Im looking into changing out carbs. Im not happy with the stock q-jet and thinking of edlebrock. How much difference is there between a 600 and 650 cfm? Should I spend the extra money for the thunder series or stick with the performer which is $100 less. See everyone at Big Al's this weekend.

Here's the difference's between EDELBROCK's Performer & Thunder series carbs:

-The Performers come in 600 or 750 cfm, non adjustable secondaries.

-The Thunders come in 650 or 800 cfm, have adjustable secondaries and some cosmetic differences.

Back in the day CARTER put out a chart that claimed a perfectly running small block chevy could only effectively use around 650 cfm. I doubt you will notice much of a difference between the two. Most people dont need adjustable secondaries.

Most 4x4 guys will tell you that a Q-Jet is better for hill climbing and off-angle use, but thats only if its in good running condition. Most original GM Q-Jets are getting really old and becoming un-rebuildable.

If you go EDELBROCK, I would recomend you upgrade to the OFFROAD needle and seat kit and definitely dont be affraid to take the top off and spend some time adjusting the floats.

~John

I think John would be the one who would know the difference... he sells them and probably has to know the difference because he gets that question often! BTW John- thanks for getting all that stuff in one pile for easier quicker shopping for me so I didn't have to wait for them to look up each part and possibly forget something. As it was, I forgot to add that I wanted a thermostat and housing...but I got that now. Now I am stumped on brackets for my BBC... I got a lower alternator bracket and a lower PS bracket... but need the top ones! I might end up having to order your chromie kit unless you have it is stock.

sounds like john giving you some good honest info
i agree with what he had to say . how ever stay with in your budget you can allways up grade . and gives you good trading stalk. good luck man

Is there another carb out there that would be better? Supposedly the Thunder is the best on the market but it seems everyone says their brands the best.

I have heard a lot of good things about the Holley Truck Avenger... but no personal experience since I am a small dollar guy!

I am too. I don't make much working and there always those bills to pay. Theses bogs get me through working.

We get a lot of positive feedback on the Truck Avenger for all around 4x4 use. They aren't cheap. We (General Store Auto Parts) are still selling it for $399, but that wont last long. Prices are going nuts. Summit is already up to $426 plus handling on it. Its a 670 cfm unit w/electric choke (#0-90670).

If you're just bogging and not side hilling and climbing you cant beat an old-school Holley double pumper for straight line pure performance. You can save a little money by getting a factory re-man unit. We sell a 650 DP re-manufactured for $318.99, same as Summit but w/o the handling fee.

~John

I've looked at those too. Been wondering if it would work good with the Edlebrock torker II intake manifold I bought. I haven't installed it yet because I don't want to be moved up a class. Am I going to see much improvement or should I just start building a new engine this winter? I kinda like what I hear about the 383.

well if you ask me... $318 for the Holley and $399 for the Avenger... you are tossing out $300+ out of your pocket whichever you decide on. I would suggest the better carb even if you are only planning on straight line racing... the extra $81 you are spending is so litlte compared to how much is coming out of your pocket already. If you buy the $318 carb and decide to upgrade to the $399 carb that will soon be $426... that is nearly $800 out of your pocket after sales tax and gaskets! Buy the best part the first time if you are gonna spend the money. Wish I always followed this advice myself!

I went ahead and bought the Edlebrock Performer. Installing it tomarrow. Will post the out come.

I guess if you already bought the edelbrock go out and spring for the available offroad kit for it too. It is not that expensive . As crummy as those carbs' are in off camber situations this should help some.

THe spring kit will also help with bouncy conditions too. I was going down hill over some rocks with the local IH club, and the Brown Trout kept wanting to die on me every time I suddenly dropped the nose off a rock. Inertia would keep the floats up, and the carb would thing it was full, thus starving itself.

I know, I know. But I just found this site. Now for those of you that want to make the Edelbrock performer carb. work in all conditions I have a few tricks that will make it almost as good as F.I. Call me and we can talk 467-4177