So as you know I have fitted a new carb, turns out it is a EMPI weber copy (bah!) I searched online and found the jet sizes that it was fitted with are apparently the right ones but I've been told that I'm overfueling so my main jet is wrong. Does anyone know what the correct jet sizes are?
I found this info on the samba. Does thins sound right to you guys? 'Primary idle, 45-50 at sea level, 40-45 @ 5k'. Secondary idle 10-15 larger than primary idle. Weber supplies them with the primary idle larger than the secondary, WHICH IS STUPID. It runs too rich on the primary, then leans out when the secondary opens. Main jet. 125 primary. 180-190 secondary (not a misprint). I've even seen some engines need 210 secondary mains. If you do not stagger your secondary jetting, you WILL have the same problem of severe lean out when the secondary opens up, since airspeed drops so much due to air flowing thru 2 bbls. You want to be lean on the primary (for mpg and cool running), but richen up to 13:1 when the secondary opens. Most clowns jet the primary and secondary the same. So when airspeed drops to <1/2 when the secondary opens, the vac signal the main circuit sees is also < halved, and your pride and joy leans out like crazy. This is why the secondary main MUST be much larger than the primary main. I'd like to slap the morons that recommends square jetting on the main jets. They are clueless. Air jets. 160-180 will work, I generally use 160 on primary, and 180 on secondary. If you use a 180 secondary air, you may need to go up 10 more on the main, to a 190-200 secondary main. Do NOT be scared of the "huge" secondary jet, it WILL WORK PROPERLY. I've setup hundreds of these carbs, and know what works and why. If you are at elevation, for every 4k' drop both idles 5 drop both mains 5 increase airs 10-15. These guidelines will work for a heated intake, properly setup carb (float, fuel pressure), with no ignition "issues". Sea Level, run 45/60, 125/190, 160/180 @4-5K', run 45/55, 120/180, 175/190 @8k', run 40/55, 115/175, 190/205.'
Hi I have been working through the progressive over 10000 miles since I bought one in 2012 and the jetting that it comes with is quite rich. But if you dont use the stock air cleaner that is what it needs. I use a setup where I made a box that bolts on top of the progressive feeding air from an oil bath cleaner with the hot air feed from the cylinder head using vacuum from the carb through the thermo valve as with stock 34PICT3. I started with the quoted advice but I find that145 secondary with 60 secondary idle and 180 secondary air is enough for a 1641 in a bus. 45 primary idle 125 primary main and 160 primary air. I use an AFR meter and it shows the transition hesitation as dipping to lean as suggested on thesamba.com This was with a twin quietpack exhaust. Just bought a freer flowing stainless exhaust from JKnand havent given itnmuch of a road test since. As I left the flywheel loose and it took £ 320 to fix the dowels coming loose .. Will double check these numbers tomorrow the log book is in the bus.
Jetting is all new to me so slowing trying to get my head around it all. The advice I have been given is drop the jet size one and test it, keep going till it sounds right. Now to me, being a logical computer man, this doesn't make sense. Working 'by ear' sounds wrong, without getting it all on a flow bench or rolling road surely there is a more precise way of measuring the flows and jetting it the right way?
Using the log book Primary main 125 idle 45 air 160 Secondary main 137 idle 60 air 180 Checking AFR with a PLX technologies AFR meter on the dash, and checking different settings by driving the same daily commute and trying speeds on hill climbs and level motorway running. This is with a stock SVDA distributor. 12.5 afr at 67mph indicated on a level road. This combination takes a little off the top end in return for low end performance
