Carb cfm stock?

[guitarfreak235]

Just curious what would the 4 barrel carbs cfm be on a stock 86 305 with electric choke?

 

[Jims86]

750....But I think they tune that down for smaller engines with the Upper butterflies on the secondaries.

 

[guitarfreak235]

Ok so there is no reason I get a new carb correct? Does upping the cfm increase power or would it just be too much?

 

[Jims86]

Ok so there is no reason I get a new carb correct? Does upping the cfm increase power or would it just be too much?

If your engine is stock, with the stock manifold, you do not need, nore does your engine have the ability to use any more. If you are experiencing power issues, you are better off making sure the carb is working correctly, and you have a mechanically sound engine, I.e; good compression, good tune up, clean filters...and then make a plan based on that. a 305 was only rated at 155-160 from the factory in the first place.
If you have a vacuum gauge, you can tune that carb for optimum performance, unless it needs an overhaul. I would recommend staying with the q-jet...its the best you can get.
Even if you were to install a high flow top end like heads, cam, manifold, I would still stay with the q-jet.

 

[guitarfreak235]

Ok thanks reason I ask is I soon will be in a position to do some major work on the truck and wanted to see If it would improve performance. I know I will be doing dual exhaust and headers. Not sure about cam etc

 

[HotRodPC]

Unless your going to be doing some biggo work, a 600cfm carb is plenty for small blocks up to 350cu in. I've heard of 500cfm's being used on 305's and it didn't hurt performance at all, but increased off the line performance and added 1.5 to 3 mpg to the vehicle depending on other paramters like intake used or exhuast set up. 305's are called Wee O Five's for a reason. Not a power house by any stretch, but tuned right they can actually do better on mpg than most might think. I've even heard of a guy getting 18mpg with a 267cu in V8, w/ a 500cfm, 3.08 gears and a Th350.

 

[Jims86]

A good wee oh five, With a good breathing exhaust, no larger than 2" dual, should push close to 21-22 mpg with a properly tuned q- jet. in that truck.