For an older engine like this the lifters could easily be the problem.
Even if the cam is fine, the lifters might not be working well. I once had
a rebuilder set the valves in my wife's '62 corvette as if they were
hydraulics, when any goober knows that a 340 horse 327 has solids. Didn't
run well.
Old hydraulic lifters often pump down, giving erratic valve opening and
lousy performance. That might explain your funny compression tests.
-----Original Message-----
From: Brad Kahler [mailto:brad.kahler@141.com]
Sent: Thursday, October 17, 2002 9:33 AM
To: Tom Strange; fot@autox.team.net
Subject: Re: generic question on compression checks
Hi Tom,
To the best of my knowledge its still using the stock type of lifter.
What I don't know is whether or not he replaced them when he put in
the new cam. Thats a question I need to ask him.
I'll keep you posted as to the outcome....
Thanks for the feedback.
Brad
On 16 Oct 2002 at 18:31, Tom Strange wrote:
> Hi Brad,
> I agree with you, I would be inclined to worry about the cam. I
> agree with the leakdown check for sure. Then, you could put a dial
> indicator on the push rods. (it seems this engine should have
> hydraulic lifters... which will make checking it a little touchier...
> if it is solids, just check the rocker arm clearance.)
> This will probably tell you if you have a cam going away. This may
not
> be
> definite, if it is just starting to go, and you dont use dummy lifters
> to get a real accurate reading, but it might just tell the story. This
> would also give you a chance to check for things like broken valve
> springs etc....
>
> It doesnt make sense to me for the compression to come up, then down,
> then
> back up again, I'd like to hear some opinions on that.
>
> Good luck, I'm interested in what the outcome will be on this one.
> Tom
> ----- Original Message -----
> From: "Brad Kahler" <brad.kahler@141.com>
> To: "Bill Babcock" <BillB@bnj.com>; <fot@autox.team.net>
> Sent: Wednesday, October 16, 2002 5:17 PM
> Subject: RE: generic question on compression checks
>
>
> > Hi Bill,
> >
> > The air pump has long been removed from this engine. It originally
> > came with a catalytic converter but some PO removed that. I forgot
> > to mention its a 79 jeep 360 engine.
> >
> > I didn't ask if he had done a leak down test or if he only did a
> > compression check. I'll ask him about that when I talk to him
> > again. Thanks.
> >
> > Brad
> >
> > On 16 Oct 2002 at 15:04, Bill Babcock wrote:
> >
> > > How old is this Jeep?
> > >
> > > First thing I would do is a leakdown test on all
> > > cylinders--compression testing doesn't tell you what going on
> > > unless it's gross failure. If
> they
> > > are all holding well, then my assumption would be that the
> > > emission control stuff was cattywumpus. On newer vehicles
> > > virtually every system that could emit vapor or stuff feeds back
> > > into the engine for burning
> and
> > > catalyzing into warm mothers milk plus CO2. It doesn't take much
> > > for all this stuff to stop working right, and when it does, you're
> > > screwed. In a simpler time I'd say check the PCV valve, but new
> > > motors hardly even
> have
> > > them.
> > >
> > > I consider myself a decent mechanic, which means I don't B.S,
> > > myself
> about
> > > my limitations--I don't touch anything under the hood of any
> > > engine
> newer
> > > than 1970. I don't even change the oil. A rebuilder will be
> clueless--they
> > > are machinists and parts switchers. Here in Portland we're lucky
> > > enough
> to
> > > have one garage owned by a guy who has all the equipment and
> > > understands all this stuff. I take everything that's off warranty
> > > except the Ferrari to him.
> > >
> > > Find a guy like him.
> > >
> > > -----Original Message-----
> > > From: Brad Kahler [mailto:brad.kahler@141.com]
> > > Sent: Wednesday, October 16, 2002 2:04 PM
> > > To: fot@autox.team.net
> > > Subject: generic question on compression checks
> > >
> > >
> > > Amici,
> > >
> > > This isn't really Triumph related (other than its a tow vehcile!)
> > > but
> I'm
> > > looking for guidance on an engine problem.
> > >
> > > We had an engine rebuild in our Jeep last spring and over the
> > > course of the next year we had over heating problems, lack of
> > > power and apparent blow-by.
> > >
> > > We took it back to the rebuilder multiple times to try and get the
> > > problem(s) corrected. Never did have much luck. However, trying
> > > to get past the state emissions test last month this almost new
> > > motor failed miserably.
> > >
> > > Here are the apparent symptoms. OIl in the air cleaner coming
> > > from the valve cover. Compression check shows approximately
> > > 140-145 across all 8 cylinders at first. However on the 3rd
> > > revolution of each compression check (which is what the manual
> > > says to check for) the pressure drops to 115-120 but comes back up
> > > to 140-145 on the 5th revolution.
> > >
> > > This doesn't sound like a piston ring problem to me. It would
> > > seem to be more of a bad cam. The cam shaft was replaced, the
> > > heads were given valve jobs. Basically it was a complete engine
> > > rebuild.
> > >
> > > Any thoughts on what to look for? Should he just pull the heads
> > > and cam on the assumption that the rings are probably ok? Or does
> > > this sound
> like
> > > a ring problem AND a valve/cam problem?
> > >
> > > Any help on this would be greatly appreciated!
> > >
> > > Thanks
> > >
> > > Brad
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