[adamo]

So the recommended lash is .006 hot? I set mine at .006 cold. So this means my hot lash is too loose?

[Larry Navarro]

may not be in other applications but it worked for me.

[adamo]

So I guess check my lash once the engine is nice and hot. Then subtract the difference from whatever my hot lash is to .006. Then tighten up the cold lash the difference then check the hot lash again?

[Overkillphil]

Originally Posted by adamo

So the recommended lash is .006 hot? I set mine at .006 cold. So this means my hot lash is too loose?

Hot would be tighter in this scenario, perhaps too tight.(?)

[adamo]

**** now I am confused lol. When I first set up my combo I set the intake at .006 cold and exhaust at .008 cold. So is that what the lash should be when it is hot?

[Larry Navarro]

Given the example from Darby, set the cold lash at .003" (instead of .006").......and after engine gets to operating temp., check the lash hot and adjust as required to achieve the lash of .006".
The thermal expansion in components can lead to confusion, as it did with me, but after thinking about it more, it made sense.

[goatman65]

Dave mentioned that Marcel has a 271/278 @ .050 cam in his street 468, Now that sounds like my kinda street cam.

[grandville455]

.006 x rocker ratio, so if 1.5 the hot lash shouldn't be more then .009...., all depends how much expansion when warm to achieve the desired amounts...

[grandville455]

Originally Posted by goatman65

Dave mentioned that Marcel has a 271/278 @ .050 cam in his street 468, Now that sounds like my kinda street cam.

My cam is 265/270 @050 , on a 110 LSA its really not that aggressive sounding to me, depends how the tune is on the idle sound. Imo

[adamo]

So with a 1.65 rocker I should have .0099 hot lash

[grandville455]

Originally Posted by adamo

So with a 1.65 rocker I should have .0099 hot lash

Correct, you dont want to go over that, or your off the end of the ramp and not doing your valve train any good according to mike jones of jones racing cams, So set it cold get it good and warm drive around etc and see how much it opens up hot , then adjust accordingly to stay in that window or just below ,he's the one that designed my cam.

[Steve C.]

Response from Mike Jones / cam designer that Darby mentions here....

A few years ago I e-mailed him and asked if 150 lbs seat pressure might be ok with using solid roller lifters with the Comp Magnum High Lift hydraulic roller lobes number 3122 & 3120 used for the Old Faithful cam. His response:

"I don't know enough about the ramps used on those Comp lobes to be able to tell you what seat pressure you need. If they're gentle, 150# might be fine, if they're aggressive, it could take 180# on the seat. Some hydraulic roller cams have an opening ramp that's too aggressive to run with a solid roller lifter. You'll need to check with Comp, so you don't run into any issues."

.

[Formula8]

Updating this post. Turns out I had the opportunity to take the heads off and took the 1000 mile old 99838's to Paul K for a pressure test. He came up with 150 lbs at 1.8" which is pretty much what the catalog specs them at. Either way, since I had things apart and the motor will likely see some higher RPM this time around, I took the opportunity to upgrade to Crower's 68380X2 spring. It turns out this spring fits perfectly in the same space as the 99383 and depending on what installed height I want to run I can use the retainers Dave set my heads up with and I have sufficient seal clearance etc. Paul K tested this spring as well and it produced 210 @ 1.8 which puts me at 470 over the nose. Crower says it should be at 197 @ 1.8 FWIW. https://www.crower.com/valve-springs...-w-damper.html

With my combination of retainers and locks, I can achieve pretty much anywhere between 173 and 210 lbs (calculated) on the seat. My coil clearance is .09" at the 1.8" installed height. What do you spring experts suggest for a seat pressure?