Register now to get rid of these ads!

Technical FRUSTRATED AND MAD!!!!

Discussion in 'The Hokey Ass Message Board' started by kscarguy, Jul 14, 2014.

  1. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    I have about had it with my "new" 406 SBC. After countless messing around, I still don't know what is wrong with it. It runs like complete crap.

    It was a completely new rebuild by a pro builder, It ran very strong at first, but had an issue with ex oil coming out of the seal on the front timing cover seal. After giving it 100 miles of break in and replacing the seal, I drove it on a 200 mile road trip and en-route, I broke a valve spring. It still ran good down the highway, but idled like crap when I pulled off the highway. I limped it home, and pulled the plugs at that time and they looked fine. Also, the dished pistons did not appear to hit the valve (luckily, it had an inner spring and I was not revving the engine). I replaced all the valve springs and readjusted the lifters twice (second time was running adjustment but I only went 1/4 turn past stop of ticking. After farting around with it some more and it running like a "turd-burger", I discovered a broken chrome distributor clamp that allowed the distributor to retard itself to the point where it almost wouldn't run. I replaced the clamp, moved the vacuum hose for the distributor to a full time manifold vacuum port and it seemed to run better. SO... I changed out the leaking timing cover...and road tested it. It is still running terrible and leaking oil from the timing cover seal yet again. I ran a compression test today and the readings are 200, 205, 205, a bunch of 210 and one 215. I also looked at the plugs and they look half oil fouled (on the side facing the valves) and half tan on the side facing the piston. (AC Delco R43TS). It almost looks like bad valve guides, but the heads were checked, reworked and vacuum tested. I pulled the rotor off and checked the mechanical advance on the HEI and it is clear and free. (I also rotated the cap clockwise and it snaps back easily too). I sucked on the vacuum advance hose and it operates fine. I checked the PCV valve and it sucks great at idle, but I don't know what happens at speed. It is connected to the port on my Quadrajet carb right under the fuel line on the very front of the carb, same place as always. The engine ran fine on day one, so the cam is set up right. I run M/T valve covers with no baffling in them, so I wonder if the PCV valve sucking in oil and fouling the plugs? Should I try different (stock) valve covers? Is my gas too low of octane? It revs in the driveway fine, but knocks when under load, when I accelerate. I had set the timing at 4 degrees BTDC (stock 400) and it pre-detonates like crazy. If I retard the timing, the knock goes away, but there is no power. When I set the timing (with the vacuum advance disconnected) the engine almost wanted to stall as I moved the distributor. As soon as I plugged the line back in, the RPM's jumped up.

    I have no idea what to do to fix it. I can really use some assistance...please!!! Ask questions, I'll answer as quick as possible and do whatever checks I can.
     
  2. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,793

    tfeverfred
    Member

    As soon as it gave you trouble, you probably should have contacted the pro-builder. Is it too late to get it back to him? I'd add a baffle to one of those valve covers. Engines got to breathe.
     
    bchrismer likes this.
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 47,772

    squirrel
    Member

    The plugs might be a little cold? not sure though.

    The valve covers do need baffles in them.

    Sounds like it has a bunch of compression. Are you using the highest octane fuel you can?

    The broken valve spring is worrisome....I've experienced that with used springs on an overhauled engine, I always replace them when redoing an engine. Do they look new, or old? new springs pretty much always have a line or two of paint on them, as a code to what part they are
     
  4. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    I would start with the timing issue. Not a chevy expert, but don't see why any engine would knock at 4deg BTDC. We run the fords (Cleveland and Windsor) up to 15 to 20 degrees BTDC. I know there is a difference in what the engines want and can use (has to do with combustion chamber design), but still 4 degrees? I would suspect a possible distributer problem. Any idea were it was timed when you first ran it? Hope some chevy guys can jump in and help you.
     

  5. hdman6465
    Joined: Jul 5, 2009
    Posts: 652

    hdman6465
    ALLIANCE MEMBER

    Do you have 400 heads or at least steam holes drilled in 350 heads?
     
  6. FlynBrian
    Joined: Oct 5, 2007
    Posts: 759

    FlynBrian
    Member

    I see you have 15psi difference between your lowest and highest cylinder readings, thats right at the limit, being you only have a couple hundred miles on it, it may not be completely broke in yet, hence your compression numbers from cyl to cyl. I had a 406cu chevy a while back and it took 500 miles of pretty hard driving before the rings were fully seated and i got consistent compression numbers cyl to cyl, plus you don't have any baffling in your valvecovers which could compound the problem if your rings haven't completely seated yet, do you have breathers in the valvecovers and are you getting any visible blow-by? What kind of valvestem seals were used? When you put the new valvesprings in did you check to see if you could rock the valvestems in the guides, checking for any play? Did your machinest line hone the mains in block? I understand your frustration I've had a few give me fits.:mad:

    Posted using the Full Custom H.A.M.B. App!
     
    BORRACHO13 likes this.
  7. oldolds
    Joined: Oct 18, 2010
    Posts: 3,107

    oldolds
    Member

    I think you have a bad dist. or a vacuum leak. I once had a dist. that would stick in the advance postion and would do things like you are saying.
     
  8. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    I checked the hose from the PCV valve to the carb and it is very oily inside, so it strongly appears that the valve is sucking oil from the valve cover and sending it down the intake. BUT could it also be a symptom of high crankcase pressure?

    1 Valve springs are now all new and matched to the cam...they were just stock ones before.
    2 It was not supposed to be a high compression engine. It has dished pistons and large chamber heads, but the builder decked the block. I calculated 9.4:1 static compression. Is a reading of 210 high or normal-ish?
    3 Could the oil sucked in by the PCV valve cause the plugs to look oil fouled on one side?
    4 Could the half fouled plugs cause the poor running / detonation issue?
    5 How do I add a baffle inside a Mickey Thompson aluminum valve cover?
    6 I have low octane fuel in it...perhaps another issue? On my break in and road trip I ran high octane.
    7 The heads are stock 350 (882 castings) with the steam holes drilled.
    8 Could the builder have put hardened rings in it and maybe they are not seating, causing a lot of crankcase pressure?
    9 Should I tear it down and install another set of new rings and perhaps thicker head gaskets?
     
  9. sounds like maybe its not broken in or maybe worse the cam has ground down from not being broken in maybe? I worked on an engine that ran like that and turned out to be improperly broken in cam, and was driven hard before being broke in
     
    chris' 38 likes this.
  10. Torana68
    Joined: Jan 28, 2008
    Posts: 1,238

    Torana68
    ALLIANCE MEMBER
    from Australia

    Put the vac advance tube back where it belongs, manifold vac will just give you full advance all the time ( and a heap of pinging) re set the timing. What crankcase ventilation do you have? Ok sounds like it may be pressurising the sump , new PVC valve fitted?
     
  11. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Who broke in the cam? What oil was used? Was a cam break in additive used?
     
  12. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    Machinist did pretty much everything on the block...I have a breather in one valve cover and the PCV valve in the other. No visible blow by at idle or even revving it in the driveway, but on the highway, I blow oil out of the engine. You are right about no baffle inside valve cover....I did check and nope, the valves did not rock. They all felt gfreat. The machinist did a vacuum test (?) on them to make sure they sealed correctly. He also went through the heads and checked all the valve stems and guides. I am not sure what seals he put on them.

    I suspect the distributor too, but I can't say why. It just seems like it isn't working correctly. I am really tempted to install a new one just to eliminate it as the cause.
     
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 47,772

    squirrel
    Member

    With that much compression, it is not surprising that you need to run preimium fuel. The chamber design, and the dished pistons, are not very good at resisting pinging.

    You might check that all the valves are opening fully, my guess is the cam is probably ok, but only you can tell.

    you can rivet or jbweld a plate under the holes in the valve covers. Are there bosses for screws there?

    Did you check the timing at idle, and at a few thousand rpm, with a "dial type" timing light?
     
  14. I like to install breathers straight to the crank case, will give less back pressure inside engine. Maybe the case is not getting enough breathing
     
  15. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    Cam was broke in on their engine machine. I also did the varied RPM, to break it in, when I fired it up. Builder used the lube and zinc. The builder/shop is a reputable business and the builder has been doing this for years. They won engine of the year last year too. Not saying they didn't make a mistake, but I doubt it. As I went through and adjusted the valves, nothing seems odd or flat. The rockers are all at about the same location down on the studs.
     
  16. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Then we're most likely back to the distributer and the poor quality fuel mixed with some oil through the PVC. That could make for a bad running engine for sure.
     
  17. well that sounds like a pretty good break in, your cam is prob ok. I would make sure your pcv system is operating correctly before you make any large purchases :D
     
  18. oldtom69
    Joined: Dec 6, 2009
    Posts: 529

    oldtom69
    Member
    from grandin nd

    intake gaskets leaking from the lifter side would cover most of your issues- even a small amount of oil coming in the cyl will cause a ping,probably sealed ok to start and then started to leak.decked block can make intake fitting tricky.hope you aren't using the rubber end gaskets!also make sure your dist. is touching the intake before bottoming out on the oil pump shaft,its the main cause of breaking those junk chrome dist hold downs.p.s. compression tests are about worthless,do a cyl leak down to a true idea of engine condition
     
  19. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    What is "normal" for factory motor compression numbers? I cranked it five times and got those numbers. They seem high to me, (but what do I know).

    Should I swap on thicker head gaskets?

    The cam seems fine. I adjusted it running and it did not seem flat at all. However, I only have it tightened 1/4 turn, should I crank it down to 1/2 or 3/4 turn?
     
  20. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    I would stick with the distributer/timing, fuel & oil issues for now. At this point need to slow down and work one thing at a time.
     
  21. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    Not sure how to do a leak down or if I can do it with my compression gauge. The cheap chrome distributor clamp was pot metal! It was actually hollow on underside and easily bent and cracked. It was also "slick as goose poop" where it touched the distributor. Basically worthless...

    Could oil sucked in from my PCV valve cause the detonation issues?
     
  22. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Timing, fuel and oil caused your detonation issue!
     
  23. FlynBrian
    Joined: Oct 5, 2007
    Posts: 759

    FlynBrian
    Member

    I think it's a real possibility you have rings that haven't completely seated yet, my 406 pushed oil out just like yours is doing when under load rolling down the highway, once the rings finally seated it was fine, reason I asked about the valvestem seals if it has the Viton type seals I have seen them ride off the guidebosses before, they have a spring clip that holds them tight around the valveguide boss, sometimes when installing new valvesprings it's easy to bump a few of them loose. Front seal you might have to open the dowel-pin guide holes up a little to get your timing cover centered, had to do that a few times and definitely learned to pay a little extra for the good felpro seal. If your distributor swap checks out, then your timing problem is more than likely from the oil fouling on the plugs, you could always do a good cleaning on the plugs and pop them back in and see if it runs good for a bit, if it does then you know your problem is oil fouling, a lil easier to do then swapping out dizzys.

    Posted using the Full Custom H.A.M.B. App!
     
  24. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    if your sucking up motor oil it will knock as it will drop ( dilute) the octane numbers like diesel fuel or ATF , put a baffle under the pcv it as if its near a rocker tip the tip will throw oil right into it, its only to see vapor not liquid or try to run the pcv to a collector can then to the engine the can catches the oil and lets the vapor only thru ( also what s the PCV valve out of ??? they came in different vacum ratings ( weights on slug) a high reving motor ( pick up truck ) needs a different one than a cruiser (Car )
    but sounds like it needs to finish breaking in the rings . when you drive it do not lightly load it , vary the loading and speeds for distances to help set them . we used to get the completely warm ( 10 -15 minute drive ) then do some get on it hard from a stop to 60 runs ( 2-3 ) then drive it normal for a while then do it again or act like a passing manuever at speed ( allow the trans to kick down ) this ussually sets them ,
     
  25. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    SO...what I am thinking is:
    I can install stock valve covers with the built in baffle for now. that would at least help that issue.
    I can install new plugs...any suggestions as to temp range?
    I can borrow a different distributor from a friend (or neighbors car if the street lights are out...Ha!)
    I can install a timing tape and set total timing to 32 degrees with the vacuum advance disconnected.
    I can move Vacuum advance hose back to original port on carb that worked early on.
     
  26. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547

    stimpy

    valve covers first and then you going to have to dry the manifold by spraying carb cleaner in it while reving the motor to get rid of any oil . if the plugs are tan and the strap is not blued go up 1 number
     
  27. tltony
    Joined: Jan 11, 2009
    Posts: 293

    tltony
    Member
    from El Cajon


    Winner winner!!!
    First I'd set the total timing at 3500 RPM at about 35 to 38 degrees or so. If it doesn't run good/better after doing this , take off the valve covers and run it with them off and look for rockers that aren't moving as much as the others.
     
  28. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    And get some good gas in it. Sounds like a plan.
     
  29. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    OK, plugs, baffle the PVC valve, see if I can try a different valve (have no idea what Chevy engine it is from) and put in some high test gasoline. Sounds like a good place to start.

    I really think that it is sucking in quite a bit of oil, as the hose was wet with oil inside. [theory - Oil drops into cylinder and fouls the topside of the plugs (on valve side) causing poor running engine, excess heat builds up, detonation ]occurs.
     
  30. kscarguy
    Joined: Aug 22, 2007
    Posts: 1,579

    kscarguy
    Member

    I watched the rockers as I adjusted them, they all moved the same...at least to the eye. But I will check it again when I swap valve covers.

    Can the 400 handle that much total advance? I thought 32-34 was all it should have. 3500 RPM, ok. Was I right about pulling the vacuum advance hose off to set the total timing? I do not have an adjustable timing light...wish I did. I will install a tape.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.