Can I change the jet spread for better cruise??
#1634296
06/16/14 10:40 AM
06/16/14 10:40 AM
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Joined: Dec 2006
Posts: 1,178 Indy
FlyFish
OP
super stock
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OP
super stock
Joined: Dec 2006
Posts: 1,178
Indy
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I was jetted 88/100 at part throttle and the air/fuel ratio was good, but the WOT A/F ratio was too lean. I had to jet my primary up higher than normal because I didn't have jets larger than 100. When I changed it to 92/100 the car was too rich at part throttle, but ran great at WOT. So currently the carb runs like crap driving around town, but runs great at the drag strip when at WOT.
My question is, will it work the same at WOT if I reduce the primary jet by 4 numbers (making the cruise A/F ratio closer to optimal) and add 4 numbers to the secondary? I was thinking of buying a set of 104 jets to make it 88/104....any issues with this thought before I order the jets?
My car is mostly drag, some street with a 750dp on a single plan intake, running on e85.
Thanks in advance.
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Can I change the jet spread for better cruise??
[Re: FlyFish]
#1634297
06/16/14 11:35 AM
06/16/14 11:35 AM
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Joined: Jan 2003
Posts: 12,813 Benton, IL.
DaveRS23
Master of nothing...
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Master of nothing...
Joined: Jan 2003
Posts: 12,813
Benton, IL.
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If you're running a power valve in the primaries, open up the PVCRs for the extra fuel at WOT. That is what they are there for.
Master, again and still
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Re: Can I change the jet spread for better cruise??
[Re: Bad340fish]
#1634300
06/16/14 06:24 PM
06/16/14 06:24 PM
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Joined: Apr 2009
Posts: 3,433 Toronto
mshred
master
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master
Joined: Apr 2009
Posts: 3,433
Toronto
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Quote:
Quote:
If you're running a power valve in the primaries, open up the PVCRs for the extra fuel at WOT. That is what they are there for.
Yep, thats what I did with mine and it has worked great.
How to tell how big they need to be opened up?
I have the same problem with my carb
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Re: Can I change the jet spread for better cruise??
[Re: mshred]
#1634302
06/16/14 09:09 PM
06/16/14 09:09 PM
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Joined: Jan 2003
Posts: 12,813 Benton, IL.
DaveRS23
Master of nothing...
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Master of nothing...
Joined: Jan 2003
Posts: 12,813
Benton, IL.
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Quote:
Quote:
Quote:
If you're running a power valve in the primaries, open up the PVCRs for the extra fuel at WOT. That is what they are there for.
Yep, thats what I did with mine and it has worked great.
How to tell how big they need to be opened up?
I have the same problem with my carb
This really is wideband territory. But without a wideband, you can ball park it by using the formula in Emmanuel's Holley book. But you won't know how close you are to a good ratio, only that it drives okay or not.
You can just drill the PVCRs, they do not need to be tapped for jets. If you go too big, slender wires can be inserted to bring the flow down.
The Double Pumpers are good carbs for the track, but are calibrated very rich for the street.
Master, again and still
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Re: Can I change the jet spread for better cruise??
[Re: DaveRS23]
#1634303
06/16/14 11:13 PM
06/16/14 11:13 PM
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Joined: Dec 2006
Posts: 1,178 Indy
FlyFish
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super stock
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OP
super stock
Joined: Dec 2006
Posts: 1,178
Indy
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I have a wideband, and can drill the PVCR if needed, I was just curious if putting the larger jets in the rear would do the trick ( it sounds easier).
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Can I change the jet spread for better cruise??
[Re: Thumperdart]
#1634311
06/18/14 09:51 AM
06/18/14 09:51 AM
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Joined: Dec 2006
Posts: 1,178 Indy
FlyFish
OP
super stock
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OP
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Joined: Dec 2006
Posts: 1,178
Indy
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In the past few weeks I have already dropped my HSAB down to a 0.028 (from 0.036), and that helped a lot. I got to thinking about it and I probably could just mix my e85 to be more like e75 and be able to jet down more. Currently the e85 pump closest to my house has been 92% ethanol. If I blend in more gas I should be able to run less jet, which might fix the issue....or maybe it wouldn't since the ratio would still be off....idk, just thinking out loud.
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Can I change the jet spread for better cruise??
[Re: Cab_Burge]
#1634313
06/18/14 01:53 PM
06/18/14 01:53 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
I would be very careful on adding pump gas to the E85,I'm sure there are other additives in the E85 to help keep the alcholol and gasoline mix that could be foul up by not having the correct ratio of additives
Pump regular is what they blend the E-98 with to get the E-85
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Re: Can I change the jet spread for better cruise??
[Re: Cab_Burge]
#1634315
06/18/14 02:54 PM
06/18/14 02:54 PM
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Joined: Dec 2006
Posts: 1,178 Indy
FlyFish
OP
super stock
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OP
super stock
Joined: Dec 2006
Posts: 1,178
Indy
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Quote:
I would be very careful on adding pump gas to the E85,I'm sure there are other additives in the E85 to help keep the alcholol and gasoline mix that could be foul up by not having the correct ratio of additives
I'll be careful, and thank you for your concern Cab. I'm a Chemist Monday-Friday, mixing chemicals is what I do.
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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