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Old 08-12-2019, 12:22 PM
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Intake Vacuum leaks?

while tuning up my electric choke i noticed a sucking noise on the intake manifold. Its coming from four holes. Put you finger on them and its sucking, all four hole. Quick google and these are the four bolt holes on a edelbrock performer RPM 2 intake #7562. These four bolts are specified in manual as hand tighten only.

Mine have no bolts and you can see the gasket covering the holes between block and manifold. Never was a bolt in any of these four holes.

The question is this, is there any reason this would have been done intentionally? The car runs great, its dyno'd at 638 hp 652 torque. When i plug all four holes the idle drops way down and car barely wants to keep idling.
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Old 08-12-2019, 12:33 PM
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Is this a joke? Give full info on heads please.
" No provisions for exhaust heated chokes or exhaust crossover.
7562 is similar to 7561, but is designed to fit high performance rectangular-port cylinder heads.
Will not fit oval port heads."

"When i plug all four holes the idle drops way down and car barely wants to keep idling."........... YEAH, I"LL BET SHE GOES A LITTLE FAT!!!!!

The more I read, the more confused I become.
https://edelbrock-instructions-v1.s3...brock/7562.pdf

"WARNING: There is no gasket support for the manifold under the four bolt holes which are numbered #5, #10, #11, and #16 in Figure 2.
Damage to the manifold will occur if these four bolts are over-tightened. Hand tighten these bolts with a 6” box-end wrench. DO NOT use
a torque wrench. Torque all remaining manifold bolts in two steps by the sequence shown in Figure 2 to 25 ft/lbs."


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Last edited by techinspector1; 08-12-2019 at 01:00 PM.
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Old 08-12-2019, 12:38 PM
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Quote:
Originally Posted by techinspector1 View Post
Is this a joke? Give full info on heads please.
Joke? Interesting first post first response to this group.

Patriot 320 cc heads with rectangular ports. Edelbrock intake with rectangular ports.
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Old 08-12-2019, 12:39 PM
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What BBC heads do you have? Some BBC heads have an additional bolt in that area.

If your pulling vacuum then you have the wrong gasket and there may be a bolt hole there.
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Old 08-12-2019, 12:42 PM
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Quote:
Originally Posted by engineczar View Post
What BBC heads do you have? Some BBC heads have an additional bolt in that area.

If your pulling vacuum then you have the wrong gasket and there may be a bolt hole there.
Patriot 320 CC heads, rectangular ports, intake is rectangular. The engine was built in 2010 and has been that way since is why i thought it was intentional for some reason.
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Old 08-12-2019, 12:47 PM
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If it's pulling vacuum then the gasket might be too large compared to the ports. You might need to go to a gasket where you have to trim the port openings to size.

It might have always leaked and whoever originally tuned it just compensated for the additional leaking air.
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Old 08-12-2019, 01:05 PM
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Quote:
Originally Posted by engineczar View Post
It might have always leaked and whoever originally tuned it just compensated for the additional leaking air.
Thank you engineczar. That's what I was trying to get my head wrapped around, that someone would have actually done that. Go18Go, that's why I began with "is this a joke?" Not trying to be a smart aleck, I just could not imagine that someone built and tuned this motor with four vacuum leaks left in place.
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Old 08-12-2019, 01:08 PM
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Must be the wrong gasket or the gasket has moved.
More than once I have put thread inserts in those 4 holes and a short bolt as people get upset when they see big open holes on their engines.
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Old 08-12-2019, 01:21 PM
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So it sounds like it shouldn't be that way. If the head has bolt holes in those locations ill install bolts. Maybe best to just remove the intake, replace with correct gaskets, retune?
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Old 08-12-2019, 01:40 PM
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I would go that way. I don't believe that Patriot heads have that bolt hole but I would wait to order the gaskets until it's apart.
Once apart you'll see on the old gaskets where it's leaking from.

You'll probably just need to tune the idle circuits but depending on the size of the leak it could effect it all over.
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