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Discussion Starter #1
I have a 351w about to be turned into a 393 stroker that is used for circle track racing. It's already bored 30 over. This past race season was my first ever. I have to use a vacume secondary carb on there and I had an 850 on there with really big jets in it. The Motor was very laggie on the starts at 2500 rpm's. I'm trying to figure out if the 850 is to much carb for my motor or if I could keep it on there for the stroker motor but I have no clue what jets would be a good starting point if it's reasonable to keep it on there. Any help out there for me.
 

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That's a rather large carb, but can be used for the 393. The jets/springs/valve/orifices/cam you need can only be found with tuning, so start with what you have in there, and the engine will tell you what it needs.

David
 

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Re: Vacuum secondary carbs

I have seen strong-running 390+ engines with 850 carbs if that's what you mean. Whether you use a vacuum secondary or an 850 DP is do-able, but proper tuning of the combo is an absolute necessity. If you haven't tuned a carb for racing before, be sure you get some experienced help, as it will make a big difference, but will also drive you nuts if you're trying to do it the first time alone.

Carb tuning, engine tuning, chassis tuning, etc. are all skills. To be competitive in racing, you must either pay someone with the skills to help you, or develop the skills for yourself. Welcome to racing!

David
 

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Discussion Starter #5
Re: Vacuum secondary carbs

This might be the stupidest question ever but would it but would it make be possible to put the 850 metering blocks on a 750 to flow beter or is that like the most pointless thing to do ever. I'm not that sure about carbs and I kinda get how they work but no clue how to tune. Is it reasonable to combine the too carbs like use the 750 middle but everything else be 850 parts. Idk if it makes sence but I probably sound stupid. I mean I have a fully built motor but just need to figure out the carb thing to top it all off.
 

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Not a stupid question, as carbs are often modified or parts swapped to accomplish specific tasks better. However, they are done to fill a gap or need in tuning, and for a specific purpose. We're back to tuning. Without knowing what it needs to perform best, you can't know what mods to make—if any—to do that. Same goes for ignition tuning. So, unless you can grab a racer buddy or pay an engine pro, you will have to break-out the books and begin learning how to do it yourself. What are your competitors using? How are they tuning it for fuel? What do they use for ignition and how are they setting it up?

I can't say how yours needs to be set-up, as there are all kinds of restrictions to specific classes, and variables to different cars and tracks—even drivers. Start talking to some of the other racers you've met at your track, and hit some of the web sites and forums for your particular racing class. Learn everything you can, and you will start to see what you need to do and why. Then, it's only a matter of knowing how, if you didn't learn that at the same time. Build your skills. As you have already found out, it's not all about driving. The driving is only to prove everything else you've done.

David
 

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Discussion Starter #7 (Edited)
Does it really mater that the rest of my class is Chevys. I am the one and only proud Ford in my class of 28. Problem is I'm up against guys that have no clue about anything to do with a ford. Were not aloud stroker motors and a 750 carb is supposed to be the biggest were able to use. But if u saw these Chevys you emeditly know there over 366 cu in. So I'm just bettering myself a little bit lol. Cuz my driving skills are way below par. But I've got 2.02 1.60 heads. 580 lift lunati cam KB forged flat tops scat commecting rods just need crank. Duel plain intake Mallory ignition coil only aloud. Do you know of any circle track forums that are helpful in the street stock divisions. I rally didnt get to know many ppl out at the track being the new guy in the class and being to Only ford. They kinda shuned me. But that's typical Chevy guys. Our class is more like run what you brung don't ask don't tell. Rules ate pretty much out of the water in this class. So it's hard trying to figure out what all I need to do cuz my motor was built to the rules this first time. But soon to be not anymore.
 
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