I'm not sure I understand this??? If you set .005" cold and when the block expands there will actually be lash in the system more then likely, therefore no pump up would occur. Ofcourse, other problems will arise then. It's been said that the ls blocks expand roughly .010" when warm.

Edit: Are you suggesting the valve train components expand more so then the aluminum block and heads do???

 

Net, net, net...is this all a case for solid lifters in a modified engine?

 

That was .005" of the bottom not the top. The discussion was about limiting compression in the lifter. It would expand with the block expansion when hot, because, as you said, the block expansion is greater.

 

Sorry, i'm rather slow at times. Could you please elaborate??? Thanks.

edit: Nevermind, see above. The confusion was generated from the gentlemen above you speaking of .005" pre-load, not .005" from bottoming out. I got it now

 

As I mentioned, there are a lot of variables. For example, what if the car has a great cooling system and say a 170 thermostat, but is being track raced with an inadequate oil cooler. The oil in the sump reaches 275 F. but as is known, may well be 25 higher internally. This means the lifters and push rods are running 130 degrees hotter than the block and expanding proportionally...

And yes, I think there's a great case for solids: More power and RPM potential, even with similar lobes, tons of lobe families to choose from (I think CC alone has probably 20 or more, with dozens of lobes in each) and they don't need attention all that often unless you go pretty radical on the profile and use the top end of the tach often. (My factory solids '70 Z28 would go for many thousands of mile without adjustment, but the rocker arm 'lock' nuts would back off any time I ran it over 6,000, until I switched to aftermarket ones) And if you do drive it hard all the time, you should be checking things regularly anyway. Running the lash is a fine opportunity to look around...

 

Yes as the oil pump spins and creates a void with lower pressure, the air in the crank case is pushed up the oil pump pickup tube and into the pump's low pressure inlet side of the housing. At best the pump could drop the inlet pressure down to absolute zero PS1 so the true pressure differential existing between this low pressure side is directly dependent on the oil pan pressure. This is also why you start seeing rods flying often when peoiple run a lot of vacuum on wet sump engines as well.

 

I love your sig, yeah everyone is a mechanic here with a 10 second car.

 

I love "Z"'s signature too.
It looks like we race books, not cars in this section.

Rich

 

So why isn't every one here running solids?

 

Well, I now have an aluminum 495 big block in the Camaro, with the factory ZL-1 solid flat tappet cam (Trivia question: What engine has the highest lift cam ever factory installed in a GM production vehicle? Hint: It's not the LS7...), soon to be replaced by a custom solid roller, and my last two daily drivers ('87 Metro and '03 Vibe) both were factory-fitted with solids, so I'm doing my part!

 

I'd conisder a solid cam for a weekend driver. Valve cover access on my second
gen is a snap.

I don't think most people are prepared to spend the coin to properly fit a solid
cam and valvetrain in a daily driver. I doubt they'd want to check lash every
other week on top of that.

A friend of mine runs Top Sportsman and he will check/adjust the valves after
every pass. It's a high maintenance setup, I think that's the main reason most
shy away.

 

There is a thread elsewhere on LS1Tech where people discuss how much they spent. Doesn't sound like $$$ are the issue. If using an AFR, ET, Dart, or World head, the cost is set of shaft rockers.

Your friend is probably a great racer, but not the last word on valvetrain maintenance. They have been used extensively before the latest phase of emissions laws. For example, my Supra TT's direct action valve train is solid.

 

Actually my friend isn't all that good at bringing home the win, but that's Ok.
I wont say he's god when it comes to motors, but he's pretty good at what
he does. Checking valves after every pass might seem overkill, but when
you're spinning a motor to 8000 RPM rods can bend, and things come loose.
It's a sanity check if nothing else and could save the top end from damage.

I'd say people will shy away from solid cams due to maintenance over costs,
and possibly the justification of actually needing a solid setup.

As for the mechanical considerations, I wouldn't stop at rockers alone.
Depending on the lobe profile springs might need to be changed, harder rods,
maybe stronger studs or a girdle. Maybe costs are an issue for some at that
point. Who knows. Just sharing some info.

 

Shaft rockers don't need girdles and replace the studs with bolts.

 

Yes, the adjustable shaft rockers would be a nice upgrade for high RPM stability.

 

I installed my stock rockers on my 408,afr headed motor,with 7.4 pushrods.I tighten the rocker to zero lash and then turned it 1 full turn then it got tight,am I good as far valve lash is concerned?

 

I'm sure you'll be fine for the most part, but it's tough to gauge the seat
depth using the 'wrench turn method'.

I think it's a little too much when comparing the wrench angle for 0.005-0.020"
on a standard thread stud. For example, 0.005" is about 1/8th turn of the
wrench.

With a roller cam, you don't need much pre-load at all. You will pick up some
RPM and power with a well adjusted valvetrain.