View Full Version : Carbon problems

11-25-2007, 09:09 AM
I am doing some cleaning of my classic this winter and I just pulled the heads off of my 3.9 liter. If I diddn't know any better I would think the was a chocolate factory in each of the cylinders. There is coabon everywhere. some cylinders worse than others but some have chunks of cabon, layer upon layer. Does anyone have any ideas about the causes? What comes to my head are to rich a mixture, bad ignition, weak spark, octane of fuel to low, oil seeping past rings. Any ideas? I can send pictures too if anyong would like to have a better look. Oh and the gasgets looked like they where not leaking and had been replaced with 10 bolts in each head instead of 14! thanks if anyong has any ideas!

11-26-2007, 07:00 AM
carbon is a hard brittle coal like substance which normaly occurs with use of leaded fuel, if two bolts were missing in each head oil probally migrated from the top down into the cylinders accumulated and with heat hardened up,in that case (where the bolts were missing those cyl's were most likely more contaminated) and you might want to check for worn or tight valve guides and replace the valve seals ,clean the residue up and reassemble with new gaskets and all the bolts required.....

11-26-2007, 07:26 AM
What I believe happened is at one time the old 14 bolt metal head gasgets were replaced with composite 10 bolt gasgets. They do not look like they where leaking through the walls but I do not know about the guides. the heads themselves are very clean (IE no sluge build up on the top end unlike the rest of the block) which makes me think they may have been refurbed. The cylinder walls overall look bretty good. The camshaft looks like it might have a bit of wear, I havn't checked the condition of the lifters yet though. Any idea about rebuilding vs. cleaning up and slapping everything back together. What might have caused the carbon if infact the heads have been sealed well? Another hint, this moter was burning some oil comming across the country this last fall. When I would step on it (3000 RPM) I could smell oil burning and see my tailpipe puffing. Rings, guides?

11-26-2007, 11:00 AM
the head bolt thing doesnt seem right, is there threads in the extra holes? can you thread a head bolt in the blocks holes that werent being used? if there is threads in the block and there is corresponding holes in the head than there is supposed to be bolts in there holding the head down,(possibaly wrong gaskets were used) the only way to be sure about the heads is to remove each valve spring see if the valve is sloppy in the guide (it should have no side to side movement) and also should move freely up + down + rotate, and check condition of the faces and seats,the time to do it is now or you will regret it later if over 100k you should probally send out to be reconditioned.....

11-26-2007, 11:06 AM
its too bad the heads are off you could have performed a comp test to tell you if the rings are bad before you disassembled and if you have blow by,1) check for ring ridge, 2)and if its been severely overheated then that cooks the rings, both of theese cases indicate new rings needed.....

11-26-2007, 04:48 PM
I have a fealing that there was some blow by in the rings because before i put the rig up i drove across the country and the truck was using about a court of 15-40 oil every 500 miles. A lot I know, that was my first indicator that something was up. I have decided to pull the moter, and pop a few pistons out and see if I can find some more clues. I am also pondering over trying to find a newer 4.6 liter moter to swap with the older 3.9! Any thoughts?

92 classic
01-04-2008, 10:33 PM
man roverteck is right why did u pull the motor apart with a oil consumption problem without first doing a compression test and or a cyl leak down test. hey but now u can buy an even more expensive hole bore gauge set and check the cylinder for out of round specs. and carbon is a fact of life and for one reason u have so much time to get ur cats heated for emmisions and what better way to do that than to flood the cats with fuel to be burned .use a fuel additive to keep the fuel sys clean. hey roverteck where abouts do u work.i used to work at landrover birmingham worked their for about five years.u ever meat a guy named dale dickinson in school o my name is harry blalock

01-05-2008, 10:13 AM
its apart anyhow just do a complete overhaul,install a new cam for some pep (d&d fabrications/ aluminumv8.com).
why risk a good valve job while uncertaint of the condition of the rings.
the hardest part of the bottom end is removal from the frame.

01-15-2008, 10:38 PM
With your oil consumption I think you found the source of the carbon.