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  1. #1
    Join Date
    Jun 2010
    Location
    Ocean City NJ
    Posts
    55

    Default Intial timing setting needed, can I use the setting from the orginal engine

    Hi, I finally got my Chris Craft in the water yesterday, after a year almost to the day when I bought it. I had run the motors before, to make sure everything worked. Started up yesterday, let them warm up, got them off the high idle, backed out of the slipway, all is good. I run it for 15 minutes just checking that every thing is good, run it up to 2600 rpms for about a minute, turn around and dock it at the slip.

    Anyway my question is this, the boat originally had crusader 270's, I swapped out the long blocks with new 350 cid crate motors that was marinized by a shop in Florida. I want to check the timing of the motors to be sure they are correct. The originally crusader plates are still on the bell housings, can I use those values as a starting point? The starboard engine seems not to have the quick start like the port motor. They both start very easy, just concerned as I had to disturb the starboard distributer during install. Even tho I marked it and seems right, better to check now.

    I found online a spec for carb crusader was to be 26 degrees at 4000 rpm, is this value more important then the initial timing say 12 degrees btc?

    Thanks
    little video showing startup
    http://s765.photobucket.com/albums/x...t=IMG_0215.mp4

  2. #2
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,099

    Default Re: Intial timing setting needed, can I use the setting from the orginal engine

    Quote Originally Posted by paw2000 View Post
    Anyway my question is this, the boat originally had crusader 270's, I swapped out the long blocks with new 350 cid crate motors that was marinized by a shop in Florida.
    Does this mean automotive engines?

    I want to check the timing of the motors to be sure they are correct. The originally crusader plates are still on the bell housings, can I use those values as a starting point?
    As an initial starting piont, Yes! But there is much more to this!


    The starboard engine seems not to have the quick start like the port motor. They both start very easy, just concerned as I had to disturb the starboard distributer during install. Even tho I marked it and seems right, better to check now.
    Agreed...... this is nothing to Foo Foo since TA is so critical!

    I found online a spec for carb crusader was to be 26 degrees at 4000 rpm, is this value more important then the initial timing say 12 degrees btc?
    TA or TAT is always much more imortant than BASE or Initial advance.
    These engines fire and idle on BASE advance.
    If within an acceptible range, that's about all BASE/Initial offers us.
    We should see NO progressive advance begin until approx 1k rpm.
    A correct and progressive TA is what brings the engine into the performance range, and at the same time, checks or prevents un-wanted "detonation".
    These crate engines are very likely fitted with full dished pistons.
    What this means in a Marine application, is that your TA # becomes even more critical, since marine load ignition induced Detonation becomes more of a potential (apposed to a Q/E built sbc marine engine).

    A TA of 26* BTDC @ 4k rpm appears to be a good TA (for an engine w/ this piston type), but the 4k rpm portion would appear to be high! IOW, what's it doing @ 3.5k rpm?

    Are you sure that this is the correct spec?

    Which ignition systems do you have? Example: EST or Mechanical Advance?

    What are your limitations as to adjust TA w/out causing an issue with BASE?

    NOTE: when correctly setting/checking TA, you'll want to have the harmonic balancer marked off to approx 35* BTDC.
    You will then strobe this and plot this out on paper @ 1k, 1.5k, 2k, 2.5k, 3k, 3.5k and perhaps 4k rpm.
    See how this jives with your correct OEM advance curve.
    (yes, I'll take some crap from the Digitally Advaning Timing Light guys! )
    However, this allows you to view the progressive advance in Real Time/Real Degrees.


    Be sure that you DO NOT use a TA spec for a Q/E built engine if these are fitted with full dished pistons.
    TA spec for a Q/E engine will usually be greater than what these can safely use.

    .
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  3. #3
    Join Date
    Jun 2010
    Location
    Ocean City NJ
    Posts
    55

    Default Re: Intial timing setting needed, can I use the setting from the orginal engine

    Hi, the engines were GM 350 crate motors, so I would assume dished pistons. The engines were fitted with edelbrok manifolds and 1409 carbs, I had the pan off and verified that they were 4 bolt mains. They are half systems, the block is closed system, the manifolds are raw water cooled. The distributers are mechanical advance. I'll be down at the boat all weekend, and will mark the balancer and see what each motor is set at. I installed these engines and need to double check linkages and alignments. I think auto-zone has balancer tape with the markings printed. I had put a light on the starboard engine before launch to make sure I hadn't moved it to much.

    The plate on the bell-housing had values, but I can't remember the exact value. I rather have the advance timing set for the correct operating rpm. If I move the dizzy base timing moves, no provision to adjust advance unless I change springs. These are electronic dizzys, so I need to get the model off them to look them up.

    The boat is used for fishing, about 20-25 miles off shore. Would timing off a few degrees show up as a 15 degree temp difference between the 2 motors? I realize everything is new and will need to be "run-in", I'm just trying to protect my investment

    Thanks for the help.

  4. #4
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,099

    Default Re: Intial timing setting needed, can I use the setting from the orginal engine

    Paw.....
    Quote Originally Posted by paw2000 View Post
    Hi, the engines were GM 350 crate motors, so I would assume dished pistons.
    Yes, even if the Marine version, GM installed this piston!

    The engines were fitted with edelbrok manifolds and 1409 carbs, I had the pan off and verified that they were 4 bolt mains. They are half systems, the block is closed system, the manifolds are raw water cooled.
    Being a CCS allows for the automotive aluminum intake to be used.
    You'll want to be using the Dual Plane Edelbrocks... such as their "Performer"!

    The distributers are mechanical advance. I'll be down at the boat all weekend, and will mark the balancer and see what each motor is set at. ................ I think auto-zone has balancer tape with the markings printed.
    Mr. Gasket provides a decal, but it must be correct for the diameter of the balancer.

    I had put a light on the starboard engine before launch to make sure I hadn't moved it to much.
    Just remember that BASE is BASE all day long...... and has little to do with TA until you check it.

    The plate on the bell-housing had values, but I can't remember the exact value.
    This is most likely BASE or Initial ONLY. Again, TA is the most important #...... and any TA without an associated RPM, is meaningless!

    I rather have the advance timing set for the correct operating rpm. If I move the dizzy base timing moves, no provision to adjust advance unless I change springs. These are electronic dizzys, so I need to get the model off them to look them up.
    Yes, any change to BASE is a "like" change to TA when a mechanically advancing distributor is used.
    IOW, if a correct TA creates a BASE of 8* BTDC, when specs call out for 10* (for example), it's not a deal breaker, IMO.
    BTW, any change to BASE that changes TA, will not change the value related to "Full-In" RPM or "limit"..... only the degrees of advance will change!
    If a change to "Full-In" RPM or "limit" must be made, this will require an internal adjustment.

    Once you see this while strobing it at the various RPM......, it will all make better sense!

    Would timing off a few degrees show up as a 15 degree temp difference between the 2 motors?
    I can't say for certain, but if timing is creating a border-line detonation scenario, then it may contribute to greater temperature! Do NOT allow this to occur!
    Ignition induced "detonation" can be self perpetuating.

    I realize everything is new and will need to be "run-in", I'm just trying to protect my investment.
    And you WILL be protecting it with the Ignition Advance set correctly..... in particular for this break-in duration.

    Thanks for the help.
    Here's a fairly well written artilce by Allen W. Cline.
    While not written specifically for a Marine Engine, he gives the basics pertaining to the dynamics of Detonation. Although Allen does not use this term, he will clarify my term "Ignition Induced Detonation".
    Also read his "Muddy Water" explanation.
    For the gasoline Marine Engine (in particular the SBC using full dished pistons), this is of particular importance.
    (see his first sentence of his second to the last paragraph)


    Don't mean to scare you.... just pointing out some of the more important aspects of ignition advance.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  5. #5
    Join Date
    Sep 2007
    Location
    Egg Harbor, New Jersey, USA
    Posts
    1,572

    Default Re: Intial timing setting needed, can I use the setting from the orginal engine

    Rick,

    Your posts are always highly informative and detailed. I enjoyed reading the article on detonation (particularly about the dragsters). Never had much thought about its real effects as I usually keep things well within stock "previously engineered" specs. My days as a rebuilder are likely over. Besides, my engines were usually v-twins or inline 4's ignited by magneto. Our boat has been my only deep foray into v-8's. Thankfully my initial search led me here years ago where I have continually learned volumes.

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