68thumper

I purchased my car from a forum member last year and decided it was time to check the valve lash. The motor is a 468 with a solid roller cam and roller rockers. I don't know the specs on the cam. I have received Lars write up and performed the check today. I found the valve lash set at .029" +/- .001 on both exhaust and intake. I don't know if this correct; seems high to me. It has AFR aluminum heads. Any suggestions would be appreciated.

cv67

Probably hot lash did you check it cold or hot?
Some cams require more than others.

68thumper

Warm...I ran the car earlier in the day. Nothing I touched was more than maybe 90 degrees. I understand the difference between cold vs. hot lash. But .029 seems real loose to me. I've used .020 on other motors. I like to run the lash a little on the tight side.

TimAT

Lars papers give you the show. I run mine at .030, some cams like .024 or .026. I've tried all combinations of .024/.026 and didn't see/feel any real gain for the extra hassle. .030 is easy enough and it seems to work fine for me. If you can figure out what cam you have, the specs from that will give you a good place to start.

68thumper

I am concerned about having to much slop and beating the solid roller lifters to death. A wide lash seems to be the root cause of roller lifter failures from what I have read...

Are you running solid roller lifters?

Les

It seems like the previous owner would have that info. At the risk of sounding like Captain Obvious, have you tried to contact him? Out of curiosity I checked Comp and Crane cams for their lash specs on street solid rollers and they all came in at .016-.020. I'm really not sure if older solid rollers ran with more lash.

68thumper

You won't believe this but I emailed the previous owner about 2 weeks ago and he just replied to me about half an hour ago confirming that the comp cam spec card I have in the binder he gave me is the correct cam. There are other camshaft notes with other grinds so it was confusing...so mystery solved.

Odd thing is the cam card says .026 on both exhaust and intake. But when I checked them with the motor a little warm it was closer to .030. Guess I will adjust to .026 or maybe a little tighter....020????

Les

Well there's some good news! If you're going to adjust them cold, which is my preference, a quick call to Comp should get you a good number to work with. Off the top of my head I think a difference of .003-.004 is about right.

oldalaskaman

if they're 'close ? to 30', and if specs are 26, you're not to tight, sound good actually, if they're not rattling and not to tight , why adjust?

68thumper

The motor sounded loose (rattling) hence the reason for me wanting to check them. Since I have solid roller lifters I am thinking of running them a little tighter. I am going to call Comp Cams in the morning...

cv67

My hot lash cals for .026 also
I run them between .021 and .022 cold seems like anymore might be a bit too tight. Shouldnt hurt a thing. You could go .020 but I wouldnt go further than that

oldalaskaman

that makes sense

TimAT

No roller lifters- just the old time solid flat ones. Rollers ususally have much tighter lash so things, as you correctly pointed out, don't get beat to death.

Now that you have the specs, you're all set.

68thumper

Update....I found information on Comp Cams website that said it is ok to run the valve lash .006 tighter with aluminum heads so I adjusted all the valves today to .020; spec on the card is .026; they were set at .030. Car sounds sooooooo much better at idle and when I am driving up along side a wall or another vehicle I cannot hear the rattling as before. Performance does not seem any different...it's still a handfull...

Scottd

Let me ask this silly question.....does .004 really matter? I build guns and for most specs, if Im within .005, Im golden. I would just assume that if you are within .028 and .032 you would be fine??? I guess I just doubt the accuracy of a feeler gauge down to this level of accuracy. If it was a dial caliper, sure....
(not being a dick here, Im genuinely curious)

68thumper

Not silly at all...you would think a few thousandths here or there would not be a big deal..but in fact on a high performance motor with all the vibrations, harmonics etc...going on there is a huge difference between .026 and .030 and the .020 I settled on. I don't know all the physics involved but I can tell you from experience by having a couple "we blowed the motor up parties", performance and reliability is all about maintaining strict tolerances. I'm pretty good with a feeler gauge..

TimAT

Clearance is important. Everywhere. I worked in a diesel shop for a while- did a bunch of tune-ups on the OTR diesel stuff. The standing rule was you had to be within 10% of the engines rated horsepower on the dyno after the tune. Over 10%, it was set the overhead again- and the second time was free working flat rate. I consistantly between 5 to 7%. Just because of the "feel" of the feeler gauge and injector depth gauge.

68thumper