AFR 195 CC eliminators....what to do with carb tuning?
11-08-2006, 08:50 AM
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AFR 195 CC eliminators....what to do with carb tuning? I dont know a great deal about carb tuning. I can only assume that I am now undercarbed since I upgraded to the AFR 195 cc Eliminators. I am using a Holley 670 street avenger that is box stock. I am afraid that I might be running lean and was looking for some advice from some who have tuned a similar setup so I dont start throwing jets and whatever else at it blindly. There seems to be a slight surging at 2500 rpm which I have heard could be a lean condition. Any other thoughts on timing and such are appreciated as well.
11-08-2006, 09:10 AM
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Is the 670 a 4 barrel design? I know after adding my AFR's to my 355 I had to bump the primary jets from 68's to 72's and the secondary's to 76. The AFR heads flow great even more so with your Eliminator's over my older Street's. I also run full timing. I like a 750 at least even though you can get by with a 700 carb. The little loss down low is made up on the big end. My carb is a Holley Dbl Pumper 4150 750cfm.
11-08-2006, 09:32 AM
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Yeah the 670 is a 4-barrel and is a vacuum secondary design. I run it with the vacuum hooked to full manifold vacuum. I guess you are saying I need to richen it up a bit. I am borrowing a stock 750 double pumper this weekend at the track to see how much faster it will make it. What is your compression and total timing?
11-08-2006, 09:20 PM
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Originally Posted by joewee350
Yeah the 670 is a 4-barrel and is a vacuum secondary design. I run it with the vacuum hooked to full manifold vacuum. I guess you are saying I need to richen it up a bit. I am borrowing a stock 750 double pumper this weekend at the track to see how much faster it will make it. What is your compression and total timing?
I've ran the AFR's and 750 with two different engine combo's. First was a 10.2-1 Solid lifter setup, second was a tame 9.6-1 setup. Future build will be a 10.6-1 hyd roller setup. The VE for my setups were high 600's but it liked the larger 750 setup.
11-09-2006, 08:07 AM
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I am sitting at 30 degrees total at WOT but it seems everything I read says that 34-36 gets the most power. I borrowed a stock 750 DP and wow, the difference is huge. Instant throttle response and pulls much harder. Thanks for the responses.
11-09-2006, 06:46 PM
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Yeah I have an adjustable vacuum advance and its set to full manifold vacuum. I pulled some timing out of the vacuum canister so that it wouldnt ping. I will be testing it at the track either tomorrow or saturday. I will put it at 34 total and see what she does.
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11-09-2006, 10:45 PM
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At steady cruise I think I have about 42 total. I found I have better idle and throttle response with the vac advance. I am pretty sure I set my vac adv to add about 8 degrees. Seems to work good
11-10-2006, 02:11 AM
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I have read countless articles saying that 50-52 degrees advance at cruise including vacuum is the best for gas mileage and throttle response. I currently have mine set around 45 just to be safe. Before the aluminum heads I had it at 50 with no detonation. Will be going to the track tomorrow for some new times.
11-10-2006, 04:38 PM
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Full mechanical timing before vacuum advance is 30 at the moment. I plan to up it to 34 at the track tonight and pull some of the vacuum out to maintain the 45 total including vacuum.
11-10-2006, 09:50 PM
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Dont worry about pulling the vacuum out. At full throttle you have no vacuum so the vacuum advance will not work. You will just use mechanical. KNow what I mean?The vacuum is created when the throttle plates are close to closed like at steady cruise where the throttle plates are cracked slightly. ONce you stomp on it and open the throttle blades fully all vacuum is gone so there will no longer be vacuum advance just mechanical. ONce you let off the vac advance will start to advance more as the vacuum climbs
11-13-2006, 11:07 AM
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Yeah I know that. I pulled vacuum out for when I am cruising. I have to cruise from the end of the track back to my trailer too lol. Just wanted to post an update. I ran a 12.705@107.45 with a 1.94 60ft with 36 degrees total timing. I ran a 13.0@105 with the timing set at 29-30ish degrees.
11-14-2006, 12:38 AM
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I just noticed that you use the same cam as me. I have a 383 though. I havent run my car at the track or even tuned it much for that matter but am sure it is a solid mid to high 12 car with radials on it. Cant wait till next year when i put some sticky rubber on it. Good times by you. Bet there is still more in it
11-14-2006, 12:53 PM
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Thanks for the props. You would be surprised what it runs at the track. I swore up and down it was in the 12s my first trip out and it pulled a 13.8 then down to 13.6 the next trip. After more mods it is in the 12s with street tires. I am pulling the 750 double pumper off that I borrowed and putting the sluggish 670 street avenger back on today. Gotta get some more funds together to get another double pumper.
11-15-2006, 12:05 AM
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Seriously, if you want it to run really good I would look into a carb from Patrick at prosystems. More $$$$ but apparently well worth it. FOr about the hundred or more posts of VERY positive feedback about his carbs I think i have seen one that was negative, yet the owner still hadnt worked out the bug as it ended up being a bigger problem and not the carb. Cant remember what though. Hes good.
