Blown 350 leaned out
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 14 of 15

Thread:
Blown 350 leaned out

  1. #1
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default Blown 350 leaned out

    I run a 350 Chev 671 Weiand blower. We had a river race weekend recently. First day was about 20 miles up and back again. Coming down the second leg my engine starting loosing power so I backed well off the pedal and cruised down.The engiene wouldnt rev properly nor make much boost. My fuel was running very low. We checked the engine over, couldnt see anything obvious wrong so topped it up with fuel and took it out for a spin. It was back to normal,going hard so my thoughts were that it must have been struggling to suck up the gas when the tank was so low. Next day we were to go 45 miles up stream and then back again. Half way up the first leg my motor bogged pulling about 10psi boost and lost power. It then started fuming badly, thought I was on fire. We backed off and limped up to the top, that was me finished. I haven't pulled the motor out yet, but I think its obvious that the fuel supply was compromised. I run and Edelbrock 110gph mechanical fuel pump which dosent require a regulator. Would this pump be the likely cause to my fuel supply problem? I also run a Mallory marine filter/water separator 10 micron, could that create problems? To note I ran the same race 2 years ago without issues, only thing I have changed since is run a coarser blade in my unit to lower revs and boost to 10psi, hence I now have my foot into the pedal more as before I couldn't run hard down as I was over boosting. I should say too that my engine is a poor mans setup, no forged internals, but it has given me good service and I don't run close to detonation. Thoughts appreciated.

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Senior Member
    Join Date
    Dec 2007
    Location
    corona calif
    Posts
    1,119

    Default 10 lbs of boost

    Quote Originally Posted by Huffa View Post
    I run a 350 Chev 671 Weiand blower. We had a river race weekend recently. First day was about 20 miles up and back again. Coming down the second leg my engine starting loosing power so I backed well off the pedal and cruised down.The engiene wouldnt rev properly nor make much boost. My fuel was running very low. We checked the engine over, couldnt see anything obvious wrong so topped it up with fuel and took it out for a spin. It was back to normal,going hard so my thoughts were that it must have been struggling to suck up the gas when the tank was so low. Next day we were to go 45 miles up stream and then back again. Half way up the first leg my motor bogged pulling about 10psi boost and lost power. It then started fuming badly, thought I was on fire. We backed off and limped up to the top, that was me finished. I haven't pulled the motor out yet, but I think its obvious that the fuel supply was compromised. I run and Edelbrock 110gph mechanical fuel pump which dosent require a regulator. Would this pump be the likely cause to my fuel supply problem? I also run a Mallory marine filter/water separator 10 micron, could that create problems? To note I ran the same race 2 years ago without issues, only thing I have changed since is run a coarser blade in my unit to lower revs and boost to 10psi, hence I now have my foot into the pedal more as before I couldn't run hard down as I was over boosting. I should say too that my engine is a poor mans setup, no forged internals, but it has given me good service and I don't run close to detonation. Thoughts appreciated.
    When your making these long runs how much boost were you running? Do you run pump gas with 10 lbs of boost?

  4. #3
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default

    This years race we were running at 10psi most of the time. Previous year we would run more like 12 or 13 psi but less throttle. Those boost readings are just taken off boost gauge which is hooked into manifold, I dont know how accurate that is,maybe someone can tell me. Yes 96 or 98 pump gas.

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Seriously off center slowride's Avatar
    Join Date
    Dec 2007
    Location
    Anaheim/BHC- the Shack
    Posts
    2,439

    Default

    Where is your fuel pump mounted relative to the bottom of the fuel tank(s)?






  7. #5
    Some guy obnoxious001's Avatar
    Join Date
    Dec 2007
    Posts
    3,570

    Default

    Quote Originally Posted by Huffa View Post
    I run a 350 Chev 671 Weiand blower. We had a river race weekend recently. First day was about 20 miles up and back again. Coming down the second leg my engine starting loosing power so I backed well off the pedal and cruised down.The engiene wouldnt rev properly nor make much boost. My fuel was running very low. We checked the engine over, couldnt see anything obvious wrong so topped it up with fuel and took it out for a spin. It was back to normal,going hard so my thoughts were that it must have been struggling to suck up the gas when the tank was so low. Next day we were to go 45 miles up stream and then back again. Half way up the first leg my motor bogged pulling about 10psi boost and lost power. It then started fuming badly, thought I was on fire. We backed off and limped up to the top, that was me finished. I haven't pulled the motor out yet, but I think its obvious that the fuel supply was compromised. I run and Edelbrock 110gph mechanical fuel pump which dosent require a regulator. Would this pump be the likely cause to my fuel supply problem? I also run a Mallory marine filter/water separator 10 micron, could that create problems? To note I ran the same race 2 years ago without issues, only thing I have changed since is run a coarser blade in my unit to lower revs and boost to 10psi, hence I now have my foot into the pedal more as before I couldn't run hard down as I was over boosting. I should say too that my engine is a poor mans setup, no forged internals, but it has given me good service and I don't run close to detonation. Thoughts appreciated.

    With a forced induction engine, one of the most important gauges you can have is fuel pressure, even with the unregulated pump. Also, what did you find in the fuel separator?

  8. #6
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default

    Fuel pump is mounted about half way up the height of the tank which is directly in front of engine under back seat. There is no sign of water in the bottom of the seperator, I havent taken the filter out yet, do I split it open to see how much crap is in there? By memory I think the filter flowed 90gph, is that enough?

  9. #7
    Senior Member jetboatperformance's Avatar
    Join Date
    Dec 2007
    Location
    Atascadero Calif
    Posts
    7,463

    Default

    "no forged internals".... 10 lbs boost and cast pistons ? just curious and making sure i'm reading right , so have you pulled the motor down or done cyl leak down/compression test ?

  10. #8
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default

    Yes you sure are reading right no forged internals, no I haven't stripped the motor yet but is going to happen in the next week. Its only running 7.8:1 comp. do the maths and 10psi boost should be fine. I am adamant that the engine failing is not because its not forged. Sure if it was forged it would have kept going for longer when it leaned out but if an engine leans out big time forged or not it going to shit it self isint it? This engine given me 2-3 years of good service without issue, racing, skiing and river boating. If it was going to shit itself because its not forged I am sure it would have done it before now.

  11. #9
    Seriously off center slowride's Avatar
    Join Date
    Dec 2007
    Location
    Anaheim/BHC- the Shack
    Posts
    2,439

    Default

    Quote Originally Posted by Huffa View Post
    Fuel pump is mounted about half way up the height of the tank which is directly in front of engine under back seat. There is no sign of water in the bottom of the seperator, I havent taken the filter out yet, do I split it open to see how much crap is in there? By memory I think the filter flowed 90gph, is that enough?
    On a blower motor I would change over to an electric and mount it BELOW the tank bottom. To continue beating the dead horse..... where is the filter housing located and on the pressure or suction side?






  12. #10
    Some guy obnoxious001's Avatar
    Join Date
    Dec 2007
    Posts
    3,570

    Default

    Quote Originally Posted by Huffa View Post
    Yes you sure are reading right no forged internals, no I haven't stripped the motor yet but is going to happen in the next week. Its only running 7.8:1 comp. do the maths and 10psi boost should be fine. I am adamant that the engine failing is not because its not forged. Sure if it was forged it would have kept going for longer when it leaned out but if an engine leans out big time forged or not it going to shit it self isint it? This engine given me 2-3 years of good service without issue, racing, skiing and river boating. If it was going to shit itself because its not forged I am sure it would have done it before now.
    You are correct, but look back above at my previous post, likely to be a fuel delivery problem. I personally would not run 10psi on cast pistons.

  13. #11
    Senior Member
    Join Date
    Dec 2007
    Location
    corona calif
    Posts
    1,119

    Default 10 boost

    Quote Originally Posted by Huffa View Post
    This years race we were running at 10psi most of the time. Previous year we would run more like 12 or 13 psi but less throttle. Those boost readings are just taken off boost gauge which is hooked into manifold, I dont know how accurate that is,maybe someone can tell me. Yes 96 or 98 pump gas.
    What kind of timing are you running. If it's the center of the piston is melted more than likely leaned out if it's the side of the piston detonation might be the problem.

  14. #12
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default

    Thanks for the feedback everyone. The filter is at about the same level as the pump on the suction side. Not sure what timing is, I left that to the engine builder, I know he changed the weights/curve in the MSD dzzy to suit the blower. So I will change to an electric pump with a fuel pressure gauge in dash. What pump should I get or what should a pump be capable of GPH to suit my engine?

  15. #13
    Some guy obnoxious001's Avatar
    Join Date
    Dec 2007
    Posts
    3,570

    Default

    Quote Originally Posted by Huffa View Post
    Thanks for the feedback everyone. The filter is at about the same level as the pump on the suction side. Not sure what timing is, I left that to the engine builder, I know he changed the weights/curve in the MSD dzzy to suit the blower. So I will change to an electric pump with a fuel pressure gauge in dash. What pump should I get or what should a pump be capable of GPH to suit my engine?
    I would install the gauge first before you have to feel like you need an electric pump. I have mechanical pumps on a number of blown BBC engines that have worked out fine. At this point you should be worrying about finding what caused your damage, have you inspected the filter yet?

  16. #14
    Member
    Join Date
    Oct 2012
    Posts
    47

    Default

    What make/model pumps do you run? No I havnt looked at filter yet. Its a cartridge so do I cut it open and hav a gander?

+ 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