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  1. #16
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    compression?

    i'm like you, olds ain't my native langauge. i'll take the 440/t-quad, too. 180 psi comp. sounds kinda high to me. and with a cam, with more overlap and duration, cranking compression would be lower, imo. were the heads cut for compression? with an aggressive mill job, and non adjustable valve train, could the lifters be compressed too much to start, and pumping up at higher rpm's? just a wild thought, because i think it would pop or spit when the lifters pumped up. but they might increase the duration/overlap enough to cause issues, without backfiring. loosen your rockers, get one cylinder on tdc, and tighten the rockers down until that cylinder's pushrods are just touching. no slack, but no depressing the lifter. then tighten on down, and watch how much the pushrod moves down. i don't know how much is too far on an olds, but i would think anything much more than .080 to .100" would cause a problem. this spec should be similar to mopars. i've had this problem on my '73 charger, had to go to adj. rockers. but it always popped or backfired when the lifters pumped up. what you describe acts like some tight valves might act on a solid lifter cam. it can cause the vacuum signal at the carb venturis to be wrong, and cause surging/flat spots-acts just like a fuel or spark issue. a valve job not done completely could contribute, too. grind the seat, and you move the valve deeper in the head. if you don't grind the stem, it is higher in relation to the valvetrain. same as milling the head, it will compress the lifter further. can happen even if you use new valves. i would check valve installed height, along with everything else.you can do this without taking off more than the valve cover-for both checks. unfortunately, the fix takes more dissassembly.
    AIRWALK
    gettin' old ain't for sissies

  2. #17
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    Mite wanna

    Unload it BBC parts are cheaper, more available too.
    Or ya could put a HEMI in it
    "Where is Lee Harvey Oswald, Now that we really need him?"

  3. #18
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    mopar only

    Quote Originally Posted by BUSHWACKER View Post
    Unload it BBC parts are cheaper, more available too.
    Or ya could put a HEMI in it
    gotta be a hemi, or maybe a low deck (B) stroker, at least tazweld and i could fix it .
    AIRWALK
    gettin' old ain't for sissies

  4. #19
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    If your lifters pump up, there might be an easy way to tell. Mine ended up binding the springs and bent some of my pushrods. I had to shim the rockers up a little with a Mondello shim kit. There wasn't much to the kit though. They were just hardened washers. 180 might be too much compression for pump gas. Might try backing the timing way off or run some race gas. Detonation would prevent the motor from revving up too.

    I would recommend checking the fuel tank pickup tube as well. Remove the fuel pickup tube from the fuel tank and make sure the screen on the end is clear. Mine would idle and rev on the trailer, but would die as soon as I hit it on the water. I found the little screen on the end was almost plugged, just a little pinhole to get fuel to the motor.
    Last edited by Propster; 08-07-2007 at 03:49 PM.
    1990 Cougar 25 MTR w/twin 300 PM's

  5. #20
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    lifter pump up

    Quote Originally Posted by Propster View Post
    If your lifters pump up, it is easy to tell. They will bind the springs and bend the pushrods. 180 might be too much compression for pump gas. Might try backing the timing way off or run some race gas. Detonation would prevent the motor from revving up too.

    I would recommend checking the fuel tank pickup tube as well. Remove the fuel pickup tube from the fuel tank and make sure the screen on the end is clear. Mine would idle and rev on the trailer, but would die as soon as I hit it on the water. I found the little screen on the end was almost plugged, just a little pinhole to get fuel to the motor.
    don't want to argue, but lifters pumping up won't necessarily bend push rods or bind/break valve springs. the valves would need to hit something for that to happen, most of the time. over revving can do that, though. as long as the lifters pump up enough to affect valve operation (duration, closing or not closing), they will cause running problems. not enough to cause contact, just enough to affect operation. like a valve adjusted too tight. won't close soon enough, opens too early. may not spit or pop, but sure can cause issues.
    AIRWALK
    gettin' old ain't for sissies

  6. #21
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    Quote Originally Posted by moparbarn View Post
    don't want to argue, but lifters pumping up won't necessarily bend push rods or bind/break valve springs. the valves would need to hit something for that to happen, most of the time. over revving can do that, though. as long as the lifters pump up enough to affect valve operation (duration, closing or not closing), they will cause running problems. not enough to cause contact, just enough to affect operation. like a valve adjusted too tight. won't close soon enough, opens too early. may not spit or pop, but sure can cause issues.

    you are correct, pumped up lifters usually wont cause bent p/rods or broken springs, but lifters that have not been primed and failed to pump up or lifters with collapsed springs will, you adjust your valves and the hydraulic/spring action of the lifter acts as a sort of shock absorber, if the lifters bottomed out, and you adjust your valve the traditional way, theres gonna be trouble.....

    more and more i feel that tazwelds problem will most likely be traced to his valvetrain/cam combo, if a higher lift cam was installed, along with the standard decking of blocks, milling of heads associated with a rebuild, with the stock configured valvetrain components it is possible his pushrods are too long, and with a non adjustable rocker system there may be a problem, if the valves arent opening enough to intake/exhaust effectively his rpms are limited to what will flo.....if they are opening too much (bent pushrods/binding springs) will also ulitmately resulting in valves not opening properly, so far all the things we are discussing he can check with only his labor, so it costs him nothing but time
    Wile E. Coyote: (acceleratus vulgaris)

    Its amazing how heavy a GPS can be.....

  7. #22
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    tazweld, if this was already stated im sorry for repeating the question, but just out of curiosity, does the motor rev limit to 3500 always or only in the water under load?
    Wile E. Coyote: (acceleratus vulgaris)

    Its amazing how heavy a GPS can be.....

  8. #23
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    Thanks to all those who gave advice on the problem at hand, I finally gave up and pulled the heads off, we found the valve seats had been ground down way to deep and once we pulled the intake valves you could see where it was burning back into the intake. I dropped my heads off at a reputable head shop and they are going to rework the heads for me and only charge me the labour and seats, when i called the shop that rebiult the engine they told me that they never check valve hieght when redoing heads, Its obvious they don't do alot of Olds or Mopar heads or they would know about this issue and how critical the valve highth is.

    Thanks again for all the advice.
    Older is better. When it runs!!

  9. #24
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    Quote Originally Posted by moparbarn View Post
    i'm like you, olds ain't my native langauge. i'll take the 440/t-quad, too. 180 psi comp. sounds kinda high to me. and with a cam, with more overlap and duration, cranking compression would be lower, imo. were the heads cut for compression? with an aggressive mill job, and non adjustable valve train, could the lifters be compressed too much to start, and pumping up at higher rpm's? just a wild thought, because i think it would pop or spit when the lifters pumped up. but they might increase the duration/overlap enough to cause issues, without backfiring. loosen your rockers, get one cylinder on tdc, and tighten the rockers down until that cylinder's pushrods are just touching. no slack, but no depressing the lifter. then tighten on down, and watch how much the pushrod moves down. i don't know how much is too far on an olds, but i would think anything much more than .080 to .100" would cause a problem. this spec should be similar to mopars. i've had this problem on my '73 charger, had to go to adj. rockers. but it always popped or backfired when the lifters pumped up. what you describe acts like some tight valves might act on a solid lifter cam. it can cause the vacuum signal at the carb venturis to be wrong, and cause surging/flat spots-acts just like a fuel or spark issue. a valve job not done completely could contribute, too. grind the seat, and you move the valve deeper in the head. if you don't grind the stem, it is higher in relation to the valvetrain. same as milling the head, it will compress the lifter further. can happen even if you use new valves. i would check valve installed height, along with everything else.you can do this without taking off more than the valve cover-for both checks. unfortunately, the fix takes more dissassembly.
    Actually you are quite close to the heart of the issue, after pulling the heads it was indeed a valve issue, the seats were ground to deep, easy fix though install new seats and all should be right with the world again,
    Older is better. When it runs!!

  10. #25
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    valve seats

    if the valves aren't recessed into the head far enough to restrict/impede flow, you can have the stems ground. shorten them to set installed height. but, only if the valves aren't "shrouded". a recessed seat is almost like reducing lift, regarding flow. even though the valve is opening the proper amount, it isn't far enough above the head/combustion chamber surface-restricting flow. i think new seats are the BEST way to go, just not the cheapest. like i mentioned, i had a similar issue on the ex. valves in my charger. ran old school leaded heads on unleaded. beats the seats out of the ex. side. valves recessed, caused the same type problem you had. i knew it would happen, just didn't have the $ for hardened seats at the time. got late model magnum heads ( off a p/u truck), hard seats, and stock, they flow better than even 340 6 pack heads . the heads were cheaper than having seats installed in the old heads. the other stuff to make it work on my old school small block wasn't. new push rods, lifters (to oil thru the push rods), intake and valves covers. glad i could help . let us know how it runs, when you get it back together. still like the idea of a hemi or a low deck stroker .
    AIRWALK
    gettin' old ain't for sissies

  11. #26
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    Quote Originally Posted by Wile E. Coyote View Post
    tazweld, if this was already stated im sorry for repeating the question, but just out of curiosity, does the motor rev limit to 3500 always or only in the water under load?
    When the boat was in the water, it would max out at 3500, we have since reworked the heads and now can hit 4800 to 5000 but not smoothly, either fuel or spark
    Older is better. When it runs!!

  12. #27
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    Quote Originally Posted by tazweld View Post
    When the boat was in the water, it would max out at 3500, we have since reworked the heads and now can hit 4800 to 5000 but not smoothly, either fuel or spark
    so, if your sittn on the trailer, in neutral, what will the motor rev to, and is it smooth? obviously not revving it and holding it there, but goosing the carb....will it rev? also, since you have owned this rig, has it ever worked right? or did all your problems start after rebuild? could it not be a motor problem at all, but mabye a binding jet pump or a transmission issue?
    Last edited by Wile E. Coyote; 08-12-2007 at 08:00 PM.
    Wile E. Coyote: (acceleratus vulgaris)

    Its amazing how heavy a GPS can be.....

  13. #28
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    Quote Originally Posted by Wile E. Coyote View Post
    so, if your sittn on the trailer, in neutral, what will the motor rev to, and is it smooth? obviously not revving it and holding it there, but goosing the carb....will it rev? also, since you have owned this rig, has it ever worked right? or did all your problems start after rebuild? could it not be a motor problem at all, but mabye a binding jet pump or a transmission issue?
    When its on the trailer if you open it up slowly it will rev up nicely but if you snap the carb open quickly it hits 4500 and starts to surge and when you watch the vacum guage you can see the vacum surge with the engine 0 to 3 inches of vacum. I haven' had the boat back in the water since we added the 600 center squirt, also the jet is OK we checked that out since it was rebiult as well as the engine. Ran awesome before the rebiuld. The speedo only goes to 55mph but it was GPSed it to 68mph at 5000 rpm. We searched the 280 cam on Comp Cams site and they discontinued that model we are already considering changing the cam to the specified 290 i wanted to do it when we had the heads off but everyone was saying its not the cam and that the cam is good to 5000rpm obviously it isn't cause i think the surge is from the the valves floating but I may be wrong.
    Older is better. When it runs!!

  14. #29
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    valve float occurs at high rpm, the springs cant snap the valve closed before the next cycle comes around, usually happens on hydraulic cams around 5500-6000 rpm (in a sbc) dont know what valve float is on a olds big block, it still sounds like timing/valve adjustment to me, but the cam could be an issue as well, if you changed the lift of the cam drastically that could cause problems.....i hate to sound redundant but are you 100 percent sure the lifters were primed properly and arent collapsing at higher rpm?
    Last edited by Wile E. Coyote; 08-15-2007 at 11:26 AM.
    Wile E. Coyote: (acceleratus vulgaris)

    Its amazing how heavy a GPS can be.....

  15. #30
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    surging

    did the surging jhappen with the other carb? didn't you have a q-jet on it for a while? if it's just started with the holley, check the power valve. it opens on low vacum, to supply extra fuel under load. if the vacum range is wrong, or too close to what you're running at, it can open and close. causes the surge, by varying the extra fuel. they come in different ratings, to tune around this type of issue.has it EVER backfired with this carb? newer holly's are supposed to have a check ball to protect the power valve, but i've still seen it happen.the power valve is under the float bowl, under a 4 screw cover. if there is any gas in the cover, it is bad-blown out. holley's tech site can help with the correct power valve for your application. the "280" cam you have is the same as the current magnum cam offered by comp today. 280 duration, .490 lift. older jegs and summit catalogues are worth saving. now, they list duration at .050 lift=230. same cam, different way of listing specs. i would suspect the fuel system. if this problem is just with the holley, have you checked float level? what pump are you running now? a volume (not pressure) test might help. you can have good psi, and still not have enough volume of fuel. get with the pump manufacturer and get the specs, and procedure. usually involves running at a set rpm for a specified time. then you see if enough fuel is pumped into a container. you can have killer pressure with no quantity. could mean you have a restriction between the tank pickup and the pump. including the pickup and screen in the tank. not sure it's valve float, rpms seem too low. and lifters not primed/pumped up generally make some noise. just some thoughts, hope they help.
    AIRWALK
    gettin' old ain't for sissies

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