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Thread: What are normal engine coolant temps? Need help with intermittent overheating

  1. #16
    Fuel Injected! MAC's Avatar
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    Quote Originally Posted by Kitch View Post
    There is some good info here on the Vortec coolant bypass
    http://www.gearhead-efi.com/Fuel-Inj...Manifold/page2

    I run a 94 water pump because the factory coolant bypass passage now works with the hole I drilled in the Vortec head.

    Dude! What a great thread. Thanks for this!!

  2. #17
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    Just have a sec to reply, I looked at your pic and your heater core setup is identical to mine. From the back of intake it goes to the core then from core to the radiator, just below the cap. Ill have more time in a bit so Ill be back with some more info for you.

  3. #18
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    Maybe you could look at temporarily bypassing your heater core so the return goes straight back to your radiator and see if that makes any difference?

  4. #19
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    Good idea. I think I'll pull the tstat also. Get back to basics. Prove that radiator and pump work.

  5. #20
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    My 350 Vortec in my 1997 Express van ran hot until I put a 454 radiator, a HD fan clutch and a diesel mechanical fan on it. Hotest I have seen it run is 203F and that was towing a big trailer and coming to a dead stop in rushour traffic with the A/C blasting.

  6. #21
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    Quote Originally Posted by Fast355 View Post
    My 350 Vortec in my 1997 Express van ran hot until I put a 454 radiator, a HD fan clutch and a diesel mechanical fan on it. Hotest I have seen it run is 203F and that was towing a big trailer and coming to a dead stop in rushour traffic with the A/C blasting.
    I hope I don't have to go this far. Any chance the 454 rad is a bolt for my 93?

  7. #22
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    Was hoping someone could help with the other stuff too. I am really confused on the constant spark knock counts and no spark retard. Also the random blips in my log and lastly the block learn cells. Much obliged to anyone who can offer some assistance.

  8. #23
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    The spark knock count is cumulative, if it isn't continually incrementing, you are fine.
    Square body stepsides forever!!!

  9. #24
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    Quote Originally Posted by jim_in_dorris View Post
    The spark knock count is cumulative, if it isn't continually incrementing, you are fine.
    Thanks Jim. Good to know. Is it normal to have a few knock counts at startup?

  10. #25
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    Quote Originally Posted by MAC View Post
    Was hoping someone could help with the other stuff too. I am really confused on the constant spark knock counts and no spark retard. Also the random blips in my log and lastly the block learn cells. Much obliged to anyone who can offer some assistance.
    the knock senor is a microphone

    the knock sensor is connected to a circuit that converts analog acoustic waveforms to "knock events" if they are a certain pitch and amplitude that the filter thinks might be knock

    the ecm recieves these events. it then computes knock retard from those events based on your calibration. you have some software control of this behavior, including attack and decay.

    the knock count itself is just a total of knock events, like an odometer, and is only for datalogging, the ecm doesnt use it for anything (just like you dont look at your odometer to see how fast you're going)

    a knock count may cause zero retard if your tune doesnt allow kr in that condition, for example if your max timing retard vs rpm is zero, or your min coolant temp for kr isnt reached yet.

    also other things may cause knock retard depending on your ecm's program

  11. #26
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    Quote Originally Posted by steveo View Post
    the knock senor is a microphone

    the knock sensor is connected to a circuit that converts analog acoustic waveforms to "knock events" if they are a certain pitch and amplitude that the filter thinks might be knock

    the ecm recieves these events. it then computes knock retard from those events based on your calibration. you have some software control of this behavior, including attack and decay.

    the knock count itself is just a total of knock events, like an odometer, and is only for datalogging, the ecm doesnt use it for anything (just like you dont look at your odometer to see how fast you're going)

    a knock count may cause zero retard if your tune doesnt allow kr in that condition, for example if your max timing retard vs rpm is zero, or your min coolant temp for kr isnt reached yet.

    also other things may cause knock retard depending on your ecm's program
    This is much clearer now. I understand microphones, frequency/pitch and amplitude a lot better than EFI so I get this.

    My tune started with a read of the stock BIN so the knock retard settings should be whatever GM put in there. I haven't changed them. It seems that I am getting a few knock counts at startup but none while driving so I'll stop worrying about the knock.

    On to the block learn cells. Is there a recommended setup here or do most people leave this set the way GM has it?

  12. #27
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    knock counts on startup are 100% normal.

    you want decent blm coverage. in a 3x3 grid you want low/medium/high load and low/medium/high rpm. you dont need coverage where power enrichment takes over. this can change as your engine build produces different ranges of map and rpm. the idea is you don't want high load corrupting low load memory, etc.

  13. #28
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    I would consider finding a GMT400 Tahoe or Suburban and getting the larger radiator mounting brackets and fan shroud before trying to fit the 454 radiator. Perhaps even grabbing the radiator. You would be surprised how many newer radiators and other parts are in junked vehicles. Those vehicles have a 34" wide radiator with a double wide core. I went to the 454 radiator in my Express because it already had the biggest small block radiator offered for that application in it. Those SUVs also had a larger plastic fan with about 11 blades on it.
    Last edited by Fast355; 5 Days Ago at 10:23 PM.

  14. #29
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    is the water pump the same as before you made head changes? some pumps are made to pump in reverse. could be the radiator starting to clog to. fan clutch weak fan shrould not fitting .

  15. #30
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    Updating thread in case someone else has a similar problem and finds themselves here.

    After drilling 3 holes of 3/16" diameter into my tstat my overheating problems have disappeared. Note that it now takes at least 10 minutes for the truck to get to operating temperatures and this may be problematic in the winter. Also I will be adding an aftermarket water temp gauge because the gauge on the dash has proven itself to be unreliable.

    My setup is a 1993 TBI block with vortec heads, General Motors Performance Parts (GMPP) TBI to vortec intake, TBI water pump (without a bypass connection), and 195 degree stat.

    Analysis: I was not getting bypass flow around the thermostat to prevent localized hotspots. Adding the 3 holes in my tstat allows for enough coolant to always flow from radiator, through the water pump, through block, through heads, out of the intake manifold, through the holes into the tstat, and back into the radiator.

    As to why the holes in the tstat were needed....... I can tell you it worked and it got rid of my overheating problems. Overall I think it was a combination of many factors including my timing tables being waaaaay off from what is needed for a vortec head on a TBI setup. Here is what I have gathered as to why this worked. The TBI trucks have continuous bypass flow (with the idea being the closed thermostat is what is bypassed) that is internal to the pump, block, and heads. So with the thermostat closed the flow path would be from rad, through a dedicated passage in the water pump, through dedicated passages in the block, through dedicated passages in the heads, out of the heads into the "common" coolant passages in the intake manifold, out of the manifold and through heater core, and finally back into radiator (this back into the radiator part here is where flow returns "after" the closed thermostat thus bypassing the closed thermostat). From what I can tell the TBI trucks do not have a heater control valve so with the stock heads there is always flow bypassing around the closed thermostat through the heater core. It does not seem to matter what way the heater core is connected but if your heater core was clogged you may see overheating problems. My trouble arose when I added the vortec heads - these heads block the passage of coolant from the block to the manifold. Apparently the vortec can be drilled out to allow for it but if you are reading this it is probably too late for you. Your best (easiest) bet is to drill holes in your stat. I may add the newer (1996 and later) water pump with the bypass connection at a later time but for right now I am going to stick with my current setup.

    I will try to remember to come back and update this thread with how annoying the long warmup times are when the weather turns cold.

    Hope this helps someone else out there one day. Thanks,

    AC

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