Does alum block deck height grow, or just the lash?

[sjvalleydave]

Totally agree on the rockers ratio also..We run 1.8 straight across...Very similiar engine with 1.9/1.8 split has his intakes hanging open a couple of thou when they are accurate at temp...I wish it was mid 70's here...107* today!! LOL

[MadBill]

The case can be made for quickly just measuring, but to save cool-off time not adjusting, one pair of valves hot off the track, then determining at leisure the difference to cold and using that spec to cold lash them in the future. However some would point out that all cylinders do not reach the same equilibrium temperature, so all eight should be checked. Perhaps doing one bank, then running more laps and checking the other, would capture any variations and going back to re-check the first would show how much lash changed in the time it took to go through however many cylinders.

Then again, perhaps we obsess to excess over the issue. After all who knows what the true running lash is at 8,000 RPM with the exhaust valve head a bright red at 1500° F., chamber temps well above the bulk coolant temp, etc., etc...

PS: A reminder that tight lash cams are not your friend with big all aluminum pushrod engines...

[Barry_R]

My junk is all FE Ford. May not directly relate to anything.
All aluminum working on dyno, a room temp lash of .003 with give a hot lash of .016-.018 pretty much every time.
My deck height is a nominal 10.17, rocker ratio is 1.76, valves are +/- 5.5" long, and pushrods range from about 8.9-9.4 depending on type and heads...

[ultra19]

aluminum 10.180 deck height Brodix BBC wth aluminum heads. I set cold lash at .004/.0016 and end up at .020/0.030 for nearly every pair of rockers. it grows quite a bit and if the engine is dead cold i have to warm it, shut it off and let it heat soak, and then warm it again to get it to fully expand before i can check the hot lash.

[Caprimaniac]

I usually get it warmed up properly. Set one ex and one in. Sit back in the chair (or do some work?) to let it cool & then set cold lash for all compared to these two. I did the mistake taking measurements this year with engine in the 140- range (guesstimate) and now moving up to the 180- 200 range, I find lash too big.

It looks like I should be in the 002-003- range cold with the 1.6 ratio rockers SBF compared to Barry's rresullts on the FE.

RS