VR Oil Pump and Timing Chain.

[Stag76]

Thanks for the good info.
The Oil-Pump fitted has 6 splines (2 groups of 3) separated by two 27mm sections, and this was being driven by the cog with 2 flats.
The cog that came in the chain kit has 6 evenly spaced splines and it doesn't match the pump so I've ordered another one.
The tensioner that came with the chain kit I purchased fits OK.

[Stag76]

I'm still in trouble with this.
The first chain kit I got had 6 evenly spaced splines that didn't fit the oil pump, which has 2 flat sections and 2 sets of 3 splines.
I have now received a double row chain kit which has a drive cog with 2 flats which will fit the 2 flat sections in the oil pump,
but it didn't include a tensioner. It's a Rollmaster CS6130 to fit a VP V6.
The instructions with it say to use a .030" steel reinforced cover gasket, and to machine .030" off the rear cover of the oil pump
for clearance.
It also says to remove the balance shaft...will I have to remove the actual shaft, or just the drive cog?

Is this the best way to do it?

[vlad01]

Just pull the shaft out, it has a needle roller bearing pressed in the back of the block, so no oil feed to block like in the ecotec engines. The bearing just stays in the block, the whole shaft slides out once you remove the retaining bolt and plate, might need a slide hammer type of deal to pop the shaft out as the front bearing is a very light press fit.

Removing the shaft improves engine revviness a lot (rate of acceleration/deceleration) and really helps them take off a lot quicker, there is easily 3kg of rotational mass deleted.
However, because the V6 were balanced weird from factory with a 36.8% reciprocating weight balance instead of the typical 50% in most engines, they get some funny shuddering at exactly 1600 rpm at least in a commodore chassis, stock mounts etc... like harmonic with the rest of the car. It might not happen on yours. I know others who didn't have this, I think it's a harmonic with the greater car, not just the engine in isolation. A typical 50% balance was perfect on my hot VP, well perfect for a Buick anyway.

I believe GM did this 36.8% to tune the natural vibration out of one other planes and try move it all into a plane that was most effectively canceled via a balance shaft and/or engine mounts, So removing it leaves this vibration that is strong in one plane, where a 50% balance is a little vibration distributed in multiple planes where it's mostly not noticed and absorbed by the engine mounts to a large degree. At least all of this to the best of my knowledge, balance is a very maths complex subject and I don't understand all aspects of it, but I do know that the delete of the shaft causes a narrow band but strong harmonic where a 50% after a delete is not much worse than bone stock. I still think it was worth it, for the performance alone it was great! Also I found that one of my engine mounts (hydraulic type) exploded early on and was a total loss of fluid, rendering the damping practically to nothing, it was only found 10 years later (a few weeks ago) after I removed the engine, I had only done 9k, so the mount lost it's oil very early on and may have made this vibration worse than it needed to be, but I always recall that shudder from day one of the shaft delete.

The roll master chains do not use a chain damper normally, although you can in theory add one, but it might wear funny over time. The late VR and I think all ecotec? dampers are the wide type which does cover 3/4 of the double roller chain. But it's like offset iirc. I never fit one, but I did test mount one to see if it was feasible which it seemed to be, but I hardly know anyone who ever ran those chains with one. I even asked if any of the Formula Holden guys did, not a single person had and none of their chains ever broke or had issues as far as they reported and they used the actual roll master ones. Those engines are the peak of wild for the Buick, high rpm (7k) and huge cams with 260deg 0.050" cams which make me feel confident in them being durable, even with no damper combined with worst case valve train loads and harmonics in the case of the Formula engines. The chains do stretch with use to a point, but it doesn't seem to bother them. I have the double roller in my mild/hot VP and it runs no damper either.


I just ran the machined oil pump cover from Mace and the factory gasket (not sure how hard they are to find now) But even just a replacement gasket should be fine with the machined pump cover.

When assembled, I used a feeler gauge between the pump cover and the pins in the chain rollers and then a spatula or something to force the chain over to the front as much as possible and measured with the feelers to see if I had room spare and nothing was touching. I reckon I had well over a good 1mm or so which is heaps, they normally center, when running so that is the worst case when forced to the front. Also, when checking this, tap the crank with a soft mallet at the rear to make sure that the crank float is also taken into consideration.

https://www.maceengineering.com.au/Mach ... ec-and-L67

[Stag76]

Once again...thanks very much for the great info.
I've ordered a pump cover from MACE so hopefully that will be all I need.
Thanks again.

[vlad01]

No probs at all

[Stag76]

Is there a secret to removing the oil pump cover, and what tool fits the studs.
The locating studs are very tight, so tight that I've sheared off the torx bit that
was the closest fit I could find.
I don't want to force them in case they're left-hand thread.

[vlad01]

They are normal thread, I think they are T-30 torx and you need to just abruptly crack it briskly to crack them open, slowly applying the force often strips the heads or the bit, it's the shock load that cracks the screws or any bolt like that loose. Else you can use an impact driver (the type you hit the back with a hammer) or you can use a impact battery drill to do the same, former is safer and works first go normally. Sometimes a little heat on the heads can help easy them loose

If it's stuck with the head rounded out, you can carefully drill the heads out of the old cover, and just wind out the remaining threads with your fingers normally, or carefully with pliers.

[Stag76]

Thanks for that.
I got them all out bar one using a Torx bit in an impact driver.
The one that stripped out was the top one, so I was able to cut a track
across it with an angle grinder cut-off wheel, and use a blade bit in the impact driver to remove it.
I got some new studs and the new pump cover is fitted.

However...the RollMaster dual-row timing chain cog I bought will not fit easily on the crankshaft.
It's just a bit too tight to tap on, and I'm concerned that I may get it on and wedged
in the wrong place by a few thou, just enough to destroy the chain. The cam-wheel fits OK.

I've got 2 other cog wheels, one new and one used, and they both push on firmly but easily,
which should indicate that the crank is OK.
Is this a common thing? It feels like it may slip on if I heat it, but I would still have
the location problem.

I've worked on a lot of British engines, and I thought they were bad, but this one is
driving me to distraction.

[vlad01]

The rollmaster sets can be like that, it's not uncommon. Normally an engine shop would hone that on a Sunnen machine and give it maybe half a thou, but not always easy for the home mechanic.

Oiled well and some heat will get it on. Also when the oil pump drive and pulley is installed, that will drive it home. You can use that and then remove the pulley again before finishing off the timing cover side of things, just be careful with keeping the cam sprocket parallel at all times as you drive the crank sprocket home, if you go too far on the crank before the cam one gets onto the cam, it will not allow you to get it on the cam at all since the chains are so tight on these and then you'll have to get a puller and remove the crank one and try again, this can also cock the chain and cause unseen damage light a slight bend or a roller to get pinched/bound which might cause it to bind and jump later on in operation, ending in catastrophic damage.

The OEM chain sets have always fit well for me, the Melling ones fit perfect, but they no longer make them as of 2024, I happen to replace mine in 2023 and they were low on stock, later on they were nowhere to be found and pulled from the Melling catalog. The Cloye ones are another option, but I've heard Cloye are hit and miss with other makes of engine, so I have not tried them personally, I think Nason have chain sets too, but I am not sure who makes them, all that I have used had USA on them. The rollmaster are the best, at least from a performance stand point, but like any performance part, they might need additional machine work.

[Stag76]

I've got the cog machined and the chain fitted.
Is it necessary to replace the Cam-Wheel locating bolt?
The VR engine I've got is running a VP ECU, with the Cam Angle Sensor disconnected,
so I'm guessing that it isn't necessary to re-fit the magnet to the cam-wheel. Is this OK.