Re: [ihc] Weird engine problem - calling the experts

[Steven Stegmann <steve.stegmann@xxxxxxxxxxxxx>]

Scott,

On mine, before MSD and Holley EFI, mine was
backfiring.  It was caused by a failing ignition
system (Prestolite).  The MSD fixed it very nicely
before the EFI was installed.

This would probably not cause the revving though.  At
first I thought valves out of time, probably not, but
I think the carb is not adjusted properly.  Back in
the '70s it was tough to get an engine to idle well or
come off idle without a stumble.

I presume you've checked the timing with a light??  Is
the reading steady?  I once had the bearings in a
dizzy go bad.  I found it with a timing light. 
Readings jumped all over the place as the shaft
wobbled around.

Steve

--- Scott Machalk <smachalk@domain.elided> wrote:
> Ok, I haven't posted here in a while so I hope this
> goes through.
> 
> I rebuilt the heads on my Scout. Actually they
> aren't the same heads, the 
> old ones were cracked so I got new ones at a junk
> yard and had them rebuilt 
> and Magnafluxed (sp?) etc.
> 
> So I got the engine all back together and we can't
> get it to run smooth. I 
> really have to mess with the choke to get it to run
> at all until it warms 
> up, then it still runs bad.
> 
> Here's what we've checked:
> 
> My friend who is a real mechanic :) pulled the
> intake manifold back off and 
> replaced it making sure that all seals and gaskets
> were good. He also 
> replaced the plug wires and air filter. Still ran
> bad.
> 
> I took it in to a local garage. They are considered
> one of the best around. 
> They looked it over and said I needed a new Carb.
> Well, I wanted a Q-Jet 
> anyway so I got one. Still ran bad.
> 
> They also suggested that maybe one of the valves
> wasn't closing so I pulled 
> the valve covers off and ran each piston up to TDC
> and felt for tightness 
> in the push rods. They all felt fine. So, I ran a
> compression check. Every 
> cylinder is around 120-150 dry.
> 
> I put it all back together and it still runs bad.
> 
> So, here's a detailed description of how its "bad".
> 
> I start the Scout fully choked and it fires up and
> revs quite high. Then it 
> will settle down and threaten to stall. So, I pump
> the throttle a bit and 
> it revs way up again.
> 
> This cycle repeats until it's warmed up. Now, I had
> it warmed up this 
> morning and as it sat there idling, Every once in a
> while it would backfire 
> through the carb. And once, out of the blue, it
> revved way up again.
> 
> I am at my wits end here. If any of this is ringing
> a bell with anyone, 
> please help
> 
> Thanks in advance
> Scott