rojs234

iTrader: (5)

I'm posting this here because we don't have a separate carb section, but this is where all the carb questions end up!
I have a new Holley blue race pump on my '34 coupe with 6.0 LS2 engine. It's mounted on frame in front of back wheel and is siphon fed with a 3/8's line with a metal inline filter. It has 3/8 line to the regulator that came with pump. I have a Jeg's oil filled guage on one port of regulator and the other feeds the carb. Since I noticed this problem, I also installed a Jeg's guage between the pump and regulator.
Here's the problem; When I start the engine, the gauge at the engine reads normal at 6 1/2 LBS, the one between pump and regulator reads normal, pegs the 15 LB guage. Within 10 minutes, they both start dropping. Within 15 Min., one at carb is at 3 LB, other at around 10LB. At 20-25 Min. the one at carb is at or close to 0 , the other is down to 7 Lb. Engine idles and seems to run fine, no flooding or any thing unusual. Shut it off and restart shortly after, stays at 0 LB and 7-8 Lb. Let it set overnite... goes right back to 6 1/2 and 15 LBS. I thought it might be restriction in line to pump so I set a 5 gallon jug about a foot above and siphon fed direct to pump..no change. I've had 3 different guages and 2 different regulators on it.. no change. I have a wideband oxygen sensor on it... shows no abnormalities at idle or otherwise. I've had 2 different carbs and 2 feed lines to carbs on it..no change. This can't be normal. Has anyone else ever noticed this? Any thoughts or ideas? I can't try it on the road yet because of some small changes I'm making, but if I do , I may be looking at the back end of a tow truck, LOL Ron

topher455

iTrader: (6)

I had a similar problem. Are they liquid filled gauges? If so, the hotter they get the lower they will read. If you drive it and its not nosing over on you at higher rpms its probably just gauge inaccuracy due to heat. That is why when it sits the problem goes away. Try a non liquid filled gauge like the aeromotive.

rojs234

iTrader: (5)

Thanks! a bunch for that reply *topher455*. I had gotten to the point where I was suspecting the guages, but they are brand new and I had never heard of that problem before, and yes, they are both liquid filled. What was really bugging me was, I have basically this same setup on my other street rod, and while I don't have a guage on it now, I have had one on it quite awhile back and the way I recall, it held 6-7 Lbs. ALL the time.
Anyway, thanks, and I will definately try a non-liquid filled guage. Ron

rojs234

iTrader: (5)

It appears that your diagnosis is correct. I bought a MR Gasket NON- liquid filled guage and installed it between the regulator and the carb and left the Jegs liquid-filled guage on the port of the regulator. After 20 minutes of run time the Jegs guage read 0 LBS and the NON-liquid guage was rock solid at 6 LBS. I guess the old saying is true...you're never too old to learn something new! Maybe this will keep someone else from making the same mistake.
Thanks again, *topher455* Ron