I agree with Solid LT1, you may want to check to verify your vacuum advance is working and that you are porting it to manifold vacuum. It really helps at low rpms.
how hot is too hot?
Thread Starter
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
how hot is too hot?
what kind of temp can I run on my BB without melting my alum heads? I'm working the bugs out with some short runs , I noticed I got to about 220 at the stop light the other day. I ve got be-cool alum rad , dual elec fans , with water and wetter water.
Pro
Joined: Oct 2003
Posts: 641
Likes: 2
From: Storm lake Iowa
Sounds odd to be getting that hot with your setup. Have you verified that the fans are kicking in when the temp goes up? My next question would be if your thermostat and/or guage is accurate. Simplest way to check is with a high temp thermometer stuck directly into the coolant and compare to your guage reading (but don't pull the rad cap off when the temp reads 220! 
). Could be a collapsing lower radiator hose or a bad water pump...others will chime in with their thoughts. My '68 BB used to behave like yours, but not with the new rad and Zirgo 16" electric fan 
). Could be a collapsing lower radiator hose or a bad water pump...others will chime in with their thoughts. My '68 BB used to behave like yours, but not with the new rad and Zirgo 16" electric fan
Drifting
Joined: Mar 2003
Posts: 1,608
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From: Canberra AUSTRALIA
St. Jude Donor '05-'06
Originally Posted by Todbo
what kind of temp can I run on my BB without melting my alum heads? I'm working the bugs out with some short runs , I noticed I got to about 220 at the stop light the other day. I ve got be-cool alum rad , dual elec fans , with water and wetter water.
Not sure about the temp but.....
I have a friend who has 383 in a Monte Carlo. He had Prestone (the orange coolant) and water wetter in his engine. the BE COOL radiator started to leak at the welds (or seams). He ended up getting a replacement at half price from them but they did not want to admit fault. Apparently Water Wetter/ Prestone and ALuminium in combination do not get on. the Dex??? (green coolant) is OK though.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
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From: Fremont CA
You need to check your timing to make sure it is advanced enough and set you fuel curve. Valve seat damage will happen at coolant tempratures above 255-70 degrees. You should check you "true" water temprature with a cooking themometer (my wife hides her's now!) and make sure the reading is correct. If your BB is running 220 now how high do you think it will get on a 90 degree summer day? Timing too retarded or fuel mixture too lean, assuming all is well in the cooling system and the water pump is circulating water properly, no air pockets on cooling system (easily happens on our Vettes) and the radiator is in good shape (Edelbrock H2O pump would be on my Vette along with a De Witt's aluminum radiator, in-fact, they ARE!) You are running a theromstat or 5/8"-3/4" diameter restrictor at the thermostat housing, right? Did you fill the motor from the radiator or the thermostat housing (I do ALL my Vettes from the thermostat housing.) will the motor cool down when driven down the freeway? what temps does it run while driving down the road? Good Luck!
Last edited by Solid LT1; Apr 8, 2005 at 04:20 PM.
Thread Starter
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
I ve got a new water pump (edel high flow) I ve got an overide switch on my fans , i filled the system from the rad cap , i'm wondering if i've got an airpocket , car runs 170 - 180 on the road , I haven't had it out alot yet so i'm not sure how its going to act out on the highway. The hoses are new , but haven't checked to see if the lower hose is collapsing. If I'm going to check the temp with an external thermostat , carefully check it at the cap or housing to verify the temp gauge is reading correctly? what about using one of the laser temp sensing guns on one of the hoses ? are they accurate? thanks , Todd
Safety Car
Joined: Feb 2002
Posts: 4,286
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From: Guam
A properly setup and tuned motor should never run over 190 degrees at idle. C3 vettes are notorious at not being able to move a proper amount of air at a stop. My vette was running about 210 on real hot days while stopped at a light. I readjusted my valves, rejetted the carb (richer), and retarded the timing 2 degrees. Now it runs steady 190 in the hot sun at a stop light. Anything over 210 will eventually cause some damage. Over 230 is getting dangerous. And over 250 begins a slow meltdown. And a quick jaunt to 270 will blow a head gasket and may sometimes cause a head to warp.
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Pro
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From: Flower Mound Texas
Melting Slicks
Joined: Oct 2001
Posts: 3,025
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From: Pleasant Grove AL
Originally Posted by Todbo
I ve got a new water pump (edel high flow) I ve got an overide switch on my fans , i filled the system from the rad cap , i'm wondering if i've got an airpocket , car runs 170 - 180 on the road , I haven't had it out alot yet so i'm not sure how its going to act out on the highway. The hoses are new , but haven't checked to see if the lower hose is collapsing. If I'm going to check the temp with an external thermostat , carefully check it at the cap or housing to verify the temp gauge is reading correctly? what about using one of the laser temp sensing guns on one of the hoses ? are they accurate? thanks , Todd
Since your problem seems to be at slow speed or idle, I would suggest that you have a timing issue or an airflow issue. You can verify the timing in a matter of a few minuets. If that checks out, use the IR gun or other temp device to check the temp that the fans actually turn on.
Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
I run a aluminum rad with tex cool, not prestone, not the green stuff, the orange stuff from GM or aftermarket,
You should be running alot cooler then 220. Even with my big blower I run at about 185 using a good aftermarket gage.
I found running withou a thermostat really helped. On the open road I don't run any fan, both electrics are manual and I turn them off. With any thermostat I found I need one fan all the time.
I did numerous test running with and without and decided for me running without had numerous avantages and kept the motor running in the range I wanted.
You should be running alot cooler then 220. Even with my big blower I run at about 185 using a good aftermarket gage.
I found running withou a thermostat really helped. On the open road I don't run any fan, both electrics are manual and I turn them off. With any thermostat I found I need one fan all the time.
I did numerous test running with and without and decided for me running without had numerous avantages and kept the motor running in the range I wanted.
Thread Starter
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
thanks guys I'm going to try and verify what my timing is and look at a couple of diff things and see if I can work this out , I'm trying to go to bowling green later this month for the birthday bash!
Race Director
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From: central FL, near the beach.
Tech Contributor
Joined: Aug 1999
Posts: 14,377
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From: At my Bar drinking and wrenching in Lafayette Colorado
Make sure you're running enough timing advance, and make sure your vacuum advance is hooked up to manifold vacuum for maximum advance. This will run you cooler at idle. You can also fatten up your mixture slightly, and this will run you cooler. If the temp keeps running high, keep in mind that the C4 Vettes with factory aluminum heads have the "fan-on" switches set to not even start the cooling fans until water temp hits 232... My C4 runs 230-240 in summer traffic with the A/C on, and it's no problem - you won't hurt the heads until you get above 260.
Former Vendor
Joined: Jan 2000
Posts: 5,593
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From: Brighton
Some good stuff here but the key is the IR gun. Check that gauge reading with another device before concluding anything. The temperature sending units that have been sold for the last ten years or so can read 20-30 too high. There are new reproductions coming out now that claim they read right but I'd still check to verify them. A lot of people blame the guage when the reading is off when the actual problem is the sending unit.
Thread Starter
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
Matt great paper , lars , tom D thanks great info , one of the reasons I started this was because I didn't know what would be normal with my modified motor. I started my car up in my garage yesterday verified my fans are engaging @210 , and that my hoses are not colapsing , the next thing no my list is check the gauge , and the sending unit , and then drive and enjoy this classic.
Matt - one question you said "remember to run a grnd wire" , when talking about checking the gauge with pot of boiling water, do you run a grnd to the pot?
Thanks again guys it's been a long restoration , but worth every cuss word
Matt - one question you said "remember to run a grnd wire" , when talking about checking the gauge with pot of boiling water, do you run a grnd to the pot?
Thanks again guys it's been a long restoration , but worth every cuss word
Thread Starter
Burning Brakes
Joined: May 2001
Posts: 988
Likes: 1
From: Dyersburg TN
Ok , it's as most of you guys thought, the sending unit and/or the guage are not reading correctly , I used Matt G's method and put the sending unit into a thermos of boiling water. The reading is off but how much , I started looking at my gauge and how it's marked and it's kind of strange , in the center it is marked 210 , then two sections to the left it starts at 100 , and two sections to the right of center it marked 250. So the sections on the cold side are worth 55 deg each (100-210/2) ,and the sections on the warm side are worth 20 deg (250 -210/2) , whats up with that? anyways I guess my gauge is reading about ~215 when the actual temp was 200 , so it looks about 15 deg high.