Left bank going lean with Edelbrock Performer RPM LS1 manifold?
06-05-2013, 12:58 PM
#22
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Well all the runs are with the hood off. As seen in the dyno video in the OP I haven't put the body back on yet. There's really no downside to trimming the manifold for my application and other Edelbrock versions come with it already done. Also, the guys at Pro-Systems (who built my carb) said they always use the dual planes with a cut divider for road race use.
06-07-2013, 05:18 AM
#24
EDIT - If you meant the sniffer, then yes. Putting the sniffer in the passenger side where my onboard wideband is resulted in them both reading mid-12s. Sniffer in the driver side pipe resulted in mid 14s. I'm going to put a bung in the driver side pipe and mill the plenum divider some.
There have been quite a number of articles about wideband accuracy. Most show the Innovate brand to be much faster responding and better calibrated than other brands. Some years ago there was a member with a dual channel Fast unit. His would read about a point different left to right. Always made me wonder if it was real or just the dial.
I have seen engine master challenges where they used exhaust gas temperature gauges at each exhaust port to super fine tune each cylinder. This particular engine was running dual quads. The builder put a different type of booster in just one of the venturis cause one cylinders kept running lean. I suppose you could try mounting the carb backwards to rule out any issues with it.
Fun stuff. IIRC you have the class rules limiting peak HP, otherwise I would suggest a single plane.
06-24-2013, 05:58 AM
#29
Launching!
07-11-2013, 03:43 PM
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Update - Dyno'd again today. The plenum milling fixed the air/fuel imbalance. Car was only 0.3 air/fuel different bank to bank.
Car made 323/351 hp/tq with 13:0 AFR and only 22 degrees timing. Couldn't get the car to fatten up any. Upped the jets in the secondaries from 79 to 82 to 86 and air fuel only fattened up to 13 which is way less that it should have. Turns out the air bleeds had all been drilled out haphazardly and we only had four blanks. Going to have Pro-systems send a fresh set and try yet again. Trying to get air/fuel in the mid 12s before advancing timing. Car has a good bit more power/torque left in this stock LS1.
Car made 323/351 hp/tq with 13:0 AFR and only 22 degrees timing. Couldn't get the car to fatten up any. Upped the jets in the secondaries from 79 to 82 to 86 and air fuel only fattened up to 13 which is way less that it should have. Turns out the air bleeds had all been drilled out haphazardly and we only had four blanks. Going to have Pro-systems send a fresh set and try yet again. Trying to get air/fuel in the mid 12s before advancing timing. Car has a good bit more power/torque left in this stock LS1.
07-12-2013, 07:48 AM
#32
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Well... the carb hasn't been changed at all between dyno sessions. Milling the manifold took the imbalance from nearly two full points to 0.3 points. However, in moving forward with the tuning it was discovered that the air bleeds had been drilled out previously and done poorly. Who knows what it would have done the first time with the air bleeds all sized correctly and evenly. Have to get new bleeds and get back to the dyno yet again.
07-30-2013, 11:02 AM
#33
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Interesting! I have the same intake on a 2000 5.3l. I've been concerned as well.
What do you mean by one bank being lean...1 side of the motor?? or left side of the intake? . My carb is on still, but looking at the runners... and looking at my spark plugs it seems to me that the one half of the intake flows...two cylinders on each side of the engine. (ex. 1 half of plenum flows 2,8, & 3,5 am i wrong?)
I put a set of new plugs in yesterday let it idle in the drive way maybe 10min... rev'd it up a few times here and there....Checking things out.
Pulled the plugs after...
This pic shows plugs in order: 7, 5, 3, 1
This shows : 2, 4, 6, 8
Im confused.... not sure whats going on. but these are not close to the same.
What do you mean by one bank being lean...1 side of the motor?? or left side of the intake? . My carb is on still, but looking at the runners... and looking at my spark plugs it seems to me that the one half of the intake flows...two cylinders on each side of the engine. (ex. 1 half of plenum flows 2,8, & 3,5 am i wrong?)
I put a set of new plugs in yesterday let it idle in the drive way maybe 10min... rev'd it up a few times here and there....Checking things out.
Pulled the plugs after...
This pic shows plugs in order: 7, 5, 3, 1
This shows : 2, 4, 6, 8
Im confused.... not sure whats going on. but these are not close to the same.
07-30-2013, 04:33 PM
#34
But if one half of the carb was running richer than the other then opening up the plenum and allowing them to mix might mask thecarb problem
07-30-2013, 06:58 PM
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Having the same problem with my 5.3 with RPM intake.
so i went with a vic jr on my 6.0, i been following ur thread.hopfully somebody has some good advise and we can fix this problem. Good luck Mr Cobra4B.
so i went with a vic jr on my 6.0, i been following ur thread.hopfully somebody has some good advise and we can fix this problem. Good luck Mr Cobra4B.
