Hello all.... I have purchased a new gm performance 250hp 350 and am now having some problems with the install.... We managed to run the engine for 30 minutes to break in the cam but it ran up to 220 on the temp and it will do so every time I run it for any longer 30 minutes or so.... It seams that it doesn't heat up as fast if it is just running without a load, but does heat up.... I have had the 3 row Radiator rodded out, put in two different Mr. gasket high flow 180 deg thermostats, replaced the water pump, heater core has been flushed and added a fan shroud to the flex fan.... It seams that it takes a little longer to heat up then it did before but it still gets right up 210 within 35-40 minutes....

This engine has all new parts top to bottom
Edelbrock performer intake (non EGR)
Edelbrock 600 CFM performer carb
MSD Street Fire Hei dizzy
Summit racing plug wires
acdelco plugs gapped 35
Summit mechanical fuel pump 6.5psi line pressure

any ideas would be helpful as I have ran out....

Is this w/the car sitting still, w/o any airflow through the radiator except for the fan?

If so, you need to reevaluate it after you get it out on the open road to see if airflow through the radiator is enough to keep it in check.

As an example, cop cars are set up to idle at a higher than normal speed and sometimes have advanced timing at idle to keep them cooled down- and they're just idling. With the engine running 2K- 2.5K RPM, I can see it heating up.

Anyway, you can try more initial advance on the timing- but don't go too high (36 degrees or so) on the total timing.

If the water pump is underdriven, you can change the pulley ratio back to 1:1 or overdrive the WP.

Lastly, flex fans are the WORST! A clutch fan w/an OEM-type fan and a shroud having the blades 1/2 in, 1/2 out is the way to go. A flex fan not only cools poorly, but robs the engine of HP as well.

First off, did you check the thermostats in hot water before you installed them? over the years I`ve gotten I don`t know how many bad thermostats, from the 99 cent ones to the 7 dollar jobs. is 220 is hot as it`s getting? 220 isn`t running hot, but is hotter than you perfer.
What is the timing advance set at?
Have you checked the carb to be sure it`s not too lean?
What kind of vehicle?
does it get hot at idle only or going down the road?
Is the coolant system vented?
Is a overflow/resivoir system in place?

check bottom rad hose to see if it collapses when you increase rpms.
(comon problem with cheap rad hoses)

35 to 45 minutes of idle, even a high idle, is a lot of time, I don't see that you have a problem.

If you do this again, it may be helpful to put an industrial sized electric room ventilation fan in front of the grill to add airflow as if the car was cruising down the highway, not that a fan will come close to 60 mph air flow, but it helps. The radiator fan is intended to pull air thru the core at idle, while it's moving a lot of air at cruise, most of the air flow thru the radiator in that condition is ram air from the passing streamline not the fan. In fact you could take the fan off entirely and find that cruise cooling is sufficient with a 60 mile an hour breeze blowing into the radiator. Of course this wouldn't cool more than a couple minutes in stop and go traffic or at idle when stopped.

Keep in mind that a 60 mph breeze is a lot of wind, if you were a biker (Hells Angles type not a bicyclist) and you rode bare headed in spite of the state giving you a ticket for doing so, you would know that at 60 mph the skin of your face cheeks blows in waves from the passing air like a flag waving in the wind. You can stick your head under the hood, and open the throttle to WOT and the air from the fan ain't gonna come close to blowing waves in your cheeks. So that should tell you how much more air gets driven into the radiator at speed than ever happens with fans, water pump driven or electric.

As far as high flow thermostats go, think about what's going on, then ask yourself; does the term "high flow" and thermostat belong in the same sentence?

Bogie

I am glad to see that this question was asked.

It is the very first question that should be addressed as it is the #1 cause of running hot or overheating anytime the distributor has been removed and replaced and is often the cause for concern when starting a "new" engine for the first time.

If the timing is somewhat retarded, the heat buildup will cause the engine to run hotter than it should. One clue that this is the cause is if you see the exhaust pipes close to the exhaust manifold glowing cherry red.

Since you should not run a new engine at an idle until after the cam break in run, the timing can be set fairly close by doing the following.

Hook up a timing light and a tach. Dis-connect the vacuum advance hose from the vacuum advance cannister and plug the hose. Start the engine and bring the RPM up to around 2500. Check/set the timing to 32-34 degrees BTDC. Re-connect the vacuum advance hose (I prefer, recommend and use the full manifold port). Continue with the cam break in run.

Most of the other posters mentioned running a "box" fan in front of the radiator for additional air flow.

This is very important if you have a clutch fan because that style of fan will barely be pulling any air when the engine RPM has been increased. I would even suggest not running a clutch style fan during the break in run, but use a standard solid fan instead.

After the break in run, change the oil and filter immediately. Re-start the engine and you are now ready to set the timing to where you want it to be. After the timing is set, you are then ready to make any carb adjustments needed. Attempting to adjust the carb (other than the curb idle) before the timing has been set will prove futile.

So, your old 350 engine didn't run hot with the same stuff (fan, radiator, pump, et)??????

I am getting hot even running down the road..... I have the total timing coming all the way in at 2600 rpm @ 32 deg. The base timing is @ 14 deg.
This engine was put in an 89 jeep wrangler that had a chevy 305 in it when I got it... The 305 never pushed 210 on the temp.... I am starting to question head gasket or warpage.... I havnt checked the thermostat in boiling water but I do know that it is working as I watched it open and flow threw the top of the radiator.... It is odd that when its parked and with the radiator cap off you can watch the flow stop then go when the thermostat opens and closes for several cycles and it will stay down 185 or so then when you put the cap on is when it starts getting hot.... I just dont know what else to do with this thing that I havnt allready done...

Install a chin spoiler under the rad support so that air does not flow under the jeep as easily. Air will only flow thru the rad if there is a pressure difference between the front of the rad and behind the rad. If the air flows easyist under the jeep instead of thru the radiator, it will go under the jeep.
A SBC V8 in a Jeep really restricts the engine bay airflow. (it has no place to get out) Adding some air escape ducts to the fenders just behind the wheel or the sides of the hood will help. The water pump may be defective. As mentioned, check the lower radiator hose. Some require a internal wire spring to avoid collapse when hot.
Most flex fans leave a lot to be desired.

32 isn't enough timing. Try 6 more degrees. this will help keep it cooler but this isn't the problem.

A friend of mine is also having trouble keeping his 350 goodwrench engine cool also. I'm not sure if it is the engine or not. We are planning to replace it with an old GM block to check if the new casting over heat.

He did have better luck with a high flow T-stat. You could try a t-stat washer or gut the valve and spring out of a cheap t-stat and try it like that.

You should use a clutch type fan (not a flex fan). And the shroud should fit the fan blades with a 1/2 inch to 3/4 inch side clearance. Plus the blade width should be 1/2 in the shroud and 1/2 out.

And he did have better results using a ford taurus electric fan than a mechanical fan setup. But these fans pull some serious power. a 2 speed fan with 2800 cfm on low and 4000+ cfm on high speed (25 amps+)

If you are not running Vortec heads, increase the total mechanical timing (with the vacuum advance dis-connected and plugged) to 36-38 degrees. Re-connect the vacuum advance using the full vacuum port. You may have to re-adjust (lower) your curb idle after connecting the vacuum advance to a full vacuum source.

Another thought. where is your temp sending unit installed? If it is in the head, the reading you will see is about 20 degrees higher than what you would see if the sending unit were installed in the intake manifold close to the thermostat housing. This is because the sending unit when installed in the head is in close proximity to the exhaust port.

Also, you should be running a 180 degree thermostat and a 16 lb. radiator cap. An overflow tank is also suggested. If you have anti-freeze mix it should be no more than a 50/50 ratio.

I beleive that the heads are just 194 heads... I purchased this long block from summitracing.com it is the gm performance 250hp 350..... I called summit and they said that this engine should be run with 10deg of base timing and 32-34deg of total mechanical without the vacume advance hooked up.... well I tryed different springs on the weights and all kinds of tweaking and all I could reach was 27 total with the base set at 10 so I just set the total up to 32 and that puts the base at 14 if I go up to 38 I will have 20deg base timing and I would think that is a little much for a jeep that will do most of its driving putting around in low gear..... Another thing about this build that I am wondering about is the carberator..... I have had two different carberators right out of the box that I put on this that were leaking fuel out of the secondary butterfly shaft..... Someone told me to put a regulator on it but my mechanic is sure that I dont need it..... I put one on and dropped the preasure down from 6.5lbs to 5.5lbs and no more leak.... I am starting to wonder if this heating up is from the carb..... I have the 600cfm 1406 edelbrock carb and they say it should be good up to 7lbs of pressure....

PS: to awnswer the question about the temp sensor.... It is on the head and it is a mechanical sensor.... but I also took the same readings from the fill cap of the radiator with my wifes turkey temp thermometer... The gauge was dead on to what the thermometer was saying....

I'd be lost for ideas and frustrated as hell at this point.

A long shot but could it be junk in the block ? Can you pop one of the freeze plugs and flush the block ? I don't know if that would be too much work.

When you wrote "head gaskets" I wondered if they can be reversed like on my ford fe's and still seal perfect


Best of luck.

As for both of these questions the block is brand new and the entire system was flushed and rodded out before the new long block was installed.... The coolant looks verry clean... If the head gaskets are backwards then GM has some hash smokers working for them..... I didnt put this engine together as I was lazy... I wish that I would have though because atleast I could blame myself for the unknown....

Have you tried the non-contact thermometer (infrared). By using that you could locate a hot spot and further isolate the trouble that way.

Or is the cooling system possibly airbound

Unless you've found the solution.

This is getting down to really remote possibilities.

Once again, good luck. I'll be watching to read how you made out.