need to do it right this time

Discussion in 'Small Block Tech' started by partsrparts, Nov 18, 2016.

  1. partsrparts

    partsrparts Silver Level contributor

    well i need to humble myself and admit that i don't know sh*t about buick motors. i thought i knew more than you guys and ended up with a poorly built motor.

    now i would like to do it right and listen to your advise!
    what i have is a 1968 350 with a th400 out of a Lesabre in a 76 skylark, 3:23 posi, 2500 stall.
    the pistons are said to be 10to1 hyper pistons. numbers on #3 piston are H552CP 030 353-03-10-C #2 are H522CP 030 25206-06-B

    the pistons are .060 down in the cyls.
    i hope to shave the heads and not the block as i hope to leave the bottom end alone, it has less than 5000mi. on it.
    in the pics it shows #5 comb. chamber and piston running a little lean and #8 exhaust valve clean as a whistle.
    i'm going to put the TA front cam bearing in and up size the oil pick up.
    i've done Larry's re-curve and power timing on a TA HEI dist., TA headers, 2 1/2 exhaust, stage 1 intake and holley 750dp 20161118_132437.jpg 20161118_132506.jpg 20161118_132550.jpg 20161118_132636.jpg 20161118_132452.jpg
     
  2. Mark Demko

    Mark Demko Well-Known Member

    What exactly is wrong?
     
  3. alec296

    alec296 i need another buick

    Actually the lean cylinder looks like a clean burn and the others seem rich/wet to me. And are you sure all Pistons are .030 or maybe you have more over bore then .030 as wall clearance seems about much in pictures. Maybe it's just how they look on phone.
    The 522 should have a 1.855 compression height. So I'm surprised they still sit so low . I would think they should be about .040.
    I believe they have a 10 cc total dish/valve recessions. Which would net about 9.3 with a felpro gasket. .
    .020 off heads should net about 9.8ish guesstimate.
    Get an Air fuel meter . I think carb is rich.
    You did clock front cam bearing as per TA directions? Should not line up with block oil holes. Just my thoughts.
     
  4. 8ad-f85

    8ad-f85 Well-Known Member

    By chance do you have oil gopped up on the intake valve stems in addition to your carb issues?
    This appears to be a general engine issue more so than a Buick specific one.
     
  5. Mark Demko

    Mark Demko Well-Known Member

    No biggie, I know I have screwed up many times in the past with Buick engines, but with the advent of the internet, I/we are learning stuff ALL the time!
    The biggest "screw up" is letting a machine shop clearance the mains and rods like a Chevy, TOO LARGE:rolleyes:
    What is your hot cruise/hot idle oil pressure?
    What weight oil you using?
    Start from the crank and work your way to the top of the engine.
    Getting your heads squared away wont do you any good if the bottom end is weak:(
    I'm running those same pistons @ .005 "in the hole" I had my block decked .050 Pistons were at .055 "in the hole"
     
  6. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Piston depth is typical with that piston.
    Another issue with the dual plane intake on the 350 is mixture distribution. It's not uncommon to see clean and wet chambers side by side. Be sure to cut the intake manifold when cutting that much off the head or deck.

    What cam are you using?
     
  7. FJM568

    FJM568 Well-Known Member

    You have 2 different pistons listed, a 552 and a 522. Is that just a typo?
     
  8. partsrparts

    partsrparts Silver Level contributor

    not happy with the amount of power, strange little things going on.
    vibration under hard throttle on last pass went from mild to bad, decided to start from the beginning and do it right this time.

    broke in cam as per machinist and ended up with a few loose pushrods, he couldn't figure out what happened so he made longer pushrods and installed new lifters.
    i just realized a few weeks ago that it probably wore out the cam lobes or lifters.

    as long as the bottom end is good i don't want to touch it and focus on the heads and cam. i'm going to pull off the oil pan and have a look. what should i be looking for?

    also going to pull cam out and look at lobes. but still going to replace it

    didn't get the chance to dial in the carb because of vibration
    will install TA front cam bearing with new cam
    only #2 & #3 piston have any numbers on them

    will check for oil on valve stems

    10w-40 oil, hot cruise 35lbs-hot idle 20lbs

    it has the comp 260 cam and kit in there right now
     
  9. partsrparts

    partsrparts Silver Level contributor

    no, double checked more than once, thought that might be different from side to side, that is why i posted both #'s.
    if i remember right the machine shop didn't recieve all the pistons at once
     
  10. 8ad-f85

    8ad-f85 Well-Known Member

    Here are some 'if's'...
    IF you have the what looks to be leaky valve guides and possible oil consumption problem, THEN you would certainly notice the engine vibrating or acting funny as the engine got into detonation or improper combustion/misfire. Oil causes that.
    Although hypothetically the bottom end 'could have' started out AOK with decent oil pressure showing and proper clearances, etc., it's possible to have damaged the bottom end (bearings and rods of the oiled up holes), requiring more teardown to be certain, starting with the oily topped pistons.
     
  11. alec296

    alec296 i need another buick

    552 is a number off piston? Probably a typeo the should be 522. As far as getting zero deck , so far it calculated to 10.41 with hyperutectic pistons. I would mease and do your math first. .020 down hole should be about 10.1 to 1
    I would look at a different cam . did you get the correct 68-69 lifters?
     
  12. partsrparts

    partsrparts Silver Level contributor

    i'm going to pull the pan and have a look, not having a oil consumption problem though. oil got on a couple pistons when i pulled the heads (#7 & #8) i believe, will be back out again tomorrow
    i'll measure how far all the pistons sit down the hole and shave the heads to get what i need to maybe run the crower #3?
    will take the heads to a different machine shop this time for shaving and complete go through again.
    i don't remember if it was the first set of pushrods and lifters or 2nd set that i pointed out where not the right ones, yes i'm still running the 68 valve train

    should the tips of the valves all be the same height? the exhaust sit between .018-.020 lower
     
  13. 8ad-f85

    8ad-f85 Well-Known Member

    I wasn't inferring that you had an oil consumption problem... IF that is oil coming down the valve guides and into the cylinder, THEN it would cause issues such as detonation or misfiring. The valves appear to be wet from oil, but I cannot place my hands on them or shine a flashlight into the intake port. You wouldn't see a consumption problem in the short amount of time you've ran it. It doesn't take too much oil to cause a problem.
     
  14. Mark Demko

    Mark Demko Well-Known Member

    They "should" be all or nearly all the same height.
    Buick uses net lash, so when yah tighten the rocker shaft down, that's all the preload the lifters get.
    So if the valve stems are sitting all at different heights, some lifters may not be getting enough preload
     
  15. sean Buick 76

    sean Buick 76 Buick Nut

    Tell us more about the "vibration". Was the engine balanced?
     
  16. Mark Demko

    Mark Demko Well-Known Member

    A couple other thoughts came to mind:eek2:B
    Being your hot (after a long drive on the highway I assume) idle pressure is 20 lbs. your bearing clearances are PROBABLY ok, BUT your cruise pressure of only 35 lbs. tells me you still have the stock spring in the pressure relief for the pump, you NEED at least the 60 lb. spring.
    At least take the pan off and Plastigage the mains and rods, .002 max on 'em, and check the bearing condition. Copper showing is a no no.
    Also I'm going to assume you have a good aftermarket oil pressure gauge?
     
  17. 8ad-f85

    8ad-f85 Well-Known Member

    Too bad you missed a diagnostic opportunity like vacuum gauge and compression/leakdown testing before ripping your engine apart.
     
  18. partsrparts

    partsrparts Silver Level contributor

    no, i wasn't thinking that you were, just trying to throw in as much info as i can. i will look further and see if i can tell if it is oil or gas will try to get close up pics
    new valves, valve seats and guides were installed when engine was rebuilt and i don't know if the cam kit came with new pushrods and if so they were all the same length. i do know that when the machinist made new push rods they were made 2 different lengths
    around town normal driving everything is good, under hard throttle, probably 3500+rpm it has a i guess you could call it roughness to it, not a shake like tires or suspension.
    the engine had about 35,000mi on it when it was pulled out of the lesabre, then it sat outside pretty much uncovered for 30yrs, water had gotten into 1 of the cyl. that created enough rust that you could'nt get the piston to go past it. it cleaned up with a .030 over bore. was told the crank was in good shape and only required polishing, so no, i don't think it was balanced, there are no weights on the flywheel, thought maybe the balancer had slipped but checked it out using dial indicator to get piston up top, intake lobe down, mark was right on
    asked machinist when he was doing motor and he said new oil pump, so i'm sure it is stock tension spring. (that will also get changed). pans coming off today and i will plastigage the rods and mains. (was wondering if plastigage was still being used, thats what we used in the 70's).
    gauge is a summit electrical oil pressure gauge, probably not the highest quality, i have had my interior oiled down before using mech. gauge. almost crashed the harley from a ruptured line also
     
  19. partsrparts

    partsrparts Silver Level contributor

    i do know that from the beginning the vacuum was always real erratic between 13-15in at idle, tried different vacuum gauge, same result. the original odd-fire v6 had the same erratic vacuum
     
  20. 8ad-f85

    8ad-f85 Well-Known Member

    Vacuum under partially open throttle and load would have been more telling.
    You can see the difference between a misfire, a low compression or dead hole, leaky guides or seats, rings, etc.
    It would have eliminated much of the forum's guess work along with visually verifying things like oily valve stems.
    Compressed air into a cylinder shows up leaky valves and rings.
    Detonation might have been happening at 3500 rpm...your plugs and piston tops might show that
     

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