Olds 455 timing help
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Olds 455 timing help

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    Default Olds 455 timing help

    I recently rebuilt my 455 Olds and I'm not sure if I have a timing problem or something else. I'm not sure what any of the timing marks on the indicator are according to degrees except 0, but I have it set on the last notch on the indicator. I have been easy on it while breaking it in for several hours. Today, I was cruising at 3K rpm and decide to open the 4 bbl for a second or 2, I gave it about 3/4 throttle and at a little over 4K rpm as soon as the power hit, it started pop/crack/backfire. Where should I be on the timing indicator? I'm pretty sure it's a timing issue, but I could be wrong? Thanks for any input!
    1974 Taylor SJ - 455 Olds, .030" over, Basset O/T headers, Lunati cam, Holley 750 DP carb, Accel HEI Dist. fully restored interior w/Hardin gauges.

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    Senior Member GA Jet's Avatar
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    are you running a points style distributor?

    If so, then your points are probably corroded or in need of replacement
    Last edited by GA Jet; 07-17-2011 at 08:34 PM.

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    I'm running an Accel HEI distributor.
    1974 Taylor SJ - 455 Olds, .030" over, Basset O/T headers, Lunati cam, Holley 750 DP carb, Accel HEI Dist. fully restored interior w/Hardin gauges.

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    • Do you have the vacuum advance hooked up?. My olds deal in a v-drive hydro ran best @ 40* total...tried to run it locked out ie no vacuum advance and the mechanical advance locked in the fully retarded position....some interesting info about phasing...
    • http://www.msdignition.com/uploadedF...or_phasing.pdf

    Idled best with lots off timing but tended to have some hot start issue. I ended up moding the mech advance so it had 32 while cranking all in @ idle...You will need to come up with an adjustable timing light and using the tab and mark on balancer is kinda worthless without checking their accuracy.Somebody used to make tdc checker...screws into #1 plug hole..very carefully rotate engine over until piston just touches tool. put a mark on the balancer where the tab says 0....rotate the other direction careful...until piston touches tool...mark balancer again @ 0....exactly half way between marks, lined up with 0 on the tab is tdc #1
    ...or #6.......mine was only off 4*......As far as how i came up with 40*
    total....i put a load of 92 octane and stop watched it several dozen time from 1500 to 5K and kept twisting the dizzy until i came up with the best number.....actually 40* and 42* were the same and i picked 40* for a bit of safety margin...although olds doesn't seem to have much of a detonation problem, with 92 octane it will have an obvious part throttle misfire
    "A liberal paradise would be a place where everybody has
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    Senior Member jetboatperformance's Avatar
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    Rule of thumb , 34* to 36* total depending on altititude and compression ratio ,Carb, exaust , fuel...... more info would be helpfull Tom

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    Thanks Sold Honda Bought Hondo!

    Jetboatperformance - I am usually around 800' in altitude give or take 100 depending on where I'm boating. Compression ratio is stock, but I'm not sure what it is, the engine is a 1973 model with J heads. The carb is a Holley 750 double pumper, intake manifold is Edelbrock Performer and I run 93 Octane fuel and have bassett over transom heads, no baffles. The cam is 270*/.501 if I remember correctly. Anything else that would help, let me know! Thanks!
    1974 Taylor SJ - 455 Olds, .030" over, Basset O/T headers, Lunati cam, Holley 750 DP carb, Accel HEI Dist. fully restored interior w/Hardin gauges.

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    Senior Member jetboatperformance's Avatar
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    Quote Originally Posted by Joel74TaylorSJ View Post
    Thanks Sold Honda Bought Hondo!

    Jetboatperformance - I am usually around 800' in altitude give or take 100 depending on where I'm boating. Compression ratio is stock, but I'm not sure what it is, the engine is a 1973 model with J heads. The carb is a Holley 750 double pumper, intake manifold is Edelbrock Performer and I run 93 Octane fuel and have bassett over transom heads, no baffles. The cam is 270*/.501 if I remember correctly. Anything else that would help, let me know! Thanks!
    There are/were a couple options on OEM pistons from that era this can be told by the "dish" in the top . you may be able to see in the combustion chamber with a good bright flash light , the low comp (8+) is around 5/32 while the Higher (10+) is closer to 3/32 as I recall. You could run significantly more total timing with the low , but with modern fuel the Higher compression can detonate among other issues , Not sure your "popping" is neccesarily timing related IMO

    BTW your will likley need mods to the advance weights to get 30+* of total (without having to run an enormous amout of initial)
    and ditch the vac advance

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    Quote Originally Posted by jetboatperformance View Post
    There are/were a couple options on OEM pistons from that era this can be told by the "dish" in the top . you may be able to see in the combustion chamber with a good bright flash light , the low comp (8+) is around 5/32 while the Higher (10+) is closer to 3/32 as I recall. You could run significantly more total timing with the low , but with modern fuel the Higher compression can detonate among other issues , Not sure your "popping" is neccesarily timing related IMO

    BTW your will likley need mods to the advance weights to get 30+* of total (without having to run an enormous amout of initial)
    and ditch the vac advance
    The olds t/r 660's deal i have for my hydro needs major lead to get a decent idle out of it.With a normal curve and 22* initial and set the idle @ 900 in gear neutral idle was 1600 and it was lazy off idle. With 36-38 initial i got it down to 600-650 in gear....kinda necessary to even get close to no wake speed...and it would hold that idle all day and 1000 out of gear and from 1k in gear i can pin the gas and no hesitation... But it
    did the timing stall every once in a while...I think i ended up with an little allen head bolt and a nylock through the advancer base plate to limit the advance to 6-8 degrees...mostly because it would start so quickly you couldn't hear the starter run....and used 2 really loose springs...just enough to pull the advance back when the dizzy wasn't turning
    "A liberal paradise would be a place where everybody has
    guaranteed employment, free comprehensive healthcare, free
    education, free food, free housing, free clothing, free
    utilities, and only law enforcement has guns. And believe it or
    not, such a place does, indeed, exist: It's called prison."

    Sheriff Joe Arpaio
    Maricopa County Sheriff's Office

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    Senior Member sleekvino's Avatar
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    your timing gears are off, pull your front cover and check to see if your on the right mark for your timing gears.
    PORNO RACING INC WHERE ITS "HARD" TO WIN

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    Senior Member H20MOFO's Avatar
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    Quote Originally Posted by Joel74TaylorSJ View Post
    I recently rebuilt my 455 Olds and I'm not sure if I have a timing problem or something else. I'm not sure what any of the timing marks on the indicator are according to degrees except 0, but I have it set on the last notch on the indicator. I have been easy on it while breaking it in for several hours. Today, I was cruising at 3K rpm and decide to open the 4 bbl for a second or 2, I gave it about 3/4 throttle and at a little over 4K rpm as soon as the power hit, it started pop/crack/backfire. Where should I be on the timing indicator? I'm pretty sure it's a timing issue, but I could be wrong? Thanks for any input!
    The last time I was "shootin ducks" I had an intake valve too tight....good luck.
    Another Hot Boat refugee

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    Quote Originally Posted by Sold honda.bought hondo View Post
    The olds t/r 660's deal i have for my hydro needs major lead to get a decent idle out of it.With a normal curve and 22* initial and set the idle @ 900 in gear neutral idle was 1600 and it was lazy off idle. With 36-38 initial i got it down to 600-650 in gear....kinda necessary to even get close to no wake speed...and it would hold that idle all day and 1000 out of gear and from 1k in gear i can pin the gas and no hesitation... But it
    did the timing stall every once in a while...I think i ended up with an little allen head bolt and a nylock through the advancer base plate to limit the advance to 6-8 degrees...mostly because it would start so quickly you couldn't hear the starter run....and used 2 really loose springs...just enough to pull the advance back when the dizzy wasn't turning
    When I put the distributor in, I set the distributor by eye to get it started to see if it was going to run. It was very hard to crank, but when it fired up it was the same as you said, so fast you didn't even here the starter or the engine roll over. It fired at the snap of the finger so I knew the timing was off. I'm guessing I took it back 12-14* to get it where I have it now. It's possible I took too much away and the indicator is useless to use as a reference point. This might be something I just need to do some trial and error with and find out where it runs best and leave it.

    jetboatperformance - Ok, I have the low compression pistons based off of your info.

    Thanks everyone for your help! I will start troubleshooting with your suggestions!
    1974 Taylor SJ - 455 Olds, .030" over, Basset O/T headers, Lunati cam, Holley 750 DP carb, Accel HEI Dist. fully restored interior w/Hardin gauges.

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    The carb is to small. I'm running a 750 Dominator on my SBO. Bigger jets, squirters and 50cc pumps and U B N bizziness.
    No more Mr. Nice Guy !

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    Quote Originally Posted by Joel74TaylorSJ View Post
    When I put the distributor in, I set the distributor by eye to get it started to see if it was going to run. It was very hard to crank, but when it fired up it was the same as you said, so fast you didn't even here the starter or the engine roll over. It fired at the snap of the finger so I knew the timing was off. I'm guessing I took it back 12-14* to get it where I have it now. It's possible I took too much away and the indicator is useless to use as a reference point. This might be something I just need to do some trial and error with and find out where it runs best and leave it.

    jetboatperformance - Ok, I have the low compression pistons based off of your info.

    Thanks everyone for your help! I will start troubleshooting with your suggestions!
    That is exactly where you need to be. Set the timing where it idles best
    ie the best throttle response right off idle....and not necessarily the smoothest and put timing light on it...and it doesn't matter if the marks are off...just so you know where it's at. Then take it out and run it and figure out a way to accurately measure it..GPS for top mph or tach for max rpm or stopwatch from 2500 to 4500...and carefully advance the dizzy a little at a time... It should run better and better..and then the same and then worse....back it up to he second 'better' and put timing light on it.
    The first number is base/initial timing..if it will start clean an easy that is the number you use...if not back the timing until it does...The second number is TT..Total timing and the difference between the 2 numbers is how much you need to limit the dizzy from advancing.

    Just make sure you are nice to olds motor...They do not last if ya rev them past 5000 rpm...they won't last long if ya rev them past 4500 for extended periods...Make sure you have an accurate oil pressure gauge
    and watch it like your future boating budget depends on it.
    "A liberal paradise would be a place where everybody has
    guaranteed employment, free comprehensive healthcare, free
    education, free food, free housing, free clothing, free
    utilities, and only law enforcement has guns. And believe it or
    not, such a place does, indeed, exist: It's called prison."

    Sheriff Joe Arpaio
    Maricopa County Sheriff's Office

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    Maybe I'm stating the obvious but if you just recently rebuilt this motor, you (or the shop that assembled it) should know exactly where your timing marks are?
    If you are confident the timing marks on the timing chain are correct, did you degree the cam and check the timing marks on the balancer in relation to TDC of the engine and the cam position?
    Is it a new/aftermarket balancer?
    If run into a lot of aftermarket balancers that have the timing marks off.

    Other issues could be ignition related or valve adjustment (too tight or too loose).
    Fuel system/carb should normally not cause backfiring-
    How is the engine vacuum at idle? Perhaps you have a vacuum leak somewhere?

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