DeTomaso Mailing List: March 2000, Message #269

According to the instructions that came with my vacuum / fuel pressure
gauge, low vacuum measured in the intake system at idle will diagnose burned
valves.  This is especially true if they are not all burned, as the needle
will drop rhythmically as the bad cylinder has its effect.  However, it does
sound like you have valve float, and this test will not help you diagnose
that.

As a general question to the group:  It is my impression that I hear about a
lot of these motors rebuilt with aftermarket parts, which supposedly are
better than stock, crapping out after a fairly short time.  Any explanation?
Is it because these motors are driven so much harder?

Jim Oddie
> -----Original Message-----
> From:	Russ Jacobson [SMTP:russj@enol.com]
> Sent:	Wednesday, March 08, 2000 7:22 AM
> To:	Multiple recipients of list
> Subject:	Help! Engine won't rev past 4600
> 
> Hi All,
>     I would appreciate some advise.  When I bought #1363 the previous
> owner disclosed that the car would not rev above 4600 rpm.  He installed
> a new electronic ignition system from Hall and it didn't solve the
> problem.  The engine runs strong up to 4200 rpm where it starts
> missing.  It goes flat and sounded like crossfireing at 4600 rpm.  I
> bought the car anyway hoping to cure the problem with new wires and
> plugs.  Didn't work.  I took the car to a highly recommended shop to
> have them troubleshoot the problem.  They say the ignition system and
> carburation is OK.  After consulting with their machine shop they think
> the problem is burned valves or weak springs causing valve float.  The
> previous owner after installing the new Hall ignition without fixing the
> problem consulted with Hall.  Hall said if the new ignition system
> didn't fix the problem then it was probably valve float.
> 
>     The engine was rebuilt about 10,000 miles ago with all new Crane
> parts including valve springs.  It now has a total of 37,000 miles.
> What I am wondering is there any diagnostics I can run to verify burned
> valves or weak valve springs?  Is there any thing else I should be
> looking to diagnose this problem?
> 
> Thanks in advance,
> Russ Jacobson
> #1363 pushbutton
> 
>