Demon 625

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gtxdude

gtxdude

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Currently running a 600 eddy on a mild 318. Runs fine but wondering if a Speed Demon 625 might give me a little more pop plus better mpg then my 600 eddy. Just looking for some feedback before making a decision. Currently I get a little over 15 mpg on trips, 3:23 gears. Thanks for any feedback :)
 
I swapped a 600 holley 1850 for a Demon 625 and was very happy. Better cruise and that big goggle valve worked well 3.55 gear
 
gtxdude said:
Currently running a 600 eddy on a mild 318. Runs fine but wondering if a Speed Demon 625 might give me a little more pop plus better mpg then my 600 eddy. Just looking for some feedback before making a decision. Currently I get a little over 15 mpg on trips, 3:23 gears. Thanks for any feedback :)
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15 on trips isn't bad. I have found with a 3.23 gear and 55-60 mph will get me almost 20 with a 600 Edelbrockon myHp 273 or the stock 2 barrel on my 318.
 
I put one on the 361 in my Charger. I averaged 13-14 mpg on the trip to Carlisle, but that is on a 4000 plus pound car.

IMG_20210724_123640.jpg
 
Yes, it is much better than the AFB that was on it. It does have a bit of a bog when the secondary kicks in that I have not been able to completely tune out.
 
Don't you just love it with:...much better than the AFB but.....does have a bit of a bog.
Leave the Edel on, it is the best design!
 
I have one on my 75 F250. 351M, T18 four speed, dana 60 with 3.73s. I love it. Runs great, gets incredible mileage for what it's in and zero bog. Yes it sounds like a Thermoquad.
 
Had the Dart out a couple of times today and it really does run pretty good. My trouble is every couple of years a see something new and shiny and think I should shake things up. Going to stay the course with what I'm running now. Maybe this winter I'll get the itch again :)
 
RustyRatRod said:
I have one on my 75 F250. 351M, T18 four speed, dana 60 with 3.73s. I love it. Runs great, gets incredible mileage for what it's in and zero bog. Yes it sounds like a Thermoquad.
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Planning on finishing Route 66 this Sept from Chicago to Kansas where we started last fall going West. We were going to do it this May but the weather was terrible so we pushed it back to fall. Hope you'll follow us
 
Spent the last few days tuning the 625 Demon on my 360LA.. runs great! The smallish primaries make it really responsive and the goggle secondaries are really effective.

FWIW these things are fat out of the box. If you have a lot of cam and compression you will probably not need to do much. If you have a more mild build like mine you will wanna tune it down. It came stock with an 80 jet in the primary. I stepped that down to a 74 with a .060-.050 metering rod & stepped the secondary jet down from 80 to 78.

GL!
 
Thanks for the info. I am running mine on a mild 361 big block and figured it was fat. The plugs are a bit dark. Could you get away with just a primary rod change with the stock jets?

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qkcuda said:
Thanks for the info. I am running mine on a mild 361 big block and figured it was fat. The plugs are a bit dark. Could you get away with just a primary rod change with the stock jets?

View attachment 1715964878
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That will thin it out a bit, but likely you will need a smaller jet. I went all the way up to the biggest rod in the kit .064-.056 with that 80 jet and it was still too fat. Then the 76 jet.. still too fat. The 74 with the .060-.050 did the trick with the smaller secondary jet.

Plugs I pulled this am. Dunno why it put my photo all the way up there...lol.
 
Are you running a wideband? I had one on my cuda but not on the Charger. Just worried about leaning it out too much.
 
I've no doubt mine is fat on the 351M in my truck, but it runs GOOD so I've never messed with it. Never even gave the plugs a read. I probably should. I bet I could make the mileage pick up a little.
 
RustyRatRod said:
I've no doubt mine is fat on the 351M in my truck, but it runs GOOD so I've never messed with it. Never even gave the plugs a read. I probably should. I bet I could make the mileage pick up a little.
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But if she's happy what the heck.
 
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