Curse you Rolon....

[Aleco]

So I took of the oil filler cap on my sprint and saw that the chain had started to be graunched on the outside of the chain.
Seemed a bit weird as the engine had only been rebuilt ~ 4000 miles ago.

So when the cam cover was removed along with the engine front cover this is what I found......

IMG_20160929_164118-800x600.jpg (139.97 KiB) Viewed 4335 times

Oh joy! As you can see the rubbing head has come adrift (found in sump)

It's also killed the sprockets including the sprint spares vernier pulley

Please check your chains regularly if you have a Rolon chain tensioner.

Luckily I've caught it in time before the engine grenades itself.

On the same but different note: I've got an STR 91 camshaft. Do I really need a vernier pulley? Is it worth it?
If it is where can I get one??

Alex

[Mahesh]

I see the chain is also branded Rolon, changed at the same time ?

[Mad Mart]

You can get a Kent Cams vernier sprocket from Larkspeed. Part no. S43. £160 inc. delivery.

[tony g]

Nasty, at least you caught it before you got a sump full of links like Alun did (I think)
Re the cam sprocket, try a std one on there and check out the numbers on the degree wheel, It may be near enough to make no difference but once you have the number to change it by you could get the std one redrilled with corrected degrees. That's what I did. You normally only time a cam once so its fit and forget.

Tony

[Aleco]

Yes the chain and tensioner were changed at the same time. The rubbing head on the tensioner looks as is it is glued on.

Cheers Mart I'll have a look at Kent cams. In your experience are they worth the expense and effort of getting them set up?

[Aleco]

Once again my googling skills are failing me, I cannot find an S43 vernier on the Kent Cams or Larkspeed site.

I like your idea as well Tony. I'm learning as I go with this one as I've not been involved with cam timing before.

[gmsclassics]

Don't know how long ago you rebuilt the engine (time not miles), but I would try to at least get the parts replaced by whoever supplied them - including anything and everything that was damaged. Certainly worth a try as it worked for me and what they replaced has been fine.

I don't think I've heard of anyone using a vernier sprocket with the STR91 cam. STR139, then yes.

My calculation based on the specs below would indicate a maximum inlet opening timing setting of 108 for standard, 107 for the 91 and 102 for the 139.

Standard
Timing (to 74): 12/52-52/12
Timing (75 on): 14/50-50/14

STR 0091
Timing: 40/73-68/32, Valve lift: 0.383", Duration: 286 °

STR 0139
Timing: 68/92-76/56, Valve Lift: 0.435", Duration: 324 °

Setting up cam timing is a pig of a task, takes forever, requires the patience of Job and I certainly could never guarantee my settings between plus or minus one degree at best. Therefore I can't see any reproducible difference between 107 and 108. A slightly stretched duplex chain on a head that has been skimmed a couple of times and you won't be at 108 anyway.

Obviously entirely your call, but I seriously doubt you would be able to detect any difference when driving, or even in lap times on a race track.

Hope that helps

Geoff

[Mad Mart]

Yes they are worth it if you want to get the maximum performance from your engine. If you use the standard sprocket you will, obviously, only ever be half a link out. But that can be a few BHP. Tony's suggestion is what some folk have done. Slot the original holes and add two more as permanent fixtures once you have the correct position.

[Jon Tilson]

When I timed my cam to the correct figure using an adjustable top pulley it made the biggest single difference to a car I can ever remember.

Its not that hard with a dial gauge. It was ages ago but I set the inlet valve to peak open, then slackened the adjusting gubbins and move the crank to the correct figure - think it was 106 in my case...then retightened. I dont remember it taking more than an hour and I think you get about 10-15 degrees worth of adjustment.


Sympathy on the Rolon tensioner, but this has been known about long enough now that nobody should still be fitting them. Lets get the word outr further by any and all means possible, including the f-b group.

Jonners

[Aleco]

Thanks for the replies.

I didn't fit the chain or tensioner, I bought the engine from a forum member. The engine was built in about 2010 so it may have been before the issue was known about.

[xvivalve]

My engine, I think the first to suffer this problem, failed in September 2010 on the way back from TDCIR Yeovil.

[Aleco]

After a few phone calls I've got hold of a vernier pulley anddecent cam chain and tensioner from Robsport. The only issue is that done have any of the curved chain guides in stock and neither do Rimmer's.

Can I reuse the old ones of they are not worn?

[Jon Tilson]

If you see no sign of the rubber bit detaching then yes reuse the old guide. How bad are the pulley? Be careful of the jackshaft one too as it does the water pump and timing. May also be worth check the jackshaft keep plate for wear as well as that keeps the jacko from floating in and out.

Jonners

[Aleco]

OK cheers Jonners,

In the mean time TD Fitchetts came to the rescue. I just inspected the guide and it's not great

The sprockets are pretty poor. They have burred worn to a sharper point

[Pippin]

Please check your chains regularly if you have a Rolon chain tensioner.

Wouldn't it be better to throw the Rolon in the bin and replace it with a decent tensioner for peace of mind?