Time for a change.
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Laughing Gas
Joined: Dec 2010
Posts: 924
Likes: 1
Time for a change.
Hey guys I know I have been visiting as often as used to but as of late nothing has change with my truck but last couple of times I've driven my truck I feel like I could get more out of it. Also I'm looking for a change in carburetor again. I have a street demon 625 cfm I bought it new I had it on my f250 for a while and the power is there with that carb but I'm not sure if the 625 would be to much i currently have a eddy 500 on there I feel like it's a bit underpowered. Also I'm still looking to changing the gearing in my differential. I know that will help much.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
The most the Street Demon could do is give you better throttle response, but it won't add more power. A bigger carb does not equal more power unless the engine is under carbureted. A 500 is plenty big enough. I have a 450cfm on mine, and it has enlarged valves, port and polish, and raised compression ratio, etc. and it'll set me back in my seat.
As FTF said, look elsewhere for more power. Gearing would definitely help.
But, give the 625 a try. It's usually just an hour or two to switch out a carb (when it's a different design), so give it a whirl, especially since you have it on hand.
As FTF said, look elsewhere for more power. Gearing would definitely help.
But, give the 625 a try. It's usually just an hour or two to switch out a carb (when it's a different design), so give it a whirl, especially since you have it on hand.
Tuned
Joined: May 2013
Posts: 396
Likes: 5
From: Ottawa, Canada
I have the 625 street demon on my built 300. It can be tuned to get very good milage on the highway if you have an AFR guage. I will say it is a bit challenging to get it dialed in right. I have my secondary jets set at around 15 sizes bigger than the tuning kit comes with and I may have to go bigger still. However my truck has a 4 inch lift, 35s, 4wd, built 300 and a lead foot but gets 16l/100km (14.5mpg) mostly highway.
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
Having to go fifteen or more sizes up in jet size is an indication that there is insufficient venturii vacuum signal to pull in the main jet flow; which is a good indication that the carb is sized too large for the engine.
Tuned
Joined: May 2013
Posts: 396
Likes: 5
From: Ottawa, Canada
I figure the 625 is way to big as well, I should have went smaller. The other issue with it, the secondaries open part way mechanically after about half throttle and the engine can't take it. The primaries work very well though.
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