Just how uneven is the airflow on the Vic. Jr? pics inside to illustrate
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Just how uneven is the airflow on the Vic. Jr? pics inside to illustrate
I've always wondered....seems like the two inside cylinders would get more air with the shorter runners. Maybe my plugs tell the story.
EDIT: I apologize for these being cathedral ports in the gen IV section but I'm sure the airflow does the same thing with the rect. ports Vic Jr. Just thought I'd get a more in-depth discussion here.
EDIT: I apologize for these being cathedral ports in the gen IV section but I'm sure the airflow does the same thing with the rect. ports Vic Jr. Just thought I'd get a more in-depth discussion here.
Last edited by frito1; 07-06-2010 at 01:02 PM.
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That's fuel... no oil on the threads.
Has anybody else with a EFI Vic Jr pulled their plugs out and seen the same thing? The wideband shows ~12.8 AFR at WOT. It's getting the average of this mess going on here. So I have 4 cylinders going pretty lean and 4 going pretty fat. I'd appreciate other EFI Vic Jr owners to pull plugs and chime in.
Has anybody else with a EFI Vic Jr pulled their plugs out and seen the same thing? The wideband shows ~12.8 AFR at WOT. It's getting the average of this mess going on here. So I have 4 cylinders going pretty lean and 4 going pretty fat. I'd appreciate other EFI Vic Jr owners to pull plugs and chime in.
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I think this is pretty big deal so I talked with an edelbrock rep just now. I emailed him the pics and he is going to send it on to the engineer. I doubt that will go anywhere. Of course they have never had any complaints.... but who pulls their plugs just to check?
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Thanks for the info but carb setups won't be apples to apples BECAUSE the correct AFR is there to be "had" (assuming the carb is set right). The cylinder just has to pull that mixture in (or get pushed in if it's forced induction in your case). Basically they get what they can get of this perfect mixture. The cylinders pull it past the jets. EFI is averaging the AFR and shooting the same gas amount of gas to the cylinders... the wildcard comes with some cylinders can pull more air or less air depending on runner length/shape yet every cylinder gets the same amount of gas.
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I would bet this is due to the throttle body linkage. If you install fresh plugs , make a pass, and shut it off clean.....it probably wont be the same. I think its due to the air entry at the throttle body blades, during low speed, closed throttle situations. (ie just driving around)
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I've done both the Jr. & S. Vic using both an elbow and 4150 Carb style Tb. on LS based motors...
The elbow works well for FI/blow through apps., but is not as efficient as the carb style TB on NA motors. The air entering the elbow also has to make a 90* turn before it enters the plenum... air doesn't like to turn corners or change direction.
What you're seeing is in fact the outer holes running fat and the inside cylinders running a bit lean as the incoming air has to make a 90* turn to enter 1-2-7-8 cylinders and the inside holes have a straight shot.
I've personally seen a 30rwhp/22rwtq loss down low with the Vic style intake over the FAST using a decent sizes single pattern cam, and what it picked up on top wasn't even a wash.
The only fix is to run a stand alone OS, monitor EGT's and tune A/F for each hole individually... you can also play with plugs to get it a bit closer.
Also keep in mind the camshaft/valve events/CR's that would be typical of a OEM or FAST intake are not going to be optimal with a single plane/short runner'd intake.
The elbow works well for FI/blow through apps., but is not as efficient as the carb style TB on NA motors. The air entering the elbow also has to make a 90* turn before it enters the plenum... air doesn't like to turn corners or change direction.
What you're seeing is in fact the outer holes running fat and the inside cylinders running a bit lean as the incoming air has to make a 90* turn to enter 1-2-7-8 cylinders and the inside holes have a straight shot.
I've personally seen a 30rwhp/22rwtq loss down low with the Vic style intake over the FAST using a decent sizes single pattern cam, and what it picked up on top wasn't even a wash.
The only fix is to run a stand alone OS, monitor EGT's and tune A/F for each hole individually... you can also play with plugs to get it a bit closer.
Also keep in mind the camshaft/valve events/CR's that would be typical of a OEM or FAST intake are not going to be optimal with a single plane/short runner'd intake.
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I've done both the Jr. & S. Vic using both an elbow and 4150 Carb style Tb. on LS based motors...
The elbow works well for FI/blow through apps., but is not as efficient as the carb style TB on NA motors. The air entering the elbow also has to make a 90* turn before it enters the plenum... air doesn't like to turn corners or change direction.
What you're seeing is in fact the outer holes running fat and the inside cylinders running a bit lean as the incoming air has to make a 90* turn to enter 1-2-7-8 cylinders and the inside holes have a straight shot.
I've personally seen a 30rwhp/22rwtq loss down low with the Vic style intake over the FAST using a decent sizes single pattern cam, and what it picked up on top wasn't even a wash.
The only fix is to run a stand alone OS, monitor EGT's and tune A/F for each hole individually... you can also play with plugs to get it a bit closer.
Also keep in mind the camshaft/valve events/CR's that would be typical of a OEM or FAST intake are not going to be optimal with a single plane/short runner'd intake.
The elbow works well for FI/blow through apps., but is not as efficient as the carb style TB on NA motors. The air entering the elbow also has to make a 90* turn before it enters the plenum... air doesn't like to turn corners or change direction.
What you're seeing is in fact the outer holes running fat and the inside cylinders running a bit lean as the incoming air has to make a 90* turn to enter 1-2-7-8 cylinders and the inside holes have a straight shot.
I've personally seen a 30rwhp/22rwtq loss down low with the Vic style intake over the FAST using a decent sizes single pattern cam, and what it picked up on top wasn't even a wash.
The only fix is to run a stand alone OS, monitor EGT's and tune A/F for each hole individually... you can also play with plugs to get it a bit closer.
Also keep in mind the camshaft/valve events/CR's that would be typical of a OEM or FAST intake are not going to be optimal with a single plane/short runner'd intake.
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I've seen that with small 90 elbows like the edelbrok.When we run a bigger elbow the plugs run even. So,I would gues that a 4150 setup would do the same thing at idle/part throttle due to the lack of volume in the intake.
My super victor with 105mm elbow/TB setup has all the plugs running even on color but I did port it and opened up the outside runners more.
My super victor with 105mm elbow/TB setup has all the plugs running even on color but I did port it and opened up the outside runners more.
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