1969 mach 1 bent intake valve

rbancy

Member
May 12, 2020
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Victoria, BC, Canada
Hey guys - maybe you guys can give me some suggestions here.

Took the 69 mach 1 to a shop, which told me I had no compression on cylinder 7, so took off the intake and heads and found there was a bent valve on cylinder 7. Took to a machine shop got the new valve installed by them.

Put the new felpro gasket on , bolted the heads down torqued to 70 lbs , proper sequence. Intake on - hooked everything according - roller rockers installed. Dizzy in and installed everything as is.

Problem now is - hearing a pop or 2 during idling , car drives like there is no compression. Had problems up my drive way which is a bit of a hill and under load heard a little clunk noise. One side of the cylinder head that i did not touch is very hot, whereas the otherside which the valve was replaced not hot at all. Radiator is steaming hot and alot of preasure build up, leaking from the bottom. The bottom hose is cold, while the top of radiator to water pump is filled with preasure and extremely hot (steaming ). Car jumps to 170 on the thermostat within 3 minutes of idling. I also notice no water flowing through the heater hose. Theres a restrictive flow of coolant.

I have a feeling this can be a stuck intake valve restricting coolant flow ? Any suggestions from anyone ?

Tommmorow, i'll remove the valve covers, fire it up, and inspect the roller rockers and rods. Making sure all valves are going up and down. I never opened the valve cover on the good side but i'll check that out to tommorow.

Any help be appreciated.


thanks
 
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7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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First, why was the valve bent?
Second, intake and exhaust valves do not come into direct contact with coolant unless the head gasket, intake gasket or other part has a major malfunction.
You could have a stuck thermostat, a leaking head gasket and a bad radiator causing the coolant issue. You could have a valve issue or an ignition problem causing a cold cylinder. So besides making sure your valves are moving, a cylinder leak down test came show if and where you have leaks going.
 

rbancy

Member
May 12, 2020
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43
Victoria, BC, Canada
The engine has only about 800 miles on it. 10 months old. It was dynoed and air fuel ratio at 12.8 which is good. I don't know how it got bent, I contacted the machine shop and they said it was dynoed and they did everything ok. Never was running hot at all , all of a sudden started getting little bit of a pop after heavier accelerations which gradually the popping got worse.

Thermostat is new when i was taking things apart, so not a thermostat. Head gasket I put on properly - No signs of milky oil. Did an oil change after changing the head gasket. It is a new 3 core alluminum acp radiator. I have been tinkering with the ignition running it over advanced; so i know its not that. I have a feeling its a valve issue.

Still early in the morning, but will check it out once i remove valve covers.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
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Kearney, NE
Why ask for advice and then write it off?

You likely have two problems, or one causing the other. The road to diagnosis will take longer with a poor understanding of how things work.
Valves do not just bend. They must have contact with the piston or a foreign object. So, did it stick open while running too hot, from no enough oil, valve float at high rpm, poor machining and tight clearances, or an object dropped in the intake?
The poor cooling gives us a hint, but the other possibilities need investigated.
 
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HemiRick

I'd be looking at jacking under the house
Jun 28, 2020
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was the car ever run on old gas? Are you sure the new head gasket was put on right side up? or w the front to the front?
 
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Ranger

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Jun 10, 2013
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new thermostat could be a bad new thermostat ... but I'm still thinking about the heads - from install to operation
 

rbancy

Member
May 12, 2020
29
2
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43
Victoria, BC, Canada
was the car ever run on old gas? Are you sure the new head gasket was put on right side up? or w the front to the front?
Thanks for the response - Gas I put premium. It actually turned out to be a valve adjustment . Had 2 of the roller rockers on little tight, causing the valve to be stuck open. I got the shop to adjust it properly.

Its all working now - car is running good now with more power . Just a little hotter then usual. If Use to run a lot cooler. I know 180 to 200 is quite normal. I usually run cooler then that though.

180 thermoStat
3 core alluminum rad
 

rbancy

Member
May 12, 2020
29
2
13
43
Victoria, BC, Canada
was the car ever run on old gas? Are you sure the new head gasket was put on right side up? or w the front to the front?
Yes it turned out to be a valve adjustment . I tightened my roller rockers little to much - stuck open and had no compression.

Now tackling with car heating up little quicker then it use to.
 

Ranger

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Jun 10, 2013
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Missouri
Great news!
pop that cap and watch for circulation in the radiator (start cold if you aren't sure how to safely open a hot and pressurized radiator), if it's flowing you should be good. you noted you had changed out the thermostat but never mention the temp rating on the old one ... maybe it was a 160 and was opening sooner and giving you the past "normal"
180 is or was quite normal in the '60's v8s - many people switched to lower rating in the summer and then wondered why the heater wasn't working as well
I spent a bit of time in the day on both sides of the parts counter and basing my opinion on that.
and also as an after thought, radiator caps have a temp rating as well and can have an effect.
 

rbancy

Member
May 12, 2020
29
2
13
43
Victoria, BC, Canada
Great news!
pop that cap and watch for circulation in the radiator (start cold if you aren't sure how to safely open a hot and pressurized radiator), if it's flowing you should be good. you noted you had changed out the thermostat but never mention the temp rating on the old one ... maybe it was a 160 and was opening sooner and giving you the past "normal"
180 is or was quite normal in the '60's v8s - many people switched to lower rating in the summer and then wondered why the heater wasn't working as well
I spent a bit of time in the day on both sides of the parts counter and basing my opinion on that.
and also as an after thought, radiator caps have a temp rating as well and can have an effect.


good advice - thanks yes i'll try to presurize it. I did park it on a hill and used the funnel to burp it as well. I even put temporary clear hose connected to the heater core , and return to water pump - just to see the flow. Everything is good and working.

I am currently running a 180 thermostat, previously ran a 180 as well - was told to take it out which i refused to. Had to switch to a 16 lb rad cap months ago as the 13 lb wasn't cutting it.

It is running between 180 and 200 which most people say its fine , and only should be worried if over 220 or 230. I know it ran cooler before I replaced the head. Temp drops a bit when rpm is higher on highway , Im thinking the way to solve this would be a 16 inch electric fan. I would need a low profile one as i only have about 4 inches span between the rad and the mechanical fan.

I do want to add i am running a mechanical fan - 15 inch derale which could be another possible problem - perhaps not pulling enough air.

thanks guys