273 valvetrain question

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Thanks, wasn't planning on taking the whole car apart. I'll do some research and see what I can come up with.
 
If you are going so far as to replace the cam, it would be not much more to pull the heads to check the gaskets, and maybe put in better ones. If the PO used the stock Felpro out-of-the-box head gaskets, that will drop compression ratio almost 3/4 of a point over the original .021" thick shim head gaskets, so it would be good to get any such gasket out and put in the .028" 1121G's.

BTW, what head casting PN's did you find?

While there, take a pix of the piston tops to see what you have in there. Then the SCR can be better determined and a better cam choice made. I know I would do this in a heartbeat with such unknowns in the engine at this point.

This really made me chuckle:
AJ/FormS said:
I would think that is too much duration for a Low compression 273. Your Dynamic compression will fall into lawnmower country, and acceleration below 2800rpm will be measured with a sun-dial,lol.
Click to expand...
 
nm9stheham said:
If you are going so far as to replace the cam, it would be not much more to pull the heads to check the gaskets, and maybe put in better ones. If the PO used the stock Felpro out-of-the-box head gaskets, that will drop compression ratio almost 3/4 of a point over the original .021" thick shim head gaskets, so it would be good to get any such gasket out and put in the .028" 1121G's.

BTW, what head casting PN's did you find?

While there, take a pix of the piston tops to see what you have in there. Then the SCR can be better determined and a better cam choice made. I know I would do this in a heartbeat with such unknowns in the engine at this point.

This really made me chuckle:
Click to expand...

That may be a good plan. I'm not an experienced engine builder, so thats why I am hesitant. I have an 09 Challenger and done bolt on stuff and installed a procharger system. Clutch, headers,rear ends, etc. Only motor I have helped build was father in laws Miata. haha So I haven't been on the inside of too many motors.

Head casting is 4323302 and matched a listing for 85-86 318 "fast burn" heads from what I saw.
 
Well, at least, a head R&R is not nearly as challenging as rebuilding the bottom end. There are no precision measurements and setup work that I can think of in the cam change and head R&R work. Though timing in the cam with a degree wheel would be wise, and some might consider that precision work. But it does not involve machining and measuring in thousandths of a degree.

You need to be draining the block for the cam change anyway. And you can check the valve to piston clearance with the new cam if you do this.

(BTW, I have a 09 Challenger too....)
 
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Well I think I went a little deeper into this than I thought I would.
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Now yer talken!!! ya wont regret the higher compression piston's at all! it make s a HUGE difference with our small displacement little 273's! you will more than likely have a 91 octane at best motor now. but it will run good! What pistons were in there to begin with? unless you have a loose converter (2500 & up) or 3.91 & up out back id keep the duration @ .050 limited to 220.
 
It had the flat top 2bbl pistons. At some point I'm guessing either the original motor blew up or rebuilt it a long while back and couldn't get (or afford) the domed pistons. It has the valve covers and air cleaner for the commando, weird that someone would go to the trouble to make it look like one if its not. No idea what converter is in it. That may be helpful to figure out while it is out.
 
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