Timing on a supercharged 496
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 14 of 16

Thread:
Timing on a supercharged 496

  1. #1
    21 Daytona Outlaw's Avatar
    Join Date
    Dec 2007
    Location
    Artesia, N.M.
    Posts
    5,291

    Default Timing on a supercharged 496

    My nephew is in the final phase of his procharged 496 project.
    he has a 496 with a blow thru carb intercooled M1 procharger.
    a MSD distributor and a 6BTM ignition which has an adjustable
    boost retard from 1-3 degree of retard with each psi of boost.
    currently he has the 5psi pulleys.and running pump super which here at 3500ft is 90 octane.
    Should he lock out his distributor? and how much retard should he start with?
    what about total timing?

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    He needs to lock the distributor so he can do the timing curve with his lap top. I will check my notes on the timing settings for you.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  4. #3
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    Mix up on the ignition box. (Was thinking digital) Run it at 34-36 then subtract 2 for every lbs of boost. Still lock the distributor or you are going to have 2 things happening at once. (mec advance and ignition retard)
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Member
    Join Date
    Mar 2008
    Posts
    84

    Default

    We just fininshed dyno tuning a 496 with a vortec making 7lbs of boost.

    496
    flat tops
    Edelbrock rectangle port marine heads 119cc chamber 2.25 intake valves
    9.5:1 Comp
    Victor Intake
    850 Demon blow through carb
    Iski Cam 112 lobe sep

    724HP @ 5700rpm
    34 deg total
    BTM set to 1 deg per pound so 27 total deg at full boost.
    12.1 afr
    1400 egt
    When we went to 36 deg total it lost Hp

  7. #5
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    Nice #s thmpr. I think with a 114 split it might like the 36 but I hear ya on the 34. Did you try it with less timing?
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  8. #6
    Member
    Join Date
    Mar 2008
    Posts
    84

    Default

    We started at 30 deg and went up from there. We also started at 3 deg per pound of boost on the BTM and worked up from there also. As soon as we went to 36 we lost HP so 34 deg it was.

  9. #7
    21 Daytona Outlaw's Avatar
    Join Date
    Dec 2007
    Location
    Artesia, N.M.
    Posts
    5,291

    Default

    thanks for the replies, we are going to start out very conservative.
    28 total and pull out 2 per PSI, then creep up on it

  10. #8
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    Let me know what you find.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  11. #9
    Member
    Join Date
    Mar 2008
    Posts
    84

    Default

    Quote Originally Posted by Outlaw View Post
    thanks for the replies, we are going to start out very conservative.
    28 total and pull out 2 per PSI, then creep up on it
    Thats pretty much where we started. We also jetted the secondary jets two sizes up on the Demon 850. I will have to look at my notes but the jet change made a nice improvement on the HP numbers.

    Are the heads on your nephews motor aluminum? If they are iron I would be very consevative. By the time you hear pinging with iron heads you pretty much can bet you popped a head gasket. Iron heads will require more boost retard. Aluminum is a little more forgiving. We started increasing the boost retard first then moved up with the timing. We did this because if you get a bad batch of gas you can turn the boost retard down. If you leave it at 3 deg per you have no room for bad gas. We had no detonation with our motor package at the numbers I had listed above previously. 91 octane fuel.

  12. #10
    21 Daytona Outlaw's Avatar
    Join Date
    Dec 2007
    Location
    Artesia, N.M.
    Posts
    5,291

    Default

    Yes Iron heads, thats why i figured starting with 2 per psi, so he would be able to go to 3 if needed on the water. maybe we should start out at 26 just to be safe.

    his carb is from Lance Patton, it should be here any day now. so not sure on jet size yet.

    he also has a autometer wideband AFR, so we should be able to tune it fine.

  13. #11
    Member
    Join Date
    Mar 2008
    Posts
    84

    Default

    Definitely start out at three deg per pound of boost and at 28 deg total. We made the mistake with iron heads at 36 total with 3 deg per pound and popped the head gaskets. This was with 7 pounds of boost. The metaphorical fuse is very small with iron heads. Better safe than sorry.

  14. #12
    Senior Member Sanger Greg's Avatar
    Join Date
    Mar 2008
    Location
    SFV LOS ANGELES
    Posts
    164

    Default

    great info.
    Last edited by Sanger Greg; 02-23-2009 at 08:16 PM.


  15. #13
    Senior Member MACHINEHEAD1's Avatar
    Join Date
    May 2008
    Posts
    473

    Default

    Locked out at 28 deg. then 2 deg. per pound of boost. 5 lbs.= 18 degrees total. The EGTs will be through the roof 1600+ easy. If the engine is 8 to 1 with iron heads at 3000 ft above sea level. I think 32-33deg. locked out and 1 deg. per pound would be way safe. This would be safe at sea level!

  16. #14
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    Quote Originally Posted by Outlaw View Post
    he also has a autometer wideband AFR, so we should be able to tune it fine.
    Be very careful as to putting total faith into this. Assuming you have it in the collector you are getting an average reading of 4 cylinders. Many blow thru set-ups (especially ones with typical hat )have very large disparities cylinder to cylinder.

    You need to look into every cylinder.

    Be careful.

+ Reply to Thread
Page 1 of 2 1 2 LastLast

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in

Tags for this Thread

Digg This Thread

Posting Permissions

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95