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MG MGB GT V8 Factory Originals Technical - OIL FOULING
|Hi guy's, can anybody throw any light on this problem i have of oil fouling the combustion chamber.Let me first say that the engine has had a re-bore new pistons,rings,reground crank,new rocker shafts,rockerarms,valve-guides,valves,oil pump gears+base plate,etc,ect. Oil pressure at tickover is 30psi rising to 42psi whilst on the move,[high pressure relief valve].The only thing left that i can think of is that too much oil is being delivered to the rocker area,and that oil is being drawn down the valve guides,is this possible? and if so how can i safely reduce this.[what do you think Harry]. Thanks Graham.|
|Bores honed and rings bedded in?|
|Paul. Yes bores honed, i don't know if rings bedded in or not, how do you know? the only thing i do know is that when i removed the rocker cover the oil pouring out of the rocker shaft seems too much, if i rev it slightly [1200rpm]it throws oil all over the inner wings, seems far too much to me. I just wondered if there is a safe way to reduce the flow rate? Thanks Graham.|
|Graham, can you describe exactly how you've got the crankcase breathing system rigged? How many miles on the motor? Any work on the heads ... any special kind of valve seals you're using?|
|Harry, crankcase breather "T" piece at the back of the engine venting to atmosphere, rocker cover breathers hooked up to air filter, all free from blockages. Thanks for the reply Harry,i have to go out now, will reply later. Thanks Graham|
|Harry, the motor has done no more than 2,000 miles since rebuild, only 40 miles since new rings, [just in case the rings had'nt bedded in for sme reason]. Now then valve guide oil seals are another story, i purchased valve guides that would take oil seals from R.P.I engeneering when i originally did the rebuild, and fitted the oil seals, [the trouble is that i did so much all at once i can't pin it down to a specific thing.] So when i started to have this problem with oil i removed the oil seals, thinking that the oil seals were causing the problem because half of them were destroyed, and that originally it did'nt need oil seals anyway. So at the moment i am running with no oil seals. I am still convinced that there is too much oil in the rocker area. Thanks Graham.|
|Graham, it's of course fraught with peril to try to remotely diagnose, but may I humbly suggest --|
1. When the rings have at least 1000 miles on them, advise if this problem still exists. If the rings are brand new they could be allowing plenty of blowby -- this is quite normal.
2. Hook up the breathers so that the one coming off the portside valve cover runs into the air cleaner, and the one coming off the starboard side valve cover runs to the intake manifold via a PCV valve. Nothing open to the atmosphere. This will give you a little suction inside the block, and it may help your issue.
3. Get some new oil seals. I'm only a dumb American but I have heard decidedly mixed opinions about RPI's wares. Perhaps choose another vendor? This could, in and of itself, solve the problem. But don't worry about this 'til you are convinced that the rings are not the culprit.
Lastly, I'm not the one to advise you on this except very generally -- you may want to fit oil line restrictors to the block in a couple of places. You may find it a real pain to do this with the engine in situ and assembled.
|The factory system of venting both rocker covers into the carbs and having a partially restricted crankcase breather at the back of the engine does result in a slight vacuum inside the block.|
A friend had some work done by RPI and they managed to fit a second coil ballast in series with the factory ballast, to what was a 12v coil anyway!
|Harry,Paul. Could not get into the web site yesterday. |
But found out what the problem has been, [with help from S S Conversions Ramsbottom lancs.] It was my BA**S
up as soon as i had finished explaining what was happening, they told me that i had fitted my rocker shafts the WRONG WAY ROUND! came back home 5pm job finished by 6pm, sorted VERY happy. Thanks for your input Harry,paul.
For anyone who thinks they may have the same problem. ON one end of each rocker shaft there is a small notch, this notch should be facing [looking from the front of the engine]to the FRONT AND UP on the left side [drivers side uk] and to the REAR AND UP on the right side.
Thanks again Harry,Paul.
This thread was discussed between 28/05/2001 and 31/05/2001
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