urban_cowboy

I got my new Pro Systems carb in earlier this week, but it has been raining every since. There is no point in trying to tune in the rain and certainly cannot drive it on the wet streets. Forecast is rain through the weekend. What in the world. This is the Texas Hill Country, not Seattle. We go from a 2 year drought to a very wet winter.

I currently have a Holley HP, that I have been happy with, but I have wanted a Pro Systems custom carb for a while and decided my 1 year old needed a new carb for his birthday. In looking at the build sheet, he sent a 850 with a custom throttle plate, metering block, and several tweaks to the accelerator pump, cam, and nozzle. He may have tweaked the boosters too, but I am not sure what the 850 comes with stock. What is interesting is he recommends a larger primary and secondary jet, larger primary pump, larger p/s pump nozzles, and a larger main body than I am currently running. I would think this new carb would run dead rich based on my tuning of my 750 Holley HP, but maybe he tweaked something in the metering blocks that I do not understand.

If the rains continue, I may pull the HP and do a side by side comparison to see what maybe he changed. I am not too worried because I gave him a ton of information on my setup before he built the carb and he said to call or email if I have any issues getting the final tune lined out.

valley firearms

If you don't mind, how much did you pay? You will be very happy.

urban_cowboy

Got a bit of a strange issue I will have to play with. I have the AFR and rpm set at idle using his stock LSAB, but when I open the primaries a little bid to run on the transfer slot circuit as in cruising, it goes really rich. Once I am on the jets, the AFR comes back up. So, I noticed that the primary idle screws are open currently about 2 1/4 turns while the secondary idle screws are open 1 3/4. In a four corner idle carb, should the idle screws be the same? This is close to how is came stock, so I left the portions the same. I may change that and see what happens. My next step will be to play with air bleeds...I guess I will put a smaller LSAB in so I can close the idle screws some to give me a good idle AFR and that should give me less fuel going through the transfer slot when I am at a very light throttle too.

I paid around $700 for it. So far it is amazing. It is even more responsive than my stock 750HP. It appears he adjusted some of the emulsion ports and with the changes to the boosters and throttle plate, it likes it. I would never have been able to customize my 750HP to this level without some serious help from a guru. I can tune the normal stuff, but emulsion ports, idle ports, etc are a little above my head.

kalli

well I am positive that with that carb you'll be a happy man. congratulations
I was running into the same question with the primary and secondary mixture screws. I believe if the carb is setup in such a way that both butterflies are opened the same at idle, then they should all be the same. However since they build your carb and you paid 700 for it and I don't think there's many people in the world who know so much about carbs and tuning, I'd give them a call.
Wishing you good and dry weather and let us know how you're getting on

urban_cowboy

Well was smoking crack on Friday, I guess because I had it completely backwards. I am running a 78 LSAB right now with the idle being mid 13s and light cruise at low 12s. I do not have any LSABs larger than that, so I am not sure what that means. I will shoot them an email tomorrow, but so far, it looks like it is going to work well for me.

urban_cowboy

FYI, Patrick told me to drill the LSAB or Idle Air Bleeds out to 86 since I only have up to 78 (.078) at the house and see how it does. He said you have to make big changes with the low speed air bleeds to notice anything so drill them out and see how it does.

urban_cowboy

FYI, Quick Fuel Technologies makes air bleed all the way between 23-100 (.023-.100). They are not cheap, but they have a larger selection that Holley does and they are 10-32 threads so they fit Holley main bodies. Jegs also makes blanks that you can drill yourself.