OBX256deg x 9mm cams,sort of a review,sort of a question
Posted: Mon Jul 30, 2012 2:30 pm
any input appreciated.
I was thinking of getting some regrinds but my son has been using an OBX lsd diff center in his 13b turbo for a few hillclimbs,been happy with it so far.So I thought I'd give a set of their el cheapo cams a go.$263 +$70 postage from california.They turned up in 7 days,upon unboxing they appeared to be very well machined all over,surface finish good, no chatter anywhere,nice radii,journal sizes all mic'ed exactly the same .they then went on the shelf with a lot of other stuff for 6 months.
two months or so ago I put them in without changeing anything else,exhaust cam went in no problem,took about an hour after opening bonnet.Inlet cam also in and pulley on without losing timing in 30 mins(including a cup of tea).However when doing up pulley bolt,it seized a little at about 15 mm in.I had one hand tap this size at home so tapped it in situ...tap was promptly buggered in about 1.5 turns,its a 30 mm hole.Soooo.. they forgot to put protective paste in thread when they were heat treated.
I wanted to drive the car so back in with the stock inlet cam,again without losing timing.Drove it about 600 k's over the next few weeks.definitely a change for the better in upper rev range,only a little lumpier at idle,happy so far.didnt actually expect much from just this as engine is otherwise stock and still got stock exhaust manifold.I was a little worried about the hardness of the cam but there are no wear marks on the lifter or on the cam.
I wasnt at work so I bought a triple set of hand taps locally ($32 for suttons plug,intermediate,taper) and tried tapping further starting with the intermediate...buggered that too in another turn.I machine some moderately hard materials at work and this was scary listening and watching the tap flex while winding back out.I waited till I was back at work and grabbed a handfull of machine taps(plug only but a little stronger than hand taps and with an expensive coating on them) with a and a .1 oversize drill as I suspected the hole was also a little tight.I drilled it out in my baby lathe at home(just fitted).again scary hard noises coming from this.Finally got it tapped after this,but still ruined another (machine) tap.
also found CAS slot was .04 undersize,again very hard.had to use a diamond file from work for this.
I was rained in two weeks ago so I decided to put the inlet cam in and start on more of the stuff on the shelf,timing belt,waterpump,crank seal,adjustable pulleys.(you were right Dann,sort of.I finally remembered I got them from here
viewtopic.php?f=44&t=47296&start=15
,lol)
I first put it in again without changing anything else,but when I started the engine it had a very cranky idle,I put a timing light on the ignition....waaay out.so time to pull the covers off and do things properly.
After fitting most things and deleting aircon I was still rained in and still waiting on a new crank bolt(turns out It would have been quicker to get them from the UK than from 5km away).so time to find out what these cheap cams really are.
So what do I really have,what do they compare to?
I'm mainly only experienced looking at Ducati desmo cams,and that more than 20 years ago(before kids,lol)so I dont know whats normal for these engines.
sun is shining,i've got 4 days off work,yard is almost dry enough to get car out of shed.if new crank bolt doesnt turn up shortly,i'll be just throwing the old one in and start driving.
Mick
I was thinking of getting some regrinds but my son has been using an OBX lsd diff center in his 13b turbo for a few hillclimbs,been happy with it so far.So I thought I'd give a set of their el cheapo cams a go.$263 +$70 postage from california.They turned up in 7 days,upon unboxing they appeared to be very well machined all over,surface finish good, no chatter anywhere,nice radii,journal sizes all mic'ed exactly the same .they then went on the shelf with a lot of other stuff for 6 months.
two months or so ago I put them in without changeing anything else,exhaust cam went in no problem,took about an hour after opening bonnet.Inlet cam also in and pulley on without losing timing in 30 mins(including a cup of tea).However when doing up pulley bolt,it seized a little at about 15 mm in.I had one hand tap this size at home so tapped it in situ...tap was promptly buggered in about 1.5 turns,its a 30 mm hole.Soooo.. they forgot to put protective paste in thread when they were heat treated.
I wanted to drive the car so back in with the stock inlet cam,again without losing timing.Drove it about 600 k's over the next few weeks.definitely a change for the better in upper rev range,only a little lumpier at idle,happy so far.didnt actually expect much from just this as engine is otherwise stock and still got stock exhaust manifold.I was a little worried about the hardness of the cam but there are no wear marks on the lifter or on the cam.
I wasnt at work so I bought a triple set of hand taps locally ($32 for suttons plug,intermediate,taper) and tried tapping further starting with the intermediate...buggered that too in another turn.I machine some moderately hard materials at work and this was scary listening and watching the tap flex while winding back out.I waited till I was back at work and grabbed a handfull of machine taps(plug only but a little stronger than hand taps and with an expensive coating on them) with a and a .1 oversize drill as I suspected the hole was also a little tight.I drilled it out in my baby lathe at home(just fitted).again scary hard noises coming from this.Finally got it tapped after this,but still ruined another (machine) tap.
also found CAS slot was .04 undersize,again very hard.had to use a diamond file from work for this.
I was rained in two weeks ago so I decided to put the inlet cam in and start on more of the stuff on the shelf,timing belt,waterpump,crank seal,adjustable pulleys.(you were right Dann,sort of.I finally remembered I got them from here
viewtopic.php?f=44&t=47296&start=15
,lol)
I first put it in again without changing anything else,but when I started the engine it had a very cranky idle,I put a timing light on the ignition....waaay out.so time to pull the covers off and do things properly.
After fitting most things and deleting aircon I was still rained in and still waiting on a new crank bolt(turns out It would have been quicker to get them from the UK than from 5km away).so time to find out what these cheap cams really are.
So what do I really have,what do they compare to?
I'm mainly only experienced looking at Ducati desmo cams,and that more than 20 years ago(before kids,lol)so I dont know whats normal for these engines.
sun is shining,i've got 4 days off work,yard is almost dry enough to get car out of shed.if new crank bolt doesnt turn up shortly,i'll be just throwing the old one in and start driving.
Mick