Hello all! I am in the process of adjusting the rockers on my '57 312. Can anyone tell me how to identify which ones are the intake and which are the exhaust?


Thanks!

 

Looking at the cylinder head from the exhaust side, the rockers are in E I I E E I I E order, from left to right.

Another easy way to tell is that the exhaust valves are closest to the exhaust port; on a wedge head like the Y, SBC, etc. the valves are immediately "above" the exhaust port.

Here's a couple of pics, borrowed off the Bay. The exhaust valves are smaller & this holds true for virtually all production engines:

 

Homespun 91- Thank you for the information! This is exactly what I was looking for. I took a stab at it and "adjusted" the rockers to the point that it will barely run (I probably had it reversed-I for E, etc)! Hopefully now, with this information, I can get back on track.

Thanks again for your help, it is appreciated!

 

The big thing is to make sure that the lifter is on the base circle of the lobe when you adjust it. If you get that figured out, then it's smooth sailin'.

BTW, those are some of the famous ECZ-G heads, judging by the casting #.


Bonus question for anyone: what would be a good reason for having exhaust valves that are larger than the intakes- or at least closer in size than the norm?? There are a couple of valid reasons...

 

OK, I have another question. The Eickman book says, to adjust the rockers, to crank the pully until the 1 piston is on the compression cycle. Is there an easy way to tell if you are on the compression cycle(as oppose to power, etc)?


Thanks!

 

Watch the intake valve open on the intake stroke. The next time the timing marks align, you are on TDC, with both valves closed... Hopefully... This applies to #1 cylinder, then you follow the 'rotate crank 1/X turn, adjust valves #X, .... etc'.

tom

 

Exhaust valves are always smaller than intake valves because the exhaust valves are only open when the exhaust gases are under high pressure and high heat--and there is inherently greater flow.Intake valves pass gases at ambient temperature and intake manifold vaccum --not as inherently efficient.

And smaller exhaust valves permit larger intake valves--for a given bore size.

SC/turbocharged engine wouldnt need to have the intake valves larger than the exhaust as is the norm on normally aspirated engines.Larger exhaust valves would also have the added benefit of having more of a seat area--and thereby better cooling of the valve head.

 

Bingo! That sounds like a winner! Nice explanation CBX.

 

Pretty close. I'd say about 99.5 out of a 100.

The other reason to do it, following along the same lines, (actually a little more so), is the use of nitrous oxide. It produces very large amounts of exhaust gas, often more than a turbocharged/supercharged engine, (always, of course, depending on the particular engines you're comparing, at any particular time). And the amount of liquid happy that's going in.

I have never done what I would consider to be the "ultimate" nitrous engine (nor has anyone else that I've seen), but we did several SBCs a few years back that used 1.8"+ exhausts, along with some rather radical exhaust port work. To fit a 1.8, you generally have to do unpleasant things such as relocating valve guides and spark plugs. The state of the art of heads has progressed some, but no one's really done a dedicated nitrous design casting yet, that I've heard of.

I suppose, if we split hairs, that there are a couple of cases where there has been more ex. valve area than intake. Flathead diggers occasionally swapped intake ports for exhaust; & somebody, I forget who, maybe Bugatti, used 1 intake & 2 exhaust valves on a supercharged GP car. I also know of a couple of nitrous engines with some rather interesting valve mods...but I didn't build 'em & at least two of them are still going in 2006, so I'll say no more.

 

On that other brand that wears a bow tie, I've checked valve clearance with a GO-NOGO feeler gauge with the engine running. Do any of you check valve clearance on the Y-block with the engine running?

 

You may have had another problem if it wouldn't run very well after you adjusted it.......


You could adjust all the valves at the same setting and it would probably run ok.....


ENSURE that you have #1 on TDC before you proceed.



Regards,

Rick







NOW..........how about CBX valve adjustment!......well you have to have a micrometer and a whole bunch of little tiny discs!!!! (And a lot of time!!)


I bought one of those new in 1983 (it was a 1982) I rode it for 13 years and sold it for almost as much as I paid for it!


I wish I had it back!! It sounded like a sowing machine at idle.......music to my ears!!!