Should I change my carb?

[beastliketha]

I have a 1973 Charger SE 318 with 360 heads, Edelbrock 318/360 performance intake, ect.. Who ever had the car before me put a Rochester Quadrajet 17086004 (can't find it now but thought I saw somewhere that it puts out 750-800cfm). My unlce told me they are great but my friends dad said he would switch to a lower cfm Edelbrock carb. He said he thinks the carbs for a big block engine and puts out too much cfm for the engine. Would just like some opinions (not based on if you like quadrojet or edelbrock, but based on is it worth the money to put a different carb onto the car). Thanks!

 

[Montclaire]

It all depends on the carb. You could use a 1000cfm carb on the same engine if it is set up right. The thermoquads had huge secondaries, I don't know about the quadrajet. The real question is, how does the car act? If it is running well, and the plugs look good, I'd keep it the way it is. My only concern is, if the car is an auto, what kind of cobbled linkage they have for the kickdown.

Another thought, I know that after the thermoquad was retired, mopar did run rochester carbs for a while. See what they had on the cop motors in the 80s, which were 318s with 360 heads (and awful port mismatch from the factory) it's probably a carb close to what you've got on there.

 

[rumblefish360]

No, keep it, size or CFM rating is t the issue. Reason being is that the engine will only draw as much from the carb as needed. Also being that it is a spreadbore, the small primaries are very good for general driving and mild acceleration.

When you step into it, wide open throttle, the way the carb is designed will only allow (as per engine demand) as much opening of the secondary side as needed. I have seen video of a 305 Chevy with the camera perched overhead showing only a partial opening of the secondary side.

The overall CFM ratings of the Rochester Quadrajets vary from year to year so knowing exactly which one you have is a big help to you. I have personally used the big TQ on mild 318's before without issue. Rejetting the carb is all that is needed to be done.

Now had this been a Holley or Edelbrock 800, I'd say that the comment of to big a carb actually has a leg to stand on, but, this is not the case. Even if the QJ is an 850.

 

[terzmo]

650 on that motor and it will run better and faster...750+ is far too oversized

 

[rumblefish360]

Squarebore, probably, spreadbore, doubt it, I'll wager monies on it.