So what am I looking at exactly

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gtgto

gtgto

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I decided to take off my valve covers and clean them up and give them a fresh coat of paint. I was expecting to see stock parts under the valve covers but found adjustable rockers. I don't know any history of the engine other than it is the matching 340 that came in my car. Is there anything I can assume has been done to the engine without tearing it down. Do adjustable rockers mean I have a solid lifter cam?
IMG_3395[1].JPG
IMG_3397[2].JPG
 
Although that's the only way those rockers came on the 273 was with a solid lifter cam. I kinda tend to agree it's probably a hydraulic. No way to know for sure unless you try to see if a lifter will bleed down.
 
If any of the rockers have obvious clearance,eg around 20 thou it would be a solid,i have run them on both solid and hydraulic lifter cans in 340s over the years.
 
Correct me if I'm wrong, but those don't look like stock 340 spring retainers, to me. Can't tell for sure, from the pictures, but it doesn't look like there is a damper inside the spring. Didn't 340's have dampers? Been many years since I have seen a stock 340 valve train, so I could be all wrong.
 
I don't know 340's but weren't they born hydraulic lifter with stamped non adjustable rockers? Definitely no damper springs in assays.
 
I noticed your only running a single spring for the carb linkage. If that ever comes loose or breaks your in for a WOT hell ride. I always run doubles for safety
 
gtgto said:
Is there anything I can assume has been done to the engine without tearing it down.
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- Read the head casting numbers cast on the top of the head where the runners are cast, and compare them to the year and block numbers.
- Take compression readings on all 8 cylinders and report them; those may or may not tell something about pistons
- Borrow a dial indicator and measure the peak lift on any one intake and anyone exhaust valve; this will tell you if the lift is different from the original cam lift
- Pull the rocker assembly off of one side and look down the pushrods holes at the tops of the lifters; if they are hydraulics, you will see wire clips or c-clips inside the tops of the pistons, around the socket where the pushrod sits; there retain the internal pistons . (You might even bee able to tell this by looking past a pushrod as they are but it may be tough to tell without removing the pushrod.....)
- Perhaps even borrow a borescope and look at the top of one piston through a spark plug hole

BTW, looking at the 3d spring in the 2nd pix, it almost looks like a 2nd spring is lurking in there; hard to tell. The OP should look inside the valve springs and tell us if he sees a smaller spring wrapped in the opposite direction, with small round spring wire
 
I see a U, so they could be 915 castings (same as J,0 & Z)

The rockers are from a 273.
 
DesertRat said:
I don't know 340's but weren't they born hydraulic lifter with stamped non adjustable rockers?
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1970 T/A 340s - Adjustable rockers with hydraulic cams.

All other 340s - Stamped steel rockers.

(the 273 rockers & 340-6 rockers are different & not interchangeable)
 
start the engine with the valve covers off, hydraulic lifters will spin as well as the pushrods. mechanical lifters do not spin.
 
mammlouk said:
I was just gonna say that they look the same as the rockers in my 273.
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Is there some kind of benefit of installing the 273 rockers as opposed to what would've came on the car from the factory? I will check out the springs later on and look for other evidence of my stock and original 340 not being stock. When its running it sounds good but doesn't have a choppy idle like it has a cam upgrade.
 
discharger1332 said:
start the engine with the valve covers off, hydraulic lifters will spin as well as the pushrods. mechanical lifters do not spin.
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All flat tappet cams have lifters that spin, if it doesn't spin it wipes the cam lobe.
 
gtgto said:
Is there some kind of benefit of installing the 273 rockers as opposed to what would've came on the car from the factory?
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Yes: they are adjustable. They may have been required due to the block being decked, heads being milled, or by the type of lifter being used. All solid lifters require adjustable rockers. Some hydraulic lifters require adjustable rockers. Rhodes is one brand that comes to mind.
 
Sedanman said:
I noticed your only running a single spring for the carb linkage. If that ever comes loose or breaks your in for a WOT hell ride. I always run doubles for safety
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Doubled up on the throttle return spring today. Thanks for the heads up on that
 
Glad to help. I have heard of too many crashing their cars because something went wrong
 
Took a couple pics today. There does appear to be an additional spring inside the valve spring.....I don't plan on tearing down the engine to see what other goodies have been added but what can we assume if anything with adjustable rockers and doubled up valve springs?....I'm gonna try to check out my compression of each cylinder tomorrow if I get some time.

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those are std 340 springs, i think someone just changed the rockers over. very common, the std hyd rockers are not very uniform and with adjusters you can get much more precise. but the engine looks to have been rebuilt? so could have a mechanical cam.if you look at the front of the motor where the head meets the block, can you tell if the head gaskets are aftermarket? its clear some of the other gaskets have been rtv'd. if it were mine, i would make sure it runs good, is safe and i would destroy tires at will with it. enjoy
 
spring and damper.... ran those rockers on many of my small blocks. much more robust than the stamped steel, and I usually ran solid cams anyways.
 
Take the rocker shaft off. Stick a telescoping magnet and see if you can pull a lifter out. Then you will know if it's solid or hydralic.
 
With the engine running take a Approx .005-.010 feeler gauge, and see if it will go between the rocker and valve stem. If it goes, and the engine changes how it sounds, it is probably a solid cam. If it goes and the engine changes how it sounds, but then smooths out again, it is probably a hydraulic cam, with misadjusted rockers. If it does not go, it is hydraulic cam
 
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