GT6 rockers

[PhilD]

Has anyone come across problems when fitting new rocker shaft and rockers on MK3 GT6?
Having stripped and rebuilt the engine (early 1971 model) there was significant wear on the lobes and shaft so replacement was needed, I checked the oil pump and the clearances were in line with the manual so was not replaced.  All parts were well lubricated on assembly and the engine was spun until oil light went out before starting it was run for about 5 mins but seamed to have dropped a cylinder or more.  On stripping the top to check there was a lot of condensation, a seized rocker and a couple of partially seized yet a reasonable amount of oil around the shaft.

[Anthony]

I'd like to hear about this too, as I'll be rebuilding mine shortly

[PhilD]

Problem found and sorted, spinning the engine over with no rockers and only the shaft and feed pedestal it took almost a minuet for oil to start to drip from the shaft and quite a while to get to the front of it.  Fitting the external feed pipe delivers oil in 10-15 seconds and it runs not drips!

[JohnD]

Oh, OH!
The Spawn of Beelzebub rises again.
Interesting experiment, Phil, but ask yourself.  If the oil got to the rockershaft so quickly and copiuosly with an external supply, where else is NOT getting its oil so quickly or in such quantity.  Yup, the crankshaft.
Then ask yourself.
Which really NEEDS a good oil supply?
Yup, crankshaft.

Triumph carefully designed the metered supply from the camshaft, and IMHO (and many others) that is sufficient for ordinary rockers which need little oil.   Search here and many other Triumph MsBs if you wnat to know what others think, but my advice is NOT to fit the external supply.

John

[FGRob]

I've just finished installing a top oil feed to my 1300 MkIV, the main reason was the excessive wear on the shaft and rockers, having read all the arguements I decided to fit a flow control valve in-line which still gives you the direct feed but allows you to throttle the oil flow to a reasonable level, I've taken the feed from one of the oil galary bolts using two oil feed kits to give me the correct connections either end as I required. I'll post some pics tomorrow.

This will take away the arguement of excessive oil in the rocker area (smoking) but will prevent excessive wear and also any potential damage to the crank due to oil starvation as it's not an open line.

[tiggrr1]

Sounds like you have thought it through but it is still a lot cheaper and a whole lot easier to change out a rocker shaft and associated bits than rebuild the bottom end.

Not having a pop it's just the way I see it.

[FGRob]

tiggrr1 wrote:

Sounds like you have thought it through but it is still a lot cheaper and a whole lot easier to change out a rocker shaft and associated bits than rebuild the bottom end.

Not having a pop it's just the way I see it.

Hey it's all about trying something different, I prefer not to re-build anything to be honest once done I would like to forget about it. My biggest problem is oil drainage as the car does not get used a lot, this allows me to give the top end a squirt  :B and then throttle it back once running.

[JohnD]

Rob,
Indeed, you have clearly given this a lot ofthought, and agree with the extended view that a flow restrictor in the extrenal feed can prevent it 'robbing' the crankshaft of its oil supply.
You mention, "a flow control valve in-line which still gives you the direct feed but allows you to throttle the oil flow to a reasonable level, I've taken the feed from one of the oil galary bolts using two oil feed kits to give me the correct connections either end"
Gosh!  Is that an adjustable valve?
And TWO lines!   One will go to the drilling in the back-left-hand corner of the head, where the other?
I look forward to your pics with interest!

Finally, the usual restictor in the line is an orifice, a disc with a very small hole drilled in it.  Practical exepriment has foud that the hole needs to be less than 1mm in diameter, which makes me think - why bother?   Unless the rear camshaft beraing and its metering scroll isn't ther fror some reason, or damaged, the rockers will get the litle oil they need by that conventional means.  I stopped using an external line o my engines aafter several melted thier main and big end berrings, and have never regretted that the rocker oil supply is insufficient.

JOhn

[PhilD]

My original decision was not to use the external feed based on various posts but to suffer the loss of a new shaft and a number of new rockers  caused me to re think that decision, I agree the flow rate now is probably steeling supply from the crank so I would be interested in a solution that achieves a happy medium between the two.  Based on the state of the old shaft and rockers the flow could do with a slight improvement.

[Richard B]

How many miles has the engine done?

Often the cause of poor oil flow; is a build up of carbon inside the oil gallery, in the head.

You can clean it up with 3 drill sizes, just turning the drill bits by hand.

1/8" from the top (vertical oil way that feeds the rocker shaft)
3/16" sideways (horizontal oil way accessed via the bolt at the back of the head)
1/4" from underneath (vertical oil way that is fed via the head gasket/block)

The last one needs the head off of the engine.

[Nick Jones]

I think there may be another factor at play here.  There have been reports that many of the currently available rocker shafts are not very hard.  As the rockers are not bushed it may be that the hardness of shaft and rocker bore is quite similar which tends to increase the possibility of galling and "picking up" under marginal lubrication conditions.  Perhaps especially likely under "first run conditions before the parts have bedded to each other.

As regards the external oil feed, I've never found the need for them, but if properly metered/restricted I doubt they'll cause major problems.  Worn rear cam bearing surfaces and coked up oilways can restrict oil flow to the top end on high mileage/neglected engines.

Nick

[PhilD]

The speedo that came with it shows 19k so it would seem it has been around once or replaced, as the project came dismantled I can only confirm the originality of the chassis and engine as the numbers match the heritage certificate I purchased.  
The car seems to have had multiple owners who have dismantled different bits of it.
I would believe the oil ways in the head are in a reasonable state as the flow rate via the back port is good, does the oil ways in the block suffer on these engines?

[Richard B]

No its the heat from the head that cooks it.

[FGRob]

Here you go, this is the flow control valve I've piped in, as I said I've used two of the Oil Feed kits which came with a 5/16" UNF banjo bolt which just screws into the head and the block oil gallery - not sure what the bolt size is on a GT6 though:

[FGRob]

Here's the head:

[FGRob]

Here's the block oil gallery: