Maybe I can offer something to help determine the correct lash for mechanical cam. In my experience with some "unknown" cams, I have found certain characteristics.
A hydraulic profile will have a very uniform, steady acceleration on the ramp of the lobe... right from the base circle. This can be observed using a degree wheel and a dial indicator on a lifter ( cam installed of course: ). Just for clarity, I'll use a hypothetical checking example / procedure...
From the cam's base circle, JUST as the lifter begins movement, rotate the crank 5 degrees, and note the amount of lifter rise... lets say it was .015". Rotate another 5 degrees, and the lifter would rise another .015". On a hydraulic cam, this basic pattern will continue to full lift.
A mechanical cam is different. Using the same procedure as described above, you will find that those first few degrees of crankshaft rotation ( at the biginning of lifter rise ), will result in a VERY soft, gradual movement of the lifter. That changes... QUICKLY. The contour / ramp of the lobe makes an abrupt increase in acceleration... on a good profile, providing a much more aggressive rate of lift than what the hydraulic lifter can tolerate ( this is the fundamental advantage of a mechanical cam ).
By comparison to the hydraulic profile, a mechanical cam may show figures like:
5 deg rotation... .010" lifter rise. Another 5 deg rotation... another .010" lifter rise. then the next 5 deg rotation... additional lifter rise of .020". In this hypothetical example, it's between .020" and .040", where you will find that your lash is to be set.
This can be determined pretty accurately. Rotate the crank back to the zero(0) position ( just before the lifter moves ). Now rotate the crank clockwise ( correct direction ), and watch your dial indicator VERY VERY carefully. You will be able to see this sudden increase in rate of lift on the lobe. It's the point, maybe .002" before that sudden increase in lobe acceleration, where your valve lash should be set. All mechanical cams are like this. In the case of the "hypothetical" cam that I just made up, we would have found that this sudden "acceleration" occurred at around .022" - .025" lobe lift... indicating that our lash should be set at approx .022".
Lastly, this explains why it is "safer" to run your valve lash a bit tight, rather than somewhat loose. If the above "hypothetical" cam was to be lashed at say... .030", it would allow the lifter to be off the cam lobe until that lobe enters it's "maximum acceleration" mode... thereby "hammering" the base of the lifter and that flank side of the lobe. THIS WIPES OUT MECHANICAL CAMS:eek: .
Running the lash a little tight actually makes the valve train parts more comfortable, but will often have a dramatic effect on manifold vacuum at idle, and can tax the valve springs in their effort to maintain control of the the valve train.
Hope I made sense
If you try this, watching carefully, you'll see that it becomes quite obvious
Oh... hot / cold valve lash...
I've never been able to get the engine warm enough when it's on the engine stand, so I can do a hot lash ... so, obviously, the first lashing is a cold one. I set to spec.
However, I NEVER EVER EVER leave it like thatno1: . I break in my cam, good hot engine, then do a hot adjustment... to spec. Not until I have done that, will I run an engine hard.
In my experience, with iron heads on these engines, valve lash loosens up about .002" - .004" when the engine is at operating temperature.
Haven't you ever noticed how your hot rod will have this radical vicious idle when it's cold, then kind of smoothen out when it's warmed up ?
That's the valve lash loosening, and reducing the effective duration of the cam.
Thanks again for your idea. I will try to check the travel of the rocker arms at the push-rod end. Not sure where to set the indicator. I'll try at the very top tip & in top of the ball to see it will make a difference. Lets hope it works. To see if I can find the correct lift numbers. Maybe I can find something in the Chevrolet by the numbers that way thats close.
Thank you Aubrey also. That a little tech. to me but I get the basics of it. I don't have a degreed wheel but I think I can find one.
Thank you, JIMMM!.
Cams ?... I understand .
now, that disected water pump thread ?
I'm lost . Don't have no cooling problems when it's 45 degrees outside:eek:
( yes, it really was that cold a couple nights ago ).
It's supposed to be 90:eek:
Aubrey, Your camshaft description was interesting. All sounded real good until you got to the last two sentences. Afraid I cant agree with that. In my opinion, the radical, vicious idle is the result of no heat in the engine. I believe that you could pull the valve covers off of that particular engine, increase lash by .004 and you would still have the radical, vicious idle the next time you started the engine stone cold. Besides, different people use different methods. Some set -tight, some set loose. There could easily be .002 to .003 difference in one person setting at .028 and the next guy setting .028. Just my two cents.
Aubrey, Yes, I do remember the intake manifold baffle issue. You were right and I was wrong. So, what does that have to do with valve lash? I am sticking to my guns on this one. , ( we got bigger guns in Texas) besides I have got common sense on my side this time. Think about it.
No, 283guy... but it's the same problem.
All W block factory intakes have a sheet metal shield attached to the underside. One of the purposes is to prevent oil from being drawn out through the PCV/vent at the rear of the intake.
Yes, if you don't install that little "can" in the block on a small journal Chevy small block ( 265 283 327 ), you too, WILL empty the crankcase:eek:
You better check the coin prices. That 2 cent coin you show above is now worth between $8.00 & $10.00 dollars these days.
As for the valve adjustment issue I have checked into as best I can without pulling it out for now. Using a indicator and it looks like I have a stock 64 409 cam. So I will use the 64 spec's for now. Also found that my timing chain is going so after the Woodward Dream Cruise I will find out for sure when I replace the chain.
I ran .008 intake and .016 exhaust on the 58 315hp 58 Nicholson said that you need to get as much lift as the cam can give. But on the Crain in my 58 now run .018 intake and .022 exhaust which Crain says to run. This is supposed to be a 409HP 409 cam. Roy
The original Rhodes lifters set just like regular lifters. I set mine to 0 and then 3/4 additional turn and lock down. They are just fast bleed lifters. The sound they make like solids is the valve clicking down on the seat real fast. The NEW Rhodes lifter is more like a solid lifter. You bottom the pushrod in the lifter body and back it out the required amount. Kind of like a solid with an oil cushion for the freeplay. Check the Gale Banks website for more info.