Valvetrain identity

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spinman_1949

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As I have explained the Dart I bought has what is likely a big cam and it is a solid lift cam to boot. Now I know it is unlikely that anyone identify it by the pictures I will offer here, but at least I figure you can identify the heads, rockers and possibly ffrom experience look at the fully open valves as opposed to closed. I took the pictures with crank at TDC cylinder # 1 in compression. One note. by feel it appears that I have more lash on the intake then I do on the exhaust. No measurements yet. Need to pick up a feeler guage. Also please take a look at the valve springs. Pretty sure double springs indicate a pretty stout cam.

Thx for the help.
 

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The rockers look to be factory 273 adjustable rockers. The valve springs aren't double springs, the outside is a spring, the inside is a damper.

Those springs "look" like the comp 901-16 springs that come with a lot of there mid range cams.

If I'm reading the number right the heads look like: 2531894 340 1968-70 2.02 1.60

I'm not sure if the 340 heads came with those style rockers or not. Someone else will have to verify that.
 
273 rockers
valve is a single spring with damper...not a dual spring
 
there j heads with cup and ball 273 mech rockers and its a single spring with a damper just the way ma made them
 
Stock 273 adj. rockers, "894" 68/70 340 2.02 heads and at the moment looks like single springs w/a damper. Will re look and see if anything else shows up.
 
The heads are the 68-71 2531894 with the 2.02&1.60 valve.The rockers are the 273/340 stamped steel.The springs are most likely for the high rpm range with some 300+lbs of pressure open and 160 closed.Springs is a heavy coil and a dampener inside.Mrmopartech
 
JimJim,

Heads have big X's on the plug side, so pretty sure they are X heads. Or I could be wrong. LOL !! You guys know more than I do for sure.
 
Hey Scott,

So are we a bit closer to knowing what we are dealing with? No double springs so maybe this is not such a radical cam after all. How about the lash. Seriously. The intake is looser than the exhaust. So what I am going to do is order a roller timing set and install that at zero. Then go back and do a lash adjustment. Say 20 and 24 intake and exhaust and see how she runs. Is that a plan?
 
spinman1949 said:
JimJim,

Heads have big X's on the plug side, so pretty sure they are X heads. Or I could be wrong. LOL !! You guys know more than I do for sure.
Click to expand...
they are the 894 on a quick look i thought i seen a j in one of the pics so x it is my mistake
 
Did the 340 come with solid lifters? I don't think it did. JMO
 
Yes, X heads.

I'd LOVE to see a 1971 340 installed in a vehicle that rolled off the factory line with a set of 894 heads.

Those are some sturdy stamped steel rockers. :)
 
Judging only from the pictures, it looks like the tip which rides on the top of the valve has a pronounced "arch" to it.. might be time for a trip to the machinist to have the tip machined flat again. If some are worn more than others that might explain the lash difference.. it's possible they all aren't worn evenly . Just food for thought.

Alan
 

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Good eye.

I thought the curve was engineered in. You mean that is supposed to be flat? HMMM??
 
alan627b said:
Judging only from the pictures, it looks like the tip which rides on the top of the valve has a pronounced "arch" to it.. might be time for a trip to the machinist to have the tip machined flat again. If some are worn more than others that might explain the lash difference.. it's possible they all aren't worn evenly . Just food for thought.

Alan
Click to expand...
very observant...
 
spinman1949 said:
Good eye.

I thought the curve was engineered in. You mean that is supposed to be flat? HMMM??
Click to expand...
The radius on the rocker tip is correct,if its flat you have a big problem. You really have to be careful with free info as it's not always good info.
 
I'm not claiming to be an expert in valvetrain dynamics.. just repeating what I read in How to Rebuild Your Smallblock Mopar.. and what my engine builder told me. You guys might be right.. now if it isn't flat across the tip..... Anything that wears metal to metal is going to need some touching up sometime.. and these rockers are all 35 years old at least. Just like a valve job, they need renewing from time to time.
Apparently durability or metallurgy isn't a problem! I'm just saying, it might be worth a little investigation...

Goldmember might be right. I'd have to look.. and it's been 7 years since I last looked at mine... geez. I swear, the car will get done someday.

Alan
 
think about how two flat surfaces would move in concert if both the valve tip, which should be flat and the rocker arm which shouldn't, but was flat. How would the contact patch change as the rocker surface which is now flat moves dynamically through it's range. If both surfaces were parallel, as soon as the rocker started to depress the valve, the contact point would move to the exhaust side edge of your valve tip.
 
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