Quote:
Originally Posted by jhein
I got a lot of different opinions about the fuel system when I did the motor so I thought I'd give them mechanical stuff a try.
I've got sticky tires back on it now, the Nitto NT01. I haven't tried to hook with them from a stop, but from a roll they stick pretty good. At WOT in first they get a little loose but not bad.
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The good mechanical pumps can work veery well, to a point. I have a 467 with 72cc E-heads & OF cam, 3.23 gears in a 72 firebird, I can do every type of launch or WOT runs on the street with M/T drag radials or normal street radials without any signs of starvation... originally it had an edelbrock mech pump that is similar to the high flow carter pumps and it was fine on the dyno or into low 12's on the first shake down runs using old hard BFG drag radials that were almost as bad as normal street tires, but once I got some new M/T drag radials and had some experience with launching the car it had terrible starvation issues... so I upgraded to a robbmc 1100 pump, 1/2" pickup & lines... it ran low 11's but on the best runs with decent traction/60ft, it would cut out occasionally, some times it was fine down to 11.2, but other times it would fall on its face about half track and ruin the entire run. So im now at a point where I decide to go faster with a tanks inc set up to fix the starvation issue, or just be content with a low 11 sec car running stock unported e-heads and a q-jet. car runs about perfect on the street though and its a 90% street car.
On the subject of a qjet fuel bowl going dry, there was a thread about this sometime last year that I cant seem to find, I think you (jhein) started it and "FJ" posted a test he did putting a full cup or more of fuel in a container on the garage or house counter, he said it didnt lose any fuel after like 3-5 hours so I/we/you have something else going on.... well, just last week I remembered that thread and how the test wasnt what fuel does when in a hot engine/carb... I filled a tablespoon or a little more of fuel in a small metal container, about the size & amount of fuel in a q-jet bowl, I set it right on top the carb after a short drive but fully warmed engine at ~180°. After letting it sit with hood closed for about 1.5 hours I came back to check & sure enough it was completely dry, not even a residue of wet fuel left. Granted inside the carb isnt exposed to open air but the carb is fully vented. That test is more of a real world scenario for fuel in a q-jet than a big cup of fuel at room temp, based on what I found after a short time, fuel definitely can & does evaporate at a pretty fast rate when heated like an engine. This was non ethanol fuel too.
Why some carbs/cars dont have this issues is beyond me, but it is a very real problem for many cars when they sit for a week or more, probably a combo of things from evaporation to drain back depending on the mech pump used?