kids. My parents even had some! This is one of the dumbest things I've ever read on a car forum!
We had three kids of our own plus one we adopted. They all played and rode in my old cars. They all still have ten fingers and most likely ten toes.
Other than that you've gotten some great answers.

 

Post Some Close Up Pics - "puke tank" not overflow recovery tank - wire in bottom hose important-sign of boiling over is not evident from some seepage at cap - so, overheating because what your gauge is showing you? how hot is is getting? fans on/off by temperature sensor or manual?

 

No offense? That always precedes an insult...but thanks anyway. It's the same reason I ran my pipes under the car and not the side draft ones.

 

Ok this is a dumb question and certainly won't help your heating problem but I thought the antifreeze tester and the little floaty balls were for how cold it could handle not how hot it could get.

On antifreeze you don't want more ten a 50/50 mix and Burbank you should be able to mix it a lot lighter then that like say 75/25 water to antifreeze. Basically all you are using antifreeze for where you live is water pump lube. Water is a way better coolant then antifreeze ever dreamed of being.

That probably won't cure your problem but it will help it a bit.

you have received some good advice, head gasket or busted head, sticking t stat (or no T stat), reverse water pump all good things to think about.

If it were me I would loose the pusher fan and get a puller that moves enough air to keep it cool in traffic. But my advice comes after you solve your problem, you are overheating at speed so other then the fan in front of the rad blocking flow your problem is not doubt not an airflow problem.

 

Sounds like all good advice. I hate spending money chasing an issue especially a over heating one so I'd lean towards pulling the insert and pulling the front fan to see what it does. It'll cost you nothing but time and it only looks ugly for your test run.

And to honest I'd rather look ugly going 60 mph than looking good over heating on the curb haha.

Any picks of the set up with grill in place?

 

I'll get a pic later, but it's just an aluminum water bottle that had a pre-existing fitting on top that was pretty darn close to fitting the hose coming out from the radiator neck. When I tested it out the other day just idling, the heat got to the point that puffs of steam were popping out of the gap in the top of the bottle, and it was dancing a little jig...I could hear it bubbling! Doh! I cut it off all the time at 230-235. Fan is manual switch that I flip at startup.

The instructions for the syringe with the balls in it has numbers that corresponded to boiling/freezing points on a chart, that's how I came up with that. Yeah, my concern is that it's head gaskets....but there's no milkshake on the dipstick or smoke out the rear while driving. I get a puff of gray on occ***ion at startup, but it just smells of me running rich, after that, no smoke.

I had a similar problem on my 50 Chevy until I did two things....but a new radiator and put on a mechanical fan. Foolish me trying to do it differently on this car XP

 

Well raising your boiling point won't keep it from overheating. That's two different animals right there. if it didn't boil until it hit a grand it would still be overheated @ 210+

 

Yeah, for some reason I had equated it with head dissipation....so wrong.....so wrong XP lol

 

Was the water pump on this 90 engine when it was pulled from the doner car or did you swap a new one for a 90?And you swapped the belt system to an older setup,your problem is the water pump .get a 70s long pump ,ditch the pusher and you should be fine.

 

I think airflow as suggested above is the answer...BUT retarded timing can cause hot running, too, and I would check that out even if it is not the problem here.
1. SBC likes manifold vac (you will have to reset idle when you change that). ***uming late Chevy distributor, you will also need a truck or hotrod vac can...smogger EGR Chevies have like 20 degrees or more stamped on can mount, heavy truck and hotrod ones much closer to 10.
2. GM smog distributors advance way too slowly, get a kit with lighter springs. Even if this has nothing to do with heat you will enjoy the increased engine response.

 

Nah, the engine sits as I received it....long water pump with V belt pulleys. The power steering pump was removed and I believe a tensioner? Maybe not on the tensioner...it's been a long time.

 

Ah your insert should be fine I was picturing something a bit different. Pull that front fan off and see what it does.

And to be fair if your kids had there fingers near a mech fan on that car they'd have already burnt themselves on the heads and caught a sleeve in the belts just ribbin ya. I'm sure there a way around a mech fan

 

Wait I had another look, are you sure that it isn't just protesting over being seen in public with those yellow plug wires?

 

if you think a head is cracked (under exhaust valve in pocket)beg borrow a pressure tester and test with engine hot as crack may not show until hot.I find more pressure will show leak (20 or more)may blow off rad hose or split if older so be careful(no kids around)if you have it running watch for telltale steam out of exhaust.everything listed by others this is for head gasket or head leak.you should see bubbles in rad with cap off if leak is pressurizing rad this will show on gauge if you put in 20 or whatever watch gauge it will increase pressure.