What have you done today

M

mickn

CCCUK Member
After dismantling half the rear end of the c2 the other day to take the bumpers to the chromers I took the opportunity this afternoon to underseal as much as i could get to.
 
Forrest Gump

Forrest Gump

CCCUK regional rep
On Saturday seven of us joined about thirty other yank cars for the Maldon (Essex) High Street Drive-though. It's a promotion for the nearby Museum of Power American car show the next day. Our brief was was draw attention to the cars - engine revving and horns. It's a bit of a different thing to do and good fun.
We had five C3's, a C4 and C5. You can hear Steves C4 behind me:



At Sundays show at the Museum of Power we had the biggest ever turn-out of Corvettes for an Essex region show - twenty three. A spectacular line-up:

 
antijam

antijam

CCCUK Member
antijam said:
Just spent a rather frustrating day chasing down the the latest in what has been a long term series of intermittent misfiring problems on my '71 sbc. These have cropped up at irregular intervals since I bought the car and in attempts to sort them I've so far replaced the plugs (twice) the plug leads (twice) the distributor cap, the rotor arm, the points, the condenser, the coil, the carburettor and the fuel filters so when during the latest drive it became obvious that at least one pot was not contributing to the party I was not a happy bunny.
Previous problems have usually been associated with cylinders 5 and/or 7 and sure enough after lifting the lid my infra red thermometer showed No. 7 to be on strike. Connecting my timing lamp to plug lead 7 confirmed a lack of sparks so checked the resistance of plug and lead and both appeared to be in spec. Being the sort of OCD hoarder who never throws anything away, I dug out an old plug lead and swapped it for No 7. No change - still no sparks, so swap plugs 5 and 7. Sure enough, no sparks now on 5 so I discard the plug and unearth an old one from the hoard of junk. Re-connect everything up and Bingo! - no misfire, smooth as a turbine!
So - I had a duff plug - a genuine ACR44TS - that tested OK. :unsure:
Hey Ho - wonder what the next misfire's going to throw up ?
Click to expand...
Seems I was somewhat premature in congratulating myself on sorting out my misfire problem.

Having enjoyed a trouble-free drive after my last efforts the car was unused for a couple of days but on the next start-up – down to seven pots again. Misfire now on No. 5, the one I thought I’d sorted.
Out with all the plugs again. No 5 is wet as expected and since all the others are a bit sooty I suspect I may be running a bit rich. So, its off with the carb to do a smaller rejet and with the plugs out and the carb off it seems a good opportunity to do (another) compression check. All pots are between 130 and 140 psi. cold. Not perfect but perfectly adequate.

Refit the re-jetted carb and cleaned up plugs, fire up and retune the carb. Running perfectly, no misfires anywhere. Go off for a satisfyingly powerful trouble free drive and return the car to the garage.

Two days later, start up again and misfire is back! This time it’s migrated to pot No.6 – on the other bank. :(

So, with plugs just cleaned the car runs fine. Leave it for a couple of days and it starts misfiring.
Something is happening while the car’s not running and the best suspect that comes to mind now is oil contamination. There has always been a faint puff of blue smoke on start-up – particularly from the left bank (home to pots 5 and7) but this has quickly disappeared as the car warms up. I haven’t checked oil consumption but it’s certainly not negligible. I’m wondering if worn valve stem seals could be the problem?

As part of a bling-up of my under-bonnet area I recently replaced the stock valve covers with a pair of LT1 cast aluminium items.

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As well as looking pretty, these incorporate oil drippers not present on the stock covers.

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The purpose of these is to drip oil back onto the rocker arm – and by default to the valve stem I guess – to improve lubrication. Not necessary but perhaps nice to have – unless maybe you have leaking valve stem seals?

With the motor stopped oil can continue to run down the valve assembly and past worn seals. If the valves on that pot happen to be open, it could be a cause of plug fouling the next time the engine is started?

So I’m gearing myself for a valve stem oil seal replacement, preferably without removing the heads.To this end I’m favouring the ‘rope trick’ method to stop the valves dropping rather than using compressed air. Has anyone carried this out successfully?
 
teamzr1

teamzr1

Supporting vendor
You sure this is not a weak coil issue that outputs a bit too low of voltage or weak ground for the coil or the distributor ?

Yes the rope trick works or with all sparkplugs out hand crank so for each cylinder you're working on the piston is at the top
so valve stems sits high
 
Roscobbc

Roscobbc

Moderator
I had a misfire issue issue on my original 427 after I had installed an MSD 6T high output ignition system. I hadn't been happy with the seemingly recently last owner renewed OEM braided and earth tagged steel HT leads..........they worked OK (ish) but the engine really wasn't happy running below 1000 rpm........it didn't misfire as such but on hot re-starts too much pedal pumping and it would flood the plugs and 'gas-up'.
This was even with good quality 7 or 8 mm silicon HT leads. The MSD system and new leads then installed sorted the poor running below 1000 rpm. Not so much sorted really as transformed - it would now lug down to 700rpm in 4 gear (about 10/12 mph) and pull away cleanly without a hiccup - fantastic tractibility.
Then the previous issue seemed to rear its head again - I'd pull away, give it a little gas and it would now miss on one cylinder slightly, I'd back-off and it was on all eight once more. Fueling issues? yes, thats what I thought.
Eventually I decided to remove the hood and take it out at night. It was then the issue immediately became apparent. The base of one spark plug boot (no. 3 I think) was arcing-out against the head or steel spark lead bracket.
Normal running - light throttle - nothing - all fine, engine on all 8. Keeping a light gas pedal much the same.
Hit the gas pedal and the arcing was quite intense combined with firing on only on 7 cylinders.
This is where basic electrical fundementals came in to play. The MSD system made the misfire issue worse in one way. The significant additional electrical energy meant that with electricity always following the easiest path meant that when hitting the gas pedal the resultant additional rich mixture (and extra electrical load) in the combustion chamber of no. 3 cylinder was enough for the 'spark' to follow an 'easier path'. In this case earth (flowing through the spark plug boot to earth).
Backing-off the gas pedal and with the far weaker mixture giving the 'spark' an easier time flowing to the spark plug. A re-routed new plug lead and boot (replacing the burnt lead/boot) was a simple cure.
For me that was a valuable lesson that actually took months to realise!
 
Chuffer

Chuffer

CCCUK Member
Back in my happy place again for the week courtesy of Hemi V8 power ie , North Wales - the land blessed by the Gods and the Bards . This is the 7th time we have returned to this isolated early 19th century farm house surrounded by mountains and woodland with only a few cattle and sheep for neighbors . Total peace and quiet with only bird song and the babble of a mountain stream to break the silence . With the summit of Cadair Idris to the rear and the Rhinog mountains to the front , whats not to like ??
Spent the day on the beach at Shell Island which our special place having proposed to my better half there 30 years ago . She was daft enough to say " yes" :LOL:
Clear blue skies all day and the perfect clear vista of all the main peaks of Eryri ( Snowdonia) and the summit of Yr Wyddfa ( Snowdon ) not capped by clouds all day which is a rarity .DSC_4954.JPGDSC_4933.JPGDSC_4935.JPGDSC_4950.JPGDSC_4946.JPGDSC_4940.JPGDSC_4937.JPGDSC_4939.JPG
 
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