best head gasket for 90 EX 16V

Hi,
We are getting a new rebuilt head and head bolts for the 90 Accord EX (16V
SOHC) with 200k as soon as we confirm a burned valve on the old one. What is
the recommended head gasket for this application, aftermarket or OEM? And
what, if anything, should be done to the (aluminum) block to ensure a good seal
besides thoroughly cleaning the old gasket off? The head rebuilder has
recommended NOT to retorque the head bolts after 500mi or sand any surface
pattern into the deck, as seem to be common wisdom depending on who you talk
to.

Is there anything else important to replace along with the head besides the
timing belt, water pump, and all associated gaskets that would be hard to get
to later? Example: any known problems with the front crank seal, oil pump, or
timing belt tensioner?

History: The Accord always ran great, with some valve noise when cold due to
owner neglecting oil changes, until one day there was zero compression in #1.
No noise at all, just has no power. The car overheated once about five years
ago due to a leaking hose, but nothing bad seems to have come of that luckily.
Since it is aluminum, the deck will be checked for true before proceeding.

Appreciate any comments good or bad. Don't want to let a $400+weekend job get
out of hand.

Thanks.

 

Mostly, retorquing isn't needed these days, hasn't been for a couple decades
now. For starters many head gaskets are the "no retorque" kind. Also, if
you have "torque to yield" head bolts, as many engines do, to do a retorque
means removing the head bolts and throwing them all out and putting new
ones in.

For the aluminum block, you can use a wire brush but be careful with it -
don't use a
wire brush on a drill, use a hand brush and stop brushing when aluminum
starts to
appear under the old gasket material.. There are chemical products out there
that are designed to clean off old gaskets you might try those. For a
scraper, use
a plastic ice scraper, not a metal one.

Don't sand, wire brush, or steel wool directly on the aluminum.

I would also recommend chasing the threads in the block with a tap. Some
people just drill all of them out and replace them with HeliCoils.

Yes, if the head bolts are torque-to-yield you must replace all of them.

How many miles on this? Frankly, an engine that was owned by an owner
who neglected oil changes is a poor candidate for new heads. Your better
off just rebuilding the entire thing.

Ted

 

I was going to use brake cleaner and a plastic scraper as a start and save the
aggressive stuff for later.

Ok, I've heard that there are two kinds of taps - real taps, and thread
chasers, made out of different material, where thread chasers are made for
cleaning up existing threads. Supposedly a thread chaser runs less risk of
inadvertently doing something really bad to the threads. I was planning to get
a thread chaser, but can you shed any light on this difference?

200k. Well, I should clarify. By neglected, I mean he usually let it get up
to 5-10k between changes. This is neglect by my standards, but may be within
reasonable tolerance. The reason I noticed it was because the valves were
noisy when cold and I asked him about it.

Looks like a crank kit is about $300 and rings another $80. Plus the motor
would have to be pulled to do the mains and the oil pump. If the compression
is good and there is no play in the pistons, could the bottom end be that bad?
What about just replacing the rod bearings from the bottom, and doing the rings
through the top after getting rid of the ridge? I also don't know if the
cylinder would need to be re-honed for the type of rings in this motor to seal
up again, or if cleaning it would suffice.

Thanks for the reply.

 

as the head builder says, clean the surfaces only. any scratching can
lead to leakage over time. new oem heads are mirror finished.

seals & tensioners are good.

that noise is not due to neglect. it's just a fact of life and to some
extent, a function of the oil you're using. fortunately, a burnt valve
is /no/ reflection on the wear status of the rest of the engine.

i'd be scrupulous about cleanliness for the block. new rings and seals
are debatable at this mileage, but if it was good before and was not
burning oil, personally i'd leave them. rebuilds usually fail in 1/3 or
less time than the original build. analysis shows this is almost always
due to microscopic abrasive contamination left on the cylinder wall
after re-honing. if you can avoid doing that [and you /must/ hone if
you re-ring] you could continue to get good service from this engine.
caveat: "conventional wisdom" is strip, hone, ring, etc. but the fact
remains that rebuilds don't last and for the reasons i've stated. i
would not follow my own advice in a shop environment because i cannot be
"negligent" for following conventional practice, but if it were my own
car, and i /knew/ the block was good, sure i'd leave it as is.

 

Well, that's what I was hoping at least. The biggest concern of mine is that a
new head, being perfectly sealed, will increase the load on the compression
rings causing them to fail sooner, or at least increase blowby (fouling the oil
more quickly and perhaps overloading the PCV system). But from what I've read,
this seems to apply to older ring types and not to "moly" rings that new cars
and especially Asian cars have been using, so this is nothing to worry about.
(I'd love a correction here.) If so, that would definitely be a good thing,
because most of these cars are also using OHC aluminum head designs which seem
to invite eventual head rebuilds or gasket jobs for various reasons.

Aside from that issue, I'll just be on the lookout for detonation both from
improved compression from the new valves, and from the unintended rise in
compression that comes from the head being milled down.

So the idea is, either buy a new or rebuilt short block from a professional
rebuilder with a warranty, or leave the rings alone?

How about bearings and seals? I seem to be under the impression that unless a
bearing spun, they should be safe to replace (with a factory sized replacement)
without a hot bath or crank job. Likewise seals, unless something catastrophic
happened to the part they are sealing, just to use emery cloth or very fine
sandpaper on any shaft burrs before installing the new seal.

Of course never having done any bottom end work, I'd prefer to have my head
screwed on straight and do it right the first time or to not do it at all.
That's an area where trial and error can get expensive and inconvenient, as one
error can pile on more problems very quickly.

Thanks.

 

doing the valve & replacing the head doesn't "improve" the compression,
merely restores it to the cylinder that had lost it.

to be honset, don't know what honda use these days or the dates. it's
not really relevant to a valve job.

detroit mythology. honda heads will happily stay on a block for 2, 3, 4
or more hundred thousand miles.

1. you don't get increased compression from new valves.
2. you have no reason to skim the head just because a valve burnt.
3. if you /do/ skim the head, you need an oversize gasket.

again, you have no reason to skim the head. alloy blocks & heads often
/do/ warp very slightly in use. but the important point most machine
shops [trying to sell you their services] never care to mention, is that
they warp in sympathy, so they still fit. unless you have a serious
distortion, such as caused by a cooling failure, do not skim the head!!!

why do you want to touch the block? you burnt a valve. that does /not/
affect the block.

there's no point stripping the block, unless you plan to replace
pistons, bearings, rings & seals, but again, i don't understand why
you're contemplating that course of action. you're turning a $500 job
into a $2500 job. maybe you want the experience, which is valid, but
it's cheaper to pick up a $200 [or cheaper] motor from a junk yard and
strip it down rather than be forced into much bigger $'s rebuilding this
motor. and you'd be robbed of most of the experience anyway because in
order to get any warranty, you'd have to let the shop do the rebuild.

replace the valve, clean up the head & the block, put the head back on &
drive the car until you have another problem with it. /then/ figure out
what to do. for a 90, replacing the engine with a used japanese motor
is /way/ more cost effective [and probably reliable] than messing about
with extensive rebuilds for the reasons i mentioned before.

 

Unless your engine is just dog tired and worn out this doesn't seem to
be as big of a factor as it used to be. Were it mine I would get the
head done and slap it all back together.

Unless you have a particular reason to suspect bearing problems in the
bottom end I would leave it alone. If you start having oil pressure
problems in the future you can always do the bearing then without
having to redo the work you are doing on your heads now.

Take it from someone who doesn't know where to stop.... You have to
keep the project to a managable size and avoid all the "might as
wells" that pop up along the way. If a "might as well" is cheap and
would cause you to have to redo a massive amount of work then do it
otherwise leave it for another day.

Steve B.

 

Yeah, but presumably the rings have worn too. So bringing the cylinder back to
spec may cause an issue there.

What I meant was that OHC/aluminum heads seem to invite regasketing/warpage
with mild overheat scenarios. Not as resilient as traditional heads. Though
aluminum blocks are probably a bigger culprit in this area.

Sorry, I didn't mention the new head is coming from an exchange rebuilder. So
the choice whether or not to mill it down would be theirs, not mine.

Humm. Given this, is it a *bad* idea then to get an exchange head for an
aluminum block? The new one wouldn't have the same "sympathy" warp that the
block does.

I asked the question for future reference.

That was the plan. Except now I'm not sure whether to get an exchange head or
to have this one rebuilt, given what you've mentioned above.

Thanks.

 

Solid advice, and the "might as wells" are exactly the problem I have when
knowing where to stop. I'll try not to make a federal case of this one.

 

absolutely not. all that will happen is that your car will suddenly run
well again. pistons running without load don't wear as fast as the ones
with load, so if anything, this piston will be healthier than the rest.
valves burn because they're not seating right or because they have a
defect. it's got _nothing_ to do with what's going on 0.1" further south.

cast iron heads crack & warp just as effectively as aluminum.

not if they're designed right.

any "sympathy" warp is usually minimal. don't fret it - i just
mentioned it in case you need ammo with the head shop - but i may have
muddied the water because most places neither know nor care. but it's
still best to use your old head if you can.

no problem. ask as many times as you need.

rebuild the old one. presumably it's just one valve. that makes the
job $13 for the valve, $165 for the gasket kit, $70 for the chilton, $20
for the valve tool rental, and one half of a weekend. suddenly, you're
back on the road. and pretty one-up on your buds too.

 

Thanks for your input. I may still get an exchange head for it just because of
the mileage on it and the fact that I won't be the driver for much longer
(being passed down to a teenager). Your comments give me a lot more confidence
that this will be a successful job in the end.

 

200k is really not serious mileage for a honda.

 

Is it realistic to expect no other valvetrain problems given that at least one
has already gone? Or say it's a broken spring instead of a burnt valve. The
others wouldn't be far behind?

Maybe I've got the "Detroit" perspective going here again...

 

sure. unless they're badly adjusted or you have a problem like a broken
spark plug insulator getting lodged under it, valves very rarely burn.

broken honda spring? they're as common as chicken lips. you need to be
careful with a spring - any mechanical damage such as dropping it can
leave small marks on the surface of the wire which act as fatigue
initiators, but properly installed? no, honda don't break.