God bless Lars! Re-jetted carb and it's a whole new ballgame! <long>
02-26-2002, 03:34 AM
#1
Drifting
Thread Starter
God bless Lars! Re-jetted carb and it's a whole new ballgame! <long>
I've posted a bit about this the last few days.
Based on a string that was posted about the differences between the Edelbrock carbs and original Q-jets, I found out that my carb was jetted for a 75 Chevy Pickup :cry
With much coaching from Lars, I dove into my first carb teardown.
What an adventure this has been! I put the carb back together per the spec in his tuning guide (even measured the secondary rod holder length, which interestingly Edelbrock had set perfectly at 41/64ths per Lars spec)
Everything went apart and back together smoothly, and while I was checking all the linkages I found another problem -- turns out that, for some reason, there wasn't enough leverage for the throttle cable to pull the secondaries open more than a crack! (Maybe 30deg max!). So, on top of having poor jetting, my secondaries weren't even opening -- I was running basically a two-barrel carb all this time! :crazy:
It's amazing how you can spend so much time around a car and never check the simple things.
Well, I installed a really small hose clamp to act as a "spacer" to move the cable back enough to allow full movement, so now I'm getting full WOT.
Also, (and again I'm not sure why this is happening), the car is now pulling a steady 18hg of vacuum. That's actually up 1hg from before (best I could ever get was a steady 17hg). Not sure what's causing that, but seems like a bonus! I know this is true because I was just checking my vacuum last weekend.
Took the car out for a drive tonight and it was like a whole new experience! Funny thing is, I've always enjoyed the car and felt it had decent power (nothing compared to the C5, but good). Well, I've NEVER felt a surge before like I have now. I can feel the secondaries kick in and the car pulls all the way to 4500 before downshifting (it's an auto). Before there was nothing happening at WOT and it would just groan until the RPM's dropped. I always thought it was a lack of top-end on my L48. I'm wrong.
And don't even get me started on the off-idle performance! The car also has noticeably more power on the low end - very smooth (I thought it was smooth before) -- I barely touch the throttle and the car MOVES!
In the last month the combination of installing 1.6 ratio rockers and re-jetting/tuning my carb has made me appreciate this car 200% more. The engine has really woken up. It's still not to the C5 level, but now I'm far less scared of taking on some competition in this car.
As you can tell, I'm really excited. Sorry for the rant! Lars is the man. He's the kind of guy that makes this place what it is.
:cheers:
Based on a string that was posted about the differences between the Edelbrock carbs and original Q-jets, I found out that my carb was jetted for a 75 Chevy Pickup :cry
With much coaching from Lars, I dove into my first carb teardown.
What an adventure this has been! I put the carb back together per the spec in his tuning guide (even measured the secondary rod holder length, which interestingly Edelbrock had set perfectly at 41/64ths per Lars spec)
Everything went apart and back together smoothly, and while I was checking all the linkages I found another problem -- turns out that, for some reason, there wasn't enough leverage for the throttle cable to pull the secondaries open more than a crack! (Maybe 30deg max!). So, on top of having poor jetting, my secondaries weren't even opening -- I was running basically a two-barrel carb all this time! :crazy:
It's amazing how you can spend so much time around a car and never check the simple things.
Well, I installed a really small hose clamp to act as a "spacer" to move the cable back enough to allow full movement, so now I'm getting full WOT.
Also, (and again I'm not sure why this is happening), the car is now pulling a steady 18hg of vacuum. That's actually up 1hg from before (best I could ever get was a steady 17hg). Not sure what's causing that, but seems like a bonus! I know this is true because I was just checking my vacuum last weekend.
Took the car out for a drive tonight and it was like a whole new experience! Funny thing is, I've always enjoyed the car and felt it had decent power (nothing compared to the C5, but good). Well, I've NEVER felt a surge before like I have now. I can feel the secondaries kick in and the car pulls all the way to 4500 before downshifting (it's an auto). Before there was nothing happening at WOT and it would just groan until the RPM's dropped. I always thought it was a lack of top-end on my L48. I'm wrong.
And don't even get me started on the off-idle performance! The car also has noticeably more power on the low end - very smooth (I thought it was smooth before) -- I barely touch the throttle and the car MOVES!
In the last month the combination of installing 1.6 ratio rockers and re-jetting/tuning my carb has made me appreciate this car 200% more. The engine has really woken up. It's still not to the C5 level, but now I'm far less scared of taking on some competition in this car.
As you can tell, I'm really excited. Sorry for the rant! Lars is the man. He's the kind of guy that makes this place what it is.
:cheers:
02-26-2002, 09:56 AM
#3
Drifting
Re: God bless Lars! Re-jetted carb and it's a whole new ballgame! <long> (Corellian Corvette)
What is with the Chevy/GMC pickup carbs on the Vette's? About a month ago,I had sent my carb in to Lars for a rebuild, Lars said I had a 75 76 GMC carb and it was jetted too lean for the Vette. He rebuilt the carb and re jetted it and the car runs great.
Just wondering how many others have truck carbs on their Vette's.
Just wondering how many others have truck carbs on their Vette's.
02-26-2002, 10:17 AM
#4
Platinum Supporting Dealership
Re: God bless Lars! Re-jetted carb and it's a whole new ballgame! <long> (1LE)
He is definately THE man. How about taking a look at my Suzuki Samurai carb Lars? Got a loaner one? :D
02-26-2002, 10:21 AM
#5
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Member Since: Feb 2002
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Re: God bless Lars! Re-jetted carb and it's a whole new ballgame! <long> (1LE)
Just as a quick Q, what did Lars charge for that? I have a holley 650 on mine now, and I am pretty sure it is jetted and adjusted poorly for my engine...
02-26-2002, 03:11 PM
#6
Drifting
Thread Starter
Re: God bless Lars! Re-jetted carb and it's a whole new ballgame! <long> (Black68Vette)
Actually, my carb was a brand new Edelbrock 1901!
I think the reason so many of us have "truck" carbs, is that Edelbrock, or whoever rebuilds these, use a really generic rod/jet setting. If you're not on this forum, or don't have access to Lars' tuning paper, you would never realize how MANY different combinations there for each year of Vettes -- and even within years depending on engine/tranny combos!
Edelbrock couldn't possibly build all these different combos so they use a generic "it'll work off the shelf" setup. I'm sure many of our cars previous lives have had carb rebuilds by non-experts who used generic setups as well. My old carb, which was original to the car but rebuilt, had the jets/rods changed and used (as Lars called them) "Generic commerical carb builder" parts. That thing never worked right.
So the lesson here? If you aren't the original owner of the car, or haven't rebuilt the carb before, take the darn thing off, tear it down, clean it, and set it up with the correct rod/jet setting in Lars paper. I bet a lot of people will be surprised what they find!
I think the reason so many of us have "truck" carbs, is that Edelbrock, or whoever rebuilds these, use a really generic rod/jet setting. If you're not on this forum, or don't have access to Lars' tuning paper, you would never realize how MANY different combinations there for each year of Vettes -- and even within years depending on engine/tranny combos!
Edelbrock couldn't possibly build all these different combos so they use a generic "it'll work off the shelf" setup. I'm sure many of our cars previous lives have had carb rebuilds by non-experts who used generic setups as well. My old carb, which was original to the car but rebuilt, had the jets/rods changed and used (as Lars called them) "Generic commerical carb builder" parts. That thing never worked right.
So the lesson here? If you aren't the original owner of the car, or haven't rebuilt the carb before, take the darn thing off, tear it down, clean it, and set it up with the correct rod/jet setting in Lars paper. I bet a lot of people will be surprised what they find!