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Thread: hard filled sbc overheats real bad

  1. #1
    Senior Member MASTER BUILDER
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    hard filled sbc overheats real bad

    ran my new 377 cu in chev(400 block) that is hard filled to water pumpholes.. i have a 69 camarp 3 core radiator and a summit electric water pump that kept my 355 cu in sbc cool at around 200 degrees max at the dragstrip(no hard filler in this block) asn engine was 525 horses. now running a pro built 377 cu in(400 block) sbc that is hard filed and has around 600 horses and it start overheating in staging lanes and burnout and at lights it up to a scary 240 degrees and at end of track i have to wait there ans let it cools down to 180 degrees and drive it back to pits and on this return it gets back up to that scary 240 degrees. the intake does not have provisions to run lines from front to back for cooling..... i know there are 3 tricks for cooling that MAY help. #! is to rung the cooling lines from front to back of intake(1 line on each side) #2 is to get a thick spacer that fits between intake and thermoshat housing and runs a line out of each side of spacer to the bungs on each side of the aluminum heads, with one being in back of head and one in front of head. and trick #3 is to drill and tap the sides of the electric water pump and run # 6 lines over to holes drilled above the hard fill(where water still runs in block) there, holes are drilled right at center of block( there are 2 exhaust valve above this point) and cooled water is circulated to there.. i am desperate to fix or help this cooling probles and will do all 3 things if necessary. any help would be greatly appreciated

  2. #2
    Senior Member EXPERT BUILDER
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    Chevyart, do you run a thermosat or anything to slow down the water running thru the rad it might be going thru the rad to fast and not being cooled down before returning to the engine. What fan are you running. Timing to high or to low will also make an engine run hot. I have ran 400 blocks half filled and driven them on the road with no overheating. One thing you need to think about is you are running less water now that the block is filled. I ran lines from the water pump to the heads (not the block) to keep from having a hot spot between the two center cylinders. I only ran lines like that when running nitrous. I hope some of this will help as there is alot of things that can make an engine run hot.

  3. #3
    Senior Member MASTER BUILDER
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    overheating

    one thing, now that you mention it is that that in place of a thermostat there should be a restrictor plate. there is none. there was one when i had the 355 in there and it just never made it back in with the engine swap.. it is a drag car only, 13-1 comp and big cam and big alum cylinder heard. what about me only having a 7lb pressure cap. some say it should be up in the 20s lb cap.its a small electric fan running off a relay and it did fine for the 5355(max 200 temp at the track) i have different restrictor. plates. how big of a center should should be on the plate. why the lines from water pump to the heads and not to holes in top(center) of block. why not run all 3 different cooling lines at once. thanks art

  4. #4
    Senior Member RACING JUNKIE
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    Re: overheating

    Quote Originally Posted by chevyart
    . it is a drag car only, 13-1 comp and big cam and big alum cylinder heard. what about me only having a 7lb pressure cap. some say it should be up in the 20s lb cap art
    drag race or road... you need a re-stricter in there .... i always just knocked the center out of a thermostat and used it for one

    the cap should be at least 16 -20 lb :wink:
    GOOD PARTS AREN'T CHEAP AND CHEAP PARTS ARE NEVER GOOD.........
    http://img.photobucket.com/albums/v2...lastscan-3.jpg

  5. #5
    Senior Member SENIOR BUILDER
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    I would definately put a much higher pressure cap on there, the higher pressure raises the boiling point of the water quite a bit. As to a restrictor, I wouldn't, not really needed. Just make sure you have good flow of coolant. I don't run one at all in my dragster and never have. 600 inch chevy and if I'm at 100-110 at the staging lanes before the run, I'm around 180 by the time I'm back at my pit. One of the issues with yours is the block being filled. It reduces the cooling capacity of your whole system, and it will heat up faster. The best thing you can do at this point is put in the biggest radiator you can fit in the car. You need system capacity, and the block filler just took away about half of it. Additionally, you're making more power which means more heat. The larger the cooling system, the better it's able to deal with the heat.

    So my best advice is the biggest and thickest (three or four core aluminum with the 1" wide core tubes) radiator you can get, good shroud and biggest fan you can get. Put either Redline water wetter or Royal Purple Purple Ice in the system as well, it helps. Tap the manifold for four corner cooling as well, and make sure it's only water with the additive that you're running, no antifreeze!!!! Besides being horrible to clean up if spilled, it actually doesn't cool as well as straight water.
    Mark Goulette
    Owner/Driver of the Livin' the Dream dragster
    www.livinthedreamracing.com
    Speed kills, but it's better than going slow!!!!

  6. #6
    Senior Member EXPERT BUILDER
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    Art if you put the lines in the block your not cooling the cylinder head but returning it right back to the pump. when you put the lines in the head it cools the head between the two exhaust valves were most of the heat is. As for bigger rad you will be fine with what you have. The radiator that you have is bigger than the one i had witch was only stock one row. I drove my car for around 25to30 miles stoping at red lights and only got up to 210 when i got to the track. I think if you try and restrict the flow down it will help, just remember most of the heat from the engine is from the top of the block and the cylinder heads. Check your fan and make sure it turning in the wright diraction. Hope this helps. One more thing put a 20lb cap on her it will help.

  7. #7
    Senior Member MASTER BUILDER
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    0verheats

    thanks guys. ii will be doing alot of the things i was told to do bu you guys.. they all fit into my way of thinking.i must check the electric water pump(summit brand). any advice on how to check the flow of this pump. a thanks again art

  8. #8
    Senior Member RACING JUNKIE
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    chevyart,
    i run a 377, also filled to the water pump holes, but i run a stock water pump with an electric drive motor gilmer belt drive. I run a thermostat, but drill 6 1/8" holes around the outside of the stat, same as a restrictor maybe 1/2" to slow down the flow of the water. I've run gas and alcohol and haven't had any problems with overheating. I do run a 16 LB cap, also only water (antifreeze is a NO NO at any NHRA or IHRA track) I'm on alcohol now so actually i have trouble getting the temp up, never turning on the pump until i'm driving back to the pits. On gas i would run the pump once i was moving it the staging lanes and the run, still never went over 210*
    Those electric water pumps move a lot of water and i think your question has already been answered with the restrictor to slow down the flow. I would also put a 16" shrouded electric fan on the radiator, sucking from the inside.
    Don't know who built your short blk. but i also plug all the steam holes on the blk deck for strenght.
    Don't know if this will work for you but it does for me.

    Zip.

  9. #9
    Senior Member MASTER BUILDER
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    overheat

    thanks zip. my existing setup worked perfect with the 355(not hard blocked) i think the problem now is either the waterpump went bad(c ould have sworn last week i looked at the top of the radiator where i put the water in, had the electricwaterpump going and the water was not moving. i thought that strasnge and forgot about it and am now definitely thinlking about it. i will put the 20 lb cap in and a restrictor(which i had in the 355 engine and flow check the waterpump> my fan is a shrouded electric, which is on inside of engine compartment, sucking the air in. it did work fine with other engine. im going to start with the things i just mentioned and i am sure this will cure my problem. any other suggestion i will definitely listen to. PS the steam holes are covered over with solid head gasket and solid head area over steam holes. thaNKS ART

  10. #10
    Senior Member RACING JUNKIE
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    Check your water temp at the bottom radiator hose . . If it's not 140 or so, you're putting the water through the radiator too quick . . Put the restrictor back in . .

    SBC Chevy Temps: @ the Thermostat housing 185-190
    @ the Sending unit on the Head (or Plug) 155
    @ the bottom of Radiator or hose 140

    And it don't matter whether it's a filled block, an aluminum one or the one in your Pickup . . it seems to work out the same . . .


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