Originally Posted by
1QwkSport2.5r
I am necrobumping this thread up due to a question. Hopefully some of the fellas that contributed to this thread are still around.
I recently acquired a near-new GMS .47 engine (non remote needle version) that I'm trying to get running good. I've read the whole thread with great interest and have a question in regard to the idle needle/spraybar interference issue. I already fixed the fuel inlet misalignment problem, but now I need to deal with the idle needle and spraybar interference problem. As has been noted, if the idle needle is set for good idle and transition, the high speed operation runs lean and no amount of needle adjustment on the high end will richen it up enough without having the idle needle set way too rich. Is it better to shorten the spraybar or the idle mixture needle and how much needs to be taken off to obtain good results?
Thanks in advance.
I would advise you to FIRST verify the issue is that the engine is not getting enough fuel at high speed with the LS needle set properly.
Scribe or record your exact LS needle settings that you are using now.
Then richen the LS a bit and start the engine. Tune it for best HS performance.
Ideally you could then adjust the LS needle while the engine is running full bore, and see if there is any affect on the high speed performance.
e.g. if you richen the low speed and see a High Speed improvement, then you know the engine is starved of fuel when running all out.
I don't think shortening the spray bar or idle mixture needle is going to help, short of increasing the spray bar fuel hole size. Neither of the former will buy you more fuel flow at high speed as the idle mixture needle will be out as far as it can go already, and the modification will merely ruin the low end.
You may want to see if there is anything you can do to improve the fuel flow at high speed without involving the LS needle...
e.g.
Is there anything you can do to increase the fuel passages sizes?
What about pressurization? ( but don't use a one way valve ).
Are your lines SHORT.
Can you put a bigger nipple on the muffler?