Jump to content
Sign in to follow this  
Drummerbro44

38/38 weber jetting

4 posts / 1156 viewsLast Reply

Recommended Posts

I have a 38 on a 9.5:1 with a mild cam. I have great low end torque but my mid to high range RPMs dont produce the amount that I want. What jetting do you guys recommend for this setup so I can get good torque throughout all RPMs.

Chris

Share this post


Link to post
Share on other sites

Based on lots of experimenting, a wideband A/F gauge and the advice of others, I can offer some general comments (which you probably already know). Have a look at your plugs after some higher rpm driving and if they are very light tan to grey then you're lean. Tan to light brown is better. Light to medium brown is getting into power.

Idle jets mainly effect the 0-2500 range with normal throttle inputs (ie not foot to the floor and pop the clutch). It sounds like you have this dialed but I tend to favor a little richness.

Main jets run mid range 2500-4000 and beyond which corresponds to more throttle and highway cruising. I would try going up one jet size from what you currently have to see what the difference is. If the 4500+ is still weak then it's on to the air jets.

The air jets allow you to tune for best power at WOT by effecting the air/fuel ratio at higher rpm. One size smaller will richen and one bigger to lean. I would go at least one size smaller then your current.

Most of what you're after will be found with the main and air jets. If you have decent performance low and mid then go smaller air jets to richen the A/F at higher rpms. My vote for first change is at least 10 points (ie 195 drops to 185) on the air and see what that does. If you notice a change then increase the mains by 5 (ie. 145 - 150).

Experiment to find what works best. You can do the same program to tune for best economy, best performance or best all round combination but the first two are mutually exclusive (sigh). Downdrafts are a blunt instrument but simple and reliable with great power to 4500-5000 and then diminishing returns.

Doug

Share this post


Link to post
Share on other sites

Thank you very much Doug. Your info is a great help. Im going to go futz around with the damn thing now.

Chris

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  



×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.