Classic Mustangs (Tech)Technical discussions about the Mustangs of yester-year.
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I'm switching out my 600cfm Edelbrock to one of those new Summit carbs. My question is what size? They come as 600 and 750cfm. I have a decent breathing 302. High rise intake bolted to 351 port matched heads, headman headers, upgraded ignition ect...
Will I gain anything by going to the 750CFM??? Will I be able to lean it out enough to run right?
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Does Summit make their own carbs or are they rebadged from another mfg? The Edelbrock Performer coincidently also only comes in 600 and 750. Maybe see if they look the same as Summit's.
The vacuum secondary carbs are much more forgiving of over-carbing. VS only
uses what it needs, whereas a mechanical secondary (double-pumper) just dumps gas down wheather it needs it or not.
I got an Edel Performer VS 750 on my stock 351C and it runs great. It increased the top end HP quite a bit over the old Motorcraft 735cfm and low end seems a little better too.
If you're drag racing, I think a 750vs would be better. For low end torque on the street, you may be better off with a 650. Tough call, it looks like you're setup for the drags, presuming you have a hot cam too. It probably
could use the bigger cfm. Maybe shoot a question over to Edelbrock or Holly.
It does have a pretty heavy cam, however its driven on the street 95% of the time. (50% of that time its driven like its on a track but that's besides the point
I'm replacing this block with a 347 stroker this coming winter, so my thought process was to go for the 750 if I can get it to run right to save me from having to swap it down the road. Sounds like I better go with the 600 though.
FYI, I have done alot of reasearch on the Summit's. Seen plenty of teardowns and bang for the buck it doesnt look like you can beat it. Its a little wrough around some of the castings, but nothing that 1hr of polishing cant fix (if it even needs it). For half the price of a comparable piece, you cant go wrong IMO.
depending on the improvements they made over the 4010 I dont know if I'd use one with a really big cam, I used a 4010 years ago on a 351w, ported 351 heads and comp 268h cam and it was a nightmare to tune, I even had to put small strands of wire into the emulsion tubes to tune it, it was super rich idling and had a transition stumble I could never cure, I swapped it onto a milder 351w in another vehicle and it worked perfect.
With a big cam I lean towards a mighty demon or holley HP because of the high level of tunability, good thing with summit is they have a great return policy, the 600 is fine for a 302 other wise a 575 demon is a good choice.
67 vert, 408 stroker 205cc TW heads, CI cust hyd roller,Dougs 1 3/4 try y's, global west neg roll,lentech aod...etc etc etc
A rule of thumb is to double your peak horsepower and that is the cfm carb you need. So if you are going to have a 325hp small block you need a 650cfm carb. If you are going to build a 500hp big block or big small block, you need a 1050. That is the old school was of thinking. Another way is to use a carburetor calculator and with max rpm the engine will see and volumetric efficiency of the engine you will get the cfm the engine needs.
Speaking from experience, there is power to be had from over carbureting but you have to live with issues you run across on the street which is often over rich conditions at certain throttle settings and poor fuel atomization.
"Yeah, were runnin a little bit hot tonight. I can barely see the road from the heat comin' off of it." Van Halen
12.20sec 1/4mi @ 115.50mph http://www.hardtohandleracing.com
The Edlebrock is finicky, it probibly just needs to be cleaned up or rebuilt. I'm just learning about carbs, so I was looking to get a cheap replacement while I tear down and learn how to rebuild my edelbrock since its such a popular carb.
One major issue with the Edlebrock is heat soak, the other is choke. Warmed up its finiky about starting. When its cold, the choke doesnt seem to do anything. (its electric and it does heat up) I have to keep cycleing the pedal for the first min to keep from stalling.
I also have a 68' Holley that came with the car to tool around with.
I have an Edelbrock 650 AVS that was having some issues. I recently took it apart and cleaned it up. There was crud in the bowls. I replaced the needles/seats, and adjusted the floats. It seems to be working good as ever now.
Are you sure the choke isn't working? Take the air cleaner off and with the car cold, turn the key on but don't start the car. Watch the choke for a couple minutes and see if it opens. Also check that it is hooked up.
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