MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Rocker Holes & Oil Pressure

On the question of oil pressure the latest issue of TTT2 has an interesting article on rockers. (TTT2 can be downloaded free if you've not read the article). My two heads & a third rocker assembly in pieces, all have the holes unplugged. This seems to be quite common & no doubt is the cause of the fountains you hear about with the rocker cover removed, as well as oil covering the underside of the car, along with slightly reduced oil pressure.

What do you guys think? If recommended which method would you employ? The ball bearings sound attractive but if one ever came loose I'm pretty sure the outcome wouldn’t be good!! Cheers
Peter TD 5801
P Hehir

I think the factory had a lot of experience pushing these engines to the extremes in rallies and racing, and knew what they were doing with oil delivery. I see no reason to change anything. If oil pressure is low, something is amiss and it should be found and remedied. Restricting the oil flow to the head is only going to increase wear on the rockers, rocker shaft and push rods, and possibly even the cam and tappets since that's where the oil from the head drains to. Just my opinion, others are sure to disagree.
Steve Simmons

Another purpose of oil flow is cooling. Less oil flow..less cooling of the mechanism. The engineers had been designing, building and racing these for decades by the time our cars were built. I have no idea how many life times I would have to live to have that much experience. I try to have my starting point..now that I am older than dirt..to be perhaps these guys were not incompetent in their jobs. Regards, tom
tm peterson

I have a vague memory that Mustang V-8 rockers arrived with holes, but were supposed to be welded up after the engine was broken in.

Pressed-steel rockers are not found in MGs, and I agree with Steve - if you have low oil pressure, rebuild the rocker gear and oil pump (equal culprits).

I've never seen an XPAG rocker gear with the holes filled in. and prefer the cooling effect of the oil on the head - which I think is real. Although I can't think of why, a TA engine may have some different characteristic that makes it necessary there. Why is there no specif XPAG factory service notice between 1939 and 1955, if this is a problem?

I'm not reluctant to open up a rocker cover while the engine is running, and although it gets a bit messy, I don't usually see oil squirting to the heavens from too much oil - they tend to ooze and flood. Not a problem to me.

Tom Lange
MGT Repair
t lange

The following is a quote from the TTT2 article.

"There was a Morris Engines Service Sheet published in March 1938 that told dealers to blank these holes off by hammering 1/8 inch ball bearings into the holes".

The article goes on to say;

"I found an article by Don Jackson in an old ‘Octagon Bulletin’ #198 dated July 1986. It explains that “these holes should have been blanked off in production, so you are only correcting a fault that shouldn’t have occurred in the first place. The result will be proper pressure fed lubrication of the rocker bushes, improved lubrication of the tappets, and a vast reduction in the amount of oil swilling around in the rocker cover. You will also gain a few pounds per square inch oil pressure as a bonus!”

I have nothing to contribute to the debate other than to agree with Tom about "the cooling effect of oil on the head", which seems to make sense to me... I'm not suggesting this is cure for low oil pressure. Just curious is all, however I would like to know whether Abingdon really intended these holes to be blanked off. If they did then I struggle to understand why they allowed engines to leave the factory with unplugged rockers UNLESS it was an essential part of a breaking in protocol, as Tom states, citing the Mustang V8's. The Morris Engines Service Sheet published in March 1938 mentioned above, that told dealers to blank these holes off, seems to suggest just that. Clearly more research is needed. Cheers
Peter TD 5801
P Hehir

I was a member of the Octagon MG Car club with Don Jackson. I took his advice and welded up the holes in the rockers about 1984.Those same rockers and camshaft are still in the car, still quiet or as quiet as xpags ever are.Probably 130,000 miles since, not sure as I have had spare engine in occasionally.
He also suggested to shim out the camshaft retaining plate to make sure all lobes were properly off centre to ensure cam follower rotation to prevent wear.
Ray Lee

Thanks for your post Ray. Your experience certainly suggests this mod does no harm. If it were a factory to dealer break in procedure, someone, somewhere, surely would have a copy of this protocol.. or is there perhaps a mechanic still out there who was working in a dealership way back when with a clear recollection of this?

I was going to ask you to elaborate on the "all lobes properly off centre" comment, which initially struck me as most odd, but after pondering the statement for a couple of minutes I think it must suggest that if the lobes were precisely centered on the follower, the followers would not, could not rotate because follower rotation clearly requires an off centre up force applied by the lobe? Obviously cam follower rotation is desirable to avoid wearing a groove in the face. If so, thanks Ray. I've just learnt a little more about the XPAG. I guess/hope this is not a problem with roller lifters.
Cheers
Peter TD 5801
P Hehir

Hi guys,
Here is another alternative I learnt from Tony Ohlmeyer, an old MG expert, in about 1972.

I always turn my rocker shaft upside down. Due to the keyways this needs to be "end over end". A new supply hole has to be drilled (after local grinding to get through the case hardening). My theory is that when the load is off the rocker, oil pressure forces oil to exactly where it is needed. Some of the oil can then ooze round to the top where it can exit and run down to lube the valve stem top. Note the other hole which sends oil to the adjuster ball.

I have run my road car (42 yrs) and my last two race car engines (both 19 yrs) like this. The supply hole is a weak point in a race car so I now drill the new supply hole in the side of the shaft and grind a groove around inside the rocker post.

Bob Schapel
R L Schapel

I'd love to see some pics on this mod Bob or even a sketch or two. When you say "oil pressure forces oil to exactly where it is needed" it suggests the original design didn't achieve that quite as well as Tony's modification does. I'm all for improving the lubrication system as more effective lubrication means a longer lasting engine. Any thoughts on the hole in the rocker question? Cheers
Peter TD 5801
P Hehir

Bob Schapel, I'm not quite understanding your modification. Do you have any photos that would further explain this. I, like Peter, are building engines with roller cams. I'm running roller lifters as well. How does this or would this affect their operation?

Cheers
Bill Chasser
TD4834
W. A. Chasser Jr

Bob, I like your thoughts about the oilsupply. Last week I was checking my worn rockershaft and got puzzled about the design of the oil groove in the bearing bush and the location of oil supply. Hard for me to understand why the those days engineers decided to bring the oil in at the non-load side of the bearing (top) and to make oil grooves in the (pretty heavy) load side. But these oilgrooves are not activly fed by oil supply nor are they transporting oil. So, the only job these grooves can do is to provide a hiding place for any oil that makes it into that bearing load side, almost to assure metal to metal contact. And that's what happened in my worn rockershaft.
I also want to create an oilsupply in that lower bearing part but without taking away that o so important oil splashing from the rockershafts. And I also do not want to create a larger oilflow at the shaft in total as to maintaine the oilpressure. My plans now are to block all 8 topholes with a tiny M3 setscrew (loctite and screw them in just below surface), to drill 1,8mmholes next to the previous holes for rockertop oilsplashing and to drill 8 holes in the bottomside also 1,8 mm to provide oil to those heavy loaded bearings richt there where the load is. The current holes have a diameter of 2,5 mm. The two 1,8 mm holes make the same square. Instead of using those oil grooved bearings I want to make new ones without that groove. Greetings, Huib
Huib Bruijstens

Interesting topic, seems strange two well known XPAG engine gurus, Neil Cairns and WKF Wood, make no mention of this issue in their documents.

Graeme
G Evans

Unless I'm missing something here, oil is already delivered right where it needs to be. The tappet is only under load for a short time, then it's at rest for another 1.5 (roughly) cycles. During that time, additional oil is pumped into the bushing which is now overflowing, and this ensures that as it comes under load again that the two metal surfaces are separated by a layer of lubricant. The oil will not retreat into the groove in the bushing, it will continue outward because the groove is already full and has more oil being pushed in from the rocker shaft. It is delivered to the top because gravity is working for you by draining downward and this is more efficient than trying to push it upward. The clearances between bushing and shaft affect oil pressure. The dribble of oil out of the top of the rocker is the result of resistance by the clearances between bushing and shaft. The dribble is on the unrestricted side of this assembly, therefore you can have 80PSI coming in yet a dribble coming out. In other words, there is plenty of oil pressure to supply the rocker bushings with oil AND have a hole in the top. Just my views on the subject, and I have no plans to try to improve what seems to still be working after 70 years.
Steve S

Sorry, I don't have any photos and I don't know much about roller cams. I also agree that the original design has worked well for a long time. There is probably no real need to change things (esp. in a road car) as long as everything is in good condition. BUT I can't stop trying to improve things. I race a S/C race TC in Historic Races and so I constantly try to find ways to improve reliability.

When a valve lifts, the load is on the underneath of the shaft. Yes, oil will get there with gravity and other means but I like the idea of a direct squirt of oil pressure from holes in the bottom of the shaft in between load cycles. Oil will still easily work its way to the top where it can ooze out and shake down to the top of the valve stem. Blocking the holes might reduce the lubrication of the valve stem tops so I would not do that. It seems to me that in the standard system, the oil comes out the top of the shaft and most goes straight out the top of the rocker before doing much lubricating. It is a bit like crankshaft drillings. They used to be like XPAGs with the hole in a position which was easy to manufacture but now, big ends are all cross drilled like MGBs, so the oil comes out at the load points.

I once broke a rocker shaft. A few racing rivals have too. They break at the oil supply hole in the rear pedestal because the hole underneath makes it a weak point where the shaft is in tension. That is why I no longer have a supply hole at the bottom. At the side, the metal is not in tension, so it is a good place to have the hole. It just necessitates the grinding of an oil groove inside the pedestal to get the oil from the pedestal hole to the rocker shaft side-hole.

Cheers, Bob
R L Schapel

An unrelated point about rocker shafts .... also gleaned from Tony Ohlmeyer in the early 70s.
Each rocker pedestal, COMPLETE WITH ITS SPACER WASHER, should be clamped (across the big bolt hole) in a vice with the shaft in position. This simulates being bolted up tight in an engine. The shaft should then be wiggled and twisted by hand to see if it is in fact clamped tightly in the pedestal. In my experience they rarely are! To fix the problem the spacer washer can be ground down thinner until the shaft will clamp tightly. Repeat for each pedestal.(Then don't mix up the spacers!)
If the shaft is not tight in the pedestals, it slops up and down and becomes even looser. This could create noise and makes it hard to set valve clearances accurately.
If you have a spare old rocker shaft lying around, have a look at it and see if it has a hammered/worn appearance at the points where it sat in the pedestals. If it has been clamped nicely, those sections of shaft should look brand new!

Bob
R L Schapel

Thank you for your comments thus far. It seems the more I learn the less I know! The two schools of thought on the rocker holes suggest much more info is needed. I've written to the Editor of TTT2 suggesting it would be helpful if the author of the article could possibly enter the discussion. If a factory paper can be presented this would give some legitimacy to the suggested modification.

I'm intrigued by both of Bob's suggestions but confess I still don't understand the first. I now have a spare complete rocker assembly & will do the clamp test, however a quick visual examination of the shaft does suggest some wear & a very slight rough feel seems to confirm this. Bob, once clamped, should the shaft turn fairly easily with the fingers or require some force to get it to rotate? Obviously too tight is probably as bad as too loose. As I have a torque wrench, which could be applied to the slot head at the end of the shaft, can you suggest a figure at which the shaft should begin to turn? Also if a shaft is just showing very minor wear can the spacer washer at that pedestal be adjusted or should the shaft be replaced? Cheers
Peter TD 5801
P Hehir

Hi Peter,
I normally just thin down the washer, not replace the shaft. I do it until I can't turn the shaft by hand. I have never used a torque wrench to test the tightness. The only problem with them being too tight would be the risk of the pedestal cracking across the top.

Re the first mod..... if you put the shaft in backwards, this results in the oil holes pointing down instead of up because the keyways still have to be on the big-bolt side of the pedestal. This also results in the oil supply hole pointing upwards inside the front pedestal instead of aligning downwards in the rear pedestal where the supply comes from. Hence a new supply hole must be drilled.

I once dismantled a rocker assembly which had been (accidentally I assume)put together upside down but with no new supply drilled. Surprisingly there was no major wear! It was a race engine so might have done very few miles.

Bob
R L Schapel

Thanks Bob. I've got it now. Do you bother to close up the original oil hole which is now at the top of the front pedestal? Cheers
Peter TD 5801
P Hehir

No, That is blocked off by being clamped in the front pedestal.
Bob
R L Schapel

Thanks Bob. Just got a reply from John James the Editor of TTT2 who has contacted Brian Rainbow, the author of the article that instigated this thread. Brian is now aware of the discussion & has indicated he will be in touch with us when he gets back from his Xmas vacation. Cheers
Peter TD 5801
P Hehir

This thread was discussed between 18/12/2014 and 24/12/2014

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now