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Chevy 350 v8 issues

Discussion in 'Off Topic' started by Weebs, Sep 19, 2011.

  1. Weebs

    Weebs Clackamas County Member

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    First let me say that I'm not a big gear head. I don't know a ton about cars and their engines. I purchased this project as a learning tool to help teach myself some auto repair but at the moment I'm a bit stumped.

    Vehicle: 1971 Toyota FJ40 Land Cruiser
    Engine Block: 1971 Chevy 350 V8 from a K10.
    Engine Heads: Who knows, but they're from a newer than 71 chevy.
    Carb: Holley 4 barrel

    Anyways, 2 weeks ago I went to start up the FJ and experienced a loud back fire. I restarted the engine and was able to drive. As I drove the engine began feeling as if it was running down a couple cylinders. I parked for the evening (Out of town at my parents house) and decided to check my plug wires and plugs. All the plugs looked fine and the wire didn't look to have any physical damage. I left their house and drove home. If I pressed the pedal harder and got it higher in the revs it seemed to smooth out and drive fine. I made it 2 blocks from my house before it died. I got towed into my house and went back to the drawing board.

    My first attempt to get it back running right was changing the HEI distributor cap, coil, and rotor. This restarted the FJ but I had to press the gas pedal to keep it running. Black smoke was coming out the exhaust and the carb started flooding. Literally flooding gas out of the carb.

    After looking online I found that Holley is notorious for blowing powervalves after a backfire. So I replaced the power valve, metering block gasket, and the fuel bowl gaskets and started it up again. This time it was able to idle but it still has a major shutter. I rolled it out of the garage and reved the engine. It never really smoothed out. I pulled it back into the garage and let it sit.

    Does anyone have any ideas as to what my issue could be?

    On my list of possible problems...
    Timing - I have a timing light but I can't seem to find the timing mark on the flywheel...
    The whole distributor is toast
    vacuum leak? not really sure where to look to figure out if the vacuum system is good.

    Are any of you masters of the 350? Generally good mechanics and have an idea where I should start? :thumbup::thumbup::thumbup: Thanks in advance!!!!!!!!
     
  2. coop44

    coop44 Tacoma ,WA Well-Known Member

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    run a compression check, should be somewhere around 120 depending on your setup, no more than a few pounds deviation between highest and lowest this will tell you where you need to go next. If comperession is good, rotate crank to TDC (on #1 cylinder) and highlight with a dab of white. check timing
     
    Gunner3456 and (deleted member) like this.
  3. Weebs

    Weebs Clackamas County Member

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    I'm going to run to the store at my lunch break today and pick up a compression tester. I'll run a compression test tonight when I get home and see what that shows. After for hitting TDC... Never done that. Reading online on how to do it. Looks like there's 23423789472 different methods to do it haha. Wish me luck!
     
  4. Unka-Boo

    Unka-Boo Milwaukie Active Member

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    Timing marks are on the crank pulley, start @ 8btdc and play from there. HEI distributors need a full 12v to run, if someone wired it to the stock coil wire it may not be getting full voltage. Holley+backfire= blown power valve, easy fix, default to a 6.5 if you dont know whats in it.
     
  5. Weebs

    Weebs Clackamas County Member

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    yeah the power valve was an easy fix (hardest part was scraping the old gaskets off). You're right, it was a 6.5 :)

    So if my battery was low it might cause my HEI distributor to run weird? Hmm, maybe I'll throw it on the charger and see if that helps anything. I've got a red top ultima that has never seemed weak until the day it died. I also blue a electric fan fuse the day this all happened and didn't think anything of it...
     
  6. Gunner3456

    Gunner3456 Salem Well-Known Member

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    This. The weak link on a 350 chevy is the valve train. Your timing gear may have jumped a tooth, or you might have a flat cam lobe or two, and with that a dished lifter or two. If a compression test shows all cylinders low, maybe it's the timing gear. If it's just a couple of cylinders it could be a bad cam/lifter issue or burned valves.

    If you have to pull the heads, be sure to have the valve stems and guides checked and fixed if needed when the valves are ground. They are notorious for wearing.

    Having the ignition out of time (timing light mentioned) won't affect the compression.

    Be sure to pull all plugs before checking the compression. A remote starter switch is cheap and sure helps here, or you need a helper to turn the engine over. Read the directions.
     
  7. deadeye

    deadeye Albany,OR. Moderator Staff Member

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    If you ran it with a bad power valve (flooding) I would change the plugs (fouled a little) check timing 6-8 deg BTDC. I would wonder what caused the initial backfire and check the HEI module in the dist if it is orange change it, they are notorious for going bad. Always carry an extra dist. module and power valve in the glov box (chevy's.....). If you want a good fix change out the carb. (quadrapuke/holly) and put an edelbrock 1406 on.
     
  8. buick455

    buick455 se portland Member

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    If the new power valve fixed the running issue off idle then i'd change the plugs and see if the idle gets better. the initial backfire sounds like an advance problem. The first question a good mechanic would ask is has this rig ever run right with this combo of parts. if not then check to see what year the dist. was made and get the info on how the advance is set up GM had different set ups on different aplications and they are not interchangeable you will need to follow the instructions on how to test the advance after you make sure that the correct springs are used for the mechanical advance (i think there is three to choose from) and that you have the correct vac. advance for the dist and application. you will see about 10 deg mech. and something like 32 deg all in at some give rpm like 2500 check specifically for your application and cam.
     
  9. swoop

    swoop Milwaukie, Oregon Well-Known Member

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    Just an idea, but if it has been stored for a while could have water or vapor in gas which can cause a back-fire which can cause a blown power valve. Sometimes floats can lose ajustement when bowl gaskets are changed, and a float set to high could cause the flooding and smoking you mentioned. I would check float setting, clean pluges, check choke setting, drain gas if it shows signs of water, and change fuel filter. If that doesen't help, you can always move on to more expensive parts. Hope that helps..
     
  10. Trlsmn

    Trlsmn In Utero (Portland) Well-Known Member

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    Timing chain. Probably an original fiber gear.
     
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  11. Gunner3456

    Gunner3456 Salem Well-Known Member

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    +1. A Compression check is the first order of business.
     
  12. SDR

    SDR Clackamas County, Oregon Silver Vendor Silver Vendor

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    Compression test is always good for testing the overall health of the engine...
    A quick and easy way to confirm a timing chain issue is too remove the distributor cap and rotate the crank pulley back and forth a quarter revolution or so, The distributor rotor should closely follow the crank shaft back and forth moments... Moving one direction and then back, If the rotor doesn't respond it is a sure sign of slack in the chain... Poor valve timing or flat cam can make a engine appear to be flooding...
    Questions call 503-636-7935 ask for Shawn, I'm in from 5AM to 1-3 PM ...
     
  13. Unka-Boo

    Unka-Boo Milwaukie Active Member

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    Voltage comment is because of the conversion...granted, it's speculation on my part, but, from past experience a lot of guys just hook up the HEI to the factory "Hot" wire. Being that it was a breaker ignition originally, the wire will be too small of a gauge and if it was externally resisted, won't supply a full 12 volts. HEI's like plenty of voltage. ( You can fix both by running it through a simple 30a 4 pole relay ) Also make sure it's grounded correctly and the engine has a ground to the frame.

    Take up SDR's offer if you get stuck, he knows a thing or two...maybe three....:cool:
     
  14. Gunner3456

    Gunner3456 Salem Well-Known Member

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    Weebs, do just one thing at a time. When you make a whole bunch of changes, you lose track of where you are.
     
  15. Unka-Boo

    Unka-Boo Milwaukie Active Member

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    Best advice yet.....
     
  16. techieguy

    techieguy Well-Known Member

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    And we need pictures...some of us are TLC junkies!
     
  17. bruzer

    bruzer Grants Pass, OR Well-Known Member

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    V8 TLC junky too. Although my V8 needs to get back in the rig along with tranny and tranfercase. Good luck with yours.
    Mike
     
  18. deadeye

    deadeye Albany,OR. Moderator Staff Member

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    Just had a thought as I just had a learning experience a while back on a neighbors 56 f100 with a 350 that had been installed by a previous owner. When you checked the timing with the light and saw no timing mark was that with the light or did you not see one physicallly on the dampner? What I ended up finding is that the installer of the motor had used a crate motor, new balancer but older timing cover, this is a big mistake that is easy to make for the non knowing. If you have an older motor and timing cover but a newer balancer your timing mark will be off many deg. as the older v-8 has the timing mark on the side of the cover and the newer motors are at the top using the longer watr pump as the acc. on the newer motors dont allow the side marker. If you manually/by ear or vaccum level time the motor to run what seems to be good but cant see the timing mark with the light shine it behind thewater pump at the top or just aim at the top from the front and see if you can see the mark....hope you could follow that.
     
  19. Buddhalux

    Buddhalux Hillsboro, Oregon Active Member

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    Easy way to test for vaccuum line leaks is use a can of carb cleaner and spray small puffs on the ends of your lines. If your engine revs up then you know where to look at least. Some people just use soapy water and look for bubbles. Also, if you get a new battery don't get a Red or Black top. They sold their rights to a mexican company and they're turning out nothing but junk. I went with the Excide Eliminator for my whip.
     
  20. Jamie6.5

    Jamie6.5 Western OR Well-Known Member

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    It sounds like our e-10/e-15 gas loosened up some fuel system varnish and some of it is lodged in the needle/seat assembly(ies) on your Holley.
    If you don't know how to use the sight plugs on Holley fuel bowls, google it or get a book. It's easy to set the floats on a Holley, and pulling the sight plugs will tell you whether the needle/seats are working properly, and regulating fuel flow like they should. They can be replaced easily enough if necessary.

    And don't let anyone talk you into scrapping that Holley for the far more complex and inferior edlebrock carb!