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.

Make sure you tighten the valve lash lock nuts more than the valve cover bolts!

The valve cover bolts don't need much torque, generally about 1/4 turn once they stop moving easily. I use a ratchet and one finger but try to stay around the 1/4 turn.

I torque the lock nuts down about the same 1/4 turn after they stop moving easily, maybe a little less.

regards
Mech

I would not put Seafoam in the crank case. It is pretty harsh.

I have Seafoamed several different cars' intakes via a vacuum line. It shouldn't harm anything. You will have a lot of white smoke out of the tail pipe though.

On a 1990 CRX, the torque spec for both is (IIRC) 10 lb-ft. Kind of a pain to use a torque wrench on the jam nuts, but I sure don't have a feel for 10 lb-ft...

-soD

Wouldn't they wear to larger clearance?

Answers for DOAX and some other dave.

First SOD.
One way to retorque them is to just put them exactly where they were when you started. 10 foot pounds is 20 pounds on a 6 inch wrench. I find with the regular wrenches it's a pretty good pull and have never had one strip, pretty strong material. I usually break them loose with a palm whack to the wrench and go back to exactly the same spot when tightening.

Second DOAX.
I can not remember a valve lash adjustment where the valves wore to a larger gap. Most of the wear (assuming the engine was decently cared for) is the valve to seat interface on the exhaust valves. This is especially true on air cooled motorcycles. My GZ250 was at the minimum tolerance at 5200 miles, so I adjusted to .001 above the maximum tolerance (.006, versus .005). I can hear the valves more than before from .003 to .006 lash. I did go one over max in order to avoid doing adjustments at the recommended intervals. Every valve on my VX was in specs at 62k miles, never having been adjusted.

The only case where the valves wore open that I can remember is the early Nissan Z cars that had a spray bar for the camshaft. Later ones had a hollow cam with holes for each lobe. The early spray bar type would get clogged up and wipe out that cam lobe, but that was just neglect, not good maintenance.

In most vlavle "adjustments" if you check the recommended service intervals, it calls for a valve lash "check". Basically this means, even though on my bike the exhaust valves were at the minimum spec, they would still "check" OK if the tech was not very scrupulous he would not attempt an adjustment.

I always checked the balance of wheels when I was asked to do an rebalance. If the wheels were in balance I charged less for the check since it was less work.

When doing a valve adjustment, I set every valve to the spec that would allow it to go the furtherest distance before requiring another adjustment. On my 73 Alfa GTV, which required removal of both cam shafts (DOHC) a micrometer measurement of the shim which was below the bucket that rode the cam lobe and a replacement shim that got you the proper lash at 58k miles. 100k later and every valve had tightened by exactly .001. All 8 valves were exactly the same. The engine was liquid cooled with hardened seats. I think the exhaust valves were sodium cooled.

regards
Mech

I'm too inexperienced, so I'm gonna need another torque wrench that will measure the 14ft/lbs I need. Mine bottoms out at 20 and has a long handle. If I put that cover back without complete confidence I'll be bugged by it all the time.

(Philosophy for ecomodders: I think part of good modding and maintaining, like life, is knowing how and when to compensate for our limits. Knowing the "when" might be the trickiest part. But the experience of failures builds an "intuition" like sense of when we need assistance with a task.)

Why buy another tool?

When you break the bolt loose, you get a good feel for the amount of torque it had unless it was basically frozen in place and took a lot of force to break it loose. 6X1 MM bolts, into aluminum are about 6 foot pounds from memory.

The rubber gasket does the sealing and I think the bolts either bottom out or have a shoulder or spacer to keep them in at same depth after tightening.

Use one finger on your ratchet and pull it down tight. If you are worried about it not being tight enough, check it after a couple of drives and see if it is still tight.

Almost every fastener I have ever tightened would be good at 45-90 degrees past the point where it required any force to tighten it further. If you are worried about stripping it, then go 30 degrees or 1/10th of a revolution after force is necessary. Once you have done it a few times it gets instinctive.
Bottom line is too loose and you can tighten it, too tight and you get to helicoil it.

While I would not apply that principle to fasteners that are not accessible, for valve cover bolts it works perfectly.

I stripped the wing nut (shifter tension) on my Schwinn bike with just my fingers, but it was brass and I had a spare.

Anyone here ever have to helicoil every cylinder head bolt thread, into the block, on a Nissan Z28 motor? How about the broken off rear exhaust manifold stud. I managed to do that one, on my own car, without removing the manifold. Got so good a drilling out studs, they looked as well aligned as a gun barrel when I got them out. I could drill them out so close to the threads that the remaining thread came out like a spring and the replacement bolt spun in by hand easily, but of course not when it was steel into aluminum.

regards
Mech