Triple Weber carbs for L28 follow-up
GERRY ROOP
All,
Back in July I sent out a question to the Zroad group about the pros and cons of using a triple Weber carb setup on my L28 to replace the Holley 4bbl that had always been a source of problems for me. Thanks to your responses and subsequent discussions, my Z is now running better than it has ever run in the 32 years I’ve owned it. For those of you mildly interested, here is the rest of the story.
More than one of you wrote to say that your Holley setup was (or had been) completely satisfactory, which got me to wondering what might be different/incomplete/incorrect with the way my car was configured. In poking around on the internet, I stumbled on a picture of a Holley oriented perpendicularly to the engine, which was different than the way my carb was positioned. The discussion about this orientation said that it was necessary because of the need to evenly distribute the air/gas mixture to all six cylinders. When I converted my car to the Holley, some 20+ years ago, the only manifold I found then was a Clifford, with the parallel orientation. Well, this was a head-slapping moment for me, since in retrospect it is obvious the primary barrels would tend to favor cylinders 1-2-3 with the (old) parallel setup.
Not really wanting to spend the money for the Webers or EFI, I ordered a new intake manifold from Dave at Arizona Z Car in Phoenix. But during installation, I discovered that there was an interference with the #2 tube of the exhaust header. So a friend came over to my place with an acetylene torch and we heated/bent in the header some to clear the new intake. (I was concerned that this might affect performance, but it hasn’t seemed to so far.) Of course, I needed new throttle linkage now, so I installed a Lokar brand throttle cable and bracket.
With this setup, the car ran better, but still had the usual issues, to a lesser degree, than it had before – flat spot during acceleration, poor idle, etc. My tuning skills are average, at best, even with an exhaust gas analyzer, but I soldiered on anyway and experimented with different primary jet sizes. Success was limited. Luck seemed to intervene at this point, and I discovered a shop in Loveland with a Dyno.
Scott at Automotive Performance did his thing, and it run like a different car now. He installed slightly bigger primary jets (from .049 to .050), and increased the accelerator pump nozzle from 25 up to 33. He also found a small gas leak inside the carb due to a bad O-ring. Timing-wise, he said that the quality of today’s pump gas is such that using vacuum advance is no longer recommended, so he set the timing, at idle, to 15 degrees BTDC, relying strictly on mechanical advance for higher RPMs. Scott’s Dyno recorded 143 rear wheel HP at 6000 RPM.
Since my car is not headed to the track, no effort was made to optimize each setting and squeeze out additional HP. No doubt, there are ways to improve performance further, but it’s a fun car to drive now, and I appreciate your help in getting it fixed. Thanks.
Gerry Roop
Ft. Collins
j...@smithautomotiveartwork.com
--
You received this message because you are subscribed to the Google Groups "ZRoad" group.
To unsubscribe from this group and stop receiving emails from it, send an email to zroad+un...@googlegroups.com.
To post to this group, send email to zr...@googlegroups.com.
Visit this group at https://groups.google.com/group/zroad.
For more options, visit https://groups.google.com/d/optout.
Daniel Bailin
Daniel