Best 4bbl

12many said

Well I don’t know what to say when it comes to the cost of a carb kit that comes with the correct primary and secondary jets, the multitude of metering rods, and all the springs. If a guy wants to spend time and money ordering individual pieces have at it. The 750 kit DOES NOT give you duplicate rods. You get a set of richer and a set of leaner, sane with the primary jets. Pretty sure the 625 kit doesn’t come with a duplicate set of rods either IIRC, just 3 sets leaner and 3 sets richer, along with more primary jets than the 750 kit. First pic is the 750 kit, second the 625:View attachment 1715772842View attachment 1715772843


Best of luck on those Edelbrock springs working, they’re not the same dimensions as those used in the Street Demon. Thought I could use the Edelbrock #7 springs but no go.
The colors and strengths of both are not the same. All I can say is when it came to properly dialing in the light throttle, light acceleration, heavier throttle and WOT I was able to really zero in on each circuit using the kit as I drove and tested. I had a chart I made up of all the rich to lean combos of rods and jets. Knew exactly the combos I needed to fine tune.
The carb is one of the cheapest in cost as it is, and adding in the kit combined is still cheap, gives you all you’ll ever need, and if/when you ever sell the carb the kit goes with it for the next guy that obviously won’t have the same engine.
Buy the carb and kit and be done or buy only what you need, modify something else to fit. Not me. Gimme the kit with the carb.

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So I'm pretty known out here for not getting on the Internet and saying buy this and buy that..
Here's my point you get a new carburetor and you slapped on and pretty much don't have a prayer of it running correctly but you drive it and see what it does so you know what to do with it. If you're like me or like you probably haven't AF gauge.. and like my customer that I'm working on is 750 today. It's rich in the primary and the secondary not by a whole lot but it is rich. We ordered one set of metering rods one set of primary Jets and one set of regular Holly jets for the secondary....
In my case I have two 625 Street demons and they're not even using 625 metering rods or jets.. kind of a mixture of 750 and 625 stuff... And since I have two carburetors that would have meant ordering two 625 and two 750 kits... In the end I bought probably enough stuff to build up to one kit to get them correct.. and it took more than a dozen tries and probably weeks worth the research it's been a couple years now.. I actually drilled 9/16 holes in both sides of my secondaries.. a trick I learned from online research where the only known Street demon dual-quad application was ever written about... A lot of what I learned about tuning dual carburetors was from the Edelbrock site and what they actually put in there dual quad setup...
Apparently you've done like me a side by side comparison of the step up Springs and found that the Holly Street demon Springs and the Edelbrock Springs have the same coloring pattern except the Holly uses a I can't remember if it was a six or the seven greenspring Factory but the Edelbrock offers the other one. I think I'm using the pink edelbrocks and the orange edelbrocks in mine.. also I changed the squirters for a larger pump shot and those are holly... I'm definitely don't come in a kit...
I'll report back later today on how the $20 my customer spent on the next step down for his jetting worked whether I was wrong or right... That will be a straightforward application where mine is terribly unique... Also really wouldn't recommend dual quad Street demons for most as they don't have an infinite amount of metering rods and primary Jets like edelbrocks do... I have about 12 different available metering rods and primary Jets where Edelbrock has hundreds...