I was wondering if any of you guys have more aggressive aftermarket cams, and know if messing with the exhaust valve lash has netted you any additional gains.

Not too long ago I did a valve lash on my JUN cams and noticed that the intake side was very tight and the exhaust side was very loose. I set it to 7/8, but was wondering if you guys have found power with a loose exhaust lash on bigger cams.

Thanks,

Paul

 

As a matter of fact, i noticed the same, the Intake valves were tight and exhaust valves were loose...like you we set them to stock. I never thought of playing with the lash on the valves.

 

well you can make your lash tighter and that would make your cams open the valves larger.

 

ive always wondered that too, how the valve lash affects performance, i always do it as per spec of the manufacturer

any advantage of tighter spec of intake side? looser exhaust side? both?

 

one thing I would guess as an issue to think about would be the timing of the valves. Scavenging would be effected a bit, due to valve lash settings correct? As stated in a previous post, the tighter lash would open the valve farther, and would allow more flow. So, would that lead to better overall head flow charicteristics? I run my JUN IIIs at 7 on both sides.... I was thinking about going to 6 or 6.5ish...

 

We're talking about a couple 100th's of a millimeter of difference in valve lift and some duration. Not worth fussing over unless you're at your rope's end looking for power.

 

One thing to note: if you go too tight, your idle quality will suffer, and in extreme cases, you can burn valves.

 

I wouldn't think it would be worth it. Say you close up your settings by an extra 2 thou, it ain't gonna make much difference. I can only see bad things from running incorrect clearances...

 

if u look on dseries.org they are all about tighter valve lash. they tighten to about .005i and .006e go there and just read up, the tighter valve lash in most opinions give most gain to low end.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by deepgreengsr &raquo;</TD></TR><TR><TD CLASS="quote">well you can make your lash tighter and that would make your cams open the valves larger.</TD></TR></TABLE>
sure, but you run the risk of burning the valves if they don't close correctly

 

I adjust the intake valves a little tighter, and keep the ex stock. They are the only ones that will burn from being too tight.

 

Loose is better. If the valves are to tight it will leak compression and it will lose power fo sur.

 

Tightening the lash by 0.001 gives about 1 degree more duration. That's the effect. This is how you test if your motor likes more duration.

That's the benefit of playing with the lash.