290H Cam vacuum

Discussion in 'Street/strip 400/430/455' started by rcolosi, Dec 16, 2015.

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  1. 8ad-f85

    8ad-f85 Well-Known Member

    It could be anywhere as it is now.
    You need to verify some cam events before determining what/how to do.

    Have you tried a different timing light?
     
  2. rcolosi

    rcolosi Gold Level Contributor

    Yeah, I'll double check the light. Someone just used it not long ago for a tuneup, and it worked fine, but it can't hurt to check.

     
  3. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    Did you make sure that on the (crank) gear you had the inner #6A lined up with the crankshaft keyway, and the outer #+6 straight up (12:00) aligned with the camshaft gear dot (which should be pointed straight down 6:00)? Page #86 of the T/A Performance Online catalog has a nice diagram and explanation of how to set up the gears. That can confuse people and could be the root of this issue. Post #6 second last question.
    Larry
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If that was the case, we could all just put every cam we install in straight up. There would be no need to degree a cam. The best way to think of it is there is no correlation between what is on the cam card and the markings on the key ways. You have to check everything, and unless you degreed it, it could be anywhere. You'll never know unless you actually check it with a degree wheel.
     
  5. rcolosi

    rcolosi Gold Level Contributor

    My 1st grade teacher always said "haste makes waste" You'd think I would have learned to take the time to degree the cam the first time, eh? :Dou:

    Yup...I was re-reading this and it may well be the problem.
     
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  7. Jim Weise

    Jim Weise EFI/DIS 482

    Here is a simple way to check to see if the cam is installed way off..

    Rotate the motor over until your at split overlap on number one cylinder. Split overlap is defined as the point where the intake and exhaust valves are open the same amount, on the exhaust stroke.

    Use a small steel scale or ruler to get a good eyeball on when the intake and exhaust retainers are at the same height.

    Now look at the timing mark.. it should be very close to zero.

    JW
     
  8. rcolosi

    rcolosi Gold Level Contributor

    Awesome... gonna try that in the AM for sure.

     
  9. rcolosi

    rcolosi Gold Level Contributor

    Problem potentially solved. The rockers seemed to line up perfectly at 8* advance. At TDC the rule showed the intake slightly further open. I happily accept the dumbass award.
     
  10. 8ad-f85

    8ad-f85 Well-Known Member

    Not necessarily.
    Means your cam is advanced, not retarded.
    That should make it very responsive to mild initial timing position.
    Look at the cam card and see how far off you are.
    You can average the #'s at overlap and guess closely.
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  12. rcolosi

    rcolosi Gold Level Contributor

    Ongoing problem...still not solved. Any input would be very greatly appreciated!!

    This was the engine (specs below) that only pulled 6 - 9 vacuum and would only start/run with the dist. Set for about 33* advance, advancing to 40* + as the dist. advanced under rpm. . 3 different timing lights used and all the mechanicals verified. If you set the distributor to a normal 10 15*, it wont even start and hiccups gas out the carb. The ONLY thing I found off was when I installed the cam 4* advanced, and re-degreed it properly yesterday, I found the centerline to be 104* Apparently it must be ground into the cam, so straight up it went in, now I have the proper 108* The crazy thing is other than a crappy idle and poor vacuum, the engine runs great and the car pulls like it's noones business. it's a beast. No kickback on startingreally no other issues. NO indication of 40* + of advance when I'm getting on it...no knocking...and the engine stays together. Compression check appeared good. all around #165. Plugs look great. Is there anything else that comes to mind as to why that much advance is seen? Would the 4* degreeing error be responsible for that much timing variation?

    - Cam: T/A 290H
    - T/A balancer verified correct mark
    - T/A timing cover verified correct timing mark
    - T/A billet double roller timing set
    - MSD distributor Curved properly
    - MSD 6AL digital
    - SP1 intake and performer intake, same results
    - Quadrajet just re-worked by Everyday Performance, still will only idle on transition ports, almost no control with idle screws
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    Without re-reading the entire thread, are you by chance using the dial back feature on these timing lights?
    They don't always play friendly with MSD's.
    (Maybe this has been posted already?)
     
  14. rcolosi

    rcolosi Gold Level Contributor

    Nope... we used 3 different timing lights...all indicated the same. A 4th was actually a dial back, and said the same thing.
     
  15. 8ad-f85

    8ad-f85 Well-Known Member

    It's been mentioned a few times that you need closer to 20* or more initial timing to have a decent idle with acceptable vacuum.
    It's also common to have hot starting issues unless you follow the previous advice of either recurving the distributor, locking it out and using either an ignition interruptor or start retard.
    Also mentioned was to make sure the throttle blades were starting in the correct position, possibly having to drill some holes in the butterflies to get enough idle air without opening the blades past the transition slots. (some carbs came this way from the factory)

    It sounds like where you are at is what everyone has to deal with in one way or another when putting a combo together like this.
    Just a couple of minor tweaks and you are enjoying your fun ride as it was meant to be!
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The problem Bob is having is that the engine refuses to run at all, or even start, with even 20* of timing. The engine also has low vacuum even with 30* + timing. In the past I have seen that symptom with a vacuum leak into the valley because the intake manifold isn't fitting correctly. It's either that or there is something seriously wrong with the cam.
     
  17. rcolosi

    rcolosi Gold Level Contributor

    What Larry mention just makes this all the more confusing. If I set the distributor at, say, 12 to 15 degrees, the car will not start and belches fuel out of the carb. Advance the snot out of it, and it's good.
     
  18. 8ad-f85

    8ad-f85 Well-Known Member

    This would definitely be a lot easier being in front of the car :cool:

    Valve seats not sealing or too much lifter preload?
     
    Julian likes this.
  19. rcolosi

    rcolosi Gold Level Contributor

    We did a compression test and got all of them right around #165. I have the T/A rollers so I do plan on re-adjusting the valves again when I put it back together later this week.
     
  20. Julian

    Julian Well-Known Member

    Update? Two years later...
     

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