ned
|
| posted on 8/7/03 at 09:08 AM |
|
|
Cams - reground?
I've picked up a set of cams (QED 38H with setup sheet) with a job lot i got off ebay. I'm selling on a couple of injection bits but have
started thinking about some of the bits I intended using.
Is there a simple way of telling if cams are outright/purpose made or reground standard jobbies? The ones I have have all the same GM stamp and
numbers on them and look to have a smaller diameter (ie could have been standard then machined and reduced to the current profile). Is there a simple
way of checking this?
Vernier Pulleys:
Does anyone with Vauxhall knowledge know if they used 2 types of cambelts on the Xe engine? I only ask as the vernier pulleys I have appear to have a
different type/size of teeth to the standard road ones. (smaller and squarer whereas the standard ones are slightly larger and have more inverted
semi-circular teeth.)
The cam followers were meant to be solid but some of them 'squish' like hydraulic ones, though are different looking from the underside to
the standard ones I already have.
I believe these bits are from a late Xe. I think my original engine is an early one. Are there that many differences between them?
I know the earlier blocks had better cranks and forged pistons, but the head appears to be ok (although is a GM casting whereas my early one is a
coscast casting.)
Any help/comments/knowledge appreciated.
Ned.
[Edited on 8/7/03 by ned]
beware, I've got yellow skin
|
|
|
|
|
Findlay234
|
| posted on 8/7/03 at 09:21 AM |
|
|
People regrind them to give you a more suitable profile, including opening and closing times and duration. Now comes the guesswork............ the
problem is that when you do this you actually take material away from the cam, so the total valve lift will go down. From this i deduce that you would
need to run oversized shims on the valve buckets (if thats what the Xe uses, id have to do that with my 4age) If you compare them to the OEM cams and
they have a lower but wider profile then i guess theyre reground, but if they have a larger lift then i reckon they are forged/cast like that.
Anyone know better than me please let me know.
|
|
|
Stu16v
|
| posted on 8/7/03 at 10:16 AM |
|
|
Ned, the early and late XE (in fact all VX engines) cam belt tooth profiles are different. IIRC the early engines have a 'square' profile,
whereas the later ones are 'rounded' with a finer pitch.
IIRC the QED solid lifters are actually converted hydraulic lifters. To adjust clearences, you have to assemble head, measure clearences (if any) and
work out what shims are needed to give required clearance. There has been (rare) instances where converted hydraulic lifters have actually converted
themselves back to hydraulic at high revs, with obvious consequences....
I would doubt that the QED ones have had this problem though.
Camshafts are probably going to be regrinds, especially if they can be used with standard pistons (they can, cant they??....). IMO, the standard cams
are already about as wild as you can get, and camshaft changes in these engines rarely make a big difference, unless pistons are pocketed and
'proper' cams put in.
HTH Stu.
[Edited on 8/7/03 by Stu16v]
Dont just build it.....make it!
|
|
|
ned
|
| posted on 8/7/03 at 10:33 AM |
|
|
Thanks for the info. I have done a bit of reading (my QED catalogue helps!). From the bits I have, I think the early pulleys are the (bigger) rounded
ones and the late ones are the (smaller)squarer ones.
I suspect the lifters are converted hydraulics and some have either failed or I have a mix of the two types.
The cams would fit in the profile of the standard ones, they are wider at the peak of the cam ie longer duration and different lift. they are supposed
to be 210bhp+ on carburrated engine. These are QED's fastest road/hydraulic lifter profile and yes Stu, do run with standard pocket pistons. If
these hadn't've come along I would only consider 'proper' cams as an upgrade route, along with high compression 'flat
top' or 'high intruder' type omega or accralite pisons.
Anyone running a late Xe head need any (Piper) vernier pulleys?!! if not they'll go on ebay.
I also have a late Xe (slightly heavier) polished crank if anyone requires one. surplus to requirements (would rather have my early, lighter one
reground).
thanks again,
Ned.
ps I think I'll know most of what there is to know about Xe's by the time I'm finished rebuilding this bloody engine!!
beware, I've got yellow skin
|
|
|
ned
|
| posted on 8/7/03 at 10:35 AM |
|
|
Just had a thought as to why the lifters could be bugg***d.
The guy I got the bits off was running nitrous on his Xe engined Nova. (he's now running it on his yamaha R1, which he says scared him when he
turned it on and wheelied at 100mph!!)
That could well explain things....
Ned.
beware, I've got yellow skin
|
|
|
ned
|
| posted on 8/7/03 at 10:47 AM |
|
|
incase anyone's interested the bits discussed look like this:
beware, I've got yellow skin
|
|
|
Peteff
|
| posted on 8/7/03 at 05:46 PM |
|
|
Reground cams
I thought this had died out years ago. Used cams were built up using a metal spray technique then reground to their new profile before being
rehardened. They were usually on an exchange basis but now the manufacturing process is cheaper so they don't seem to be available any more.
Check a standard cam lobe height with your vernier caliper then compare it to your new ones, there shoul be a difference and the profile is a
governing factor as well giving different overlap etc.
yours, Pete.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
|
|
|
david walker
|
| posted on 8/7/03 at 09:00 PM |
|
|
You'll find the square tooth profile is from the earlier XE (up to about '90 I think). The round tooth is later. Change the crank pulley
and water pump and run the round tooth pullies per your verniers.
Most QED hydraulic profiles are regrinds. Cam grinders (ie Kent, Piper, Newman) will still regrind cams. No metal spraying though - I think that went
out years ago.
Hydraulic profiles can give 200 bhp with appropriate head mods and carbs.
It sounds as though you have hydraulic lifters, there are different profiles for these and it may be that you just have a mix following an earlier
rebuild. The ones that feel solid are probably just full of oil or knackered.
The QED hyd lifter conversion kits are good and I have used them a few times. They cost about £70 a set, whereas proper race solid lifters are more
like double that depending upon where you source them.
If you are shimming at home you'll find it difficult. Shims go up in 10 thou steps, you use the nearest, thickest shim and then reduce its
thickness on a shim grinder (small surface grinder). Better to take it to a race engine builder and pay him!
Back on this point about early engines having better pistons, I'm not sure I agree. All the XE range used squeeze cast pistons from Mahle as OE.
These are sometimes mistakingly referred to as "forged". Trivial point really as they are still very good!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
|
|
|
Stu16v
|
| posted on 8/7/03 at 11:21 PM |
|
|
quote:
Back on this point about early engines having better pistons, I'm not sure I agree. All the XE range used squeeze cast pistons from Mahle as OE.
These are sometimes mistakingly referred to as "forged". Trivial point really as they are still very good!
Agreed. The story goes that a few very early engines were made with forged pistons (possibly homologation specials). Mahle AFAIK is standard fit,
whatever age engine, if it has anything else, they have probably been changed at some stage. I personally wasnt aware of crankshaft differences
either....???
Dont just build it.....make it!
|
|
|
ned
|
| posted on 9/7/03 at 08:43 AM |
|
|
Well,
not disagreeing with what anyone says, but my engine (that i got complete) which is an early one, early crank and cosacast head had the round teeth
standard pulleys on it. the head i bought, advertised as a late head, which came incidentally with a late crank has vernier pulleys which have the
squarer teeth (the pulleys are slightly smaller too). Am i missing something here?
The cams are regrinds as the profile is ground within the profile of the standard cam (i'll put a pic up shortly showing both)
Ned.
beware, I've got yellow skin
|
|
|
ned
|
| posted on 9/7/03 at 08:51 AM |
|
|
beware, I've got yellow skin
|
|
|
davef
|
| posted on 9/7/03 at 10:00 AM |
|
|
cams
Hi guys just to clear something up here you can have cams reprofiled and finish up with more lift. you must remember the cam follower does not see the
cam ctr it see the base circle of the cam. imagine a cam wich is 20mm from ctr to lobe tip and 12mm from ctr to base circle, so subtract 12mm from
20mm gives you 8mm lift. now machine the cam taking the bulk of material from the base circle. now you have a cam 19mm from ctr to lobe tip and 10mm
from ctr to base circle. result 9mm lift. thats why you see many reprofiled cams were the base circle is nearly down to the cam diameter. cheers
davef.
|
|
|
ned
|
| posted on 9/7/03 at 10:02 AM |
|
|
Dave,
I had realised this, hence the pic! though thanks for clarifying/backing me up!
Ned.
beware, I've got yellow skin
|
|
|
david walker
|
| posted on 9/7/03 at 06:37 PM |
|
|
Hello gain,
I wasn't aware of difference in cranks either. I've ground plenty & never realised there was a difference, there again we learn
something every day! Any chance of posting comparison pics?
Pulley on left in picture is later type of profile. It sounds as if your engine has been messed with during its 15 year life!
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
|
|
|
Stu16v
|
| posted on 9/7/03 at 10:42 PM |
|
|
I've got it mixed up too. The round profile is the earlier type, but if you look at the pitch of the teeth, there are less per cm/inch compared
to the other pulley (I was right on this bit!!). I will check on my car tomorrow night to confirm (also early engine).
However, if nothing else, at least we are all aware that there are different cambelt teeth options on this engine. I know of quite a few people that
didnt know this, and have fitted incorrect water pumps to their engine. Not nice....
Dont just build it.....make it!
|
|
|
ned
|
| posted on 10/7/03 at 08:50 AM |
|
|
if anyones interested I've put the vernier pulleys on ebay!
I took a couple of pics last night of cranks, so sohuld have them up shortly...
just to add, it doesn't suprise me that my engines have been messed about, they both came out of novas and one of them had at some point been
nitroused! I spoke to a friend last night who commented that the squarer teeth profile pulleys might be from an ecotec engine??
Ned.
[Edited on 10/7/03 by ned]
beware, I've got yellow skin
|
|
|
ned
|
| posted on 10/7/03 at 09:14 AM |
|
|
Early crank, as in coscast head engines, engines with extra webbing by starter motor (see my website), engines with early forged (another point of
debate)pistons:
Later crank, heavier as in later engines (& possibly the ecotec?):
Ned.
[Edited on 10/7/03 by ned]
beware, I've got yellow skin
|
|
|
david walker
|
| posted on 10/7/03 at 09:37 PM |
|
|
Thanks for the crank pics Ned, easy to spot when pointed out!
BTW the Ecotec crank is slimmer at the oil pump end and is in fact same as the Cavalier 8v (Eng code NE)
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
|
|
|
Stu16v
|
| posted on 10/7/03 at 10:57 PM |
|
|
Just to confirm (because I've been and checked) the round teeth pulleys are early engine, the square type with finer pitch are the later type
(which is the same profile teeth as fitted to the Ecotec funnily enough).
Dont just build it.....make it!
|
|
|
ned
|
| posted on 11/7/03 at 08:48 AM |
|
|
thanks for the clarification there Stu.
Ned.
beware, I've got yellow skin
|
|
|
fastavatar.jpg){kind=avatar}
