From the Reference Section:
- Musclecar Enthusiast March 06 - the Jim Burek 350 porting article
- Ancient mid 12's secrets for your Buick *350*
- Poston Camshafts, Buick 350
    - 350 casting Numbers
- Buick 350 Drag Strip Tests from Kenne-Bell
- 350 Engine Specifications
Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: 71 350 timing issue

  1. #1
    Join Date
    Jul 2009
    Location
    A, A
    Posts
    14
    Rep Power
    0

    71 350 timing issue

    I have my 71 Skylark w/ 71 Buick 350. It is back-firing from the exhaust and the from the carb (more pipe than carb). I checked the timing and it is off the chart. When I put the gun on it the mark is showing approx an half inch above the gauge lines. I want to ask before I adjust the distributor. This just seems to far off and before I go adjusting I wanted to find out if anyone else has had this problem.

    It starts up fine (after a couple of pedal pumps) and runs. It backfires from the exhaust after approx 10 sec of running. When idling low then it backfires from the carb. (please don't send messages correcting "backfire" you know what I mean)

    1971 Buick Skylark
    1971 Buick 350
    Rochester QuadraJet

    Please, I am looking for answers not comments about junking this or that.

    Thank you in advance

    Happy Father's Day to all.

  2. #2

    Backfiring Problem

    To lostinmyhead: If you have recently worked on the ignition system I would check the following (and basically start from the beginning): 1. Check to make sure the spark plug wires are on the correct plugs, the No. 1 wire is in the correct location in the distributor cap and the wires are in the correct sequence. This info can be found in a Motors Manual or online. 2. Make sure the rotor tip hasn't been broken or bent (sometimes this happens when putting the distributor cap back on). 3. You are using the No. 1 plug wire when hooking up the timing light. 4. If your timing marks are off only by a 1/2 inch I wouldn't think it would be enough to cause the backfiring you are describing. Aligning the timing marks to the recommended point shouldn't cause any problems (but, please be sure to read suggestion No. 5 next). 5. My last suggestion may cause this type of backfiring - Check the crankshaft dampner to see if it has slipped. I don't know for sure about Buicks but other GM dampners (Chev and Olds) are actually made of two pieces with a piece of rubber in between. After several decades of age the two pieces can slip in relation to each other and cause all kinds of havoc when you go to time the engine. I had this happen on a 1960 Olds 371 and I had to time the engine by "ear" - another words, by turning the distributor back and forth until the engine ran/started the best (The marks were a good three inches off). A dampner replacement cured ALL problems. Determining if the dampner has slipped will be difficult - you will have to compare yours to a known good one and see if the relationship between the timing marks on the outer piece of the dampner is the same to the crankshaft keyway on the inside dampner piece. I hope this helps you. These recommendations are the result of my years of messing around with GM cars and I hope you get yours figured out. Thanks, BluesBrothersBuicks

  3. #3
    Join Date
    Jul 2009
    Location
    A, A
    Posts
    14
    Rep Power
    0
    Thanks for the help. The only changes I have done is that I changed the plugs and pvc valve. I gaped them correctly and took each wire off as I did each plug to insure no wire swapping. I did check and they are still in the right order. I pulled the dist cap and (it's points) that seems to be new also (nice and clean w/no bends burn marks etc)
    I bought this a year ago and it ran well until I put it away. I took it out once this year and it ran rough but no back firing. Then when I went to take it out again it started running rough w/backfiring.
    I have not had an old car for 20 years and back then I never had problems with that one (76 camaro w/ 69 327) so am a little rusty and stumped.

  4. #4
    timing chain issue?
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  5. #5
    Join Date
    Nov 2008
    Posts
    623
    Rep Power
    0
    dunno know a lot about 350s, BUT; if there is a vacuum leak - that could cause the backfiring

    also a stuck valve (intake and exhaust valve open at the same time) = firing with an open intake valve would cause backfire thru the carb.

    I'd check out all the vacuum lines - and the vacuum canister for leaks.

    I like having the set of guages (including vacuum)
    on the firewall.

    64 Wildcat 445
    64 LeSabre 310 (I know you're gonna say; you mean 300), it's 310 ftlb torque
    73 Skylark 455 (on bench)
    Butch

  6. #6
    Join Date
    Apr 2006
    Posts
    450
    Rep Power
    0
    Did you unhook the vacuum advance hose from the distributor when you checked the timing? If it's hooked to a manifold vacuum source it would give you full advance at idle and would move the timing mark quite a ways. Un hooking and plugging this line should bring the mark back down where it should be. As far as backfiring goes, if it ran good when you parked it, I would look for a problem with the easy stuff first. Carb and ignition. Sounds like you tried the ignition and that's not it. If the carb isn't dumping a bunch of extra fuel from a stuck float, I'd look for valve train issues. Run a compression test and see what you get. It sounds to me like you could have a valve not working. It could have stuck while it was sitting and bent the pushrod when you fired it back up. Or a chunk of carbon could have come loose and is not letting a valve seat properly. A compression test will tell you if it is a mechanical problem with the engine or a tune up issue. If you have a low cylinder I'd pull that valve cover and have a look at what's going on with the valve train. A flat exhaust cam lobe will kick back through the carb also. Run the compression test and report back.

  7. #7

    backfiring

    i would pull the valve covers off and start the engine and watch the valve train.you may find a valve not opening due to a bad cam.i had the same problem a year ago.had 22 inches of vacuume and good compression.good luck..

  8. #8
    Join Date
    Sep 2008
    Posts
    18
    Rep Power
    0
    If it is a constant popping as the engine runs, I'd suspect valve train (flat lobe, broken pushrod).

    But if it backfires on throttle opening, that's a different critter, usually accelerator pump.

    Did it run OK before? And you did nothing else?

  9. #9
    Join Date
    Jul 2009
    Location
    A, A
    Posts
    14
    Rep Power
    0

    It is something else entirely

    Okay I checked the choke on a thought and the thermostatic choke coil became unsprung. Now I tried recoiling the choke and started the car. No more back firing but now it will not run without my foot hard on the gas. The carb won't stay open. I am dumbfounded on why, even if I pull the throttle back on the card it will only open 1/4 of the way. I am sorry but my knowledge in the carbs is really bad. I can rebuild an engine with out problems but carbs are just too much for me. Thanks in advance.
    Attached Images Attached Images
    Last edited by lostinmyhead; 07-27-2010 at 02:46 PM.

  10. #10
    Join Date
    Nov 2008
    Posts
    623
    Rep Power
    0
    Lost, I would remove the top of the carb and see if the float has fuel in it.. it might have sprung a hole while it was setting; if there was any water in the fuel the last time you drove it, it would only take a little bitty hole to allow enough fuel innit and you'd just be spinning your wheels trying to make adjustments.

    pair of 64s
    plus the 67 Impala, 327
    Butch

Similar Threads

  1. Valve Timing Issue
    By zoe sedanete in forum Straight Eights!
    Replies: 2
    Last Post: 03-29-2014, 06:38 AM
  2. Downshift Issue
    By bucmaster in forum Transmissions and Drivelines...
    Replies: 0
    Last Post: 03-26-2014, 07:14 PM
  3. Is this a Dynaflow issue?
    By Daveh70 in forum Transmissions and Drivelines...
    Replies: 3
    Last Post: 12-27-2011, 08:22 AM
  4. 455 starter issue
    By Curtis in forum Tools, Shops, and Garages
    Replies: 4
    Last Post: 04-11-2009, 11:41 AM
  5. intermittment issue
    By Century Weary in forum Tools, Shops, and Garages
    Replies: 2
    Last Post: 06-12-2007, 11:09 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
TeamBuick.com Privacy Policy