sneaky98gt

So I've had a misfire condition that has been getting worse and worse over the past few months. It's been constantly throwing codes, and has a very regular, audible miss through the exhaust (re: psh psh psh psh psh). Finally got around to doing some diagnostics this week. I did a compression test, and found Number 1 to only have about 25 psi (2, 3, and 4 all were 150+). I'm going to do a leak-down test as soon as I get the correct spark plug fitting, but based on the oil consumption (about 1 quart every 1500-2000 miles) and blow-by I'm seeing through the oil fill cap, I'm 99.9% sure that the rings are the culprit. The car is a 2001 LX coupe manual transmission, with just a tick under 300,000 miles. I've only had the car for the most recent 50,000, and replaced the headgasket and all other associated gaskets at the same time (valve cover, intake & exhaust manifolds, valve seals, etc.) not long after I bought it. Based on all the maintenance I had to do after I bought it, it was certainly neglected by the previous owner.

So while almost everyone says, "Oh, it's better to just get one from a junkyard", I'm seeing full rebuild kits with bearings, rings, and gaskets for only a couple hundred bucks, while junkyard motors are $500+ with 100k+ miles (of which I have no idea what kind of condition it's in). My local machine shop will hone and clean the block, and deck and clean the heads for around $100. So for around half the money, I'll have a "new" motor that I know the condition of. Plus, I enjoy working on motors anyway, and love having an opportunity to learn something new (I've built a couple domestic V-8s, one pretty much stock, and one a 500 rwhp supercharged build, but never any import related stuff).

OK, enough with the background. The questions I have:

1. Is there a significant difference in size or shape of the combustion chambers of the D17A1 and D17A2 head?

2. What are the combustion chamber sizes of the D17A1 and D17A2 heads?

3. Is there any comprehensive write-up concerning the rebuilding of the bottom end of these motors? I haven't found one yet.


The first two questions are related; if I elect to replace the pistons also (if the pistons or cylinders are damaged or out of round), I'm considering using the D17A2 / D17A6 pistons, as they have less dish and thus bump the compression ratio a bit (9.9 vs 9.5). More compression should equal a small power and fuel economy improvement, but I'm not sure if the lesser dish is also accompanied by a larger chamber in the D17A2. I wouldn't want to use smaller dished D17A2 pistons in combination with a smaller D17A1 chamber (hypothetical) and result in an even bigger bump in compression than anticipated.

The third question is mainly regarding torque specs and bearing clearances. I've found numbers regarding this, but no real details. For example, I have torque specs for main and rod bolts (33 and 23 ft-lbs, respectively), but it doesn't say if they are TTY or not (previous motors I've built were). Things like that.

Thanks for the help.

-Will

ezone

Valves.
Did you check/adjust valve clearances yet? These engines tend to tighten up the valve adjustments over time and miles resulting in low vacuum, low compression, and skewed fuel trims.
If tight valves are ignored for too long-- they burn.

That's ALL? ONLY a quart every 2k? That's pretty damn good for a high mileage unit.
But yeah I'd def do rings and clean out the grooves real good.

Can't say for sure, but I think they are the same. IDK of any factory info available that would tell that sort of info.
Can you cc each one?

Compression bump should have been solely done with the pistons.
Factory service manual. Search the forum, there have been manuals linked in a thread somewhere.

Found it, go to the last page for the newer links: https://www.civicforums.com/forums/1...e-updated.html

Original bearings were select fit, but after a machine shop gets hold of it and does the crank and whatnot, just let them pick out the bearings for you.
The specs are the answer.

TTY will tell you to tighten to xx ft-lb, then tighten an additional number of degrees.
Non-TTY only has you tighten to a plain ft-lb spec.

My manual says 24 ft-lb for the rods and 18, then 38 (two steps) ft-lb for the mains.
Standard bolts. Same for the head bolts, they are also standard.


HTH

sneaky98gt

That was the very first thing I checked after the compression test. I was thinking / hoping that maybe 'psh psh psh' miss I was hearing through the exhaust was just an exhaust valve not seating all the way from the lash being too tight. Not so. The lash was good on all 16 valves (I set them when I did the headgasket about 40k ago.)

That certainly doesn't mean that there still isn't a problem with a valve not sealing up the way it should be. Just sitting here thinking about it, it doesn't seem to me that the rings leaking would cause that miss I'm hearing through the exhaust. It'd almost have to be an exhaust valve leaking, no?

And that still doesn't explain the oil consumption and blow-by. It is a significant amount of blow-by. If I take the oil fill cap off, it is clearly audible, and if you hold your hand over it, it's got quite a bit of 'air' coming out of. Not enough to blow the unscrewed cap off (that's the test we've always used on diesel trucks and equipment), but it is rattling and moving the cap around.

I guess I could have both problems going on? Regardless, after I do a leak down test, I'm going to pull the head first to inspect for problems, and then pull the motor if needed.

Haha, I suppose you make a good point. But after thinking about it, it's more than that. I change the oil every 5,000 miles; I always add 2 quarts between changes, and it's always a good bit low when I actually change it. So it's probably more like 3-3.5 quarts every 5,000 miles that it burns. And while I suppose that's still not ridiculous for a car with 300k miles on it, it didn't used to burn that much. Back when I first got the car, I didn't add any over my 5,000 mile interval, and it was only a little low at the change.

That's what I've figured as well, and I haven't found any evidence to the contrary.

I can check the volume on my LX head, but I don't currently have access to an EX head to compare it to.

Do you see any issues arising from using the EX pistons and bumping the compression a bit? The EX still runs on 87, correct?

That's exactly what I was looking for.

Thanks for all the help.

ezone

Certainly likely. A leakdown test should reveal the source of leakage.

Consumption is the oil rings (unless something went drastically wrong with the valve seals).....but your method of evaluating blow-by is not really a good test. I do expect all of these 4 cylinder engines to rattle the oil cap at idle and even blow a mist cloud up.

If you want a real test, check for suction/pressure at the vent hose on the valve cover. Does the PCV system keep up with blowby (crankcase goes into a light vacuum after a while), or does excess blowby create positive crankcase pressure at idle?



I'm gonna go out on a limb here and guess you have been using "heavier" oil like 10-30 or something, or a high mileage oil.

Go back to 5w20 or even 0w20 after you get the engine all fixed up.

If you decide on 5w20
Look for and use 5w20 oil with specs of:
ILSAC GF-5
ACEA A1/B1
API SN (or higher)

Much of the Mobil-1 5w20 meets these specs.
So do many/most of the oils bearing the DEXOS-1 logo. Read the labels though.

If you go to 0w20, it's all considered kinda "synthetic" due to the necessary use of very high quality base stocks.



I don't have real experience with converting and hacking (dealer tech here, in the land of OE stock cars), but I'd run it.
Yes


HTH