FireballXL5

Replacing plugs... Curious to know the gap... Crate engine is new as of 3500 miles ago , carb is still rich and needing a tune...

Yesterday the car started running a little rough through the power range ... Been kinda hot rodding it around... Starts and idles fine/normal ... Runs through the rpm range, but just feels rougher than normal ... I'll check gap of the plugs I pull, but I'm guessing they'll be sooty... The engine seems to be consuming a bit of oil... I'm keeping an eye on that too...

68Thunder427

Depending on what the plugs look like (post pics) you may need to step up one heat range or two. Gap is typically .035 for just about any GM motor but not certain on your crate. If your motor is burning oil with only 3500 miles on it then the builder screwed up on the rings or valve seals. Your roughness could also be blow by if the rings are not the proper size or not seated correctly and may not even be your carb at all.

zwede

If you have a CD ignition box you want 0.045"-0.050" unless you have very high compression (>11:1).

FireballXL5

My 'rough' condition happened all of a sudden yesterday...

The crate motor was installed by a shop, paid for by the PO...

All my plug gaps are coming out in the .042 range... So I'm continuing that trend... So far, not as bad as I expected... Plugs 2,4,6,8 are swapped... Will try to post up pics... But they get loaded one at a time, so bear with me and my 8 pic posts as I go along...

FireballXL5

Cylinder 2


Cylinder 4


Cylinder 6


Cylinder 8

FireballXL5

This is the specs on my motor




I would assume that the rings/heads were all assembled complete and it just needed the 'add ons' by the shop... I may contact them and ask a few questions...

The PO only drove it 254 miles in two years after doing all the work, so everything is/was fresh... I'll give more of a backstory and my history after I pull the remaining plugs... ;-)

FireballXL5

Cylinder 1: a little 'extra' crusty deposits...


Cylinder 3: a little more 'deposits'...


Cylinder 5: looking better...


Cylinder 7... Uh... Yea... We've got A problem... Coincidentally I found a header bolt had backed out right above this plug... Dunno if/how that is related...




Well... It should be noted that a few of the spark plug boots were replaced for header clearance... And cylinder 7 is one of them... Could this much soot/cr@p be caused by this plug not firing? Or am I now troubleshooting bigger problems? Replaced the plug and half heartedly checked the plug end... May try throwing on an old spark plug into the boot and checking for spark... But... Thoughts? Lol

zwede

That's major oil fouling. Sorry.

FireballXL5

Rings? Head gasket? Both? Explains my smoke on startup... Never noticed any other effects til yesterday...

FireballXL5

Test drive went well... Firing on all 8 again... Smoother by far... The roughness all but went away... And for once , I didn't have black sooty deposited behind the car on startup like usual... Didn't see any 'smoke' to speak of either...

I'm not discounting anything as 'Fixed' by any means... I'm still an hour+ away from home and I will have to drive home tomorrow, no avoiding that... Will have to conduct some further tests later ... But not tonight...

worship79

Replacing the plugs would be a nice opportunity to pressure test each cilinder.

FireballXL5

Yea, didn't have a tester with me ... And had to put em all in to get home from the girlfriends house ... Will redo them later and test... ;-)

FireballXL5

Thinking I'll pull the plug on cylinder 7 again... Bout 70 miles driven on it to get home... Try a compression test... See what it looks like etc... Are you guys thinking head gasket? If I decide to tackle that, anything I should know/look into before pullin it? Been a while since I've dismantled an engine... Lol

zwede

Compression test will probably not show anything. The cylinder can have good compression and still burn oil.

No oil passages through the head gasket, so that's not the issue.

Some possibilities for oil burning:

• Intake gasket
• Piston oil ring broken
• Rocker stud hole open to the intake port and stud not sealed
• Cylinder badly machined (rings not sealing)

Since it is only on a few cylinders it is probably not sucking it in through the PCV valve.

FireballXL5

It's really only on the one cylinder... #7... So, you think intake gasket or valve seals are the 'More likely culprit'? I'll snap a pic of the fresh #7 plug here in a little bit ... Should I just bite the bullet and try a intake gasket first? Are there any ways I can help narrow it down myself before bringing it to a 'specialist' and throw $$$ at it?

FireballXL5

Pcv valve is clean and rattles nicely... All cylinders run fairly clean from what I saw pulling plugs... Just have an issue with #7... Not sure what my best course of action is... I'm not afraid to pull intake to check/replace a gasket myself... Just not sure yet how to diagnose that as the culprit here.. Or do I have to pull it to find out?

zwede

You could use a bore scope, remove the carb, and look into the intake port for oil. Or just remove the intake. Intake gasket would be my first fix. Fairly easy to do and inexpensive. Also remove the rocker studs on #7 and check if the hole goes into the port. If so, put sealer on the studs and re-install.

havesometo

If It only smokes when you first start it up. Sounds like a valve guide seals to me.

claysmoker

Who built this fine engine for you? Inquiring minds need to know.

FireballXL5

Bought the car from the PO with this engine installed... It's a 383 crate motor bought/installed by a hot rod company...

With the history of the car only being driven 254 miles in two years by the PO it's possible and likely that the rings may not have seated properly on that cylinder... Going with some recommendations I've received, I'm going to try going back to a 'Break in' oil, and learning to tune the carb/engine a little better.. I'll monitor any smoke or oil consumption and see how things go for a little while.. Will tear into her more later if needed... But this does make sense, and is a little less 'Intrusive' for now...