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Old 05-14-2018, 12:01 PM   #1
Novicecarguy
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69 chevy 250 head replacement

So I have just recently replaced my 1969 head. The cost to fix the old head was substantially more than just buying a new head. my new head I got is a 1970-72. Now I知 wondering if they池e even compatible. My motor is now running a lot hotter than it was before I also put in a 180ー thermostat. My carburetor was just rebuilt by the old carb doctor in North Carolina. My problem arises once truck is up to temperature and I am sitting at a stop sign and go to hit the throttle it sputters in spits out Blacksmoke. I got Jeff from the old card doctor on the phone and he is saying that everything is too hot it is vaporizing everything so that痴 got me wondering if the 69 block is compatible with a 70s head has anybody else run into this problem any comments would be greatly appreciated.
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Old 05-14-2018, 05:37 PM   #2
Wrenchbender Ret
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Re: 69 chevy 250 head replacement

The heads are interchangeable. The only one that is different is one from a 194 that came in early Novas. Even that would not cause overheating. Try another therm. The new ones we get now half of them are not good. There must be something with the cooling system to make it overheat like that. If it loads up with fuel before it gets hot, there is a problem with the carb. If it just acts up just when it gets hot then the carb guy is right, the fuel is perculating.

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Old 05-14-2018, 08:41 PM   #3
RichardJ
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Re: 69 chevy 250 head replacement

Agree with Wrenchbender's post.
The heads are interchangeable as mentioned, but make sure you use the right plugs. Around '70 they switched from gasket to tapered plugs with slightly different reach.
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Old 05-14-2018, 09:09 PM   #4
Old Truck Man
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Re: 69 chevy 250 head replacement

Just think about how old your radiator is. Its certainaly not as efficient as it was when new. incorrect timing and a too rich or too lean fuel mixture will also cause overheating. Be shure your heat riser valve is working properly. and your exhaust is not plugged. Be shure you don't have a leak between the intake and cyl head.
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Old 05-14-2018, 10:59 PM   #5
Novicecarguy
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Quote:
Originally Posted by RichardJ View Post
Agree with Wrenchbender's post.
The heads are interchangeable as mentioned, but make sure you use the right plugs. Around '70 they switched from gasket to tapered plugs with slightly different reach.
Yes I have the tapered plugs I found the plugs in the old head did not wrk with the new one. I知 going to change the thermostat form a 180 down to a 160. Timing is set at 6*. Exhaust manifold is brand new and the intake manifold has been sand blasted. Where I知 stumped is why the sputter and black smoke once its up to temp and it only does it when I知 first pressing the accelerator on take off
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Old 05-14-2018, 11:49 PM   #6
bcfishon
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Re: 69 chevy 250 head replacement

start with the spark,timing is easy to play with and check results,as well is some carb tinkering.
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Old 05-15-2018, 09:07 AM   #7
geezer#99
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Re: 69 chevy 250 head replacement

Take some pics of the carb etc.
Someone might see something obvious.

And bump your timing up to at least 12 initial. Retarded timing makes heat.
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Old 05-15-2018, 01:27 PM   #8
Novicecarguy
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Originally Posted by geezer#99 View Post
Take some pics of the carb etc.
Someone might see something obvious.

And bump your timing up to at least 12 initial. Retarded timing makes heat.

Update!!! I have changed out the 180ー thermostat with a 160ー thermostat and bumped my timing to 12ー temperature in the truck has come way down back to normal operating temperature. I took out number one spark plug and found it to be saturated and saturated in what I知 not sure it does not smell like gas does not appear to be gas I知 still having the black smoke when up to temperature and I first hit the accelerator and now I have some lovely white smoke mixing in (not good) are there ways to check and see if the head gasket is blown with out pulling the head? Keep in mind I just put a brand new head and gasket on this thing. Torqued the head to 95#.
Also I was informed to not run resistor plugs and suppression wires with a points distributors? Is that accurate?
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Old 05-15-2018, 06:04 PM   #9
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Re: 69 chevy 250 head replacement

The neighbors will love all the interference you are providing them by not running resistor wires. There is no reason not to run resistor wires.

You should be able to rent a kit from the parts store to check for exhaust gases in the coolant. Do you see water and/or coolant in the oil?
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Old 05-15-2018, 06:17 PM   #10
'68OrangeSunshine
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Re: 69 chevy 250 head replacement

A compression check and /or a leak-down test would show up a leaking cylinder.

Do you still have the OEM L6 radiator? The V8 radiators are wider and will have more cooling surface. [I'm not even sure if the old school L6 radiator width is even still available?] If you have to replace the radiator, go with the V8 unit. You will only have to move the upper and lower passenger side radiator brackets, and make sure the lower radiator hose fits. For me it was a desert survival upgrade. Too high a coolant/water mix can give higher temps, add more water.

I never heard of not using resistor plugs and wires on a points ignition set-up. Pure hogwash.
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