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Topic Review (Newest First)

  • 09-02-2009, 02:30 PM
    MSCobalt220
    Check your TDC mark on the balancer first, then set total at 34 for a safe bet . You can fine tune it after you start getting dialed in . Also make sure you are getting full alternator voltage(13-14 volts) to both the ignition and fuel pump . That all needs to be corrected if it's not right .

    I'd be checking for Holley needle/seats , not generic low flow sets. Float level is crucial on this set up. Make sure you have full float drop and put a set of jet extensions on the secondary sides of both carbs . Check float drop after the extensions are installed . That is a nice looking fuel system on your engine . How do you read that fuel pressure gauge when you are flying down the river? Just saying..
  • 09-01-2009, 09:26 PM
    MACHINEHEAD1
    Kind of what I was getting at in post#21. Back in the day if you needed 2 Holley regs, you know the guy had at least 750 hp.
  • 09-01-2009, 09:14 PM
    MSCobalt220
    Quote Originally Posted by widowmaker View Post
    I'm going to go a little against the grain here.


    I have fed two holley 750dp's with a single holley regulator and a holley blue pump on a 502 with no problems the motor made over 700 hp.

    When I switched over to a different fuel system Aeromotive pump, with -10 hose feeding a magnafuel 4 port regulator with a -4 bypass line back to the tank and -6 hoses feeding the carbs, it made zero difference in performance and plug readings


    I have done extensive testing with data about the flame arrestors, the motor pulled the same rpm with or without them in. same motor as above.

    If you motor is gaining 300 rpm when you choke off the air flow, it sounds like your jetting is off huge. I would have the carbs looked at by C&J or Lance Patton, both very knowledgeable carb guys or at least return them to the factory holley settings.

    I would start simple first, don't buy any parts until you know it is a problem. Make sure your timing is right to start, check for any obvious fuel blockages. Your fuel lines look plenty large to supply fuel to the motor.

    I'll probably get slammed for this but whatever.
    good post
  • 09-01-2009, 08:58 PM
    Boat 405
    I'm going to go a little against the grain here.


    I have fed two holley 750dp's with a single holley regulator and a holley blue pump on a 502 with no problems the motor made over 700 hp.

    When I switched over to a different fuel system Aeromotive pump, with -10 hose feeding a magnafuel 4 port regulator with a -4 bypass line back to the tank and -6 hoses feeding the carbs, it made zero difference in performance and plug readings


    I have done extensive testing with data about the flame arrestors, the motor pulled the same rpm with or without them in. same motor as above.

    If you motor is gaining 300 rpm when you choke off the air flow, it sounds like your jetting is off huge. I would have the carbs looked at by C&J or Lance Patton, both very knowledgeable carb guys or at least return them to the factory holley settings.

    I would start simple first, don't buy any parts until you know it is a problem. Make sure your timing is right to start, check for any obvious fuel blockages. Your fuel lines look plenty large to supply fuel to the motor.

    I'll probably get slammed for this but whatever.
  • 09-01-2009, 08:38 PM
    MACHINEHEAD1
    Is it possible these carbs are really Holley List #6109/750s. I think those jet sizes would be lean and explain the lack of sec. P.Valve. Just a thought. I have a pair if we need to compare blade size/venturi/jets ect.
  • 08-26-2009, 03:38 PM
    gn7
    Thats really only a concern on enclosed engine compartments. Any one with an enclosed engine compartment that doesn't have flame arrestors is tempting fate.



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  • 08-26-2009, 10:16 AM
    autobutler

    flame arrestors

    Don't we need flame arrestors to be safe? I know it's clean air on the lake most of the time but what about backfire issues?

    Thanks, Chuck
  • 08-25-2009, 06:24 PM
    Bigtorq
    Quote Originally Posted by monster View Post
    I was looking at the photos you put up of your carbs... They look just like the Holley's on my tunnel ram... I don't think you have 4150/4776 (4776 is a double pumper) yours are single inlet like my 4160/1850 with the secondary plate kit added in. That why you have no power valve in the secondary side.... Hope this helps
    They are double pumpers and were modified so that the primary inlets are on one side and the secondary's are on the other. I think when they replaced the metering blocks on the secondary sides they must have used the ones without power valves. The blocks don't have the threaded inserts for pv's.

    I also agree with the last statement that I need to focus on the timing. I thought I had it right until I started messing with it. Time to reset and start over.
  • 08-25-2009, 06:11 PM
    Bigtorq
    My fuel pressure gauge is on the output side of my regulator so doesn't that mean that I have pressure at the bowls at wot?
  • 08-25-2009, 05:19 PM
    monster
    Quote Originally Posted by Bigtorq View Post
    The carbs are Holley 600's part number 4776 (4150 series) and the exploded view shows power valves on both primary and secondary sides. When I openned mine up they did not have power valves on the secondary side and the metering body didn't even have a provision for one, yet they still had the stock 73 secondary (main) jets in them. So is this the choke point? I thought if you pulled a secondary power valve, you had to go up on jet size significantly or you would go lean. I guess I'm more confuesed on why the schematic shows power valves and I don't have them. The carbs were worked before I got them so who knows. Since I am going lean I'm thinking to go up on the jets, just don't know where to start.

    I was looking at the photos you put up of your carbs... They look just like the Holley's on my tunnel ram... I don't think you have 4150/4776 (4776 is a double pumper) yours are single inlet like my 4160/1850 with the secondary plate kit added in. That why you have no power valve in the secondary side.... Hope this helps
  • 08-25-2009, 01:08 PM
    ap67et10
    Quote Originally Posted by havasubyou View Post
    if you pull the reg and look at the inlet size as this post by jocko shows 7/32 hole is trying to feed 4 carb bowls at wot with only 7 lbs of inlet pressure.

    pull the reg and run it once. 7 lb pressure from that pump is not going to push past your needle and seats so give it a try.


    If you look at the pics of his engine (as mentioned above) the pressure gauge is after the reg. If it reads 5 psi at WOT it has sufficient fuel volumn. You cannot create that pressure after the reg without adequate fuel.

    I have never seen a decent engine tuner that sits and fine tunes or even touches the carb/s before setting proper ignition timing. Stop messing with the fuel until you have your timing set properly and you know exactly what it's doing.

    AP
  • 08-25-2009, 11:54 AM
    havasubyou
    Quote Originally Posted by jockorace View Post
    Some good information and points presented. I'd like to point out an often ignored issue.....Fuel Volume. You are currently running all of your fuel to feed this motor thru only one small Holley regulator. Attached is a pic of one opened up, showing the small 7/32" (less than 1/4") orifice that the check ball seats on. Even though this motor is not huge (450 HP ?), this is not adequate. Fuel volume is actually more important than fuel pressure.
    Just .02 Jocko
    if you pull the reg and look at the inlet size as this post by jocko shows 7/32 hole is trying to feed 4 carb bowls at wot with only 7 lbs of inlet pressure.

    pull the reg and run it once. 7 lb pressure from that pump is not going to push past your needle and seats so give it a try.
  • 08-25-2009, 08:28 AM
    Bigtorq
    So, if I'm getting fuel pressure at wot, doesn't that mean that the flow is fine? I would expect if I had a restriction somewhere it would show up on the pressure guage by dropping to zero or some value below the minimum needed to keep it running. the pump and reg are new and I can up the pressure. I'm at around 6.5 lbs at criuse and 5 at wot.
  • 08-24-2009, 08:43 PM
    havasubyou
    run this simple test,pull the fuel reg out of the system near the carbs and run it wot,the small port in that reg trying to support 4 carb bowls at wot is futile and the larger jet you go the faster it empty's the bowls
    also the holley blue pump does not pull fuel very well if your filter is between the tank and pump move the filter to the pressure side of pump just to be sure of not starving the pump and make sure the fuel line is not collapsing the fuel line(line my be too soft)
    also might look at putting a rebuild kit in that blue pump,cant hurt 5 lbs is the min i would run @ wot at the bowls

    hope this helps.. best of luck
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