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By Deyomatic - 4 Years Ago
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What is the purpose of the notch between the left and right holes in this intake? 
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By Joe-JDC - 4 Years Ago
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Started out years ago for the Holley Three barrel carb with the single butterfly in the secondary. Later, folks thought it helped with high rpm power, but in dyno testing, it causes a torque dip, and in some instances, it causes turbulence and loss of flow in the rear ports on that plane. Joe-JDC
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By Ted - 4 Years Ago
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Joe has summarized both why and what effect the plenum slots have on the performance. Here’s the link to the article that was published in the Jan-Feb 2014 issue of The Y-Block Magazine that goes into much more detail and also gives dyno testing results on those intake manifold plenum slots.
Intake Manifold Plenum Slots – Eaton Balancing
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By darrell - 4 Years Ago
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im surprised they never included something with that manifold to fill in that gap if you didnt want it.
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By Ted - 4 Years Ago
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No surprise there as when the Blue Thunder intake was first introduced, it was done so mimicking what the rest of the industry was doing in regards to plenum slots. Having a plenum slot was thought to be the best option so there was no option allowing the purchaser to use the BT manifold out of the box as no slot version. It was only when John Mummert introduced his manifold did it become apparent that maybe the plenum slot was not such a good idea in all instances. Once it was proven that the plenum slots were detrimental to low end performance, Blue Thunder simply did away with the slot. There are those on this forum that have taken the early production BT manifolds and filled in that slot area.
Here are some additional links to threads on this forum regarding the Blue Thunder intake manifolds and plenum modifications. Doing a search may bring up some more.
4 Barrel intake differences (y-blocksforever.com)
New Member & Intake Manifold Question (y-blocksforever.com)
Blue Thunder intake manifolds (y-blocksforever.com)
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By Deyomatic - 4 Years Ago
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Thanks for the info. This is the first I've even heard of the Holley 3 barrel. Probably a reason for that!
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By slumlord444 - 4 Years Ago
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What would be a practical way to fill that slot?
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By Ted - 4 Years Ago
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slumlord444 (12/30/2021)
What would be a practical way to fill that slot?
See if this link to a past thread helps.
http://forums.y-blocksforever.com/FindPost133096.aspx
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By bird55 - 3 Years Ago
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Sounds like an improvement I need to tackle. Nice explanation. Thanks!
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By slumlord444 - 3 Years Ago
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Will J B Weld hold this piece in place permanently? Don't really want to pull the intake if I don't have to. Concerned about the JB weld someday failing and the piece being sucked into the engine.
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By Joe-JDC - 3 Years Ago
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No, don't trust the JB at that point in the manifold. I have been porting for 49 years, used JB Weld in lots of intake manifolds, but in areas where you can stake the pour, or pin it. If you can stuff clean rags into the intake and vacuum it afterwards, you might create a groove in each end of the slot and make a corresponding but opposite groove in the piece you intend to install in the slot. Drill through the new piece down into the manifold, and stake that, then add JB Weld, it would be acceptable. Blend, vacuum the area diligently, and remove the rags while using the vacuum to make sure nothing enters the engine. It depends on how diligent you are in the modification if I would sanction it. I have JB Weld that has been in a pair of SBF aluminum heads for nearly 30 years. The other option is using Splash Zone A & B, A-788. Easier to work with, but still needs the same prep work to ensure the added piece does not get injested in the engine. Joe-JDC
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By Ted - 3 Years Ago
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slumlord444 (1/2/2022)
Will J B Weld hold this piece in place permanently? Don't really want to pull the intake if I don't have to. Concerned about the JB weld someday failing and the piece being sucked into the engine.
I'm in agreement with Joe. That would be a NO on trying to glue something in that opening. That piece coming out at a later date can prove to be catastrophic. What Doug did with the V’s cut in both the divider and the fitted piece for the opening gives the added piece some real support and is there for the long haul. What Charlie did in having the slot welded shut is the ultimate fix.
Another option besides the two aforementioned methods would be to machine a 1” aluminum spacer so the spacer is approximately a quarter inch thick but leaving a protrusion sticking up that matches the slot in the plenum divider. That would allow the slot in the divider to be ‘filled in’ while not having to remove the manifold. If using a 2” spacer and machining it just enough to leave the same aforementioned protrusion, then you would have a taller spacer.
But manifold removal on the Y is reasonably straight forward as the distributor does not need to be removed to do so. Regardless of the method used to fill in the slot, eliminating any potential gaps in that opening gives the best results.
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By DryLakesRacer - 3 Years Ago
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I haven’t heard the words “Splash Zone” in years. That was the best epoxy I every used in the power plant industry. It was indestructible and could live in anywhere we put it. Worked with any fuel and could be applied underwater. I’ve been using an intake manifold for 20 years that I reconfigured with JB weld. It was a life saver.
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