i have a 69 dart gt with 76,000 original miles the original 273 engine and 2bbl carb with a/c
was having some problems with overheating so I had the original radiator pressure tested and boiled out, was good for about a month. put in new water pump and thermostat still overheated, So i got an aluminum radiator. Worked great no more overheating but it ran hot.
I started to notice some pinging in the motor after it ran for a while.
played with timing still the same overheat ping.

Fed up I figured maybe one of the head gaskets failed.
I did a compression test the drivers side was great
Dry all cylinders on drivers side 160 wet 180
passenger side.....big difference..
1st cylinder toward front 120 dry 120 wet
2nd cylinder 150 dry 150 wet
3rd cylinder 155 dry 155 wet
4th cylinder 150dry 150 wet
test done with all plugs out and carb flap open

any ideas if this infact could be the head gasket?
The oil is clean and the radiator has no oil in antifreeze.
I'm puzzled... At this rate i know i have to pull the heads.

 

Take the car out for a drive before you do the compression test..... You need to get everything expanded on the old gal to make sure you get the rite reading...
Drive it back home and redo the test and see if that reading changes....

How is the performance of the car other wise?
I dont think you have a gasket problem at this point....

Cam Might be going flat.... Worn rockers only on the one side from a oil restriction,..Cam my have jumped time.... Timing not rite due to spun balancer?

180* Thermostat?
Did you change pulleys?
IS there a fan shroud in the car?
6 Blade Vicouis fan and clutch?

Will help you get it fixed....
Lots of great help here !!!!!!!

 

There are a few things that can cause low compression.
1) valves
2) rings
The next question is does it burn oil ? Pinging can be caused by oil consumption OR poor fuel and we Know the fuel with ethanol cuts down the octain and play havoic on old engines.. Does it have blow by ? Your #2 cylinder is low and I suspect that the valves are not seating as it doesnt matter if its wet or dry you still have the same compression. Like you said the heads are going to have to come off. At that time you will have to make the call as to just freashen the the whole engine if it were mine that is what I would do. But that is just my 2 cents...Bill

 

ok to answer some questions when i did the compression test the car was heated up to operation temp, drove it about 10 min, man was it was hard taking out the plugs, 93 fuel being used...the car runs rich so it has some black smoke when you get on it. Does not burn oil , no white sweet smelling smoke. the car runs ok but i do not know if it could run better it's been the same since i got it. It does have condensation that drips from the dual exhaust and that water I tested that.
the car is stock except for the radiator which is aluminum and it has a fan shroud.
Cam and rockers seem fine I had the manifold off 6 months ago lobs all look good rockers nice and tight.
no bent push rods

 

I think I'm with Pro-tech on this one....
@ 76,000 It has more than likely taken the valve seating out.... I would say time for a freshen up at this point....
Just my 2 cents....
Keep up posted....

 

ok going to pull the heads and see whats up and send them in for a rebuild and go for the harden seats.

Could I tell from the metal head gaskets, if they failed? what should i look for??
I'm assuming they will be in one piece.

does any one think that maybe the heads could have warped thus creating a small gap in part of the gasket? or could the head be cracked somewhere creating the overheating problems and poor compression on the one side??
I never had any oil or antifreeze drips and never had to add any.

i really hope the block is not cracked but i guess i would know from the oil at this point.

 

I'm Not sure you found what the overheating problem is yet......
All we might do with this fix is more than likely build more heat and make it worse???
Got to find the root cause if your going that route...
All so you might put it back together and it might start using oil. Once you get a good vacuum back in it from a fresh top end, Sometimes those old rings just start letting all the oil past them.... Just food for thought....

How long dose it take to over heat?
Dose it build enough pressure to boil over?
There may be a lot of rust blockage... Have you performed a Block Flush yet?
With some shop air you see if that cylinder is seeping or leaking with the valves closed...
Try that before pulling it down.

 

thanks for the help on this.
regardless I still have to pull the heads.
with the compression being so low with the 1st cylinder on the passenger side there is a problem. that being said I'm going to pull them and send them out to be redone.
the compression is excellent on the drives side 160 dry all across.
this way i can check the water jackets and also see if the correct head gaskets are in the car as well

we will see what happens.

 

the new fuel will tear the old valve seats apart so it may be the issue. when u look at the head gasket you will notice if it was leaking. if i were you i would just pull the engine and do a nice solid rebuild on it

 

69 Dart is the best model year.. I would stick the 273 in the garage and put a 318/340 in it. Never cared for the 273. I had one in a 66 Coronet, what a dog, put it in the trash can and put a 383 in the car back in 1972/73

 

I agree with Bob you should do a cylinder leak down test.. And I would pull the engine out and go through it with a complete refresher build...Rings, Bearings, Boil the block and heads, Hone or bore the block. Valve job, new oil pump, Etc... Truthfully it would be easier to just find a low milage 318 and drop it in and then rebuild the original engine as you can. IF YOU NEED TO DRIVE THE CAR..This would also let you know if its the engine causing it to overheat or the cooling system....LOl..It is all your call just listing some options... Around here you can buy complete low milage engines for $350 from bone yards so it makes it worth it...Bill

 

Random thoughts............

Somewhat lower compression on one side could be...........

at some point the head was replaced with a later head, lower compression

or maybe this engine suffered a head gasket failure and one side is thicker than the other

Overheat.................

Someone over at FABO posted an idea that sometimes older radiators (maybe from thermal cycling) he believes can crack the fins loose from the tubes, causing poor heat transfer/ radiation.

I ran into something which sounds like this very thing. My original 273 rad was checked out and the rad guy claims it flows like mad, should cool a stock 360. I have a 318 in the car and it would not cool. I swapped an unknown used /6 rad and both are similar size. The temp gauge dropped to the floor. I'm not even running a shroud on the newer /6 rad.

 

440, I think he said he put an aluminum radiator in the car. I agree with you on maybe one head has been off and maybe the valves were done on one side, and the gasket could be a composite gasket and the other one is steel. I think it needs to be torn down and checked to further diagnose...Bill

 

well i tore down the 273 today, I was amazed how fast it went.
Both head gaskets were metal. The gasket on the passenger side had rust on the top and bottom of the 1st cylinder the rest of the gasket was fine. Drivers side was fine. Noticed and cleaned out 2 water ports that were clogged. So im bringing the heads in on monday for a rebuild 300.00 both sides with hard valve seats includes milling if needed.

two things i thought was weird were.....
the 2bbl intake the rear water holes were factory filled with metal...

and the front upper water hole where the head fits gets covered by the factory mopar head gaskets even though there is a hole for the head and hole in the motor, it's like that on both sides, thought that was kinda strange... maybe the wrong gaskets were used? is that possible??? or perhaps it's fedfrom the intake??

i could take pics

 

Got a call today from the guy doing the heads.
Drivers side head may have a crack in the water jacket, He is going to double check again tomorrow, Good news is the guy found a pair of 1969 273 heads that someone never picked up with the same casting number, he's had them for 10 years.
He said he will freshen them up and give them to me for 350.00 the price I was paying anyway. I am still in shock that he's not going to charge me additional $$$$$$$$$$$$ at least this maybe the reason for the overheats.
I'll know better when it's back together!!!

While I'm waiting I took off the water pump and changed the timing chain as well, Old one was not too bad but changed it anyway while it's apart, now painting engine

 

This would be a great time to remove the small plugs in the side of the block and flush any sediment that has collected, you'll be suprised how much there could be.

Be careful with the stock bolt installing the damper. If you don't get alot of thread engagement you can tear them out.

 

that was probably the issue it would build psi and exploit that crack

 

Took the Dart out for a long ride today. Water temp way below what i have been used too. Much more power and the engine runs so quite now, it's really hard to believe. It's a dream. Acceleration has never been better, it takes right off now. New hei distributor coming tomorrow, can't wait.

It's really amazing what you get used to, that you thought was good.

 

Great News Im glad it all worked out for you...Enjoy...Bill