[DMCForum] Re: Mechanical & Cosmetics (backfiring)

["content22207" <brobertson@xxxxxxxxxxxx>]

Message #7416 said car was backfiring through intake. Sorry.

Don't remember plug/thread message, but if I recommended hotter plugs
were probably fouling or otherwise getting incomplete burn. Didn't you
"gas" someone following behind a couple of months ago? Louie has black
lung after following me on 3 dead cylinders.

(And I still maintain: oddest thing about PRV is you can lose one
whole bank with minimal noticeable effect from driver's seat. Has to
be the odd firing order.)

If your plugs are white & clean, combustion is too hot -- move to next
heat range down (assuming fuel mixture OK, no carbon buildup, etc). If
they're black & sooty (dry), is too cool -- move up. If they're black
& oily it's time for new rings or valve seals (compression test will
tell you which). You want caramel color.

BTW: If anyone with an oil burner wants practically new set of HR9's
(60 miles) I have 6 to give away, no charge. Even though insulator
LONGER than R42's and electrode is nothing but a little dot, they burn
much hotter. Go figure.

Vacuum leak on my driver's side totally toasted 3 plugs. Passenger
bank was a little too hot (ground prong clean, minimal discoloration
of insulator), but driver's physically melted. Will get someone to
digi photo tomorrow for Walt. Is not "cool", but not warping anything
definitely is...

Bill Robertson
#5939

>--- In DMCForum@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> Ok, first:
> 
> I know I messed w/the timing scale but it had very visible "clean 
> spots" that the mounting screws left on it. When I put it back, I was 
> very careful to line them back up. Also, when I put the engine back 
> together I used a wooden dowel to get #1 at TDC and lined up the 
> pulley mark with the scale.
> 
> But you never know...
> 
> Second:
> 
> I do NOT have flames and such coming out of my intake. After my last 
> set of adjustments I only have the -occasional- little fart. It only 
> occurs during certain conditions. When the rain quits I'll try to do 
> a compression check. I pulled one plug at Mike's. It was perfect. I 
> should check all the rest though.
> 
> Third:
> 
> I started a thread on octane some time ago. The manual's 
> recommendation of 91 octane is some kind of funky "research" number 
> that equates to 87 octane. I'm running that and I have no knock or 
> ping. I -want- as much combustion as I can get. Burn, baby burn.
> 
> Lastly:
> 
> I agree. When I was set too lean, my engine popped and farted and ran 
> as hot as a firecracker. I put in hotter plugs and a new coil based 
> on YOUR recommendation Bill. Whaddya mean put in "cooler" plugs?? At 
> any rate, I only went up one heat range. If the one I pulled is any 
> example they look great.
> 
> Rich
> 
> --- In DMCForum@xxxxxxxxxxxxxxx, "content22207" <brobertson@xxxx> 
> wrote:
> > True backfiring (flames coming out of carburetor vs muffler
> > explosions) is often plug wires out of order. Flame escapes cylinder
> > when an intake valve is open. Could be timing but would have to be 
> WAY
> > off. Do a compression test to ensure valves are closing and sealing
> > all the way.
> > 
> > Muffler explosions are usually unburned fuel.
> > 
> > Are you pre-detonating when engine is hot & under load? That was my
> > problem. Try cooler plugs. And don't lug the engine -- with no RPM's
> > AND vacuum dropped spark may come too late. What octane are you
> > running? 91 factory spec was figured by some method other than what
> > our pumps use (does it translate into 87 or 89?). I can not run
> > reliably on less than 93.
> > 
> > Re: adjusting main CO2 screw -- I've said 1000 times a rich mixture
> > burns cooler than a lean one. Usually get shot down when I do, but
> > I've got 3 melted plugs sitting on my kitchen counter right now that
> > prove it! (Courtesy of a vacuum leak on that side of engine -- too
> > much air for metered fuel, duh).  What do your plugs look like? 
> > 
> > Bill Robertson
> > #5939
> > 
> > >--- In DMCForum@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> > > Walt,
> > > 
> > > I'll tell you this;
> > > 
> > > Fuel settings defintely have something to do with it because when 
> I 
> > > richen up the CO screw it largely goes away. It doesn't just do 
> it at 
> > > idle though. If I put enough of a load on the engine (toting 
> uphill) 
> > > it does it.
> > > 
> > > I'm starting to think you may be right about uneven delivery.
> > > 
> > > I'm painting the engine cover not the louvers. I don't even have 
> > > louvers. They were cracked and snapped off and flew away a year 
> ago 
> > > during the tow home. :(
> > > 
> > > Mike does wonders with paint in a can, so it can be done.
> > > 
> > > Rich
> > > 
> > > 
> > > 
> > > --- In DMCForum@xxxxxxxxxxxxxxx, "Walter Coe" <Whalt@xxxx> wrote:
> > > > Mike was telling me about your car backfiring through the 
> intake.  
> > > The cause
> > > > of this on my car was from one cylinder running too lean off of 
> > > idle.  The
> > > > injector for that cylinder was delivering about half as much 
> fuel 
> > > as the
> > > > others at idle, but above 1500 RPM it was fine.  When I 
> adjusted the
> > > > air/fuel mixture, it caused that one cylinder to be too lean 
> and 
> > > the other 5
> > > > to be too rich.  Inspecting the plugs confirmed this along with 
> > > watching the
> > > > injectors spray in test tubes.  The problem with the faulty new 
> > > injectors
> > > > must be that they are NOS and have rust in them.  I'm curious 
> to 
> > > cut one
> > > > open and see.
> > > > 
> > > > Having your timing off will also cause it to backfire through 
> the 
> > > intake.  I
> > > > would have terrible luck trying to tune it by hear like Bill 
> > > suggests.
> > > > There must be a procedure for setting/verifying the position of 
> the 
> > > timing
> > > > mark.
> > > > 
> > > > > Question of the day:  What is the best paint to use to 
> repaint the
> > > > engine cover? Bumper black or semi flat 1613, or what?
> > > > 
> > > > I have never been too fond of any paint that comes out of a 
> spray 
> > > can when
> > > > compared to spraying real automotive paints through a spray 
> gun.  
> > > Rich W
> > > > painted the louvers of D-rex with Krylon Semi-Flat Black, and 
> it 
> > > looks good.
> > > > I'm curious to see how it holds up.  Plasti-kote Bumper Black 
> spray 
> > > paint (#
> > > > 616) seems to be a spot-on match for the black part of the 
> > > fascias.  I'm not
> > > > sure how well it would stick to an engine cover, though.  Like 
> Bill 
> > > said,
> > > > preparation is everything.  If there is any residue of oil or 
> Armor-
> > > all or
> > > > Back-to-black then you will get fish-eye in those areas.  I 
> have 
> > > seen too
> > > > many painted louvers that are mostly glossy yet mottled with 
> fish-
> > > eye spots
> > > > where residue made the paint go thin.
> > > > 
> > > > Walt

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