David Jenkins
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| posted on 24/12/04 at 02:03 PM |
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X-flow cam query
Although my 1660cc X-flow is running OK, it has developed a rattle in the general area of No.4 cylinder. It sounded like a tappet, so I checked them
all - most are OK, but No.4's have opened up a fair amount.
I had total oil failure last year (going for the SVA! ) so I guess that my cam is knackered, or maybe the followers. So the first question is:
Q1. Is this a reasonable assumption?
If I'm going to replace the cam then I'll probably get a 'road' cam from Kent, Piper or Burtons (plus new followers). The
current one is a standard one for 'GT' engines, so only slightly more lively than the ordinary one. The next question is:
Q2. Can I just replace the cam, or would I need to muck around with machining the pistons, etc?
Finally:
Q3. Would I have to use an adjustable pulley, or can I use the existing fixed one? (and accept that it may not be 100% right)
Thanks in advance,
David
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jollygreengiant
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| posted on 24/12/04 at 03:02 PM |
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You would have to replace camshaft and followers.
Any other work would depend on,
Over all lift of new camshaft, - it might require; works as;
Replacement valve springs - to avoid spring crush.
Machining of head spring seats to cater for heavier/higher duty springs.
Pistons pocketing to clear valve lift.
Most of these requirement would be satisfactorily answered by the vendor of the new camshaft, if they know what they are talking about.
Vernier cam timing would be best as the timing could be set up exactly. Giving much better power increases once dailed in on a rolling road.
Oh and make sure that you get the correct camshaft and folllowers for your block. Ealier blocks had smaller diameter on the cam follower. Early ones
fit the later block but the engine rattles like F*CK until the followers fail and destroy the block. Cost me £900 to find that out and SHELLTUNE of
Northampton denied all responsiblity for it because I hadn't given them a written order. I ordered them for a 711M block and they gave me cam
and followers for an early 681 block.
Enjoy. Merry Xmas HO HO HO
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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David Jenkins
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| posted on 26/12/04 at 05:27 PM |
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Cheers JollyGG.
My problem is that no company will say "you can fit this mild road cam without mods", even though the manufacturer's web site (e.g.
Kent Cams) suggests that you can! I was hoping to get some advice based on real experience from this forum.
I have another query - usually when you start a newly-rebuilt engine the first job is to set the ignition timing properly. However, when you read the
instructions for cam fitting, they say that the engine mustn't idle and the revs must be kept to 2500 rpm for 20 minutes - you can do one, but
not the other! How have people managed?
rgds,
David
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Rob Lane
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| posted on 26/12/04 at 05:43 PM |
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David,
Q1 answer, probably cam lobe worn, causing opening of tappets and pushrod gaps. Opposite happens if valves burn into seats by using non leaded.
Q2 answer, yes, a 234 mild cam kit from Kent will fit OK and give a mild increase in tune. It would ideally accompany other mods but on it's own
won't hurt.
The reason they state 'other mods' is many expect just fitting the cam will give great gains in HP, it won't. (Kit has followers)
Q3 answer, you can use standard pulley but use offset dowel to achieve optimum timing. Dowels come from Burtons. Measure first when test fitted then
order dowel. It will usually be 'out' with standard pulley.
For timing, see the article in my pics folder.
Don't bother with the timing wheel method that comes with cam kit.
Never thought to say, you can check valve lift at the rocker for each cylinder and determine whether it's the cam and which lobe.
[Edited on 26/12/04 by Rob Lane]
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David Jenkins
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| posted on 27/12/04 at 10:10 AM |
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Rob,
Apart from (probably) needing a new cam anyway, I'm hoping that a mild road cam will make better use of the larger carb and better exhaust
system I've fitted.
Not that the extra power is a major concern - I just want to get it running nicely.
That's a good article on timing though - I'll have to print it out and give it some quality reading time...
rgds,
David
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David Jenkins
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| posted on 29/12/04 at 02:54 PM |
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Well... got the engine out, ready for partial stripping down.
Spotted the first "Oops!" - the centre exhaust manifold gasket was upside-down, which meant that about 3mm was directly in the way of the
exhaust - so much for my port matching!
The big strip (oo-er) starts soon...
rgds,
David
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David Jenkins
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| posted on 2/1/05 at 12:52 PM |
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Problem identified...
Well, I know where the problem is, anyway.
Stripped the engine and took the camshaft out. Most lobes look OK, apart from No. 7 that's a bit iffy. Took all the followers out, 7 of them
are spot on (they're almost new) with a slight convex curve and the merest hint of scuff marks, but the one on No.7 (4th cylinder inlet) is
severely concave. This is almost certainly due to my total loss of oil pressure a while ago.
So, it's a trip to Scholar Engines in the next week or so, to see whether the camshaft can be recovered, or if I need to spend more cash...
cheers,
David
[Edited on 2/1/05 by David Jenkins]
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jollygreengiant
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| posted on 2/1/05 at 05:17 PM |
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Recommend new cam AND followers, don't bother trying to recover cam. Also recommend see if engineers can/have tooling/ability to unplug/unseal
all oilway blanks, clean oil ways and re-seal. (debris left in oilways from previous melt downs can be fatal to engine later on.) Might be a case of
find new block & machine to fit internals.
Have been down this road myself back in 1980ish, thought everything was fine after rebuild caused by incorrect parts supply (re SHELLTUNE,
Northampton) ran fine for 300 miles then oil pressure went, closely followed by terminal big end & main knocking. ended up having to get new
block.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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rusty nuts
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| posted on 2/1/05 at 05:25 PM |
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David, didn't Xflow engines suffer with premature cam failure from new due to faulty hardening?? May be my faulty memory , it's not what
it was. Also modern cams are supposed to be run in when engines are first started , could possibly be a contribting factor. Doubt it is worth trying
to salvage cam , cheaper to buy a new kit? Happy new year . Rusty
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David Jenkins
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| posted on 2/1/05 at 08:07 PM |
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JGG - it wasn't a catastrophic failure, fortunately, and I caught it early. The oil had a very slight metal sheen, but waving a magnet through
it didn't pick up anything, not even sludge. There's no evidence that the cam or follower has lost significant bits and the oil and sump
show no evidence of 'solid matter'. I'll replace the cam and followers, together with the oil filter and hope for the best.
RN - I think I will buy a new cam after all. The running-in worries me - the instructions say that the engine should be run at 2500 rpm for 20
minutes, but this doesn't give any allowance for setting the timing, etc. Seems a bit harsh! 
cheers,
David
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David Jenkins
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| posted on 4/1/05 at 08:23 AM |
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I'm feeling very depressed...
Been reading a few books and magazines regarding cam replacement...
...almost unanimously they say "if the cam's worn out for some reason, strip the whole engine and clean it out, including all the
oil-ways. Otherwise the next one will go the same way"
Bugger! (and yes, you were right JGG)
Oh well, it'll keep me busy for a while...
David
[Edited on 4/1/05 by David Jenkins]
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Rob Lane
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| posted on 4/1/05 at 09:52 AM |
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Shame you're so far away, I would have happily help you strip it down. I love working on Crossflows.
One evening to strip, one morning to chemical bath clean (locally) and one evening to re-assemble and setup.
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David Jenkins
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| posted on 4/1/05 at 10:03 AM |
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quote:
Originally posted by Rob Lane
Shame you're so far away, I would have happily help you strip it down. I love working on Crossflows.
They're a bit like Meccano...
quote:
One evening to strip, one morning to chemical bath clean (locally) and one evening to re-assemble and setup.
You make it sound so easy... actually, it is easy, just a PITA as I'd rather be driving the car.
Anyone in the Ipswich area know of an engine shop that would clean a block and head while I wait? I only know about Scholar Engines, but
they're (a) expensive, (b) a bit of a journey, and (c) can be a bit 'jobs-worth', if you know what I mean.
rgds,
David
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rusty nuts
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| posted on 4/1/05 at 06:52 PM |
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David, don't know if they are close enough, but have used Cambridge Rebores in Burwell near Newmarket in the past , have always found them to be
helpful with reasonable prices. Tel 01638 743797. Rusty
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David Jenkins
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| posted on 4/1/05 at 07:47 PM |
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Rusty, bit far for me - I want to take it in the morning and pick it up at the end of the day, if poss.
Anyway, I found an Ipswich engine rebuilder who'll put the block and head in his "washing machine" for a tenner or so.
cheers anyway,
David
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timf
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| posted on 5/1/05 at 08:20 AM |
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quote:
Originally posted by David Jenkins
Anyone in the Ipswich area know of an engine shop that would clean a block and head while I wait? I only know about Scholar Engines, but
they're (a) expensive, (b) a bit of a journey, and (c) can be a bit 'jobs-worth', if you know what I mean.
rgds,
David
bob dyke enginerring in spring road in ipswich.
little engine place behind some houses in the yellow pages
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