Stumped!

[Karl Bebout]

HELP, I need somebody, not just any body....Beatles...

I've got an overheating problem that is driving me right up a wall. Never had the problem until I rebuilt the engine. I think it is being caused by a lean condition, but, its lean only on one bank. I increased all my carb jetting by three sizes and improved the overheating somewhat, but not completely. After about driving 10 miles, I'm up to 230* or more. I've installed a new 180* Fail safe thermostat, the radiator is new, running Water Wetter, have good flow, the top hose is 10-15* hotter than the bottom, I increased the total advance from 34* to 40* and initial from 16* to 20*. removed the thermostat, with no difference, I moved the tranny cooler away from the front of the radiator, I have a 3200 CFM Zirco puller fan, that is going the right way. I checked the water pump impeller and its not slipping on the shaft, I've checked all the intake manifold bolts and they are all tight. I've doused the intake/head juncture with carb cleaner, at idle, with no increase in RPMs. The plugs on the driver's side are plenty dark from the heavy jetting but all the plugs on the passenger side are very white. They did darken, just a bit, with the increased jetting, but are still not the shade of tan, I prefer. I do not have an air/fuel ratio gauge and no oxygen sensors or engine control electronics. Has anyone ever run into such a situation? I'm stumped and any advice (other than put in a Ford engine) will certainly be appreciated.

[Tommy]

Wild guess: Did you change water pump? If so, does it rotate the correct direction for your engine?

[Karl Bebout]

Tommy, no such luck. Same water pump I've been running for years and I've not made any changes to my pulley sizes. Thanks.

[lovehamr]

Upside down head gasket on the one side?

[Tommy]

A Google search reveals several discussions on other forums about engines that appear to be lean on one side and rich on the other. My sense is that the art of reading spark plugs other than after a full throttle run followed by immediate shutdown is more guessing than science. I wouldn't get too locked in on the "running lean" theory. ... I'll come back if I think of anything else to consider.

[Karl Bebout]

Forgot to mention that I'd wondered about the head gasket possibility. I used an old head gasket, traced around it, and all the bolt holes and water passages, and found that there is no way it could be upside down. The bolt holes do not come even close to aligning. I also rechecked that the head gaskets were the correct part number for my application. Thanks.

[joyridin']

Do you have an overflow bottle on the car? If so, do this...take a clear bottle and run the overflow into the bottle. Start the car and let it get to operating temperature. When the thermostat opens and closes, you will see air bubbles, but they should stop after a cycle or two. If they continue coming out at a regular pace, it indicates you have a bad gasket. If the bubbles stop altogether, the gaskets are good unless you see water in the oil.

[Karl Bebout]

And, and, and. I've tested the radiator cap and it holds 15-16#s. I tried hooking up my old electrical SW gauge to the new VDO sending unit and got the same reading as the VDO gauge. It is definitely overheating since I do get puking at the high temperatures. I have a Deadenbear thermostat housing tower that raises the coolant level higher than the heads by a few inches, so I don't think I have an air bubble. Any other way I could ensure no bubbles? No heater hoses and no water pump to intake bypass hose. Never had them. The block and heads were hot tanked and thoroughly cleaned when I rebuilt it and everything was clean and clear. I do have a new Griffin radiator, with shroud and Spal fan on order which surely shoould control the overheating, but I'm really concerned about the lean situation. The headers have not glowed. that I've seen, but the jet hot coating is not as shiney as it used to be, so I'm thinking they have gotten pretty hot.

[Karl Bebout]

Thanks Joyridin, I'll give your idea a try.

[vettestr]

I am with Tommy on much info from plugs that have mixed run conditions. What manifold you running, a single or dual plane? In the end she is hot and thats the bottom line.

What diameter is your crank pulley and what is the W/P pulley diameter?
What are your manifold vacuum readings at idle and held at 2K RPM (steady state -no load)?
Are you seeing any signs she is running fat A/F mixture yet, any black smoke or fouling?
I bet you have a 4 corner adjust carb.... can you close each corner adjust screw
and kill engine? I looking for major lean condition here, any signs? Keep jetting
up until you know she is just to rich as a testing tool.
Remove the hood and drive it long enough to be sure if there is any difference.
Last trick coming to mind at the moment is TOO PROVE timing = advance anther 10 degrees and advance until you get her to rattle and ping under a load. Once you get her to rattle back down about 4 degrees at a time until it stops. Again this is just to prove all your timing marks etc... after you find max timing point the look at and record displayed set point -does displayed timing make sense? 20 initial and 40 total seem fine but make sure something weird has not happened. Give me a call when you find it.

[Karl Bebout]

Jeff, The intake is an Edelbrock RPM Airgap, dual plane. The carb is 1 Pro Systems The crank pulley is 5 1/2" and the WP pulley is the standard 6 1/4". Got about 7" vacuum at 800 RPM idle and then 14"15" at 2000. I dropped the total timing back to 36* with about 19* initial to try to make the engine a little easier to start. It was really grunting to crank when the engine was hot. My exhaust is so loud and my ears so bad, that I really doubt that I would be able to hear any pinging. The balancer is brand new and I set the pointer at TDC while the heads were off and I was sure #1 was at TDC, so I feel confident my marks are good. Are you meaning I should close all the idle screws, one at a time to see if the engine dies? I don't know if I can get much of a vacuum increase with the screws, considering the cam specs. I'll give it a try, just for grins. I've not noticed black smoke but it certainly smells rich.

[davecobra]

Karl, how much did you bore the engine, on some big blocks if you overbore too much it will cause bad overheating.
David

[Karl Bebout]

David, I'd put over 25K miles on the engine at .060 over and went only an additional .010 in the rebuild. The machine shop had tested the cylinder wall thickness before cleaning them up. Thanks.

[Rick Parker]

New Balancer.....are the timing marks in the same relationship with the keyway in each balancer? Is it also possible that there may be an obstruction in one side of the Primary Metering Block, bad fuel pumped into new carb???

[vettestr]

Karlos,
First thanks for the feedback. I did pick up on the starter grunting when warm so my first clue she has plenty of timing, BTW stroke the throttle 1 time before you hit the starter so it will gain a little head start before clearing it's throat and trying to start.

WOW... 7" at 800 RPM. That seems low Karlos. Try closing @ corner A/F screw to prove it kills engine. I would look for leak or carb issues. call me

I see by the measurements you gave that the waterpump is UNDERDRIVEN and I really that is a problem in Phoenix heat. Now you are running the pump 15.4% slower than the crank RPM. Reverse the diameters to gain a 15% OVERDRIVEN w/p and you will gain a 30 percent increase in coolant flow. She will then move enough coolant to pressurize the cooling system (ya need 8PSI or >) to xfer heat into the coolant efficiently. Yep I know that is a HP loss but if you want to drive her on the street this makes a BBC live when 110* or more in our neck of the woods.

The pulley source for anything is here. The small W/P diameter is harder to find aftermarket but tell the guy what diameters you are trying to get. You don't need NCRS parts just a combo that will work for your hot rod. 65-68 Corvette "NOS" 108 BIG BLOCK PULLEY 3863108 crank shaft New old stock 8" | eBay

[Bill Bess]

HMMMM! Check to see if all your hoses are okay and not caving in while under pressure, burp the system, and veriy the heat problem with a temp. gun. Your gauge cold be going south so verify the gauge is correct.
When does it heat up? at idle, at speed, during acceration, fan on fan off, does it stay cool without the fan while crusing down the road at 50mph?
Could be a comb of things...what did it run at prior to the rebuild?, what's different now?
Could be a combination of issues, larger bore, fan not cutting it while under way (low amps. to fan). Maybe try to back flushing the system to verify tha no obstruction exist. Just make a list and check them off as you verify each potential cause. You might consider a Ford Taurus fan to up grade what you have (two speed), this fan has helped many cobra folks including me.
Good Luck, Bill

[CHANMADD]

A total of 0.070 thou out of the bore is going to leave very little meat on the cylinder wall.
I agree with speeding up the waterpump, but the block is probably too far gone.
You implicately believe the machine shop!!!!!!?
If nothing else changed but a devote then that's what caused the problems.

[HSC-ZL1]

I don't know if these are comparable but I have a heritage ZL1. I ran just 8 degrees of initial timing for break-in and moved up to 10 degrees at 500 miles. This motor ran at about 195-200 at this timing. This is a factory billet HEI distributor. I bumped the timing up to 12 degrees initial (about 35 total) and immediately gained 5 degrees in running temp. It will elevate to about 220 in traffic on 90 degree days but return down to 200 when moving with the 10 degree initial timing.
Might be worth trying for break-in on new motor and a quick test to see if temps come down with less timing.
cooling system carries about 4 1/2 gallons of 50-50 dex-cool.

[jhv48]

I'm having trouble wrapping my mind around this one.

So, engine rebuilt, total .60 overbore. Engine overheats but water is flowing correctly, thermostat is functioning fan is turning on at appropriate temp, radiator is shrouded. Now, the right bank plugs are white (doesn't necessarily mean a lean condition. Could be getting steam cleaned by water leaking into the cylinders), while the left bank show rich conditions. Dual plane intake should equalize, somewhat, the fuel distribution to both sides of the engine, thus ruling out the carburetor and you have eliminated a vacuum leak. Timing would effect both banks as well. Since the temps appear to be higher on the right side, I would borrow a laser temp thermometer and see how the right side header temps compare to the left side before I did anything else. My guess is that they're about equal. If the right side is significantly higher, then I agree, the head is coming off. Something is causing that side to reach higher operating temps. Either a water jacket is blocked by debris or a gasket moved during installation.

If you were losing any water, then I would suspect a head gasket leak, as the plugs could be getting steam cleaned by the water in the cylinders. That's why they still appear brand new.

My bet: intake or head gasket leaking on the passenger side. My first choice would be head gasket.

[CHANMADD]

Its a total 0.070 overbore..............another thought....could the cam timing be off?