So. Ive built myself a new 383 stroker. I got the everything done to it, aluminum heads, big cam. about 10.5:1 comp. im running 91 octane gas. Since i had this vehicle running, it would always overheat on. i had stock rad and fan in it with no fan shroud. Replaced it with a thick 2 core aluminum rad. and put a new 15" puller electric fan on it with shrouds. This thing still overheats on me. Its not doing to bad anymore, because i think the vavles were to tight i adjusted them. But it will stay in between 195ish and 210ish. then after a little bit of driving it will start creepin up on me. the only thing stock is the water pump. Seeing if anyone has any ideas?

a better water pump would help, maybe try a low temp fan switch

All of your cooling system parts need to work together. Usually one item will not make much if any difference. What temp thermostat are you using? What temp fan switch are you using? Are you using a trans/engine oil cooler? What are you using in the radiator for coolant?

My fan, is turning on when my vehicle is running. Doesnt turn off until the vehicle is turned off. My thermostat is about 195F. no oil coolers. im using regular 50/50 mix antifreeze.

what is the pulley ratio pump to crank?
my completely stock 305ci cooling system works great on my ride with my 383ci even with the temps over 90 degrees it does not go over 215 in traffic with my fan on.
is the air dam in place?
I just noticed that 195 stat. get rid of it for a 170 for starters.

im not sure what the ratio is. the air dam is in place. maybe ill have to try and more lower thermostat.

do the thermostat first.( i have a 160) you need to check the ratio of the pump to crank. its as easy as using a tape measure. you want the pump spinning faster than engine speed so go greater than 1. to 1. if the vehicle was ever underdriven pulleys that might have been ok with the stock motor, but is not with the 383.
This sound like a water pump speed problem to me.
do you still have the air conditioning hooked up?

Im not sure how to check for the ratio thing. no this vehicle doesnt have a/c. ill try the thermostat, shouldnt overheat as fast.

Yes, make sure to change the thermostat to a 180 and get a high-flow that has been drilled. Summit racing has one that I am using, part #EMP - 301. Also, I would suggest 1 bottle of Red Line Water Wetter part # RED - 80204 and a Jet fan switch part # jet-60600 and a zinc radiator anode part # FLX-32060. The anode only helps in the long term by keeping electrolysis under control. The other parts should get your temp down to tolerable levels. I have had different results with the water wetter in several cars. In some cars the temp dropped 3-5 degrees and some 5-15. GM built these cars to run hot so the only way to get the temp down is to change some parts. Jimbo

K thanks. ill give the thermostat and water wetter a try. tell u what happens.

figure out your pump!
dont waste your money on antifreeze or water wetter or some other stuff untill you know that the pump is actually spinning fast enough. take a tape measure across the pulley on the pump and do the same for the one on the crankshaft.

if one was 4" and the other 4" that is 1:1
you want your pump pulley smaller than your crank pulley by some margin not the other way around.

Hmmm? with my new 383 motor...my fan comes on right when I crank the car up too and doesnt shut off til I shut the car off..i wonder why?

Also after reading this post cause I too am thinking my car is running to hot, I AM RUNNING UNDER DRIVE PULLIES.....and now im wondering if that is the cause?

high flow Edelbrock pump, new stock rad, 180 thermo with holes...

What kind of 15in fan did you get? not all fans are created equal. My car ran hot with a 15in permacool fan but runs cool with a 15in Spal fan. The cfm ratings aren't much different between the fans so it doesn't seem like the cfm ratings actually mean much. The Spal fan moves twice as much air as the Perma-Cool did. The Spal costs quite a bit more but it was well worth the extra money, the quality and performance is much better.

For sure do as rjt76 advises since you seem to have underdrive pulleys. My 88 Iroc has stock water pump, stock dual fans and I just let it run for almost an hour in gear with the temp staying under 200. I have stock pulleys, 180 'drilled' thermostat, 200 on 185 off fan switch and 1 bottle Red Line. Does the job for me. Drove all over Orange County today in traffic and temp was the same, under 200. My engine is also a 383 with about 40k miles with automatic trans/700r4. I would like to know if the pulleys turn out to be the problem, I was thinking about trying them. Jimbo

Ya ill have to check out what size my pulleys are, when im at home next. or ill call my dad to do it. but ya. my fan is a flex-a-lite, black magic 15" fan. but i think im gonna buy a 180 thermostat anyways.

Ok, ive went and bought a 180 degree thermostat, and added some water wetter. took my car for a ride and it didnt have a change, got to like 230F. The temp outside was about 24C. Checked my pulley ratio, the balancer pulley is 7 1/4 inch in diameter, and the water pump is about 6 or 6 1/2 in diameter

I don`t see where you changed the fan switch. If you do not change it, you will still run hot. I gave you the part number for the correct switch. If you need it again, let me know.

I dont even run a fan switch. its connected right to power. its always on, i cant see how that would make it overheat.

I`ve gone through and reviewed everything from your 1st post. I don`t like to just throw money at a problem (your money) and hope it gets fixed. The ideas I gave you worked great for me and the only 2 things that jump out to me are your water pump and underdrive pullys. If you still have your stock crank pully and belt give it a try. I don`t know anything about underdrive pullys so someone else will need to advise you on that. If your cooling system has no obstructions, check the fan to make sure it is pushing or pulling the correct direction. Have you checked the accuracy of your temp guage? Are you using the correct cap with an overflow container? I have seen new radiators that are full of all kinds of crap. The last 2 I bought, I tapped the tanks and shook them and all sorts of stuff came out after putting some air to it. I`m grasping at straws here trying to come up with reasonable ideas that may help you out so bear with me. I hav`nt checked the tech section under cooling yet, that may be a good next step if you hav`nt. I would zero in on the pullys first.Who installed the heads on your 383? Is it possible to install the head gaskets or intake manifold gaskets incorrectly, blocking some of the water passages?

Also, are you still using the stock air dam and related parts?

i have everything stock from the 305 still on, for pully and water pump. the other thing i have changed is the an all aluminum rad and a puller electric fan. the gauge is mechanical was put in when the engine was put in. i have installed the whole top end of the engine, im a 2rd year mechanic, and i have someone helping me out doing it. so it shouldnt be assembled wrong. the only thing im thinking is the water pump. never checked it for anything when put it in, just came off the old engine and on the new one.

So your a 2rd year mechanic. Maybe that's the problem.
Seriously you should get a new water pump. The impeller could be half gone or something. Anyone try that plastic disk with the 3 rivits on there water pump to make it more efficient. I saw it in the summit catalogue.

I think we see light at the end of the tunnel! Water pump sounds promising. On page 180 in Summit catalog, they have high flow pumps under $100. Bottom of same page they have a "Flow Kooler". For $6.00 it`s worth it. If all else is as you say, this should be your fix. Good luck! Jim

I learned the hard way by breaking down miles the other side of Mojave at 2 am. No phone, no nothing. Everytime I build a new engine, all of the bolt-on items are replaced if over 50k miles. Depending on the distributor, I may keep it but all else I change. If I buy quality parts I have not had breakdowns or problems in more than 100k miles.`Good luck.

Alrite cool. im back at school for the week, when i go home on the weekend, ill have a new water pump, ill see how it works out. should and better be the fix. haha

Sounds good, don`t forget the gaskets, gasket sealer and torque wrench. I have the same job to do so let me know how it goes.

Took my first short desert trip and water temp got up to 220 + going uphill and quickly dropped when not climbing. Next change to my 383 is Stewart stage 1 water pump instead of stock pump and go from there. Currently using hi-flow 180 thermostat and 200 on 185 off fan switch. Looking for always under 200.

Does anyone have a part number handy for a Stewart stage 1 water pump for `88 Iroc 350 TPI with serpentine belt? Run into any problems with the install? Summit and Flow Kooler still have wrong info on their pages regarding Flow Kooler cw and ccw pumps. Thanks

Any chance temp gauge and or sensor having a problem
Not reading correctly.
Hose collapsing under pressure.

A couple other ideas.

Later

13123

Thanks for the info. I got tired of the not being sure between Summit and Flow Kooler. Jim

FWIW, my stock 84 LG4 cooling system has no trouble keeping my 383 cool.

Wow someone else that knows about Spal fans. I have tried to tell people on this site before how they are worth the extra money but I have been told o am crazy for spending that much on a fan!

If people would try them, they would know how great they are. I always get a laugh that people will spend $6k to $8k on a motor but not spend a few hundred dollars on a great cooling system part.

About time someone mentioned this. The sensor the gauge sees and the sensor the fans see are two different sensors. Our stock gauges are hardly accurate. My stock 305 gauge will peg past the red lines (250F) in town every now and then on a hot day. Engine is running just fine, coolant never boils over.

Besides, there is absolutely nothing wrong with a 195F thermo stat nor a SBC hitting 210-220F. Your 383 is not 'overheating', its running warm. As long as the temp comes back down when the fan kicks in, it is running just fine.

so... did anyone notice a difference after they put the stewart pump on vs. the stock pump? jim or hefer?

I finally put on a stage 1 w/p and summit 195 thermostat over the holidays - cooling/heating system is working great now. heats up fast and stays in the crrect temp zone

scooter, were you having the same problem as above? i'm about 190 to 200ish crusing, but temp creeps up in traffic. Changed everything but the stock pump and rad. rad is 3 core brass.

Luke84, I never replaced the stock water pump. I decided to go with a 4th gen dual fan shroud and also installed 2 new 12" fans with it. My temps never got above 200 during the hottest part of summer. The fan shroud seems to be the key to running cool. I still have the stock radiator along with the stock water pump.

thanks jim! I've been thinking of puting in an ls1 fan setup also. I think the airflow will probably be the fix. Found 3 fan setups at the salvage yard for $65 each. I'll have to pick one up.

hopefully the dual fans will do the trick for you. to answer your question
originally temp quickly rose and stayed high except when cruising @ highway speeds over fairly long distances. may have even fried a coil (although true enough I have no idea how long it'd been on the car before) thank God that's history.

What about a lean air/fuel ratio , I know combustion temps will increase but as far as overheating the cooling system , or the imfamous cracked head .

I'm definatly rich. heads are good. Just runs a little too warm and temp at idle creeps up to hot (220-230) on a 90+ degree day. ok going down the road. Thats why i thought maybe a high flow pump over stock, or the fans.

do you have a air-dam on the car? if not that will help with some of the cooling issues.

new air dam.

Heffster, several threads in this post... did you say you changed the fan control switch (to what) and are you carbing or something else? Scooter

u need a 4 row radiator, 50% reduction pulley set, or more if u can get it. i wud add more electric fans 2 ur radiator also. try www.jegs.com
give those guys a call, they r great

Alright, I tried to read through this thread quickly, I would say the water pump isnt going to help.
Things to check before spending more money.
I know it sounds stupid, but is the fan spinning the correct direction?
What gauge and sending unit are you using? Are they working properly?
What is your timing set at? I have seen cars overheat because of not properly adjusted timing on several occassions.
Check on these free things before spending more money. Especially the timing.
I have a 388CID but you cant really compare my cooling system to yours.
I have a Meziere 300 Series electric water pump, and a big griffin radiator.

EDIT: WOW I did not realize this post was 2 years old... Sorry but maybe my response will help someone else?!?!
dolarbill's bumpin up old topics huh...

try putting a 16" pusher fan in front or the radiator. Is the air dam bent back like mine was. I have a 400 small block that runs hot , and am having the same issues

To answer an old post I missed, my temps dropped about 10 degrees when I installed the Stewart stage 1 water pump(part # EMP 13123). I also use an EMP-301 thermostat, 180 degree. If your lower air dam is in place, check to make sure your fan is pulling and not pushing. I had that issue and reversed the wires and solved the overheating problem. Turn your fan on and hold some tissue paper or toilet paper, anything light, in front of the radiator to make sure the fan is pulling.

Also if this motor is still relatively new and it has new rings the extra friction from the new rings will make it run hotter than a normal engine untill the rings are broken in. I just put a 355 in my firebird and it was bored with new rings and it liked to run warm for the first couple weeks until it was broke in and it cooled down.