273 needs new heads, suggestions

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EmersonC

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Ok so I have had issues for a while with my 273 and I finally decided to have my mechanic take a look and he quickly found my problem. The number 5 cylinder has little to no pressure. He said he put his thumb over the spark plug hole, cranked the engine and it didnt even push his thumb off the hole. He also took a look at the spark plug and it looks brand new, not good. His thought is the valve/valve seat has a serious leak. So I am thinking what options I have to replace/fix this. Here is my thought process....

  • My ultimate goal is to swap out to a 360 beast :burnout:, but this is at least a few years down the line
  • Would the eddy heads fit a 273 now and in a few years could they be placed on a 360?
  • Should I go with something other than eddy?
  • Probably stupid question but the eddy heads say, "truly bolt on" But are they really? Do they come with valves, rockers, springs and all that good stuff?
  • My philosophy is to upgrade rather than just replace, but like all of you money is always a issue
SPECS: Car was origionally (according to the VIN) a /6 and someone other than me put the 273 in so I dont know what cam it is running (maybe stock?) or any of that bottom end stuff. I have on my '66 Dart GT Convert:
  • Eddy preformer intake
  • 600 cfm 4bbl
  • Mallory digital breakerless dist
  • MSD Digital 6A box
  • Ammeter bypassed
  • 100amp alternator
  • 8.75 rear with posi (3.55)
  • Ill try to get the numbers off the engine as soon as i can
Suggestions? or Links...
 
While the thumb over the spark plug hole netted you little or no pressure, a leak down on that cylinder will tell you volumes more about the condition of the cylinder. The thumb test just gave you a place to start. Do a leak down on the whole motor; it might not be a head issue at all.

Eddy's will bolt down, and they come loaded with valves, etc. HOWEVER, you must notch the cylinders for valve clearance. If you went the Eddy head route, get the closed chamber, keep the chamber sorta on the small side, so you don't loose too much compression. Though you really need to know what pistons you have in the motor; hey it could be a Commando, God only knows and he ain't sayin.

If you went the Eddy route, and later did up a 360, the heads will swap over no problem, you can adjust your final compression with pistons, deck height and gaskets.

Good luck!
 
I would take it apart and know what is needed first.
 
You'll have the same money if you rebuild your current heads or just about any other factory head. If your goal is a 360 down the road, I would fix what you have now and focus on building a 360. Keep in mind that 360 heads have larger chambers valves and ports. While bigger valves are almost always a good thing, the larger chambers will hurt compression, and the bigger ports will hurt low RPM throttle response pretty much cancelling out the gains from the bigger valves. Sure, you could modify 360 heads to work well on a 273 by milling to reduce chamber size, but then the chambers might be too small to work well on a 360. The Eddy's are great heads, but on a mild 273 you won't gain enough to justify them.

If you planned to keep the 273 I'd suggest looking for a set of the late 318 "302" castings and putting larger valves in them. But you could get nearly the same results with your current heads. Best bet would be fix what you have now and grab a 360 Magnum out of a junkyard and start building.
 
JBurch said:
Eddy's will bolt down, and they come loaded with valves, etc. HOWEVER, you must notch the cylinders for valve clearance. If you went the Eddy head route, get the closed chamber, keep the chamber sorta on the small side, so you don't loose too much compression. Though you really need to know what pistons you have in the motor; hey it could be a Commando, God only knows and he ain't sayin.
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JBurch, could you elaborate on the notching of the cylinder, I am not sure that I follow what you are getting at.

And C130 Chief, if it will cost be just about the same to rebuild origionals as it would to buy new aluminum heads then I would definately go for the lighter weight heads.

I know eddy is a big name with proven performance, but are there any other aluminum or aftermarket heads that I should be looking at?
 
Stick with the 273 heads on the 273. 1.88 intakes barely fit inside the bore. Anything larger is asking for trouble or money and time. Then get an extra engine and do whatever you want with it. Half a day to swap it in, and you won't be down very long.
 
I agree with 66fs here. Do a more thorough investigation about what's really going on inside this 273, then make your decision......as in, make sure it's a cylinder head problem only. You might be able to get away with fixing it very cheaply. But I'd definitely keep those 273 heads on the 273, then start focusing on the 360 build/parts acquisition separately.
 
JBurch said:
While the thumb over the spark plug hole netted you little or no pressure, a leak down on that cylinder will tell you volumes more about the condition of the cylinder. Do a leak down on the whole motor; it might not be a head issue at all.

Eddy's will bolt down, and they come loaded with valves, etc. HOWEVER, you must notch the cylinders for valve clearance.
Click to expand...

I agree with JBurch. A leakdown test is a much better diagnostic tool than a simple compression test. The leakdown test is great for helping you pin-point where the cylinder is losing pressure from: intake valve; exhaust valve; rings; head gasket; or a combination of them.

Notching the cylinders is required when putting the big valve head on the 273 because of its small 3.63" bore. A notch has to be machined into the top edge of the bore to clear the large intake valve. It's not as simple as just swapping heads as the engine will have to go to the machine shop to have the notches done.

There is also the issue of port size. I don't know what intake or exhaust manifolds/headers you have, but the 273 ports are a lot smaller than the Eddy or 340/360 heads. Having the ports of the head and manifolds mismatched will create flow velocity and turbulence problems.

Also don't know what year heads are on your 273. If you have 64-65 stock heads and intake the intake bolts are at a different angle than the 66 and later ones and you wont be able to bolt up the early manifold to the Eddy or 66 and later stock heads.

Since it sounds like you are looking for a stop-gap fix to hold you over until your 360 is ready, I would first do a leakdown test to pin-point the problem. Assuming it is a leaky valve, I would pull the head and fix JUST that cylinder's valves. If everything else looked ok, I would then put it back together and drive it until your 360 is done and ready to install. Just seems like the most economical way to go about it.
 
Bigger valves don't work with out work(notching)
Either find low mileage 273/318 heads you can slap on now probably can find a set next to nothing or find a low mileage 360/magnum to drop it in now.
 
Thanks for all of the feed back everyone. I think I will try to do a leak down test this weekend to get a better idea of what is actually going on. I will also pull the engine/head numbers this weekend. Then if it points to replacing the heads I will look for a 273 replacement heads (or if I cant find good ones ill have a shop fix my stock heads). It is sounding like the 318 heads might also fit? Or are the valves on 318's too large to fit without modifications to the block?
 
273/318 heads are the same except 318 magnums, 318 heads are mainly open chamber though.
 
See what casting number your 273 heads are......if they are the correct, earlier castings, they should have a slightly smaller combustion chamber volume than the '68 and up, if I remember correctly. I thought I'd also seen those '64~'67's listed at 55cc's. Got this off the 'net......

Cylinder Heads

Year Engine Service Part # Casting # Combustion Chamber Volume (cc’s)

64-65 *273 *2532080 *2465315 *57.0-64.5
66 *273 *2536176 *2536178 *57.0-64.5
67 *273/318 *2806213 *2658920 *57.0-64.5
68-71 *273/318 *2843674 *2843675 *60.0-67.5
 
Send me a PM. I live here in Yakima. We have a local 273 expert here that maybe will give you some guidance.
 
318 valve sizes are the same as 273, just a slightly larger chamber. You can use 318 heads if you use both. Small valve 360 heads make a nice upgrade for a 273 and do make more power but they take a higher level of execution. Porting exhaust manifolds, centering chambers over the bore, milling the heads as mentioned above, intake and carb changes, then making the rest of the drivetrain to hold it. It also pushes the power band higher. Not a simple way to go.
 
66fs said:
318 valve sizes are the same as 273, just a slightly larger chamber. You can use 318 heads if you use both. Small valve 360 heads make a nice upgrade for a 273 and do make more power but they take a higher level of execution. Porting exhaust manifolds, centering chambers over the bore, intake and carb changes, then making the rest of the drivetrain to hold it. It also pushes the power band higher. Not a simple way to go.
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At this point I am leaning to simpler for now and wait till later to get the power and the 360 going.
 
So I took a quick look for the EIN and couldn't find it without hacking the car up. Where can I find it on the block? I was able to find the casting date and it is 11-11-65. Found that on the passenger side.
 
Now you know why anybody with a pre-68 car that says it's "numbers matching" is full of it. Look on the left bank just below the deck.
 
I think if it was me I'd just have that head fixed. Pull it and look. If it's a burnt or sunk valve that's not a big deal to fix. Not rebuild the whole head - just fix the issue, clean, and reassemble.
 
heads: 2658920-3 also had 01216
year on block: 11-11-65
vin lp27b62501036
trans: 948-2

With the headers, power steering and brake booster it will be hard to see the block number from above. Hopefully I can find my jack (just moved to a new house) and get that to you all thus weekend
 
moper said:
I think if it was me I'd just have that head fixed. Pull it and look. If it's a burnt or sunk valve that's not a big deal to fix. Not rebuild the whole head - just fix the issue, clean, and reassemble.
Click to expand...

X2, since you want to completely redo a bigger engine in the future.
 
I'm no expert but it doesn't seem rigt to fix just the one cylinder. Because chances are the others could use some work also. Now the tricky part of trying to find a machine shop in Seattle. For those in Seattle, im trying to find a shop in the Ballard area, any suggestions?
 
Fix the old heads or too bad you can't find a pair of #302 castings to put on. Hardened seats are good for unleaded gas. Hopefully they would be in good enough shape just to bolt on. tmm
 
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