Edelbrock RPM Airgap Bolt Hole

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Edelbrock said that they were getting a lot of complaints from folks not being able to get their stock intake bolts in the holes is the reason they started working out some bolt holes. When they say 'stock', I assume it's the six sided hex bolts. I can see that being a real problem from 74Scooters picture. Poor QA/QC in my humble opinion.

This is the 21st century, the age of computers and they say we have a rover on Mars. Can't the engineers make an adjustment to the casting mold and just fix the issue?

Rumblefish, I have thought about sending it back to Edelbrock but I suspect I would just get another one just like it or worse. Maybe just not enough of us mopar folks addressing the issue with them. Think I may measure the recess depth/diameter and see if I can find a flat washer that will fill that recess and bring it back up to level of casting, then add one more to get to height of other bolts/washers. Will also have to be able to use the same diameter washers on all of the other holes so they are all the same size. If I can't make that work and look decent, definitely sending it back to Edelbrock even if it is at my expense.
 
74Scooter said:
I did not see that on mine... wonder if they are working them to make the bolts easier to install without cutting them down??

View attachment 1716017078
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74Scooter, do you know the O.D. of the holes in your 7576 pictured here? I measured the hole(s) in mine and they are 0.469" diameter. The diameter of the 3/8"-16 x 1-1/2" hex head bolts that I have measure 0.369" at the O.D. of the threads. So the holes on my intake are exactly 0.100" larger than the bolts giving not quite 1/16" clearance all around the bolt. I was able to drop these hex head bolts that I mention here right down into the holes and the threads never got close to the sides of the holes and bolt heads barely touched the intake runner, including the hole they milled down. If they hadn't milled it down, I believe the 1-1/2" length bolt would have still went right into the hole. Wonder if the holes in your manifold are smaller diameter than on mine by the looks of the angle of those small round head bolts you are showing. I did measure several of the holes on the intake and they were all within a 0.001" or two of the 0.469", so they didn't just make the hole the milled down a larger diameter.

Another thing I noticed was that the pad at the top of the holes were not cast parallel with the surface that mates up to the head. The pads on mine are thinner at the edge of the manifold and get thicker as you move in toward the valley? Does this mean that the holes in the heads aren't exactly drilled perpendicular to the mating surface of the head but are at a slight angle? I pulled a bolt out of the stock intake manifold on the engine and the pad mating surface on the top of the intake looks to be parallel with the intake mating surface and the bolt hole in the intake runs parallel with the hole in the stock head. At least it appears that way. If all contact surfaces are not parallel with each other and the threaded hole in the heads are not exactly perpendicular to those planes in space wouldn't you get an uneven torque load distribution on the bolts, washers, intake and head. Thanks

Bolt-Pad-Pic1.gif


Bolt-Pad-Pic2.gif
 
1badfish67 said:
74Scooter, do you know the O.D. of the holes in your 7576 pictured here? I measured the hole(s) in mine and they are 0.469" diameter. The diameter of the 3/8"-16 x 1-1/2" hex head bolts that I have measure 0.369" at the O.D. of the threads. So the holes on my intake are exactly 0.100" larger than the bolts giving not quite 1/16" clearance all around the bolt. I was able to drop these hex head bolts that I mention here right down into the holes and the threads never got close to the sides of the holes and bolt heads barely touched the intake runner, including the hole they milled down. If they hadn't milled it down, I believe the 1-1/2" length bolt would have still went right into the hole. Wonder if the holes in your manifold are smaller diameter than on mine by the looks of the angle of those small round head bolts you are showing. I did measure several of the holes on the intake and they were all within a 0.001" or two of the 0.469", so they didn't just make the hole the milled down a larger diameter.

Another thing I noticed was that the pad at the top of the holes were not cast parallel with the surface that mates up to the head. The pads on mine are thinner at the edge of the manifold and get thicker as you move in toward the valley? Does this mean that the holes in the heads aren't exactly drilled perpendicular to the mating surface of the head but are at a slight angle? I pulled a bolt out of the stock intake manifold on the engine and the pad mating surface on the top of the intake looks to be parallel with the intake mating surface and the bolt hole in the intake runs parallel with the hole in the stock head. At least it appears that way. If all contact surfaces are not parallel with each other and the threaded hole in the heads are not exactly perpendicular to those planes in space wouldn't you get an uneven torque load distribution on the bolts, washers, intake and head. Thanks

View attachment 1716018273

View attachment 1716018274
Click to expand...
Sorry, do not know the exact OD of those holes on mine. I used the Eddy recommended intake bolt kit 8579 as the bolts that held the previous intake on were a mix-n-match of hex, 12 point and allen head.

I did not have any issues with the bolts laying down flush. That might just be an optical illusion where the cast boss is bigger on one side but the actual machined landing is parallel to the head face. May be harder to see on the smaller photo below.. but when I zoom in on the full sized photo on my desktop the landings on mine look much like yours.

20220726_170815.jpg
 
74Scooter said:
Sorry, do not know the exact OD of those holes on mine. I used the Eddy recommended intake bolt kit 8579 as the bolts that held the previous intake on were a mix-n-match of hex, 12 point and allen head.

I did not have any issues with the bolts laying down flush. That might just be an optical illusion where the cast boss is bigger on one side but the actual machined landing is parallel to the head face. May be harder to see on the smaller photo below.. but when I zoom in on the full sized photo on my desktop the landings on mine look much like yours.

View attachment 1716018283
Click to expand...
Thanks
 
1badfish67 said:
74Scooter, do you know the O.D. of the holes in your 7576 pictured here? I measured the hole(s) in mine and they are 0.469" diameter. The diameter of the 3/8"-16 x 1-1/2" hex head bolts that I have measure 0.369" at the O.D. of the threads. So the holes on my intake are exactly 0.100" larger than the bolts giving not quite 1/16" clearance all around the bolt. I was able to drop these hex head bolts that I mention here right down into the holes and the threads never got close to the sides of the holes and bolt heads barely touched the intake runner, including the hole they milled down. If they hadn't milled it down, I believe the 1-1/2" length bolt would have still went right into the hole. Wonder if the holes in your manifold are smaller diameter than on mine by the looks of the angle of those small round head bolts you are showing. I did measure several of the holes on the intake and they were all within a 0.001" or two of the 0.469", so they didn't just make the hole the milled down a larger diameter.

Another thing I noticed was that the pad at the top of the holes were not cast parallel with the surface that mates up to the head. The pads on mine are thinner at the edge of the manifold and get thicker as you move in toward the valley? Does this mean that the holes in the heads aren't exactly drilled perpendicular to the mating surface of the head but are at a slight angle? I pulled a bolt out of the stock intake manifold on the engine and the pad mating surface on the top of the intake looks to be parallel with the intake mating surface and the bolt hole in the intake runs parallel with the hole in the stock head. At least it appears that way. If all contact surfaces are not parallel with each other and the threaded hole in the heads are not exactly perpendicular to those planes in space wouldn't you get an uneven torque load distribution on the bolts, washers, intake and head. Thanks

View attachment 1716018273

View attachment 1716018274
Click to expand...
Correct, the intake bolts are not perpendicular to the gasket surface, just not as radically as the early 273's & Magnum engines. It is not uncommon to have an intake with a fastener seating surface not squared up with the hole, I've corrected a few intakes with that issue from way back, We just got spoiled for a while & forgot old school intakes were worse than the ones in recent history. Now are We regressing?....it kinda feels that way...
 
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