Alright I've got a holley 650 w/ mechanical secondaries and a 700r4 transmission. I've read that mechanical secondaries are better when you have a manual transmission. Anyway heres the problem. When I drive the car normal it runs fine but it seems like there is more power at like 3/4 throttle than when I have it wide open, and when I floor it from a stop it cuts out and doesnt go anywhere. Is this because I have mechanical secondaries with my auto or is there some other problem?

 

Maybe the carb needs jetted down. What kind of cam are you running? You might need alittle higher stall converter to get away with the mechanical secondaries so you don't dump all that fuel at low RPM's.

 

Sounds to me like it needs jetted up.... when the secondaries open farther, there's more air, which needs more fuel to go with it.

You may also find you need to raise the power valve number.

Sounds to me like, overall, you need to do some carb tuning.

The easiest way to avoid having it bog when you stomp it to the floor, is to not do that. A mech sec carb works perfectly fine with an auto trans; however, it requires that the driver learn how to operate it. A vac sec carb, or an air valve carb (either a spring-controlled one like a Q-Jet, or a Stone-Age weight controlled one like a Carter/Edelbrock), protects the engine from that particular driver inexperience error, by modulating the actual secondary air input downwards to a level that the engine can use no matter how far the driver opens the throttle; a mech sec one does exactly what the driver tells it to do, right or wrong.

Do a search on this forum for my userID and the phrase "transition slot"; there's alot of Holley tuning info in posts that talk about that. If you've just got a Holley and took it out of the box and stuck it on your car just like it came, there's ALOT you can do to tailor it to your engine's requirements. It will never really run right until you do that. Every engine is different, every car imposes different requirements on its different engine, and every carb is different; there's no way Holley can sell you a carb that's perfect for your random combo of parts. It's just like the EFI guys, tuning their chips; chip tuning is the same thing as carb calibration and distributor curving, it's just done mechanically in the one instance and electronically in the other.

 

When I tried jetting it down it cut out even sooner at a lower RPM, so I figured it needed to be jetted up, but I was going to wait until I swap over to a TH350.

 

If your 700r4 has a stock (low)stall converter and you have a 2xx series rear gear the mechanical Dp carb is going to "over- carb" the motor at low rpm. Raising the secondary float level will help. installing larger acelerator pump shooters and trying different colored accelerator pump cams and increasing the secondary jetting will help too. remove any carb spacers/adapters.

 

On a 310 CID engine, you should be able to go WOT with a 650 DP as long as the RPMs are above ~1500 - IF it is properly tuned.

If your converter stalls below that - you need higher stall.

The "no DP with auto transmission" thing is an overstatement. Holley tells the whole story here http://www.holley.com/HiOctn/TechSer...fo/TI-225.html .

 

Right now I have a stock torque converter and I believe 3:08 gears, but like I said I was planning on swapping to a th350 and probably going to go with a 2400 stall. I'm also using the stock intake right now, so there is an adapter. What would be a good intake for the low end power?

 

Dual plane.

Since you're planning on 2400 stall, the RPM or Stealth type manifolds would be fine, since their powerband starts at about 1500.

 

Alright cool, thanks for all the info.