Slipping skunk cams

[Luderbrit]

Hi all, I've finally build and fitted my "new" H22a1 engine , after about 80 miles of real steady driving (no vtec engaged) i suddenly heard a horrific clattering from the engine and it was speed related, I pulled in and on inspection nothing could be obviously seen with the street lights, I chugged back home at 40mph and free wheeling to stop the clatter.
The next day after a bottle of wine ( to calm myself down ) i checked the oil and water which was fine, i then noticed the inlet cam gear bolts were loose by about 2 threads (Skunk 2 pro2cams) and the cam had pulled around 4marks on the Vernier scale anti clock wise,
Could this cause the valve lash like noise, n.b. engine sounded normal excluding rattle when I did rev it up a little.
I have emailed Skunk for torques on the adjusting bolts but still waiting answer or if you guys know.
The engines new build is with new piston rings, total replacement big and small end bearings, cam bearings, new engine shims etc, port polished and matched inlet and exhaust manifold and head, stage 2 high lift cams, Skunk 2 cam sprockets, Cromer heavy duty valve springs, light weight high flow valves, lightened flywheel, type R euro inlet manifold and TB. Well its taken me years to build and this happens. BIG question
Could the heavy valve springs be to much for the cam sprocket bolts as the engine is quite tight especially when starting
Just a bit more info, the cam bolts weren't fouling anything which I thought they may have been catching on the cam cover
I re-adjusted the valve clearances which all needed to be reduced to manufacturers tolerances ( probably engine bedding in)
Any help would be gratefully received before I restart the engine

Sorry for the saga

[wurlycorner]

Could this cause the valve lash like noise, n.b. engine sounded normal excluding rattle when I did rev it up a little.

Sorry to hear of the troubles.
It will cause misfires etc. because the timing is out (valves open/closing at the wrong time in comparison to piston at TDC and when the spark plug fires).
I don't know if that amount will be enough to cause the pistons and valves to physically clash.

[Vtecmec]

I have adjustable cam gears and an uprated valvetrain and I wouldn't worry about the combination.

Likely they've just backed out (did you check them out of the box?), I thread locked mine in place, so it might be worth using some locktight.

Also, the adjusting bolts on mine interfered with the plastic cam cover and I had to trim a bit away to make it all fit.

[Drax]

exactly what wurly and vtecmec say above

ive built several high n/a engines and had various issues (99% my fault). i replaced my cam gear bolts for better quality ones after the advice from someone here, but as vtecmec says they then foul the plastic cam cover so you either need to trim a bit away, or leave it slightly forward like i do - never take & leave the cover off in case anything flies in.

i would time everything back up again, double check all bolts, connections then run a compression test to check for damage before starting her up. It may be worth getting a cheap endoscope (i think you can get affordable ones that attach to your phone) to check the valves and pistons for clash, save taking the head off.

[Luderbrit]

Hi Guys, all good info.from you that know, I contacted Skunk and their "A" engineers contacted me saying the cam gears come with instructions that say to red locktite the bolts then pre torque in a star pattern to 7lb then 30lb or 40 nm using a 1\4 drive torque wrench.
I zero'd the cam then reset the valve clearances, I found that they had opened up over 0.30mm on all valves including the cam that was not effected, I re -adjusted them all to manufacturers tolerances, incidentally the engineers asked if i degreed the cams and reset the valves when i built the engine, and the answer was yes, it is a fiddly job with some fancy setting up but it has to be done as you all know.
I am now waiting for a reply. I started the car up and all is well ,a little bit quieter than previous but not yet road tested, good idea to do a endo scope test and compression test cos I've got the gear
I'll let you know the out come
Thanks lads

[Luderbrit]

IMG-20241115-WA0002_copy_2160x3840.jpg

Cover cut away only exposing cam wheels, minimum exposure

[wurlycorner]

Excellent news, well done for sorting and I'm pleased Skunk replied with the info you needed!

One query - and maybe it's the angle of the photo, but the tension on the belt looks potentially a little slack? (I'd have thought it should be tight down against a couple of teeth earlier).

[Luderbrit]

Your so right Wurly good spot, i reversed the car by hand in gear this reversed the direction of the cams and it slightly give some slack at the belt, the reason I done this is because i needed some play to adjust the cam gear to centre, the image is pre adjustment ,if you see the bolts are not central, I have a manual belt tensioner fitted which is set to 1/2" flex. soon as the cams turn the correct way the tension is fully back on both gears, double checked TDC marks afterwards
One thing i did find out which is crucial to all that own these cams the 12 mounting bolts on the cams are wrong, engineering standards say that the depth of the engaged threads should be at least 1 1\2 diameter of the bolt, The bolt length is 9.3mm the diameter is 5mm the bolt engagement is 3mm no wonder the bluddy things came loose, not to mention they are torqued into alloy, but 3mm grip I have now ordered a set of 16mm capped bolts and anti shake washers from West field fasteners LTD £9.77 inc.
On my cams there is plenty of meat on the gear hub for 16mm depth threads, but i will be cautious about how much locktite i use as the grip on the threads is about 10% more on the final torque. so no snappy bolts when I take them out

[wurlycorner]

Great spot on checking the thread depth of the bolts - are they the bolts skunk supplied with the cams? If so are you going to point that out to them!

[Luderbrit]

Answer to that is they supplied the bolts, and I did let them know. All i got back was" we're pleased your noise has gone" !!!!!
I got a bit shirty with my initial result report about the bolt length, maybe I've huffed them