View Full Version : the dreaded visitation! [diagnose-a-spark plug]

05-19-2007, 07:58 PM
hey 1geez, i need your help!

i have a '77 accord hatch with an '81 1600 8v engine, both of which have had an ugly past.

this is rusty :)


3 weeks ago i changed the oil and filter and cleaned the plugs off, which were moderately sooty. yesterday i removed number 1 spark plug to find the thread and its seat in the engine head really oily. the tip was coated in a mixture of oil and flakey carbon, much more so than i'd seen before, so i removed all the plugs to compare:

1 [cleaned up for reference] - 2 - 3 - 4


-> plug #1 was similar to plug #2 when i took it out.

the air cleaner is... doing its job it would appear. this used to be full of grime from the rocker cover vent, i didnt find a smear of oil anywhere, even in the vac/recirculation lines.


and i've been keeping the engine pretty clean so as to spot any rogue oil incursions, which havent eventuated.


despite this, i havent noticed any exhaust smoke, bad smells, pools of oil or boiling coolant dripping on my feet. rusty has been running better than ever, so i was a bit :wtf: when i saw the plugs.

what do you think is causing it?

05-19-2007, 09:04 PM
Well, with the complete lack of other symptoms, so you say, I'd conclude that the problem is that there is oil on your spark plug threads. Other than that, the usual culprits, valve guides, PCV, crankcase vent (side effect of bad rings), etc. Normally these problems are present with oil consumption and lots of smoke.

05-20-2007, 09:30 AM
I would have to say it's burning oil because there is oil on the spark plugs. But you should be able to smell it. Smoke might not be present though..

05-22-2007, 01:32 AM
i certainly cant smell oil smoke when i park it. if anything it reeks of petrol but im putting that down to it being a bad-arse racing machine, and having no carpets.

i took it on a road trip last summer and when i got home i noticed it was blowing smoke when i pulled away from traffic lights. i checked the plugs that time and didnt find anything sus, however i did find:


so i replaced the cam and rockers with those from the old engine, and it appears not to smoke at all anymore. the valve guides felt snug and the valve heads rotated smoothly on thier seats, so i supposed they must be in reasonable condition.

anyhow i cleaned the plugs again and put them back in yesterday, and this morning is was pretty cold and it barely started. and then it wouldnt idle at all, even after 5 minutes of holding it at 1500rpm. so turned it off and i twisted the distributor a bit to advance the spark, and then it started and idled perfectly. i set the distributor back to its slightly less advanced position and.. it continued to idle perfectly. so i tightened the nut, shut the bonnet and it didnt miss a beat for the rest of the day =\

guy is right that i'm assuming a problem from only one symptom [well theres lots of noises and rattles but none of them are really mysterious or problematic] so i suppose i'd just keep checking the plugs and wait for the gremlins to come out.

05-22-2007, 08:04 PM
I hate to ask this, but are you sure it was oil on the plugs? I've mistaken raunchy gas for oil on spark plugs before, and the way it sounds like it's been running, and with the carbon, fuel fouling would be nothing out of the ordinary. Pull a plug again and this time smell it.

05-23-2007, 05:31 AM
oh i did the first time, and it smelt suspiciously strongly of petrol. i'd never really smelt them before so i didnt think awfully much of it at the time. particulate would show up in the fuel filter [where is that thing anyway?] but any other comtaminant would go straight through to party in the cylinder, right?

now that you mention it, tasmania has something of a reputation for crappy 2-buck fuel, compared to the australian mainland. the cars that come down here for the targa tasmania tarmac rally pretty much all bring thier own supplies, and many fast car enthusiasts go to extra lengths to get good mainland fuel, so it doesnt goo up thier porsches.

05-23-2007, 09:52 AM
Could the piston hitting the valve have caused that rocker and cam lobe damage, just thinking the crank bearing or something could have been worn out?

Or is it just lack of lube to that area or a bad valve lash or stuck valve or some debris?

Has your new rocker and lobe shows any signs of wear on that cylinder?

Were there any signs of wear on the rest of the engine like the cylinder walls, whats the compression in that cylinder?

05-23-2007, 01:58 PM
I was reading actually that many of the early CVCC motors (pre-80) had problems with oil pressure getting to the last (or first, can't remember) cam lobe. A few people who built and raced with CVCC engines (see issue of Honda Tuning with Legend_Master's car in it), actually enlarged the "jets" or whatever that the oil flowed through to allow more flow without a huge decrease in pressure. It is also noted in my "Building Honda Engines" book about this problem with some of the motors.

05-23-2007, 02:51 PM
I noticed from your pictures that the electrodes and ground straps look suspiciously dry, while the offending liquid is concentrated on the threads of the plugs. Oil soaked plugs will have a shiny black slime coating the tips that will remain, while the gasoline will evaporate away, especially where the heat of combustion affects it, allowing the dry carbon to remain.

05-23-2007, 10:28 PM
Could the piston hitting the valve have caused that rocker and cam lobe damage, just thinking the crank bearing or something could have been worn out?

its weird eh? when i saw it, terrible images of valves hitting pistons and bolts stripping and gouged metal surfaces filled my head.

but the valve itself works fine. the guide isn't loose, no warpage to the stem, head fits in the seat, tappet isnt chipped or deformed. i didnt remove the head but i had a look in / feel around through the spark plug hole and couldnt see any sign of foul play in the bore. my compression gauge is older than the engine and optimistically reports an 11:1 ratio, more or less across all 4 cylinders though.

a couple of the other '81 cam lobes and rocker feet had some wear / deterioration on their surfaces, but nothing like the damage on No.4 intake. the whole valvetrain was stained brown-black though, and the oil i got out of the engine the first time i bled it smelt like sewerage. there was even some wear to the pivot bar at the fulcrum of the No.4 intake rocker, and i found that its little oil hole was badly clogged with gritty filth.

so oil supply could have been a problem, but the wear to that particular cam seems too severe for that alone. maybe it had a bent valve at some point and the guide / seal / valve was replaced, but the mangled cam and rocker weren't judged to be a show-stopper and were retained.

what initially had me take the valvetrain apart was a broken outer spring on No.3 intake, which i replaced with an adapted '77 spring [ground out the inside very slightly, all the '77 bits are lighter/simpler/narrower]

the '77 camshaft and rockers i put in were high-mileage parts but were in totally perfect condition, still bright and shiny. they were almost identical to the '81 parts and fitted the same, except for the final tower at the distributor end, which seemed to be just a few thousandths too short on the bottom, and would pinch the camshaft and seize it when i tightened it up. i made a shim from a tin can and now it all fits perfectly.

finally, before i run out of internet to write this on, the engine does 'tick' and 'rumble' when it runs. sort of like an old metal lathe or mill. i can record it if you wanna hear.

05-24-2007, 09:35 AM
Run out of internet? Are you at a local library or a coin operated booth or something using the net?

05-24-2007, 02:57 PM
the engine does 'tick' and 'rumble' when it runs. sort of like an old metal lathe or mill. i can record it if you wanna hear.

That's awesome. I just finished my first year machinist apprentice course, so I know all about the old mills and lathes. We have a Colchester from the 50's and a big Elliott vertical mill from somewhere around then as well. The Elliott has a sweet DRO and can cut accurately to about +- 0.01mm on the z axis.

Oh, and a deep rumbling usually indicates worn main bearings. A "clack" that shuts up under load and is most prominent at idle and when "floating" the drivetrain is usually a rod bearing. There's a variety of noises that an engine can make, I'm familiar with most of them so ask if you want.

I think you answered your own question about the cam lobe/rocker damage. Lubrication is critical.

05-24-2007, 05:13 PM
Run out of internet? Are you at a local library or a coin operated booth or something using the net?
19th century steam powered carrier pigeon internet! no it just looked like a wall of text in the quick reply box.

i'd suspected for a while that the entire engine might be worn out. the original gearbox made a horrific GRINDING noise on overrun, which turned out to be the mainshaft bearing which was missing its entire cage and a couple of balls as well :violin:

i had that replaced, but then decided to use this "new" engine and its gearbox, as it had better compression [i still dont know the actual figure, but it was markedly better than the original engine] and there was less wear in the gearbox and i wouldnt need to buy a new clutch.

not exactly best workshop practice i know. i still have the old engine, gearbox, and necessary bits to put it back in. whereas it seems to always have had its oil changed on time, and the '81 engine seems to have never had its oil changed, the original gearbox had been running DRY for a significant portion of its life, whereas the 81's box at least had plenty of oil, although it was of course filthy.

to fix either of these engines properly i would have to rebuild, which would cost heaps more than my poor-arse uni student budget will run to. is it a very terrible idea to combine the better parts from both engines? i didnt even occur to me to do fancy things like clearance-checking when i mix-n-matched the valvetrain, i just tightened everything down as it was before and made sure the camshaft turned smoothly without any load.

i guessed the big roaring turning noise was coming from something big and heavy [ie the crank assembly] but just hoped that it wasnt bad enough to cause explosions, and so far its been alright. think i'll try to get a recording of those engine noises so you can give me an idea of how severe it sounds.

ps: bent valve from broken timing belt? i think i found it was possible for the valves to meet the pistons at tdc, and with the total lack of mantinence...

05-29-2007, 06:03 PM
ok i finally got round to recording it. i used my bro's mp3 player to record:

1: cold start and idle
2: sounds from the oil filler hole, feat. escaping blow-by gas.
3: slightly more warmed up 800- ~3000rpm and back down
4: similar, from right above the carb.

and then put them all back-to-back in this mp3:
http://diversion.deadbored.net/enginesound.mp3 [about 1mb]

05-30-2007, 04:38 PM
Doesn't sound like either engines been well cared for & if enough crap built up to block lubrication to that end of the cam... it can't have done brilliant things to the rest of the engine either.

You do know that the '81 was actually a different engine to the '77 don't you?(I know some of the non-honda w/shop manuals fail to mention this). Different bigger bore & shorter stroke & 3cc bigger overall... wouldn't be at all easy to mix & match parts between the two, even the clutch is bigger & the flywheel/crankshaft bolts different sizes .If you could get hold of another '79-'81 drivetrain... Even the '82-3 drivetrain might be a closer relation in some respects.
Curious thought though...'81 77mm bore x '77 93mm stroke would almost take you to EK 1750cc capacity if it could be done.. since EK engines are almost unheard of here... '77 block & crank, '82 higher compression pistons, '81 head ( if it fit earlier block) .... though I doubt it would all fit togeather.

I'm sure you'd already have found lots of other interesting/frustrating variations putting the newer drivetrain & frt panels on the '77 shell.

05-30-2007, 06:19 PM
yeah, i sort of guessed when i compared the two engines and gearboxes that the '81 was designed to 1800cc spec but bored to 1600cc in my case. is the '81 motor oversquare or undersquare compared to the '77?

i think the long-term future of the car will involve rebuilding the original motor, however boring out the '81 and fixing its many [and unknown] ills could be a better idea. but thats long term, assuming i can hang onto it untill i have real money to spend.

also, do you know where i can get new springs and revalved struts put in the original carriers? im using the '81 struts and springs at the moment, and its much too high, giving me very neutral camber. the ride is about right but it needs to be lower - could i just hacksaw a bit off both ends of the springs to bring them down 5cm each?

05-30-2007, 07:07 PM
Here's a bit of a comparison for you:
(lots of other articles there)

The newer engine was shorter stroke making it oversquare (always thought that terminology back-to-front) so it revved better with peak power @ higher revs & torque coming in earlier even though outputs didn't seem to vary much.

Unfortunately I haven't experimented suspension wise beyond wheels/brakes but might have to think about it soon.
I'm tempted to experiment with a spare set of struts as well but would have thought lowering/stiffening frt only, without adding rr sway-bay would make it understeer more. Still wondering if '81 sedans might have had stiffer rear springs/struts than my hatch to alleviate this cheaply (put a full load of people in the back of a hatch & it almost seems on its bumpstops) though that might not help you much -rear suspension & strut mountings changed for sedans & '79-on hatches...

05-30-2007, 09:06 PM
haha, "very reachable" redline. maybe when it was brand new and if you didnt own it. i wouldnt dare these days, something would definitely go pop.

what they said about the prelude was exactly what i'd guessed - the gear ratios in the '81 are shorter, the driveshafts thicker, and everything is chunkier in anticipation of less-than-leisurely driving styles more applicable to the prelude than the accord.

so it gained some capacity at the head... that means the '77 head, if it would fit on the '81 block, would increase compression! or maybe just break the valves. this should be investigated. i know the manifolds are interchangible and the camshafts are almost interchangible, the oil pump is in the exact same place and the engine drops right into the old mounts.

on suspension, the sedan's rear struts are way heavier. i swapped the fronts because mine were hitting the bump-stops annoyingly often, and were floating a bit too. the two sets of struts are exactly the same length out of the car, so the ride height difference must just be due to heavier springs. it does handle a lot more sharply than it used to and understeer isnt that noticible on dry roads. in the wet when you cant transfer much weight it does tend to skate though.

if i swapped back the springs only, and kept the '81 dampers, that should stop some of the float and bottoming-out, but it might ride lower than it did originally because of the heavier engine. it would definitely fix the dodgey camber though. how do you disassemble those struts and get the springs off anyway? i had a go at the big bolt but was too worried it would all go sproing and kill me.

05-30-2007, 11:17 PM
Never been frightened to rev mine out, though with peak power @5300 it's rarely necessary ( not like my Vtec CR-X which will begs you to bounce it off its rev-limmiter).

Thought most capacity change was due to bore/stroke changes but gather valve angles were increased for better breathing on the later heads which might have required more space there. I didn't think manifolds were interchangeable at the head though -or I would have leapt upon the set of '77 extractors I saw at a wreckers last year.

Don't forget that by '79 Aust. spec. hatches were some 40kg heavier than '77 models though I think this was mostly due to addition of heavy door side-intrusion bars in '78(?), more body firewall insulation & general structural reinforcing rather than any signifigant change in engine weight, with sedans some 32kg heavier again. I know rear strut package was bulkier in general than pre-79 models to offset springs in relation to struts & for bulkier noise isolating rubber mountings. No idea how spring rates varied as the Accord evolved.

I once did a rear strut by keeping the spring compressed by the weight of the car & undoing the ctr bolt before jacking up rear of car & removing, but spring compressors probably a better idea & unavoidable if struts are out -still something to be wary of-see 2ndGenGuy's shock-absorber/spring change thread in the 2nd gen area.

05-30-2007, 11:26 PM
Most of the E engines from that era didn't have interchangeable heads. I'll have to look it up in my book, but they kept revising the head-bolt patterns to try to avoid the blown headgasket problems. Of course, maybe you guys will have better luck, not having the CVCC motors.

I had a head rebuilt from an 83 EL1, thinking it was an 81 EL1. Year to year, the EK and EL were supposed to have swappable heads, but as I found out, the EK1 and EL1 both changed OH SO SLIGHTLY. What I suggest before having any headwork done, or spending any money, is get a head gasket for each year and compare them. Compare very very closely!!

See this thread to see the slight differences between 81 and 82-83. Even engines with the same codes but different years had incompatible parts!


05-31-2007, 03:51 AM
Um I think I just made a discovery.
I compared part numbers from my EL Prelude 1602 parts book to those on one of the US online parts books for the EK, year for year...& the part numbers matched.
EK & EL did share the same blocks.
I'd always assumed it might have required a taller block but I guess not. So if you buy the appropriate crank, rods & maybe pistons you could turn an EL into an EK capacity wise !?

Though trying to compare '77-8 EF/G 1599 cranks to '79 EK 1751 crank part numbers didn't match so the idea of using the 77-8 parts in an EL block to raise capacity is inconclusive.

05-31-2007, 08:00 AM
this fills me with nationalistic pride nonetheless!

you should jump on those extractors, i definitely have my '77 intake and exhaust headers on the '81 head and nothing has caught fire yet.

05-31-2007, 08:09 AM
Woah, who has headers for an 81? Interested in selling? :D

05-31-2007, 01:59 PM
They are long gone now. Almost wish I'd taken some pictures of the car in the wreakers even if it was rough & tacky.

White 77-8 hatch.
Fullsize fabric sunroof.
Japanese 79-81 sedan bonnet with the ugly raised tip @ the front & plastic NACA duct cut into it.
Aftermarket sports seats.
Badly hammered out & body filler flares.
& the extractors inc. manifold for a sidedraft carb if I remember right.