Please help me diagnose this 273

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Most everything has been covered so I can't contribute much. I suspect a leaking intake manifold gasket from your original post. Vacuum leak from improper install of an aftermarket intake. Also just since it hasn't been mentioned the oil could be valve guide seals. It happened to me that way. The rest of the advice above was all pretty much spot on-good luck. It's a nice looking engine by the way compression test not withstanding-------------------you know-------------------
 
Some of yall aren't paying attention. One of his cylinders is at 65 PSI. Not too many things can cause that.
 
Where do we start? The carb needs to be proper and working correctly before it can be adjusted properly. The distributor probably needs points, condenser, rotor, cap, wires. The valves probably need adjusting. A new set of plugs is in order. The oil burning could be something as simple as valve seals or as complicated as worn rings and the engine needing a complete overhaul. Start there then report back with your findings. Don't overlook the obvious!

Some of yall aren't paying attention. One of his cylinders is at 65 PSI. Not too many things can cause that.

You're correct Rusty. Why do we even bother.
 
O.P. Just adjust the valves and do another compression test before you do anything else and let us know what happened.
 
I've preached it and preached it right here on this forum to use water in a spray bottle to find vacuum leaks and always get ignored or argued with. So, I'm just gonna let people burn their crap up. You caint fix stupid, so I'm gonna stop tryin.

I have been using a propane torch it works good. I would use water if it is a bigger leak. Propane gas finds it fast and if it lights up you leave off the trigger and it goes out instantly. always have a fire extinguisher. You can even use it under the dash on ac cars. I turn it to low. and do it in spurts. Don't lay on the trigger for a long time . It will blow the windows and you out of the car

I never tried one without having a trigger. I am not that fast in my young age to turn the knob off quickly. But I did have the torch light up from a bad wire already. I could not imagine if I was using carb cleaner what the results would have been.

My friend that lost his 75 lifted 4x4 years ago. By the time he jumped down from the truck the flames were to high to get back up there with a rag he had. So he just tried to throw it on and smother it. That was the end of that Power Wagon and then he had a mullet with no eyebrows.

I tried not to laugh but when I looked at him staring at the truck burning in amazement with no hair or Eyebrows and his chin bleeding from slipping off the front bumper. I couldn't hold it back. I had tears in my eyes and it wasn't from crying.
 
Some of yall aren't paying attention. One of his cylinders is at 65 PSI. Not too many things can cause that.
Story.... Bought an old F350 40 years ago. Had 2 dead cylinders.... broken rings in one.... the other dead cylinder had hole in the exhaust valve that you could stick a pencil through LOL. Idled fine at 700 RPM, just with the classic hillbilly logging truck 'putt-putt-putt'. With 65 psi compression, it would have idled smooth as silk. (Well, almost!)

So sure, this 273 has low compression in 2 cylinders....but that is not what is making it die at idle. I've had at least 3-4 engines with a cylinder that low and drove them and they idled fine, even 4 bangers.
 
I've preached it and preached it right here on this forum to use water in a spray bottle to find vacuum leaks and always get ignored or argued with. So, I'm just gonna let people burn their crap up. You caint fix stupid, so I'm gonna stop tryin.
Not stupid. I lit up an f150 checking for vacuum leaks. Water is just as effective. Moreso if its a good leak,it will hiss as its sucking in water.
 
I adjusted the valves and all of them were were out of spec, some by quite a bit. #1 in particular was way off, the adjusting nut was practically loose. Hopefully I can check compression again in the next day or two.
 
I adjusted the valves and all of them were were out of spec, some by quite a bit. #1 in particular was way off, the adjusting nut was practically loose. Hopefully I can check compression again in the next day or two.

Cool, maybe that will do it.
 
The valve adjustment made a big improvement, it's like a different engine. The compression on both low cylinders went up to 135. It's idling at about 750 rpm and doesn't die when I put it in gear. I think it may have a small miss and the idle is still wandering some, but things are much improved.
 
I am concerned about the adjusting nut on the #1 exhaust valve being looser than the other ones. I suspect it will back itself off again, probably sooner than later. Is there a fix for that?
 
I am concerned about the adjusting nut on the #1 exhaust valve being looser than the other ones. I suspect it will back itself off again, probably sooner than later. Is there a fix for that?


Take it out and clean the threads with break cleaner, put red lock tite on it and adjust it, you can heat it with a propane torch to set the lock tite, if you need to adjust it again heat it to 300*F and it will turn easy and when it cools it will lock up again. don't over heat it!
 
Is this engine stock? Where is the initial timing set?
 
Engine is completely stock, never been apart except for the intake. Initial timing set @ 10 degrees btdc.

You might try pulling in some more initial timing. Most times they can stand up "around" 20*. Thing is, when you pull it up that high, you need to find a way to limit the total mechanical advance, because it will be too much. As long as you can limit the total to about 34* all in by about 3000 RPM it will run great and not hurt a thing. It's just something you're gonna have to play around with to see "where" and "if" you get any spark knock.
 
Engine is completely stock, never been apart except for the intake. Initial timing set @ 10 degrees btdc.

Keep the timing where it is or close to it. The factory ran those engines on dynos for max power and reasonable mileage before they went into production.
 
The engine in question here is the 67 273 in my Barracuda. It has 80,000 original miles and I don’t think it’s ever been apart.

Symptoms:
-The car won’t idle smoothly under 1000 rpm. Anything under 950 and it starts to shake violently.
-The idle slowly goes up and down on its own, making it tricky to set the timing. Currently it reads 13 degrees btdc @ 1000 rpm. I can look at the balancer with the timing light and watch the timing move by itself.
-When I put the car in gear, it sputters and dies.
-A couple of the plugs I pulled out of it (I can’t remember which ones off the top of my head) were very fouled with wet oil.

Previous owner bought the car from the original owner 6 months ago. He pulled the original 2bbl and manifold to install a weiand action plus and a new 600 Holley 4160 w/electric choke. He also installed a crappy eBay distributor. He swears the car was running/driving and the timing just needed dialed in. I think he’s full of **** and decided to sell when he couldn’t get the car to run.

The car is a little hard to start, but fires up easily once it’s warm.

What I’ve done so far:
-Verified TDC on #1 with a piston stop on two different occasions.
-Timing set at approx. 13 degrees btdc at 1000rpm.
-replaced the burned up skip white distributor with a newly rebuilt 273 Commando piece from halifaxhops.
-installed a Mopar electronic ignition harness, ignition box, and a solid state VR and coil from Standard. Plugs and wires were replaced.
-backed out both screws on the carb, squirted in carb cleaner and blew it out with compressed air.

Nothing so far has helped at all, and it keeps getting worse. Just did a compression & vacuum test:

Compression Test:
Cylinder
1 - 65/75
3- 130/125
5- 105/105
7- 80/80
2- 105/115
4- 115/115
6- 120/130
8- 105/105

Vacuum:
It pulls 15 at 1100 rpm, 14 @ 1000, 12 @900 as the engine shakes and dies.

I’m not sure how to interpret vacuum readings, but I assume the compression test means the heads need rebuilt. Can anyone offer some insight?



Adjust the valves and redo the compression test...


Here's a good link to help you understand and interpret vacuum readings:

Vacuum Gauge troubleshooting


I would also recommend changing the timing chain... Those old nylon coated gears on the 273/318 were junk... The nylon gets old and brittle and chips off, causing a loose chain, and can even allow the chain to jump a tooth... It will also cause your timing to jump back and forth and making it difficult to set the timing... I changed the chain on a 68 318 with 80 k miles to a double roller and gained 2 MPG it was so sloppy....

Installing a new good quality double roller timing chain and gears will make your timing more consistent and your idle smoother and vacuum reading smoother and more steady...

I've run this chain for decades in all of my engines and they hold up great... It's a true roller double roller timing chain one step above the stock 340 chain... I put one in an engine and ran it 125,000 before refreshing it up, and this chain was still in good shape... I replaced it with a new one anyway because I got it for $50 bucks back then and it was worth the piece of mind to have a new one...


Here's the chain that I use....

Edelbrock Performer-Link True Roller Timing Chain Set


Here's what the original timing chain gear can look like after 50,000 or more miles....

DSC01942 B.JPG




DSC01942 B2.jpg




DSC01945 B.JPG




DSC01945 B2.jpg




DSC01949 B.JPG




DSC01949 B2.jpg
 
Keep the timing where it is or close to it. The factory ran those engines on dynos for max power and reasonable mileage before they went into production.

No, they did not. But that'll just be your little secret.
 
Adjust the valves and redo the compression test...


Here's a good link to help you understand and interpret vacuum readings:

Vacuum Gauge troubleshooting


I would also recommend changing the timing chain... Those old nylon coated gears on the 273/318 were junk... The nylon gets old and brittle and chips off, causing a loose chain, and can even allow the chain to jump a tooth... It will also cause your timing to jump back and forth and making it difficult to set the timing... I changed the chain on a 68 318 with 80 k miles to a double roller and gained 2 MPG it was so sloppy....

Installing a new good quality double roller timing chain and gears will make your timing more consistent and your idle smoother and vacuum reading smoother and more steady...

I've run this chain for decades in all of my engines and they hold up great... It's a true roller double roller timing chain one step above the stock 340 chain... I put one in an engine and ran it 125,000 before refreshing it up, and this chain was still in good shape... I replaced it with a new one anyway because I got it for $50 bucks back then and it was worth the piece of mind to have a new one...


Here's the chain that I use....

Edelbrock Performer-Link True Roller Timing Chain Set


Here's what the original timing chain gear can look like after 50,000 or more miles....

As said earlier, 67 down 273's should have a cast iron cam gear. Right on about a good double roller.
 
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