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  1. #1
    Join Date
    Aug 2018
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    3,972

    Default Fuel regulator/bypass

    Which one are yall using on a 602 with the rear mounted fuel pump?

    After chasing carb problems for the last 2 weeks, our local crate builder believed we had the wrong regulator, too small he said.(it came with the car)

  2. #2
    Join Date
    Oct 2007
    Posts
    960

    Default

    rear mount belt pumps deliver quite a bit of volume and a crate engine does not use much volume so the regulator and return line are critical ---also do not forget the fuel cell vent needs to be adequate and clear

    as for the pump---do you know what size it is 300-400-500?? this is determined by the length of the gear
    for crates we use the 300

    if the pump is bigger than a 300 definitely use a a regulator with a bleed

    the aeromotive stuff is real nice but the universal bypass regulator from them does not have a bleed---it works well with a 300 pump but if you are larger I recommend something with a bleed

    make sure there are no dips or kinks in your return line (-8 minimum -10 is better)

    Brad
    www.race-1.com

  3. #3
    Join Date
    Aug 2018
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    Default

    Thanks Brad! This is kinda baffling us. It was a 3 race old Hendren 602, tuned on his dyno. We've adjusted the floats both ways and adjusted the front squirters, but nothing seems to help. We've checked the filter and lines and there were no issues. Our local builder adjusted the fuel pressure from 6.5 to 7.5 to no affect.

  4. #4
    Join Date
    Oct 2007
    Posts
    960

    Default

    OK lets get more specific---originally you just asked about a regulator
    What is the actual on track problem?
    What fuel are you using?

    Brad
    www.race-1.com

  5. #5
    Join Date
    Aug 2018
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    Default

    Yeah, because our local builder said we were using the wrong one.(it was changed tonight)

    Our car has been stumbling at the end of the straightaway.

    We are using VP x85.

  6. #6
    Join Date
    Oct 2007
    Posts
    960

    Default

    did changing the regulator fix your problem?
    I am going to interpret your "stumbling" as a misfire
    on E85 a high end misfire is a rich condition
    we do not like dead head regulators for E85 that have 3/8 pipe fittings as they will go lean at high end---and I am going to assume that is why your local builder didn't like the regulator you were using but I do not think that was the "stumble"

    I hope your problem went away but I am guessing that it did not

    Brad
    www.race-1.com

  7. #7
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    Aug 2018
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    Default

    Dont really know as it doesn't do it until it has a load on it.

    We had the regulator with the return on it but our local builder said it was too small, so we purchased a bigger one.

    I just find it odd that it had 3 races on it with no problem or at least according to the prior owner ( we did verify that it was dynoed by Hendren)

  8. #8
    Join Date
    Oct 2007
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    960

    Default

    have you called Steve Hendren to ask specifically about the situation?
    he is pretty easy to talk to

    Brad
    www.race-1.com

  9. #9
    Join Date
    Aug 2018
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    Default

    Quote Originally Posted by brad hibbard View Post
    have you called Steve Hendren to ask specifically about the situation?
    he is pretty easy to talk to

    Brad
    www.race-1.com
    Yes, he helped us sort out the regulator.

  10. #10

    Default

    we are trying to sort out a similar problem with our 604 crate LM.... the WRC /aeromotive mech drive pump Part number is 250250LM..... does that mean it is a 250 size or 250 gph pump ? car was bought with the fuel set up on it.... pump has a check valve on top looped back into the incoming fuel line, a deadhead Reg between the pump and fuel log. ( no bypass back to the tank. so I assume dead head reg) .... never seen a set up like this.....got a stumble at corner exit... then clears .... E85...carb did not come with the car.... got to sort out and pinpoint if it is the carb or the pump / check/ reg set up.... Aeromotive / WRC web site is about the worst I have come across in a while...for finding info easily....

  11. #11
    Join Date
    Sep 2009
    Posts
    723

    Default

    Stumble on Exit, When does this happen? When you pick up the throttle?

  12. #12

    Default

    yes Sir, we raised and lowered the float level , raising it seemed to make it worse, lowering it helped a little... driver "thinks" it's carrying 6psi fuel pressure down the straights , but not for sure

  13. #13
    Join Date
    May 2007
    Location
    in a van down by the river
    Posts
    1,822

    Default

    might be too big or small of a squirter, or a cam issue or adjustment to the squirter.
    are you matting it, or rolling into throttle? does it do it when the you are on the way down with the throttle, or once at WOT?
    I think there should be lifeguards in the genepool.

  14. #14

    Default

    I will have to get with the driver and get more detail for you...... and pinpoint exactly what is going on.... It looks like, from where I was hanging in the fence... it would rotate on entry and when he would pick the gas back up it would go... but when it was in the center of the arc in the middle and really needing to GO... it would stumble / bog / not accelerate.....till it got a little way out on the exit...

  15. #15

    Default

    directly from the driver...>>>>>>>>>>>>>>>..Sure. During the feature, when I run the bottom and drive off into the corner, and go to pick up the throttle at the 1/4 mark or so of the corner, the car stumbles and hesitates repeatedly through the duration of the corner. When i get onto the straightaway, it will clean up about at the flag stand and run smoothly. It was the same symptoms at and did it intermittently in practice at Boothill, but seemed to be at its worse when really throwing the car into the corner. The biggest change we had was when we raised the floats for the feature at Vivian. It actually made it worse. When we adjusted them back down for hot lapping after, it was back to where we were in the heat race and hot laps. It makes no sense, but it does appear to be better when I run around the top versus trying to roll the bottom.

  16. #16
    Join Date
    May 2007
    Location
    Kansas
    Posts
    1,641

    Default

    Quote Originally Posted by north louisiana dirt View Post
    directly from the driver...>>>>>>>>>>>>>>>..Sure. During the feature, when I run the bottom and drive off into the corner, and go to pick up the throttle at the 1/4 mark or so of the corner, the car stumbles and hesitates repeatedly through the duration of the corner. When i get onto the straightaway, it will clean up about at the flag stand and run smoothly. It was the same symptoms at and did it intermittently in practice at Boothill, but seemed to be at its worse when really throwing the car into the corner. The biggest change we had was when we raised the floats for the feature at Vivian. It actually made it worse. When we adjusted them back down for hot lapping after, it was back to where we were in the heat race and hot laps. It makes no sense, but it does appear to be better when I run around the top versus trying to roll the bottom.
    Going off what he said it sounds like this:

    Fuel maybe over flowing and flooding carb due too:

    1. Floats being to high
    2. Too much fuel pressure thus over filling bowls and running into boosters of car or out the vents
    3. Fuel pressure keeps climbing and at end of straight its too high and overflowing and once you lift on throttle for entry (no longer consuming the fuel) it over flows into carb and thus when you pick up throttle it's pig rich and takes a while to keep out

    It may not being doing it as bad on the top of the track (assume banking on top and none to little on bottom) because the car is leaned less to the right due to banking. It's possible you need an angled spacer on carb so fuel isn't going to the right side messing with float levels and over filling enough that it's running fuel out of the vents or boosters.

    Keep in mind that large needles and seats don't require a ton of pressure, think large hose and low pressure to deliver the same amount of fuel as small hose and high pressure.

  17. #17

    Default

    thank you Sir... we are working up a plan to address these issues.... I took the carb apart today and did not see any obvious generic issues... I have never used a belt drive pump with a check valve , only bypass regulators before this.... I can't believe this was designed to Loop the excess fuel from the pump through the check valve right back into the gravity feed side of the pump and not return it back to the tank..... we are going to put the carb back on, remove the line from the check valve and run a hose to a fuel jug and crank the car and see how much fuel is being pushed through the check valve... From the first time I looked at this set up it looked wrong to me.....but the guy that we got the car from said they had no issues..... but who knows about the truth in that.... :-)

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