mr T

recommendation that ive been readign is intake 10, exhaust 20....some guys u have read run 6/16??...what are the pros of adjusting tighter?...what about people with timing advances? what would 8/18 do for me? i cruise highway 80% of the time at 1800rpms...how would it ride? responsivness?...fuel consumption?

ps i bought the valve cover gaskets from cummins and might as well look at the clearance this weekend

clutch1

just set them at 10 and 20 and be done with it, timing is just advancing fuel

Tiger Rag

I've got mine at 8 and 18. A buddy of mine has his at 7 and 17. I think 6 and 16 is the min you can go to. 8 and 18 or 7 and 17 give you a little fudge factor. It is supposed to give you a little more power. I think it sounds like it runs better with the valves tighter.

BigBlue

I know I like the way mine sounds at 10 and 20. A lot smoother and noticeably peppier.

dodgezilla04

if the valves are too tight, you run the risk of them never fully seating. that is how they transfer heat to the head, you'll burn that exhaust valve really quickly if its too tight.

Muddin_dude06

You could also run the risk of piston to valve contact, if you have extended RPM's it could make things worse. I keep mine at 10 and 20...

mr T

thanks guys...I'll set it at 10/20...these guys running 6/16 why are they doing it? what is the benefit?...

Lil Dog

Most guys try to tighten up the valves to gain a little on valve duration. But fact of the matter is, the cam lobe profile is parabolic. So the overall net change in duration on tight valves is not worth the risk IMHO. If the CTD had problems with valve recession or poor intake valve seating, then I might bicker on valve clearances, however most failures are catastrophic that I read about and valve clearance wasn't the issue.

If you want better duration, get a cam. They are not as expensive as they used to be.

pokapotato

You don't want to set the vlaves too tight. You can gutter vlaves if they don't close and seat completely. Too loose is not good either. Just feeling the valve bridges and how they rock makes me worry about having them loose. I would set them at factory spec 10, 20.

wcbcruzer

If that's the factory spec then how come you noticed a difference?

BigBlue

Factory spec is a broad spectrum. Not to mention when the valves got done the truck had 120k on them so they were getting ready for a lashing.

pokapotato

Setting valve lash is contoversial. Some people set them loose when the engine is cold with the thought that they will then be in spec when the engine is hot. Some people like to set the valves when the engine is hot, they feel that is more precise. I set them at what the spec is no matter what the temp. As far as changing timing with valve lash, your not going to change much by changing valve lash by a thousandth or two. I would not want to chance dropping a valve and destroying an engine. Engine should run at it's optimum at factory spec.

J Lent

My brother has his set at 10, 20. I have mine set at 10, 15. My engine sounds smooth....his sounds like it is gonna rattle apart. I had my valves set at factory specs before getting orings.....mechanic set them at 10, 15 & I have no plans on changing back after hearing how smooth it runs. I would go 10, 15. Just my $.02....you know what they say about opinions....everybody's got one.

dodgezilla04

the valves are set cold. so when everything is warmed up to operating temp and all components have grown due to heat, the lash is taken up. that is why the intake is tighter than exhaust. the e valve will grow more do to the heat it is subjected to. do not set them hot, as they will clatter like heck when cold. follow the cummins spec and procedure, they know more than we do.