Engine breathing problems

CastleMGBV8 · Post by **CastleMGBV8** » Sun Mar 29, 2009 5:16 pm

Mark,

I did think of that but if you do it use the thinnest shims as you will be making your rocker geometry worse, unless you have already had the pillars machined to correct the orignal design error, you could just use the blank side with a new smaller hole drilled.

If you try it as a temporary measure just to see if it cures the problem, be careful with the placement of the shims as the holes in them do not always line up with the holes in the heads if you place them square with the base of the rocker pillars so you could just try moving them slightly to restrict the flow if you can get them to stay inthe right place when replacing the rocker assemblies.

I think the oilways are at the front of the engine so you only need to do two shims, you could check by sliding a piece of wire of a suitable length, if one side stops shorter than the other then my memory has failed me

Kevin.

Post by **katanaman** » Sun Mar 29, 2009 5:24 pm

Cant you fit the restrictors in the rocker pedestals instead of the heads to save the hassle? Cant honestly remember that the holes are like in them but it should be possible.

CastleMGBV8 · Post by **CastleMGBV8** » Sun Mar 29, 2009 5:27 pm

Marki, the design of the rocker pillar bases would not allow you to fit a restrictor unfortunately.

Kevin.

mgbloke · Post by **mgbloke** » Sun Mar 29, 2009 7:01 pm

Im going to try the shims with smaller oil hole and will also get the catch tank modified.
Next track day is at Castle Combe at end of April so that will be a good test.

Thanks for your help
Mark

CastleMGBV8 · Post by **CastleMGBV8** » Sun Mar 29, 2009 9:41 pm

Mark,

Your welcome, don't forget to adjust the preload if you running less than 35 thou at the moment, othrwise you will have insufficient preload for the lifters to pump up properly.

Kevin.

Robrover · Post by **Robrover** » Thu Apr 02, 2009 2:11 am

I too have Yella Tera rollers on my 4.6. As part of the installation process YT recommended I fit restrictor grub screws into the heads to reduce the voulme of oil going to the rockers and flooding the rocker covers. This seems to work ok. YT have a part # for these, have a look at their website. I've got a KN breather on one of my P6B rocker covers and a pipe on the other going into a catch tank vented to the open air (not back into the Edelbrock).

spend · Post by **spend** » Thu Apr 02, 2009 12:14 pm

Where the oil runs up the pedestal, can you not just put a bush around the bolt to restrict the flow. Seems like it would be a much easier place to modify?

topcatcustom · Post by **topcatcustom** » Thu Apr 02, 2009 2:24 pm

The bolt might not sit perfectly in the middle and a bush could try and push it out of line, plus it would be hard to get the perfect size- and the ally pedestal may expand when hot increasing the gap!

spend · Post by **spend** » Thu Apr 02, 2009 3:09 pm

Does that matter if you are just restricting the flow? Tolerances would be different to block it?

I have cunningly different wasted bolts on mine.

mgbloke · Post by **mgbloke** » Fri Apr 03, 2009 7:32 am

Thanks for all the input.
Looks like oil restriction is the way to go.
Trawled Yella Terra site but cant find any mention of this.
One thing concerning me is wether the top end will get enough lube ad lower RPM.

Mark

mgbloke · Post by **mgbloke** » Sun Apr 26, 2009 8:55 pm

Update
I managed to tap the oil holes with heads insitue. Forced grease into the hole first and smeared grease on the 6mm tap, 1/4 turn at a time and wiping off swarf. Then turned engine over on the starter to pushout the slug of grease and hopefully with it any remaining swarf.
Drilled 2.5mm holes in grub screws and tightened them into place.
Also had catch tank outlet made bigger to 19mm.

Guess what?

On track its still the same pushing out approx 1/2pint every 15mins.
Only does it when driven hard.

Will try a 2mm hole next.
I think it is the oil holes on top of the rockers.
Really need to get this sorted.
Any suggestions

Thanks
Mark

mgbv8 · Post by **mgbv8** » Sun Apr 26, 2009 9:16 pm

Mark
Mine blows a good bit by on the 1/4 mile. I was actually blowing the dipstick out by 3". So I fitted an extra breather. Basically I turned the oil filler cap into a filtered vent. Problem solved!!

If you want to go down the route of trimming the oil flow to the rockers, you should find that an M5 tap will clear the hole in the head. Then a M6 tap will give you a useable thread to put an M6 grub screw in with a 1.5mm hole drilled though the middle.

You can experiment with the size of the hole in the grub screws. When you are happy simply use a centre punch to pout a slight lip above the grub screw hole so it cant wind itself out.

mgbv8 · Post by **mgbv8** » Sun Apr 26, 2009 9:25 pm

I forgot to mention.
If the oil slots in your rockers are too big. You will need to go down to around the 1mm mark with your restrictors.

I'm in the middle of a situation with a new build engine. It turns out the after market rockers have oil slots in the holes approx 10 times deeper than stock. No wonder the rocker are dropping enough oil to actually flood the tops of the valve guides. Not good on an early engine with rubber washer valve stem seals eh??

If you run the engine with the rocker covers off at idle you should only see a seep from the rockers and not a gush.

Perry

mgbloke · Post by **mgbloke** » Sat May 30, 2009 3:58 pm

With the Yella terra roller rockers the stock rockercovers are not deep enough with the baffles fitted but are OK with them removed.
To overcome this I had some old rocker covers machined down to make spacers. so fitting 2 rubbergaskets and the spacer gained me about 10mm.
With this in mind I thought I would try a little experiment and fit one cover without baffles and spacer and the other one with them. Then each was vented into seperate clear plastic bottles as a temporary measure.
This way I could see how much oil was being ejected each side.
I was thinking after th first 15min session on track my experiment would be complete and I could just plug the hoses back into the catch tank.

Anyway after a couple of laps I was really into the swing of things and the speedo was just off the scale going up Avon rise ( Castle Combe) ( 130mph true). Left the braking as late as poss.
Meanwhile under the bonnet I hadnt realised that one of my temporary catch bottles had slipped and fallen over. It just happened that this was the bottle connected to the side with no baffle and spacer which had blown out approx 1/4 pint of oil which had run along the bulkhead and dripped down on to the brake pedal.

As I applied pressure to the pedal my foot slipped off the oily pedal and straight on to the accelerator.

Just managed to keep it all together bearing in mind I was heading into a 120deg corner.

Anyway the upshot of all this is that with 2mm restrictor holes and baffles & spacers fitted the problem has been eliminated.

Rambling over.

Mark