[USAC97]

If you had a fuel pump going south, would that cause the motor to lean out off the corner (low end), but not at the top end? I have been through the bypasses, barrel valve (19%), and the linkage but can't find anything wrong. Last night, the temp would climb fast on yellows but would drop just as quick when on the hammer. Three races in a row I have dealt with this and it even ran great in hot laps and qualifying, but started again in the heat and got worse in the main. It seems to get worse as the race goes on. My thought was that it couldn't make enough volume and pressure at low rpm but could at higher rpms. If not the pump, what else could it be? The Mag? I appreciate any advice you might have because it's got me stumped! I put a fresh pump in it today, but we all know it's tough to test before you get to the track! I run a West Coast 360 sprint out her in California.

[TQ29m]

Just a guess, but what do you have your idle bypass set at? Sounds like it may be popping off early. Bob

[USAC97]

35 PSI. I thought the same thing too.

[TQ29m]

Are you able to obtain a good idle? With 19% on the barrel valve, it should Idle OK, but you say it get's hot at idle, maybe not enough air flow. I had several conversations with Hilborn, and they told me to just cap off the idle bypass, and set my idle mixture with the barrel valve, and it's been working. Take the fuel cap off the tank, and see what kind of return you're getting, that's why I like to run everything back to the tank, I can see what it's doing, at least at idle. that's how I caught my hi-speed leaking off early. Bob

[USAC97]

Yeah it idles great at about 1800-2000 rpm out of gear. As crisp as can be. It ran great off the corner in hot laps and qualifying too. It's like something gets hot and then it starts to run different. I came back into the pits, popped it out of gear and it sounded great. It acts like if you had too tall of a gear how it would stumble off of a corner.

[TQ29m]

Just another question, what size pump are you running? Another thought, it could be too high of idle bypass pressure, I guess at this point, I'd take a big swing at it, drop it to 20psi, and if that doesn't help, just cap it off, and try it. Sounds like you may have more than one gremlin. Good luck! Bob

[USAC97]

DSR "0" pump

---------- Post added at 10:19 AM ---------- Previous post was at 10:10 AM ----------

By the way, this is the same setup I ran the last few years and it always ran great! The only change I made this year from last was going to a cross-shaft linkage.

[TQ29m]

OK, have you ck'd your linkage dimension's, if the arm angles aren't correct, it can change the ratio that the barrel valve opens, and that could be the problem, it may have slowed it down, which is what it sounds like, to the point where it is behind the shutter shaft openings. If it is a Hilborn unit, they have an online diagram of how to set the angles. Bob

[USAC97]

It's a Kinsler, but yeah that could be a possibility. I had a problem with the billet shaft couplers connected to the barrel valve were pushing against the spring instead of the screw causing the barrel valve to lag behind the butterflies , I thought I had it, then the problem came back in the main. Maybe the arms aren't the same length on the shaft and the barrel valve? It still has me baffled though why it only does it later on in the main event!

[Geoff Kaiser]

Better check your fuel pickup in the tank. Fuel moves around alot more thru the corner and off than it does at the end of the straightaway. Also would make sense that it runs good in hot laps and quals but gets worse on teh longer races ie heat and feature.