carb
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master_cat
- Posts: 21
- Joined: Fri May 07, 2010 12:34 am
- Car: 86 nissan 300z
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Bulwyf_fjyr
- Posts: 6
- Joined: Mon Oct 08, 2012 4:57 pm
- Car: 1986 Nissan 720 Z2.4
Re: carb
I tried looking but ended up buying a weber wk646 for my 84 720 2.4z. Now I'm trying to eliminate unessesary vacuum lines and being a noob isn't helping lol. I got my carb off of webers web site cause I couldn't find them cheaper
Re: carb
You can also use the Holley 5200 series carbs off early 70's 4 bangers, these are the same exact carb but they're a mirror image of the 32/36 DGEV and the Weber models are the DFAV models, all the jets and parts will interchange also. These carbs were manufactured by Holley for Weber so all the specs are identical. I got mine as a rebuilt for a '72 Ford Pinto and had to re jet it, but the carb costed me a whopping $20 off ebay since nobody else bid on it, then another $30 or so to get the right jets, and another $40 for the adapter plate... in other words, mine costed $90 in total. I did need to make a new throttle cable bracket due to this carb being the reverse of the DGEV setup, but it does perform identically and I saved about $175 by going this route instead of buying the identical Weber.
If you do plan on buying a Weber DFAV or it's Holley counterpart, the 5200, these carbs are not created equally so you'll need to look on the side of the carb body for the "26" and the 27" numbers cast on the outside of the venturis since some of the Holley 5200's will have the smaller 23 and 26 mm venturis with the 32/36 throttle plates, so before buying, look for the venturi size that's cast on the venturi bodies, or if looking on ebay at one, ask the seller what numbers are cast there. These carbs are plentiful in the junkyards, and finding a rebuilt one on ebay is pretty easy and a freshly rebuilt one will usually sell for around $75.. but you might get lucky like I did too.. there's not really a high demand for these so people don't bid on them often.
As for jetting, there's no substitute for a dyno, but you can install a wideband o2 sensor and air fuel ratio gauge to get your fuel curve calibrated to optimal. Mine tuned out with much larger jets than recommended in the forums, but the wideband don't lie, and there's a definite difference in how smooth it runs and idles as well as the extra power when you get on it. To get mine to idle at the 14.7 AFR it took a .70 primary, and a .65 secondary idle jet, then for a 12.5 : 1 AFR at cruise the mains were swapped out for a 1.50 pri and 1.55 sec with 1.55 pri and 1.50 sec air correctors, this of course is my setup and may not work for you, things like free flowing air filters and free flowing exhaust etc will require different settings. At the air fuel ratios mentioned, mine idles dead smooth at 900 RPM and will idle lower just as smooth, starts every time without the need to hit the gas, cruise is much smoother, and at full throttle, the AFR goes up to 11.5 : 1 with no stumbles when the power valve opens.
If you do plan on buying a Weber DFAV or it's Holley counterpart, the 5200, these carbs are not created equally so you'll need to look on the side of the carb body for the "26" and the 27" numbers cast on the outside of the venturis since some of the Holley 5200's will have the smaller 23 and 26 mm venturis with the 32/36 throttle plates, so before buying, look for the venturi size that's cast on the venturi bodies, or if looking on ebay at one, ask the seller what numbers are cast there. These carbs are plentiful in the junkyards, and finding a rebuilt one on ebay is pretty easy and a freshly rebuilt one will usually sell for around $75.. but you might get lucky like I did too.. there's not really a high demand for these so people don't bid on them often.
As for jetting, there's no substitute for a dyno, but you can install a wideband o2 sensor and air fuel ratio gauge to get your fuel curve calibrated to optimal. Mine tuned out with much larger jets than recommended in the forums, but the wideband don't lie, and there's a definite difference in how smooth it runs and idles as well as the extra power when you get on it. To get mine to idle at the 14.7 AFR it took a .70 primary, and a .65 secondary idle jet, then for a 12.5 : 1 AFR at cruise the mains were swapped out for a 1.50 pri and 1.55 sec with 1.55 pri and 1.50 sec air correctors, this of course is my setup and may not work for you, things like free flowing air filters and free flowing exhaust etc will require different settings. At the air fuel ratios mentioned, mine idles dead smooth at 900 RPM and will idle lower just as smooth, starts every time without the need to hit the gas, cruise is much smoother, and at full throttle, the AFR goes up to 11.5 : 1 with no stumbles when the power valve opens.
Re: carb
Quick edit on my jetting.... after my trip to work this morning, the cruise AFR was stable at 13.2 : 1 which ran just fine but when the power valve opens at WOT it goes to 11.5 : 1 like I mentioned earlier but I'm goin gto change my mains to 1.50 in both primary and secondary since the engine didn't like that AFR at WOT. If I can get it closer to 12: 1 at WOT it should be just a tad stronger around 4000 rpm where I shift out of 3rd to 4th. My main goal for this thing is to get the power up to a more respectable level mainly so this thing can keep up with traffic better on the highway etc, but the Naps Z really won't do anything too impressive until after I put a turbo on it, but with that I'll be ditching the Holley 5200 in favor of a Holley 350 which can be better tuned to accept boost.