Qjet vs. Edelbrock cleared up by Lars
02-19-2002, 10:39 PM
#1
Racer
Thread Starter
Qjet vs. Edelbrock cleared up by Lars
I asked Lars about the differences in the Qjet vs. Edelbrock. I recently openned up my Edelbrock that a previous owner had installed and couldn't see any noticable differences except for the torx head screws. However based on its performance, I knew there was something amiss with it having 73 jets. Here are the differences that Lars helped me with. I guess I am going to have to go get some larger jets to try. I only had up to 72's in my drawer. Lars thought you guys would like to see this too. Hat's off to you Lars. :flag
" Forest,
I saw your post and question on the Forum regarding the performance of your
Edelbrock Q-Jet. I can't post to the Forum from my work computer, so I'm
sending you this via e-mail. You might want to post this up in that topic
folder so others can see the answer to your question:
The Edelbrock Q-Jets are exact reproductions of the old Rochester Q-Jets
(they're using the actual old molds). However, the post-75 versions with the
electric choke system on them are the truck carb versions, and have the
truck metering rods in them. What this means is that the power tips on the
rods are not the standard .026" diameter tips, but are the fat .036" tips.
If you have a set of #73 jets in your carb, but you have the fat truck rods,
you're getting the same WOT metering area as if you had a set of #68 jets in
that carb with a set of the "regular" passenger car rods. In order to get
your WOT metering area up to the same as a #73 jet with standard rods in it,
you have to step up to a pair of #77 jets with those fat truck rods. So
step those jets up in size a few notches, and I'll bet your performance will
pick up accordingly.
Lars "
It makes sense and I do like the idea of the electric choke and a tight butterfly baseplate for where I live. I will try the larger jets in a few days. Thanks to Lars, I may become a Edelbrock fan. I have always been a Qjet fan after an oldtimer show me how to properly rebuild one and to "ALWAYS" replace the float if it is more than a year old.
Phlash 72 BB Roadster
:seeya
" Forest,
I saw your post and question on the Forum regarding the performance of your
Edelbrock Q-Jet. I can't post to the Forum from my work computer, so I'm
sending you this via e-mail. You might want to post this up in that topic
folder so others can see the answer to your question:
The Edelbrock Q-Jets are exact reproductions of the old Rochester Q-Jets
(they're using the actual old molds). However, the post-75 versions with the
electric choke system on them are the truck carb versions, and have the
truck metering rods in them. What this means is that the power tips on the
rods are not the standard .026" diameter tips, but are the fat .036" tips.
If you have a set of #73 jets in your carb, but you have the fat truck rods,
you're getting the same WOT metering area as if you had a set of #68 jets in
that carb with a set of the "regular" passenger car rods. In order to get
your WOT metering area up to the same as a #73 jet with standard rods in it,
you have to step up to a pair of #77 jets with those fat truck rods. So
step those jets up in size a few notches, and I'll bet your performance will
pick up accordingly.
Lars "
It makes sense and I do like the idea of the electric choke and a tight butterfly baseplate for where I live. I will try the larger jets in a few days. Thanks to Lars, I may become a Edelbrock fan. I have always been a Qjet fan after an oldtimer show me how to properly rebuild one and to "ALWAYS" replace the float if it is more than a year old.
Phlash 72 BB Roadster
:seeya
02-20-2002, 03:37 PM
#2
Drifting
Member Since: Sep 1999
Location: Wylie TX
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Re: Qjet vs. Edelbrock cleared up by Lars (Phlash)
Phlash, I've got the same carb and have been playing around with jets and rods. I also have an O2 sensor with an A/F gauge.
I have found that the 75 jets (about the same as the 71 with the older .026" tipped rods) are the best in my application at WOT. Your's may (and probably is) different, but if you cannot get the jets locally make sure that you get a good assortment. I ended up getting 75 and 77 jets.
I'm also running the 48 rods with them lifted up a tiny bit via the adjuster which the power piston assembly seats against during high vacuum conditions. At the stock adjustment location, I was running lean at cruise. I'm acutally running rich at cruise right now and my next step is to drill out the plug on the airhorn and tap for a threaded plug so I can make this adjustment without pulling the air horn. As it is, my cruise and WOT A/F ratio are the same.
I have found that the 75 jets (about the same as the 71 with the older .026" tipped rods) are the best in my application at WOT. Your's may (and probably is) different, but if you cannot get the jets locally make sure that you get a good assortment. I ended up getting 75 and 77 jets.
I'm also running the 48 rods with them lifted up a tiny bit via the adjuster which the power piston assembly seats against during high vacuum conditions. At the stock adjustment location, I was running lean at cruise. I'm acutally running rich at cruise right now and my next step is to drill out the plug on the airhorn and tap for a threaded plug so I can make this adjustment without pulling the air horn. As it is, my cruise and WOT A/F ratio are the same.
