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Hot Rods timing sbc

Discussion in 'The Hokey Ass Message Board' started by dstangl, Apr 14, 2014.

  1. TheTumbleweeds
    Joined: Jul 29, 2010
    Posts: 536

    TheTumbleweeds
    Member
    from Sweden

    THis happens, and should be first thing to look at, specially when engine runs fine.

    BUt like a 6.5l diesel, its crittical when the ring has moved, do the Balance Can Change and brake the engine..
     
  2. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,325

    54vicky
    Member

    get your self a vacuum gauge it wont lie and eliminate any parts swapped damper etc. search uses it will be money well spent my11/2 pennies good luck
     
  3. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    Ok thanks for all the help guys I've got it running better now all of the floats were too high and I've got the timing close one more question I was going to start at 10* BTDC but by the sound of the motor and the vacuum gauge it wants more probably about 16* initial should this concern me? should I be more concerned about total? I haven't driven it yet with these new carbs
     
  4. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,325

    54vicky
    Member

    go with vacuum too many things for light to take into account including light itself damper shift or wrong. wear in chain gears etc read up on what gauge can tell you not being an ass.
     
  5. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    Ok guys if I set the timing using a vacuum gauge it wants a lot I've read tunnel rams like a little more anyway has anyone had experience with that? according to highest vacuum it wants close to 30* but that would put total advance pretty high is this a situation where I set it at idle with vacuum and adjust the distributor to limit total advance? how much total will a motor take?
     
  6. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    max vacuum puts the initial around 25-30 which would put total well over 40 how much total can I have (with vacuum advance unhooked) most of what I read says 36-38? would I be right in thinking I need to get the advance limiters for the dist so I can give it more initial timing like it seems to want but then limit the total to around 38? is there a way to tell what the total should be or is it pretty standard to stay under 40 on a sbc
     
  7. dirtracer06
    Joined: Sep 29, 2009
    Posts: 198

    dirtracer06
    Member

    careful setting it to far advanced, or you will have issues getting it to start when the engine is hot.
     
  8. arkiehotrods
    Joined: Mar 9, 2006
    Posts: 5,821

    arkiehotrods
    Member

    It started and ran so the distributor is not 180º off.
     
  9. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    we are all over but making progress the first problem was the balancer it had a timing mark for a pointer at 12:00 got a new pointer made anew mark that part is making sense now
    details(at least what I know)
    engine 350 mostly stock internal I think (I pulled it from a donor vehicle)
    block # 37970010
    heads 462824
    cam - no idea
    intake weiand tunnel ram
    carbs 2 600 holley mechanical secondary and progressive linkage
    exhaust zoomies with baffles
    distributor pertronix flamethrower

    I checked today and at idle it likes about 28* timing (vac advance unhooked)
    so do I limit my mechanical advance to stay below a certain number total

    I really appreciate all the help guys I feel like I'm getting there any advice is appreciated
     
  10. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    I'm assuming I can't actually go to 28* at idle as dirtracer06 mentioned I could have starting problems any idea how far I can go before that's a problem?
     
  11. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    Here's a picture to help
     

    Attached Files:

  12. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,455

    VoodooTwin
    Member
    from Noo Yawk

    I don't think the picture is going to help......
     
  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,018

    gimpyshotrods
    ALLIANCE MEMBER

    Are you using the factory groove on the balancer to read the timing, or a stick-on timing tape?
     
  14. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    smartass I know the picture doesn't help I'm just trying to get some support on why I'm doing this

    I'm using the groove that I put in the balancer after finding TDC the factory mark was for a pointer in a different position and measuring off of that with some tape and calculated marks

    I know this isn't the motor I'd like but for now it's what I have. I had a perfectly good edelbrock intake and 750 carb that ran fine for the last two years but I had this tunnel ram setup sitting there too and finally got the itch to try it heads, cam, rebuild, and probably a stroker kit are all things I'd like to do at some point but for now I was just hoping to get it to run, be reliable and not blow the thing to pieces I'm not trying to win any races I just want to drive
     
  15. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,018

    gimpyshotrods
    ALLIANCE MEMBER

    Double check your calculations. You should have difficulty starting it if it really is 28° advanced at idle. I would wager it is really not. It also shouldn't run very well there, and is likely to not accelerate, as the centrifugal advance will bring in 28-32 more degrees.

    In any case, timed, or not, you will not be pleased with this setup's performance.
     
  16. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,877

    brokenspoke
    Member

    ^^^^^what he said^^^^
     
  17. monkeywrenching
    Joined: Feb 14, 2007
    Posts: 299

    monkeywrenching
    Member
    from maryland

    Just something to think about. When building an engine all the individual components must complement each other. If you add too much carburation without cam and compression and flow from your heads, drivabilty suffers. So with your engine combination, carbs and intake are not compatable with the lack of compression or cam choice. I would bet you have an automatic without converter.That doesnt help matters also. Your timing issues are complicated by the intake and the amount of fuel your pouring into an engine that at best is going to flush most of it out of the exhaust. With your intake the best you are going to hope for is an idle with a lot of advance. Stick to one carb and set it up right. Detail your engine and enjoy driving it. Patience will benefit you with more time at the wheel and less time fixing broken parts or standing on the side of the road waiting for a tow.
    JMHO
     
  18. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    I appreciate the concern but why did this turn into a thread about why I shouldn't use a tunnel ram? there is already lots of those and I've read them here and on other sites
     
  19. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,018

    gimpyshotrods
    ALLIANCE MEMBER

    Because you are attempting to use a tunnel ram on the exact opposite of the optimal application.

    I have been tuning high performance engines for close to 30-years. Others on this board, TWICE as long as me.

    I can tell you, as many orhers will, that what you are attempting to do will not work.

    Tunnel rams are designed for optimal wide-open throttle airflow, via the straightest path.

    In order for this to work, at-all, on the dragstrip, all components in the engine must be precisely matched. From port size, valve size, cam lift, duration, lobe separation, compression ratio, header primary pipe diameter, etc.

    It is even harder to make this work properly for the street. You simply will lose most bottom end torque, even with a properly prepared engine.

    What you have, is the opposite of properly prepared.

    What you are is improperly prepared.

    I am not trying to be a jerk. You are on a board that has several thousand man-years of hot rooding experience, asking why you are not being steered in the direction that YOU want to go.

    When you are ready to listen to those whose only intention is to help you, then, and then, will you be properly prepared.
     
  20. GRX
    Joined: Mar 28, 2014
    Posts: 68

    GRX
    Member
    from MD

    Why? See your words below:
    As others here, I have been machining & building these engines for a long time. That said, you have the attention of some very knowledgeable & experienced people here. Ignore their great advice at your own peril. To reiterate, everything in the entire drive train should be considered - from air cleaner to rear tire diameter, and all between. This is what makes a hot rod truly perform.
     
  21. orangeamcs
    Joined: Jun 23, 2007
    Posts: 605

    orangeamcs
    Member

    I just went through this. I ended up buying a new balancer for $55 from summit with all marks on it. Got a new timing pointer for around $20. The motor I had had the timing tab at 12 oclock on the timing chain cover which was wasted so I replaced it with new cover w standard 3 o'clock ish timing pointer so marks were off. New balancer solved that problem. Set my initial at around 12 degrees and total was around 36 degrees. Friend said car ran great and started easily after that. Most SBC run well at 34-38 degrees total. That's what I shoot for but depending on curve in your distributor your initial may vary.

    Posted using the Full Custom H.A.M.B. App!
     
  22. tethercarguy
    Joined: Feb 6, 2010
    Posts: 21

    tethercarguy
    Member
    from Vista, CA

    Here's a mickey mouse sounding way of finding TDC. Using a flashlight, try to turn the motor to what looks like TDC looking through the spark plug hole. I take a welding rod and wrap electrical tape around it from about 1/2" from the tip back about 6". I then attach a continuity tester to the welding wire and the engine block. I slide the welding wire in the hole and tilt it until it touched the piston and registers on the meter. I hold it in that position while I rotate the crank back and forth, while marking where the meter turns on and off on a piece of masking tape on the damper. You should wind up with a line BTDC and a line ATDC. Your actual TDC in midway between these marks. As for making sure you're on the power stroke of TDC, I pull the #1 plug and turn the motor over by hand until the pointer for the damper points to TDC. I then put an air hose in the spark plug hole and apply air. If you here air from the carb and exhaust, then you're good to go. If you don't, rotate crank 360 degrees and try again with the air hose. When you hear it through the carb and exhaust, then you have the power stroke.
     
  23. dstangl
    Joined: Sep 29, 2012
    Posts: 28

    dstangl
    Member
    from central MN

    After a couple years of running this setup I thought I add to the thread for anyone reading this later. The reason for building this truck was because I thought it looked cool and that is the same reason I wanted the tunnel ram on there knowing it is not an ideal setup. In the end I have 22* of initial timing and the distributor is limited to another 16* this is probably what got me confused at first it does like a lot of initial timing. So with the old 350 a four speed manual a tunnel ram and two 600 holleys on top I have been driving it for two years and a couple thousand miles it fires right up and has no drivability issues last I checked it gets about 13 miles to the gallon. Is this a perfect setup? no but can a tunnel ram be run on the street? yes. The single carb and dual plane intake was probably better matched for this motor but with a light vehicle and a four speed I never noticed much difference in the way it drives and the tunnel ram get people looking and talking and after all the work changing to this setup and learning a lot about things I hadn't done before I love it.
     
  24. Thats the key, "timing". A lot of initial with a little total. I have run them quite a bit. Put several thousand miles on a T bucket, a Model A coupe and a 36 Ford coupe, all with tunnel rams, using Holley and Edelbrock carbs !!!
     
  25. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,249

    2OLD2FAST
    Member
    from illinois

    I'm sure you don't want to hear it but get rid of the progressive linkge , the engine will be more respnsive & no , you won't use anymore gas , plus you won't be running 1/2 the cyl.'s lean..
    dave
     

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