Page 1 of 2 12 LastLast
Results 1 to 15 of 16
  1. #1
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default SBC and Holley tuning question

    I've got a 350 SNC fitted to my Skiline Spirit, that I wanted to tune a little better.
    While I'm a confident mechanic, I'm still leaning about these motors and setups.
    I usually subscribe to the "if it's working fine and doesn't need it, don't fiddle" camp, but with this combo, I want to make sure it tip top.
    I've recent tidied up the engine. New sump, inlet, timing cover, water fittings, full seal kit (including 2piece RMS), repainted it all round. Everything apart from heads off and rotating assy out, really.
    It's all back together and runs quite well. I haven't slogged it out on the water yet, but hey, it runs pretty good.
    What I want to know is, do you set these engines up in boats like car engines ?
    I haven't played with mixtures, idle speed at all and timing is set pretty good, but it's only pulling about 7-8in of vacuum at idle. Are the settings for cars used for these engines in a boat?
    Thanks
    Cristian
    2000 Skiline Spirit 350SBC.
    Euro cars.

  2. #2
    Do you ever leave? EH179's Avatar
    Join Date
    Jan 2008
    Location
    Ipswich. QLD
    Posts
    3,215

    Default

    Is the engine modified at all...performance cam? The low vacuum would suggest it has if there are no leaks, otherwise it needs a good tune.

  3. #3
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default SBC and Holley tuning question

    Sorry, I should have mentioned:
    Stock 350
    Unknown cam, but I think it's pretty plain
    Edelbrock performer 2701 manifold
    STD dizzy
    Holley 600CFM 1850 marinised carby with vacuum secondaries that kick in about 4k rpm
    2000 Skiline Spirit 350SBC.
    Euro cars.

  4. #4
    Do you ever leave? EH179's Avatar
    Join Date
    Jan 2008
    Location
    Ipswich. QLD
    Posts
    3,215

    Default

    OK, what is the initial and total timing if you know?

    If not known, probably a good time to give it a lookover to see where it's at.

    Try and get as much initial in there as possible, keeping tabs on total, tune mixtures, and vacuum should increase.

    Being a mechanic, lifter pre-load is another to check for vacuum increases.

    Have fun.

  5. #5
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default

    I think initial at idle (@800rpm) is about 7deg.
    I have no idea what total is, as I have nothing to measure it with.
    I was thinking of bumping the mixtures back to 1.25 turns as per the Holley manuals and essentially starting from scratch, but didn't want to stuff up something that runs ok for now.
    I think I need to spend a couple of hours on the water test and adjust till it pulls good vacuums and runs sweetly
    2000 Skiline Spirit 350SBC.
    Euro cars.

  6. #6
    Senior Member
    Join Date
    Jul 2009
    Location
    Brisbane
    Posts
    555

    Default

    double post...
    Last edited by ski351; 20-12-2016 at 12:26 AM. Reason: post doubled up for some reason

  7. #7
    Senior Member
    Join Date
    Jul 2009
    Location
    Brisbane
    Posts
    555

    Default

    Agree you need to check the timing. 7deg is way too low and if it's running on premium fuel it will be even worse. I would aim for 12deg initial but total timing (what it maxes out at and at what rpm) is far more critical. Buy yourself a timing light to do it properly. Not knowing cam specs makes it difficult to set the best advance curve but it will be in the ball park.
    Is it a centremount? Is the prop driven from the flywheel or timing case? I ask because if driven from the timing case the factory harmonic balancer is long gone so you are relying on the timing marks someone has put on the flywheel...if it has any marks at all. If it does I would be checking for true TDC. If the marks aren't right the timing will be mis-leading.
    Holley 1850 is the most common for a ski boat. These are not a factory marinised carby...someone would have modified it, many carb shops do. Does it have J-tube bowl vents? (there is more to it than that).
    Set up is different to a car engine with the biggest difference between car/boat is a marine engine is always under load... like a car in top gear pulling up a never ending hill. Fuel curve is re-calibrated to for this unique type of load. Vacuum advance is not required due to the load as it simply will not 'cruise' with high rpm and a small throttle opening. If you connect a vacuum gauge to the manifold and drive it you'll find manifold vac is basically proportional to throttle opening...the more you open the throttle, vacuum will continue to drop right up until wide open throttle.

  8. #8
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default

    Thanks ski.
    I run it on 95 and stay away from E10.
    I do have a timing light, just not an adjustable one.
    It's a centre mount with a soft clutch and a normal harmonic balancer. When I tarted the engine up, I retimed from TDC as the dizzy was out to put the inlet on.
    Yes, the carb has J-tubes, but it does not have bowl fuel level adjusters. There are just plugs in those recesses.
    The advance is disconnected and capped and at the moment the PCV runs to the brake booster port on the carby. I'm not sure if that makes a difference, or if I should move it to the proper PCV port.
    Last edited by Cristian G; 20-12-2016 at 05:29 AM. Reason: spelling
    2000 Skiline Spirit 350SBC.
    Euro cars.

  9. #9
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default SBC and Holley tuning question

    When I put it all together and ran it first up, I retimed the engine from how it idled.
    I figured that as I hadn't adjusted the carby at all, it should get it into the ballpark for smooth running.
    I also think that as the inlet has gone from a factory cast iron to the dual plane performer, it will change things too, which why I am now considering how to fine tune it.
    Last edited by Cristian G; 22-12-2016 at 09:06 AM.
    2000 Skiline Spirit 350SBC.
    Euro cars.

  10. #10
    Senior Member
    Join Date
    Jul 2009
    Location
    Brisbane
    Posts
    555

    Default

    95 is good.
    If the balancer has degrees up to at least 40*BTDC you won't need an adjustable light.
    PCV hose location is correct.

  11. #11
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default SBC and Holley tuning question

    Unfortunately the balancer only has a TDC mark.
    Would one of the degree tapes you wrap around the balancer do the job?
    Last edited by Cristian G; 21-12-2016 at 05:00 AM.
    2000 Skiline Spirit 350SBC.
    Euro cars.

  12. #12
    Senior Member
    Join Date
    Jul 2009
    Location
    Brisbane
    Posts
    555

    Default

    Degree tape will be good enough.

  13. #13
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default

    Quote Originally Posted by ski351 View Post
    95 is good.
    If the balancer has degrees up to at least 40*BTDC you won't need an adjustable light.
    PCV hose location is correct.
    So once I've got the timing sorted out, do I just adjust the mixtures and idle speed as per the Holley instructions ?
    Should boats run more rich or lean than cars?
    I'll guess that as the boat uses raw water for cooling, but still has a thermostat (80deg) it would err on the rich side.
    2000 Skiline Spirit 350SBC.
    Euro cars.

  14. #14
    Senior Member
    Join Date
    Jul 2009
    Location
    Brisbane
    Posts
    555

    Default

    Correct. Start at 1.5 turns out on the idle mixture screws and adjust for the highest manifold vac.
    You have a soft clutch so idle speed doesn't need to be super low (unlike a dog clutch) aim for around 700rpm.
    I prefer a 71C (160F) thermostat.

  15. #15
    Newbie
    Join Date
    Nov 2016
    Location
    Hawkesbury, NSW
    Posts
    24

    Default

    Thanks ski.
    I took the conservative option for Christmas and left it how it was.
    I runs well and pulls better than ever, but I start getting pinging about 5k.
    To me just confirms the need for a couple of hours to fine tune on the river.
    First thing, get some timing tape. eBay looks the go, as the local shops have been very unhelpful.
    2000 Skiline Spirit 350SBC.
    Euro cars.

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Holley tuning
    By vhg304 in forum Holden V8's
    Replies: 0
    Last Post: 06-03-2011, 08:51 PM
  2. Quick Holley Tuning Question
    By davidburns in forum Holden V8's
    Replies: 3
    Last Post: 27-04-2006, 07:43 PM
  3. Tuning a Holley 600
    By 73Q in forum Holden V8's
    Replies: 7
    Last Post: 24-12-2005, 11:52 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •