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Reading plugs in blown big block chevy

Discussion in 'The Hokey Ass Message Board' started by twinturbo496, Feb 21, 2009.

  1. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    Engine specs:

    496" tall deck
    .640" solid roller 243/246 @ 50 on 114 (installed 4 advanced)
    cnc 350 cc intake ports, 119 cc chambers, 7.95 static c.r.
    871 street blower 20% under (only makes about 5 psi @ 4000 rpm)
    1407 edelbrocks jetted 6% rich in front, 8% rich in back.
    2 1/8 x 50" primary tubes (average), 4" x 12 collectors into 4" race mufflers.

    I drove about 100 miles yesterday around Portland, combination stop & go traffic and 20 miles on I-5 @ 60 mph. Then pulled #4 & #6 plugs.

    I just took off predators and installed the edelbrocks, fuel mileage went from about 5 mpg to about 9. After running hard with the predators the plugs looked great, light brown insulator with the ground strap light gray. I took them off because of the horrible fuel mileage, and I couldn't get them to idle right.

    Comments on going richer?

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    Last edited by a moderator: Jun 1, 2014
  2. TV
    Joined: Aug 28, 2002
    Posts: 1,451

    TV
    Member

    I can tell you your timing is right on by the ground strap and you won't hurt anything with that much fuel. If you were an all out race car you would want a little less fuel.--TV
     
  3. 1951bomber
    Joined: Jun 4, 2007
    Posts: 276

    1951bomber
    Member
    from atwater Ca

  4. Lazy White Boy
    Joined: Nov 27, 2006
    Posts: 99

    Lazy White Boy
    Member

    check out Dragstuff.com, look under "Racing articles-spark plug reading 101." Really good information.
     
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  5. brigrat
    Joined: Nov 9, 2007
    Posts: 5,117

    brigrat
    Member
    from Wa.St.

    Way to hot and lean. I would richin it up till break in but not to a point of washing the cylinder walls down............... JMO
     
    Last edited: Feb 21, 2009
  6. sota
    Joined: Oct 14, 2006
    Posts: 717

    sota
    Member

    The guys before me are correct,you are running way to lean which is causing the heat.If you don't fatten it up your asking for issues.
     
  7. brigrat
    Joined: Nov 9, 2007
    Posts: 5,117

    brigrat
    Member
    from Wa.St.

    No info on ing or Dist? Also make sure your timing & advance is correct for your setup. Put a timing light on the harmonic ,hoping you have it degreed, and watch the advance.....................
     
  8. Candy-Man
    Joined: Mar 21, 2006
    Posts: 1,704

    Candy-Man
    Member

    A little more rich is a good insurance policy....

    Remember you have to kill the engine immediately to get a good read of the plugs. If you idle the motor and then read the plugs, well you have a reading only at idle....

    Are your headers becoming too hot, caused by a lean situation?
     
  9. fab32
    Joined: May 14, 2002
    Posts: 13,987

    fab32
    Member Emeritus

    1. Fresh set of plugs
    2. Set timing and warm engine
    3. Make a hard pass and kill engine at full throttle without letting it back to idle.
    4. Coast to a stop and pull plugs.
    5. Take a reading

    Doing it any other way will give false readings caused by enriched idle setting.

    Frank
     
  10. kurts49plym
    Joined: Nov 2, 2007
    Posts: 386

    kurts49plym
    Member
    from IL

    By looking at your engine specs, with big roller, 2x4s, jetting, running the car on the street, etc.. I don't think you will be running lean. Yes, the plugs are not black or dark, but I wouldn't be too concerned. If it were doing some backfiring and the primary tubes were smoking or burning off the coating I may be more concerned. What I'm seeing with the plugs is pretty impressive. Nice engine. If this was a quarter mile car I would definitely richen it up more. For the street it looks good. My .02. Do you have a picture of this engine?
     
  11. yoyodyne
    Joined: Nov 26, 2008
    Posts: 866

    yoyodyne
    Member

    It looks to me like it runs rich by the soot on the base of the shell. The color of the porcelain at the top doesn't mean anything to me without knowing what the heat range is, sorts looks like stock heat range which might be too hot. I look at the color down inside around the very bottom of the insulator and that's pretty hard to photograph. Under load, I like to see a clean insulator with a tan or gray ring around the bottom, gray carbon on the shell with no deposits on the shell. Idling and low speed driving usually makes the insulator darker.

    Do the header tubes get real hot? Rich makes the exhaust gas hot and can make the tubes glow red.
     
  12. btmatt
    Joined: Nov 15, 2006
    Posts: 227

    btmatt
    Member

    Unleaded gas makes a good read really difficult; You would be better off using either EGT or wide band O2 sensor. I also agree with the comment that the plug appears to be a little too hot for your application.
     
  13. brigrat
    Joined: Nov 9, 2007
    Posts: 5,117

    brigrat
    Member
    from Wa.St.

    I was under the assumption that it was a new motor, rite? wrong?
    If you wern't confused before you must be now!
     
  14. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    More info.
    I have a fluidampr and an accurate timing marker (installed & set with a piston stop during engine build)

    I drove it about 1000 miles last fall with predators and a TH400, but the TH400 slipped in drive, so I pulled it out & installed a 4L80E converted to full manual and then also installed the edelbrock's so I could get a little better mileage, and so my wife could get it to start & idle easier.

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    Last edited by a moderator: Jun 1, 2014
  15. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    The ignition...

    That is a really sore subject for me at the moment.

    Short version: Holley sucks. They sell some decent products, but also a lot of really poor products. Even worse, they have poor product support staff.

    My engine was first fired up and ran in with a stock big cap HEI off of a 1984 suburban with over 200k miles. Certainly it is worn out, but worked ok with about 10 degrees initial advance, (about 20 degrees of vacuum advance starting at 10 inches of vacuum, and about 28 degrees of mechanical advance. I say "about" because the distributor is pretty worn out, and has a fair amount of scatter).

    I got a "great" deal on a new 890-100 holley distributor (just a knock-off of an MSD). I installed it with a composite drive gear, MSD 6AL, and MSD boost retard box. Then the ignition problems began.
     
    Last edited: Feb 22, 2009
  16. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    First Holley ignition problem: Rotor phasing.

    I have previously installed 3 MSD 8361 distributors, they all had perfect rotor phasing right out of the box. The holley was horrible, and the vacuum canister didn't have a slots, so you couldn't even adjust it. I ended up having to drill new holes to mount the pickup, and slot the holes in the canister to fix that problem.

    Next problem: stuck mechanical weights. The mount for the mechanical weights wasn't formed correctly, and the weights jammed into the bottom of the cap. I ended up using spare parts from other old GM distributors to make it work.

    Last straw: After fixing the other issues, I went down to the local speed shop to get a new cap...they couldn't find the part#. I called Holley "tech" really big mistake... after going straight to hold for 10 minutes, I hung up & called again, this time a guy answered, then put me on hold for 15 minutes, finally coming back and saying:

    "Holley doesn't make that distributor anymore, and we don't sell any spare parts for it, and no OE cap will fit, you should just throw it away & buy a new one."

    This part was still in their 2003 catalog. So apparently Holley figures if you break the distributor cap, you just throw away your distributor and buy a new one...
     
  17. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    For sale: one holley distributor minus cap. $1.00

    Side note: the lady at Baxter Auto Parts in Tigard ask me to give her the old cap so she could investigate. The next day I stopped in to order a MSD, and she handed me a new cap. The holley guy doesn't even know his own products. Turns out that the cap is exactly the same as a 1970-1980 International Scout.

    Baxter Auto parts counter lady apparently knows more about Holley products than the Holley Tech line guy. I suppose that shouldn't really be such a big surprise.

    I have a good friend who bought an early Holley Projection system (in about 1993). Guess what he thinks about holley.
     
  18. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    Headers are just painted with high temp black, and they don't really show any signs of getting hot.
     
  19. squirrel
    Joined: Sep 23, 2004
    Posts: 45,792

    squirrel
    Member

    The plugs look fine, drive it!

    explanation: Like has been said, to read the plugs you need to make a full pass, cut the engine cleanly, and look at the base of the insulator. And that will only tell you how it's doing at full throttle, of course. If you want to see what the mixture is under varying conditions, see if you can find a chassis dyno/exhaust analyzer, and see what the CO is under various driving conditions, that will tell you how the carbs are working.

    If you look at the plugs on late models with O2 sensors and closed loop fuel control, you'll mostly see bone white spark plugs, and they run for hunnerds of thousands of miles with no problems.

    Also those projected nose plugs are supposed to be white on the ends, the idea is that the tip stays hot enough that it won't collect deposits. Notice that the insulator is pretty dark about 1/8" down from the electrode.
     
  20. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    I read the info on the links listed above. Unfortunately it is fairly difficult to hold this car at full throttle on the street at less than about 40 mph. But the track in Portland opens in a few weeks, that should be enough time for me to get ready. Thanks for the input and the links.
     
  21. squirrel
    Joined: Sep 23, 2004
    Posts: 45,792

    squirrel
    Member

    no shit! :)
     
  22. Lazy White Boy
    Joined: Nov 27, 2006
    Posts: 99

    Lazy White Boy
    Member


    Not trying to hijack your thread but I had a similar experience with Holley. I bought a Holley HP electric pump while I was building my car. About six months went by while I completed the engine, put in fuel lines ect. I was finally ready to fire the engine for the first time and was just double checking everything. I put gas in the tank and turned on the pump so I could fill the carbs and check the lines for leaks. Right away gas starts pouring out of the pump. I assumed it was a fitting so I re-tightened everything and turned it on again-same thing. Gas was squirting out of the vent hole in the pump. I called the Holley tech line and explained the problem. I was just asking for help, no attitude at all. Right off the bat the tech guy is an asshole, at first he's like "Vent hole, I don't know what you're talking about." I explained it to him again and he says "Oh yeah, that happens when we install the seal wrong." Long story short, they are fully aware of the problem, couldn't give a shit, and don't replace the pump. Customer service at it's finest.
     
  23. twinturbo496
    Joined: Sep 15, 2008
    Posts: 201

    twinturbo496
    Member
    from Cypress

    I have found that edelbrock has much better customer service, a friend of mine bought a set of their aluminum heads, and found a casting flaw around on of the head stud bosses, probably only cosmetic, but they gave him a new set including shipping without much hassle, they just confirmed his details on the heads and then shipped new ones promptly.
     
  24. johnnykck
    Joined: Dec 22, 2005
    Posts: 1,025

    johnnykck
    Member

    Pretty much my opinion also, the soot on the base makes me think it's running rich, but that might be from a rich idle condition. With the gas that you can buy today any color on the insulator indicates a rich condition, except for a thin ring at the base, about a 1/16 wide. But I don't think you're running so rich that it will hurt anything. I tend to run my stuff leaner than that. I wouldn't worry about driving it like that, wait until you can take it to a dragstrip, put some new plugs in it when you get there and see how they look after a run.
     
    Last edited: Feb 22, 2009

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