Got out for a drive this morning. Ran like E36 M3. Worse than it did with the exploder cam. Was kinda bummed out.
Removed the Holley 670 and tossed on an Edelbrock 750 that was in my buddies spares inventory. Little big, I know, but lord did this thing wake up and run well.
Fuel mileage tbd
Pete
The engine doesn't care if the carb is "too big", it just cares about mixture and atomization.
It sounds really backwards to me that an Edelbrock worked better, my experience with Edelbrocks has been generally far less than good, unless you were a fan of lean stumbling while simultaneously running so rich the plugs foul (a sign of really bad atomization), buuuut those were the cars I worked with and none of those were your car. Maybe I got the bad ones, or you got the good one, or ?
In reply to Pete. (l33t FS) :
I would have prefered a 600, but this is what was sitting around.
My understanding is that the 600 would just provide better atomization at low rpm than the 750 .
If the weather holds I will go for a run and see how the mileage turns out and what the plugs look like.
In reply to Pete. (l33t FS) :
I'm also not a edelbrock fan but the mustang guys with the 289s and 302 swear by them, saying drivability and power is great right of the box.
I've got a Rochester from the Rochester doctor I'll run on my 302 unless my pops puts it on his 57 first then I'll probably just put an edelbrock on it
I'm sure you now this, but it has little to do with the carb itself. Any carb can be tuned to run well, its just that some are engineered to favor certain characteristics. Qjets are the drivabililty queens, Holleys are the power queens, and Edelbrocks are the simplicity queens.
You have changed enough about the engine that the 670 just needs re-jetted and tuned to the new parameters.
Oversizing a carb might hurt you a little in the midrange if you go nuts, but it might get you a few ponies up top. That's the thing that many of the hotrodding magazines get wrong. They do a carb shootout between the big three and "the Holley is the clear winner with 6 more hp" and pay zero attention to what it's like in the rest of the range. It might give up 15 torques at 3500 rpm and be a wicked bear in the cold, but yay... 6 more hp which you can't feel unless you're chasing that last .05 seconds at the strip.
90% of us drive between 0 and 75% throttle. Dyno tests in magazines show you WOT. Then hotrodders clamor to put an (insert carb) on their daily driver and end up going in the wrong direction because "magazine said so."
Either one of those carbs will do well for you. The Edelbrock tends to take very linear stabs at metering as it is pretty basic in the engineering category. Holley is another step in the engineering direction and does really well at WOT. Qjet is a complex thing, but it is the single most accurately metering carb you can get which will make it a wonderful daily driver with easy cold starts and throttle response.
There was something amiss with the Holley: It has 4 idle jets and only the PS rear was having any effect when I tried to tune it for the new cam and manifold.
Its running better than ever and I am at the end of the season. Might keep an eye out in FB marketplace for a dual plane and a 500 or 600 Edelbrock for future considerations. There is a sick voice in my head that wants to try the fitech now that the engine is happier and it has a single plane intake that works better than dual plane with TBI. But I dont think I will.
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