Adjusting valve clearances
 

Adjusting valve clearances on my D16y7 Honda Civic 1998 Engine. Following the Honda FSM's directions, I measured the clearances with a feeler gauge tonight.

Three questions about the below "data."
QUESTION 1: How badly do you think such clearances effect emissions and/or FE?
QUESTION 2: When I go to adjusting can I leave #2 and #3 alone?
QUESTION 3: Should I be adjusting the valves for an optimum "feel" at 8 for the intakes and 10 for the exhaust, in other words right in the middle of spec?

Here is what I measured (numbers in parenthesis mean it seems tight or loose):

Cylinder #1
intake spec 7-9
left 6 right 7(6)
exhaust spec (9-11)
left 9 right 7(6)

Cylinder #2
intake
left 7 right 7
exhaust
left 9 right 9

Cylinder #3
intake
left 7 right 7
exhaust
left 9 right 9

Cylinder #4
intake
left 7(6) right 7
exhaust
left 9(10) right 9(10)

I always set them to max specs, since they will wear to smaller clearance. That way you probably can get 60k out of the adjustment. Back off the lock nut, put the max spec feeler in place, spin the adjustment screw with your finger until it's snug then lock down the nut and recheck. After a couple you will geet a "feel" for the adjustment. Try the next higher blade to make sure they are not too loose. My VX was all in specs at 62k miles and they had never been touched before.

regards
Mech

That's surprising and great advice, thanks as always. It means I have to set them all, which is fine. How would you go about cleaning all the grime and caked carbon? I figure a little gentle manual scraping followed by a solvent on the inside of the valve cover but NOT on the valves and lifters because the solvent would get into the oil and such... maybe a plastic scrubbie could be used on the valve arms?

I took mine to the shop for adjustment, since it was starting to sound like a diesel.

FE improved, and sounds much better.

Clearance, overlap, emissions
 

The greater clearance you recommend (within spec) should reduce intake/exhaust overlap and therefore improve my emissions. It should also reduce unburnt fuel in the CAT. It will reduce fuel efficiency a little, though, correct? I'll lose scavenging and gain pumping losses, correct?

Here is some reading I am doing that gives me these thoughts/questions:

1- Gordon's Garage - Fast Cars or Clean Air?

2 - http://www.mechadyne-int.com/vva-ref...-emissions.pdf

That's encouraging. But I can't go to a mechanic. I have to do it myself for the sake of the family budget plan. "Be the mechanic you wish to see in the world" is my mantra. :)

:thumbup:

I wouldnt try to clean any "gunk" off the rockers or use any solvent that could cause the valve seals to loose their integrity and you start burning oil. The inside of the valve cover, no problem.

regards
Mech

Well, I used Marvel Mystery Oil on my 200,000 mile Metro. If Seafoam is "colon blow", Marvel Mystery Oil is a "gentle cleanse". I know if there are seals on their way out, but crud keeping the oil from leaking, Seafoam can clean the crud and allow those seals to start leaking.

The Metro had one cylinder that was around 100 psi when I got it. After 3,000 miles of one quart MMO and three quarts Mobil One, the compression had gone up. I think it was due to cleaning the lifters out and allowing them to fully flow oil in and out of them.

I also MMO'd the Civic when I first got it. I ran it for 5,000 miles. One quart MMO and three quarts M1.

The Metro forum folks swear by MMO to slowly clean out the inside of engines. It might be something to look into.

While we are on this subject, do any of you know if it's safe to seafoam a D16Y5 engine? I don't want to destroy my engine seafoaming it. Autozone is having a 'buy 2 get 1 free' deal and if so, I think I'll pick up a few.

Thanks, man! Will do.

I actually do use the MMO, sometimes. But not in the oil anymore. Two years ago or I did once and it made me nervous because it was associated with an experience of a quart of oil loss over the course of a 6000 mile oil change cycle. It might not have been the cause, but it put me off the practice. I do put a little in the gasoline sometimes. Maybe I'll use MMO for cleaning the inside of the valve cover. That sure would be gentle. But I think I'll lay off the rockers and such, as Old Mech says.

Exhaust valve maximum clearance spec is 0.011in and the intake valve maximum clearance spec is 0.009. I set them all to those specs. I'll check again tomorrow. I'm wondering how tightly to torque these aluminum parts. It says 13ft/lbs. I tightened to hand tightness only, without using the ratchet handle.