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MG Midget and Sprite Technical - Blanking off rocker shaft oil holes.

In this month's MASCOT there is an article by a chap who is carrying out a restoration on a Frogeye.
In the part where he describes the rebuild of his engine, he mentions among other things, "Then I modified the tappet rocker shaft by blanking off the 'lower' oil holes, thus allowing all the oil pressure flow into the top half of the plain bearings, where the load is. This improves oil pressure and allows the oil to act more as a floating bearing and results in a much quieter 'top end'. An ex-racing enthusiast gave me this tip from the 60's."

I'm not passing an opinion, but it's a new one on me and what is an "ex- racing enthusiast"?
What do you racing boys think?

I hope Gary won't castigate me for breach of copyright.

Bernie.
b higginson

The load is on the lower area of the bearing. Sounds weird to me.
Roadwarrior

"ex- racing enthusiast"

That would be anyone that USED to watch nascrap on TV, like me.

Im glad I could be of help to the poor chap, of coarse we were both drunk off our goard at the time in that little pub down by the holler.


My hope is someone you tubes that 1st 10 minutes of what is soon to be classic of an adventure going horribly wrong.

I cant belive I never thought of that brain fart of an idea

I wonder if peter burguss has ever tried this...myth busters to the rescue

Prop
Prop and the Blackhole Midget

New one on me, too.

As Roadwarrior says, the load is on the lower part.

I'm pretty sure that the guys at BMC put a lot of thought into where they put the lubrication holes. I've always trusted their judgement.
Dave O'Neill2

Bernie,
I'm not sure of an "ex-racing enthusiast", but is it anything like an "ex-tractor fan" ?
Graham

Your a fan of racing until your not

.
Prop and the Blackhole Midget

Yup. My thoughts entirely about the load being on the bottom rather than the top. Also agree with Dave, about the original spec being good enough.
I just thought I'd ask if anyone had come across it before. I wonder how long the engine will last?
If the guy is a contributor to the BBS, perhaps he may come on and explain it to us.

Bernie.
b higginson

Bernie
Try a 'letter' to Editor for a response from the author?
Alan
Alan Anstead

he's talking about the bearing area in the rocker pillars I think; as the valve springs are all under compression the force is trying to lift the rocker shaft so the load in the pillars will be on the upper surface won't it? Having said that, I agree with Dave O, I've always trusted time-served factory engineers over shade-tree engineeering any day.
David Smith

you only have to look at a knackered shaft to know where the load bearing surface is ... yep: on the lower half!
David Cox

There should be no rotation of the shaft in the pillars as it is held by a grub screw in one of the pillars thru a hole in the shaft. These are basically unlubricated anyway, only recieving what can splash around and what may creep past the locating stud. What possible 'lower hole' could be blanked off here?

Sounds like a load of old 'my mate in the pub' stuff.
Roadwarrior

Interesting.

"Then I modified the tappet rocker shaft by blanking off the 'lower' oil holes, --"

Could this inadvertently be the cause of high oil pressure on some engines? -- Mine included. Could those of us with oil pressure in the 80's and above on start up, have a partially blocked shaft?

I know this was asked before, but I for one ruled it out. I think I'll take a closer look.

Lawrence Slater

I would guess the high cold starting pressure is the exit to the PRV is at capacity when the oil is cold and viscous
Dan Cusworth

Doesn't drop much when hot. And the prv isn't blocked, hasn't had a stronger spring fitted, and isn't sticking.
Lawrence Slater

Lawerance

When I replaced the oil pressure spring and plunger in 2008 during my rebuild...with the new adjustable oil pressure set up, it came with the wrong spring...

When I compared the old spring and plunger plus cap to the new spring,ball bearing and adjustable cap... there was about 1 and 1/2 inch indifferance between the 2 set ups ( the new one to long)

If I had used the new setup as was shipped, im sure id have had oil pressure at 200 psi before any adjustment
I wonder if your spring is to long... have you compared your pressure spring, plunger and cap to a known normal operational working pressure spring set up

Another thought I have im not to familar with but has been discussed here before...


there are some crank shafts that have oil reducer plugs in them, not all of them, theses slow down the volume of oil flowing thur the oil passages but do raise the oil pressure...im not sure where these plugs are located exactly ... iirc ... I want to say its in the mains bearing journal

Trevor jessie may have some insights on that... I seem to recall him and Bill young discussing this several years back

Prop
Prop and the Blackhole Midget

Lawerance

When I replaced the oil pressure spring and plunger in 2008 during my rebuild...with the new adjustable oil pressure set up, it came with the wrong spring...

When I compared the old spring and plunger plus cap to the new spring,ball bearing and adjustable cap... there was about 1 and 1/2 inch indifferance between the 2 set ups ( the new one to long)

If I had used the new setup as was shipped, im sure id have had oil pressure at 200 psi before any adjustment
I wonder if your spring is to long... have you compared your pressure spring, plunger and cap to a known normal operational working pressure spring set up

Another thought I have im not to familar with but has been discussed here before... there are some crank shafts that have oil reducer plugs in them, not all of them, theses slow down the volume of oil flowing thur the oil passages but do raise the oil pressure...im not sure where these plugs are located exactly ... iirc ... I want to say its in the mains bearing journal

Trevor jessie may have some insights on that... I seem to recall him and Bill young discussing this several years back

Prop
Prop and the Blackhole Midget

As I said Prop. Original spring length. Original spring in fact. If anything it would be weakened/shortened with age.

Interesting that you mention -- " there are some crank shafts that have oil reducer plugs in them, -- ". I've not heard of that before. Where would I look for these oil reducers?
Lawrence Slater

The 948 cranks were crossdrilled and had restrictors fitted to the oil holes on the outside of the journals.

I haven't seen any in 1275 cranks.
Dave O'Neill2

As I said Prop. Original spring length. Original spring in fact. If anything it would be weakened/shortened with age.

I thought maybe if we kept bring it up the spring would give in ....haha

To be honest lawerance I really couldnt say... I just remember the converstion be cause of its timing that I had recently lost my engine due to a busted crankshaft and was able to replace it with one of the rare (r) en40b crankshafts and was taking every precaution to avoid that never happening agian

Thus I vaguely remember the converstion that bill young was discussing at the time...in all fairness it could well have been on the smaller A series...I dont recall that topic ever being raised agian or sence

There is always the arcives.... EEEKKKKS haha

It would have been late 2008 to late 2009, i want to say trevor jessie contributed intellegently to the converstion as well

Prop

Prop and the Blackhole Midget

Well a quick google search shows that it may not be to uncommon for oil restrictor to be built into the 1275

Here is a link by APT... a very popular and high priced out fit that once employed david vizard that makes the claim that they build to there crankshafts oil jornals screw in oil restrictors

Make of it what you will i guess

http://www.aptfast.com/ListItems/SubCategory/Crank%20Shaft%2C%20Components/Cranks%20APT%20Prepared.aspx

Note... if the website dosnt work, try removing all the (20%) obviously an old website...so make sure your anti virus syrum is up to date

Prop
Prop and the Blackhole Midget

Hmmm... maybe out of luck on the link, even the BBS servers are rejecting a modified version of the link

You want me to do what?, and my data pack would go where exactly? And you want me to infect myself with what agian so you can read about ... screw in oil plug restictors...

Yes HAL, thats what the BBS is asking you to do.

Hahaha

Prop
Prop and the Blackhole Midget

This thread was discussed between 08/05/2014 and 11/05/2014

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