overheating BBC and excessive crankcase pressure

Discussion in 'Engine Topic' started by mrluckies, Jan 5, 2011.

  1. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    I have a 1970 RS Camaro that I’ve been rebuilding and am currently experiencing overheating issues. I bought it without an engine, so I dropped a 454 in it and swapped the TH350 for an M-21 that I had laying around. The engine is a 1982, 2 bolt block PN: 14015445 (additional cooling holes in the deck) with early heads PN: 336781 from 1974. They’ve been pocket ported with larger exhaust valves (1.88) and hardened seats installed, I left the intakes alone. All along, the theme for the project was low-buck so I bought a summit racing engine rebuild kit PN: MHP143-400, which came with roughly 8.69:1 pistons. I also purchased a summit racing cam PN: 1302 which is 228/238 at .050 with 0.540 lift on a 114 lobe separation angle. It has an aftermarket high flow mechanical water pump, heavy duty thermostatic fan clutch and 18” GM mechanical fan off of a junk yard car and at the time no fan shroud. I am using a 180 thermostat. I am using the heavy duty copper replacement radiator available from the local parts store. It has a GM large cap HEI with a Pertronix Flame Thrower module, coil and vacuum advance hooked up. It also has a Speed Demon Vac Sec 750 carb and Edelbrock Performer RPM oval port (not air gap). I put the car together and had been driving it in NJ for over a year as a semi-daily driver on 87 octane gas (the goal of the build was to use 87 octane since it’s a daily driver) without any overheating problems at all. The temp gauge (electronic sending unit threaded into left cylinder head) never registered over 190 even after sitting in daily stop and go traffic for an hour with the air temp at almost 100 degrees in July – and yes, no fan shroud installed. One day I was leaving work on a section of highway without traffic so I was cruising about 70 mph (taching about 3000 rpm) when all of a sudden my upper radiator hose popped off the radiator. I shut off the engine and coasted to the shoulder. I was able to reinstall the hose and see the radiator was about half full, so I decided to chance running the car down the long hill (about ½ mile) with car running in neutral once I got going and then about another ½ mile of flat ground to the closest gas station for water. I added water to the radiator and headed home. It may not have been the best idea since the car now heats up every time I drive it. If I’m moving, the car will run around 210 or so (not hot, but higher than it used to run), but when I’m sitting, it starts to climb. I’ve sat in traffic and had it go up to 240 before I decided to pull off and shut it down. I know the fan shroud will help, but keep in mind, I never experienced this problem before, even in stop and go traffic in the dead of summer. I started to notice some oil droplets in the coolant, so I ran a cooling system pressure check and it didn’t hold pressure. At about that time, I deployed to Germany, so the car sat in NJ. On leave, I swapped head gaskets. After re-buttoning up the car, I thought I had it fixed. I ran the car for short trips and it seemed ok. Then one hot summer night, I drove it for over an hour and noticed the temp start to creep at a stop light again. At that time my leave was up so I had to park the car. My dad would start the car occasionally for me and noticed one day the clutch fan was free-wheeling a little too much. On my next leave, I installed a new fan clutch and a 17 inch mechanical fan so that I could install my fan shroud (the 18 inch fan came too close to the top of the shroud, as it doesn’t fit exactly centered, even though the shroud is for an 18 inch fan). I ran the car and it seems to be a little better, but I still notice temp creep when it’s idling. I re-pressurized the cooling system figuring maybe I cracked the block or heads, but it seems to hold pressure (the pressure tester I used this time didn’t seal perfectly to the radiator neck, but the leak down was acceptable according to the directions: about 1 psi in 15 min, definitely not like before, where you could watch the needle drop). I decided to run a compression test on the warm engine and found everything within 5 percent at an average of 185 psi. I then decided to do a cylinder leak down check and found leakage between 25 and 40 percent (25 was on #1 cylinder) which all came out the oil breather (I guess going past the rings?). There were no air bubbles in the radiator. I didn’t have a lot of time since I was on leave, so to perform the leak down test, I just brought the engine to the TDC mark on the damper for #1 and then took a reading. For the rest of the cylinders, I followed the firing order and would eyeball the distributor rotor with the wire location of the cap to get them close to TDC and then take a reading. The engine wasn’t hot, but it was warm. On one cylinder, I took two readings, one as previously described and one reading with the piston further down the bore past TDC and the second reading went up slightly, about 5%. I also noticed some sludge sticking to the suction hose inside the overflow bottle (attached to the bottom of the cap to pull fluid back into the radiator when it cools). I’m figuring the sludge is probably from the oil that I saw previously in the radiator. I want to run a cleaner through the cooling system, but ran out of time on my leave and had to park the car again. Oh yeah, I run 50/50 coolant water mix. I’m sitting here in Germany wondering what could be causing the problem so I can fix it when I get some more leave in a couple months. The only thing I can think of is cleaning the cooling system as the sludge may be limiting the cooling effect if it’s coated the walls. Do you have any ideas?

    Also, the leak down seems high. Could this be from running hot? The engine has about 10,000 miles on it from when it was built and they haven’t all been easy either, I really enjoy the torque of a big block! When I had my machinist build the engine, I told him I plan on putting either a shot of nitrous on the car or a small blower in the future, so he set the gaps a little looser. But it seems to me that 40% is a little too much leak down. Could the blow by be adding to the over-heating? Could the high leak down be a result of the engine running hot? Also, to fix the leak down, I was thinking about re-ringing the engine. But that’s not something I can accomplish on a week’s worth of leave, so it will have to stay for a while. I do use about a quart of oil every 1000 miles, but my intake gaskets show signs of oil leaking past the bottom. I need to get my intake manifold machined to match the heads better, but have held off since I might upgrade to aluminum heads in the future. I use a pcv valve (pn: Deutsch PCV225) on one valve cover and breather on the other one. The valve covers have baffles where these plug in. I notice oil residue on the valve cover around the breather – probably a result of the leak down pressure. Again, do you have any ideas?

    The car is a lot of fun to drive. I've weighed the car, it's 3800 lbs. with me, a 1/2 tank of 87 octane fuel and a bunch of tools and parts in the trunk, so probably closer to 3700 without the stuff in the trunk. It has a M-21 4 spd with a mechancial clutch and stock steel flywheel. The rear is a 3.42:1 - 8.5" out of a Trans-am with factory posi. The car is all steel including hood. I'm still tuning the car and only have 5 passes. Best time was: 13.45 @ 106 MPH with a 2.3 sec 60 foot time. Launched at 2000 RPM (shifted around 55-5800 rpm) to keep the 235/60R-15 BFG TA radials (not drag tires) from spinning. Also I did not perform a burnout as I wanted to see what the car would do in its every day form. And that was on 87 octane fuel at Island Dragway in NJ (close to Sea Level) in the summer.

    Thx for taking the time to read my stuff and I look forward to any advice you can provide!

    Alex
     
  2. craigblock

    craigblock Veteran Member

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    Looks like I'm the only one to read your post so far. Quite the detail!

    Anyways, I would say that at this point, there is enough ill happenings to warrant a rebuild. With oil getting everywhere, the possibility of piston damage, and so on, I think you should give in and tear down the whole thing.
     
  3. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    thx for the response. I agree. with the limited time I'll have to work on it, typically a day or two at most while on leave, I am looking for things to look for while i'm at it to maximize my efforts. Especially since I can't do a full rebuild for a while. I'd like to keep the car driveable and not have to worry about overheating for the couple days I'm in town. My next guess is to use a cooling system cleaner.

    Also, does anyone have ideas in regards to the rings?
     
  4. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

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    .

    I'm not reading all that, but the 1st thing I would do is try to see what's going on in there.
    Compression test would be quickest, leak down most accurate.
    Make sure you run it to temp 1st.

    Good luck.

    .
     
  5. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    thx for the response.

    I know it was a book, but I've done a bunch of checks already and wanted to describe what I did to see where to go next.

    I've done compression and leak down checks and cooling system pressure checks. Engine was hot, when I started with compression check, but by the time I got to leak down, it had cooled down some - i.e. the headers no longer burnt my hands, but the heads were still warm and the spark plugs still hot too hold.

    Next time I'm on leave I'll try cleaning the cooling system and see where I'm at.
     
  6. JONESYFXR

    JONESYFXR Veteran Member

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    I think you may have more than one issue going. If there's oil in the water you may have an intake gasket that shifted when the intake was dropped down. The engine running hot, that could be a bunch of things.....like a water pump not working properly, bad head gasket or even a cracked block in the water jacket.

    It's a hard thing to find when you have so many things going on at once. My brother in law had a 402 in his Chevelle. Two racing seasons ago on the last race of the season he went through the traps and a big white cloud emerged from the right bank. I told him and he blew it off. The next spring he pulled the car out and it would run like crap, temp gauge all over but no antifreeze odor. He did all the tests you did, and they were all in spec.

    After consulting with our friend and egine builder he pulled the top end. At first everything looked good, but after rotating the engine over and pulling the #2 piston down into the bore, he saw a rusty crack. Low and behold he cracked the block, se he decided to have it sleeved. So, as the bore was being cut, this is what he found.......

    [​IMG]

    The piece of the bore that was still in the block was measured and was only .060 thick!!!! The cast must have shifted while being poured.

    I'm not saying this will be your engine, but you have to look into EVERY detail instead of trying to throw parts at it. It's a long, arduos task, but will be worth it when you get it all fixed and you can say you did it yourself!!!

    Good luck!!!!
     
    Last edited: Jan 10, 2011
  7. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

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    WOW! What a LONG post!

    There are a lot of things that cause overheating. Timing, lack of a fan shroud, defective fan clutch, plugged radiator, radiator not sealed to the radiator support, carburetor lean (or rich), vacuum leak (makes the engine run lean), just to name a few.

    I think that when you overheated it the first time, that something go damaged. The compression and leak down test showed you that the rings are OK (although not perfect).

    Oil in the cooling system is a clue. It could be from a blown intake and/or cylinder head gasket(s) or a crack in the block. You used a pressure tester but that test wasn't the best as you couldn't get the tester to seal to the radiator. Any time I used that tester IF the engine was OK, the tester never lost pressure. I would advise re-doing that cooling system test and make sure that the tester is properly sealed to the radiator. I think once you do it again you'll see the resultant will be that you have a leak out of the system (be in a cracked block or compromised gasket).

    I wouldn't have the intake planed to match the heads. The correct proddecure is to mill the heads re-establish the correct angle to meet the intake.

    Did you test the thermostat before installing it? The test I use is to put the thermostat into a pan of water with a thermometer. Then slowly bring the water to a boil while observing the thermostat to verify that it is opening at the specified temperature. Then add cold water till it closes. I then repeat the heating and cooling cycle a couple of times just to make sure that it is working. You may be lucky enough that your overheating problem is just a defective thermostat.
     
  8. mrluckies

    mrluckies Veteran Member Lifetime Gold Member

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    thx for the good advice!

    Yeah, I've had a couple thermostats in it. I might try the boiling trick anyway.

    I know i should tear the engine down, but the problem is I only have a couple days to work on it. If I find something, I won't be able to repair it and the engine will sit disassembled for at least a year before i get back. I figure at that point I might as well leave the engine assembled for now.

    Fortunately, there's no smoke and the idle is ok. The vacuum is where it was before I ran into problems. I think the oil in the cooling system is from before I swapped the head gaskets. I was hoping the head gaskets were the problem and the new ones would have fixed it. Like i said, it got better. I wish I would have thought to rotate the engine and look at each bore when i had the heads off. Ah well, next time.
     
  9. rscamaro73

    rscamaro73 Administrator Staff Member

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    I would...at this point, have the motor taken down and inspected.

    You have issues that 'normally' you'd find with your test techniques. But since there seems to be a variable outcome, that's not 100% dead the same, then you have some sort of partial failure, or overlapping issues that show as a failure.

    You could have any # of issues with the heads being warped or cracked.
    Block could have a crack that opens up when its hot.
    Water pump is prolly not an issue at this point, at least to me....
    Leak down shows air is going somewhere it shouldn't. You should try it with a quirt of oil in the holes and see what kind of reading you get then. Heavier than your normal oil.
    You could have had an intake or another head gasket failure. Slipped as mentioned, or just burnt out somewhere.

    Rather than us just keep guessing, and trying to help you out...get the motor taken apart somewhere and get it mic'd upon disassembly. If you have to pay an engine build to so it, it'll be peace of mind if he finds something. I bet a good builder will find it fast.
     

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