Engine Pinging

[ron & gina]

Hi All,

On last trip I heard the engine pinging on hill climbing hard throttle,
Thought it was the mid grade gas I started buying, But on last fill just
before home, filled with 92 octane(1.31) and now at home I reset timing to
about 9d from 10 and installed new points/condenser. But today went up a
hill and it still pinged alittle. What am I missing? In for?

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave, AZ.

 

[ron & gina]

Hi Larry,

Thanks for your rely. I have about 37k on rebuilt engine/timing chain, Not
sure on carb. And the wires,plugs/cap/rotor about 3k, points and condenser
are new, and all set to 9d timing and 30d dwell @1100rpm. I have a rebuilt
kit for carb. but did not install yet, didn't think this would cause
pinging?
Again thanks for any info.

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave, AZ.

- ----- Original Message -----
From: Larry Davick
To:
Sent: Monday, November 22, 1999 1:41 AM
Subject: Re: GMC: Engine Pinging

> Ron&Gina,
>
> I haven't been very good about keeping up my score card so I don't
remember
> the particulars about your coach. Perhaps I'm not alone, and others could
> benefit from some more info too...
>
> How many miles on the engine, carb, timing chain, Ignition wires?
>
> These are the areas I'd look to first. It's possible that something like
> carbon build-up, bent push rod, etc., could be to blame, but I always
check
> the usual suspects first.
>
> Larry Davick
> Enviously Lurking
> >
> >On last trip I heard the engine pinging on hill climbing hard throttle,
> >Thought it was the mid grade gas I started buying, But on last fill just
> >before home, filled with 92 octane(1.31) and now at home I reset timing
to
> >about 9d from 10 and installed new points/condenser. But today went up a
> >hill and it still pinged alittle. What am I missing? In for?
> >
> >Ron&Gina
> >73 Pumpkin-Rose
> >Ft. Mohave, AZ.
> >
> >
> >
>
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com

 

[ron & gina]

Thanks for reply Emery,

Yeah, I had it set @ 8d, but tried 10d per advise which seems to give me
better power. Then I backed it to 9d in hopes that would be enough to stop
pinging. Guess I'll redo and take another test drive. Wanted to adjust on
the move as stated here on the net, But can't even get my boss to drive
while I make the adjustments. Saw your write up on Caspro knock eliminator,
And would be nice. But think I'm going to get Caspro's steering box and
shaft first. But still thinking. Mind works OK, was better, But wallet is
not giving me much leeway! Thanks again

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave, AZ.

- ----- Original Message -----
From:
To:
Sent: Monday, November 22, 1999 11:26 AM
Subject: Re: GMC: Engine Pinging

>

>
> Thought it was the mid grade gas I started buying, But on last fill just
> before home, filled with 92 octane(1.31) and now at home I reset timing to
> about 9d from 10 and installed new points/condenser. But today went up a
> hill and it still pinged a little. What am I missing? In for?
>
> Ron&Gina >>
>
> Ron -- The standard timing for the 455 is 8 deg. before top dead center.
> Check the maintenance manual to make sure this is correct for the engine
you
> have. This assumes that you have regular gas with the same octane as
> available in the 70's. With today's lower octane fuel you might have to
set
> it even less so as to avoid pinging on hills. When you set your timing,
be
> sure to plug the vacuum line going to the distributor at the distributor
end.
> A golf tee works great and I keep a couple in my toolbox just for that
> purpose. For the 455 set the idle at 1100 rpm when you set the timing.
>
> At one time, I experienced the same thing, especially when pulling a toad.
I
> found that I had to adjust the distributor two or three times on a trip
> depending on the type of terrain I was driving. I finally bought the
Caspro
> knock eliminator. Now I have the advance set to 12 deg btdc and let the
> Caspro control system retard it if it detects pinging. This, of course,
> gives me better performance on the level road.
>
> Gene Fisher - did you ever build the indicator light that has been posted
in
> the past? I've had a bout of the flu for a couple of weeks so that
project
> came to a halt. Hope to do it soon. Since the Caspro unit is automatic
I'd
> like to have an indicator light that would tell me that it is working,
> although no pinging on hills with 12 deg. advance must mean that its
working.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[ron & gina]

Thanks again Hopefully I don't have to get that deep, pulling heads. I've
always bought the highest grade gas possible, except for last trip ie $2+ a
gallon, then went to mid grade 89? So here's a hoping backing timing will
eliminate my pinging. Thanks Emery

Ron&Gina
73 Pumpkin-Rose
Ft. Mohave, AZ.

- ----- Original Message -----
From:
To:
Sent: Monday, November 22, 1999 12:05 PM
Subject: Re: GMC: Engine Pinging

>

>
> the move as stated here on the net, >>
>
> When I was in the position of having to change the advance, I would loosen
> the bolt holding the distributor so that it could just be rotated by hand
and
> then I would drive and my wife would lean over the box and change the
timing.
> She could hear the pinging, whereas I could not hear it from the drivers
> seat (I can't hear some pitches of sound).
>
> If you can find another person to drive it uphill for you, this is an
> excellent way to get the timing for the fuel and conditions of the engine.
> Rotate the distributor counter clockwise until the pinging just stops.
>
> If you have any deposits on the pistons or in the head they can also cause
> preignition and may require timing adjustment below 8 deg. tdc. Use of a
> good grade gasoline might eliminate these deposits or, if really bad, the
> heads may have to be removed and parts scraped and cleaned out. Which, of
> course, means that you should do a valve job, etc. at the same time.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[dave1]

>Thanks Dave,
>
>.... So there goes alot of my play money. Did talk the boss into letting
>me also include the knock eliminator, Haven't really told her the total
cost
>tho, ...

Something to keep in mind, if you plan on doing the EFI upgrade, is that
there is a version of the EFI kit avalable with a knock sensor and
electronic timing control. Maybe it would make more sense to skip the knock
eliminator now and add that option when you do the EFI.=20

Howell has a web site at www.howell-efi.com with lots of info. I would
recommend using the heated O2 sensor option as well. I know there are other
EFI kits in addition to Howell but Howell looked like the best solution a
few years ago when I did mine. =20

>... So I
>guess for now I'll just back the timing off for this weekends trip and=
see
>how she does.=20

You might want to see what other vacuum advance units are avalable for your
distributor. If I recall the original on a 73 is 12? or 14? degrees. There
is a section on testing the distributor in the service manual that has the
number. But if you replace it with a unit that has a couple degrees less
advance then you could keep your initial timing set at 10 degrees and
probably get rid of the knock that way. Its cheap and pretty easy to swap
the vacuum advance. Then you can wait a while and do the EFI and HEI with
spark control at the same time. Thats what I should have done but I did the
HEI long before I knew about the various EFI options. When I did the EFI I
didn't want to re-do the HEI so I skipped the spark control option and went
with the basic kit.=20

> Thanks again for info
>and #s!!!!!! =20

No problem. I just wish I had some of the vacuum advance numbers for the
older ignition systems to give you.

>If not asking to much, how much it cost you to switch over to
>HEI/EFI?

I don't remember what the HEI costs where. When I did the upgrade I
replaced the distributor, cap, rotor, coil, module, vac advance, wires and
plugs. These parts are all readily avalable locally but its been so long
that I don't remember the prices. You will also need to find a scrap yard
air filter housing from a 75 or later GMC or Toronado. This later version
of the air filter housing is moved forward a bit to allow more room for the
HEI distributor cap.

The EFI system cost depends on what options you get. I did the basic closed
loop TBI system kit ($1200) plus the heated O2 sensor & cable ($115).=20

Dave
Ann Arbor, MI.
73 Sequoia (26'/455/EFI/HEI/160=B0)

 

[eugene]

I have been on the road for the last 2 weeks and will be gone for 2 more
weeks .. then I will build the indicator. I had hoped to get it done
before this trip, but did not make it.
gene

>

>
>Thought it was the mid grade gas I started buying, But on last fill just
>before home, filled with 92 octane(1.31) and now at home I reset timing to
>about 9d from 10 and installed new points/condenser. But today went up a
>hill and it still pinged a little. What am I missing? In for?
>
>Ron&Gina >>
>
>Ron -- The standard timing for the 455 is 8 deg. before top dead center.
>Check the maintenance manual to make sure this is correct for the engine you
>have. This assumes that you have regular gas with the same octane as
>available in the 70's. With today's lower octane fuel you might have to set
>it even less so as to avoid pinging on hills. When you set your timing, be
>sure to plug the vacuum line going to the distributor at the distributor end.
> A golf tee works great and I keep a couple in my toolbox just for that
>purpose. For the 455 set the idle at 1100 rpm when you set the timing.
>
>At one time, I experienced the same thing, especially when pulling a toad. I
>found that I had to adjust the distributor two or three times on a trip
>depending on the type of terrain I was driving. I finally bought the Caspro
>knock eliminator. Now I have the advance set to 12 deg btdc and let the
>Caspro control system retard it if it detects pinging. This, of course,
>gives me better performance on the level road.
>
>Gene Fisher - did you ever build the indicator light that has been posted in
>the past? I've had a bout of the flu for a couple of weeks so that project
>came to a halt. Hope to do it soon. Since the Caspro unit is automatic I'd
>like to have an indicator light that would tell me that it is working,
>although no pinging on hills with 12 deg. advance must mean that its working.
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
gene fisher 76 PB/OR/CA
GMC MOTORHOME INFORMATION
mr.era
http://www.california.com/~eagle/