Intake Manifold Milling?

Intake Manifold Milling?

Joined: July 3rd, 2006, 6:24 am

July 30th, 2012, 12:23 am #1

Looking for some advice. The Cougar had not been running as well as it had with a lean miss on the top end so I started to do some diagnostics. I pulled the plugs and looked like they were running lean except for one plug ( # 7) that looked oily. I then ran a compression check and got the following results: 1. 150, 2. 140, 3. 150, 4. 150, 5. 145, 6. 133, 7. 140, 8. 145

I then pulled the intake manifold and I am finding oil on the intake ports. I am running a 1970 4V engine with flat top pistons and a Comp Cams XE 274. My vacuum is at 8 inches with some variability until it warms up and them it is fairly steady.

My theory is the that the heads have been milled at some point and the Blue Thunder intake manifold needs to be milled to properly seal the intake? Since I don't know how much the heads have been milled I am not sure how much I should mill the intake? I am currently using the print o seal gaskets. Has anyone used other gaskets or extra gasket material in this case? Any thoughts? I greatly appreciate the help.

Thanks,

Hawkxr7
Last edited by hawkxr7 on July 30th, 2012, 12:32 am, edited 1 time in total.
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Joined: May 20th, 2005, 4:48 pm

July 30th, 2012, 12:38 am #2

...of the sides of the intake. If you have access to a bore scope, look down through the plenum and see if the ports are aligned. That's another good indicator...

Brent Lykins
B2 Motorsports, LLC






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Joined: July 3rd, 2006, 6:24 am

July 30th, 2012, 1:08 am #3

Good idea but unfortunately I don't have a bore scope. I am wondering if I just apply a form a gasket solution that I might get a good seal that way? Thanks for the feedback. I greatly appreciate the help.
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Joined: June 23rd, 2010, 4:42 am

July 30th, 2012, 2:01 am #4

Looking for some advice. The Cougar had not been running as well as it had with a lean miss on the top end so I started to do some diagnostics. I pulled the plugs and looked like they were running lean except for one plug ( # 7) that looked oily. I then ran a compression check and got the following results: 1. 150, 2. 140, 3. 150, 4. 150, 5. 145, 6. 133, 7. 140, 8. 145

I then pulled the intake manifold and I am finding oil on the intake ports. I am running a 1970 4V engine with flat top pistons and a Comp Cams XE 274. My vacuum is at 8 inches with some variability until it warms up and them it is fairly steady.

My theory is the that the heads have been milled at some point and the Blue Thunder intake manifold needs to be milled to properly seal the intake? Since I don't know how much the heads have been milled I am not sure how much I should mill the intake? I am currently using the print o seal gaskets. Has anyone used other gaskets or extra gasket material in this case? Any thoughts? I greatly appreciate the help.

Thanks,

Hawkxr7
If the heads have been milled correctly, and it was only a clean up than no need to cut the intake. A minor port miss match can be cleaned up with a die grinder. Most likely the guides and seals need some attention.

If indeed miss alignment is an issue adding extra material is only going to make it worse. Since this is a dual plane, I believe, use the old gasket as a guide for the alignment.What piston rings you running? Why do you suspect a lean miss?
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Joined: July 3rd, 2006, 6:24 am

July 30th, 2012, 3:03 am #5

I have run into this lean issue before and when I increase the jet size the miss goes away. Also by looking at the spark plugs they look like they are running in a lean condition. With the oil in the intake runners I believe I have a vacuum leak which is drawing in both air and oil. I built the motor two years ago and it seems that I can change the gaskets and it will run fine for a awhile but then the leak will come back. I can't recall which rings I got other than they were a moly ring. I greatly appreciate the help.

Thanks,

Hawkxr7
Last edited by hawkxr7 on July 30th, 2012, 3:05 am, edited 1 time in total.
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Joined: December 16th, 2003, 1:59 am

July 30th, 2012, 3:37 am #6

Looking for some advice. The Cougar had not been running as well as it had with a lean miss on the top end so I started to do some diagnostics. I pulled the plugs and looked like they were running lean except for one plug ( # 7) that looked oily. I then ran a compression check and got the following results: 1. 150, 2. 140, 3. 150, 4. 150, 5. 145, 6. 133, 7. 140, 8. 145

I then pulled the intake manifold and I am finding oil on the intake ports. I am running a 1970 4V engine with flat top pistons and a Comp Cams XE 274. My vacuum is at 8 inches with some variability until it warms up and them it is fairly steady.

My theory is the that the heads have been milled at some point and the Blue Thunder intake manifold needs to be milled to properly seal the intake? Since I don't know how much the heads have been milled I am not sure how much I should mill the intake? I am currently using the print o seal gaskets. Has anyone used other gaskets or extra gasket material in this case? Any thoughts? I greatly appreciate the help.

Thanks,

Hawkxr7
many including myself have had trouble with the silicone bead tearing as the bolts are torqued... try a cheap set of Mr Garbage paper gaskets

watch the thickness, according to Summit

the 215's are .125" thick (1/8")

the 214's are .0625" thick (1/16")

http://www.network54.com/Forum/215649/t ... 51-C+PARTS

there'll be phantoms, there'll be fires on the road... and the white man dancing
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Joined: July 3rd, 2006, 6:24 am

July 30th, 2012, 4:48 am #7

Hi Tinman. I wasn't aware of the Print-O-Leak reputation that these gaskets had. I ordered a set of the thick Mr. Gasket intake gaskets and hopefully that will do the trick. I greatly appreciate the insight.

Thanks,

Hawkxr7
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Joined: December 16th, 2003, 1:59 am

July 30th, 2012, 5:30 am #8

i don't recall if mine were Mr.G Ultraseal or F/P Printoseal, not bashing a particular brand at this point but i know they had the silicone ring around the port that mysteriously got severely distorted somehow. yeah i was careful & all that but i think i'll stick to the simple kind that i can't screw up

pretty sure i had a conversation with my machist about the silicone bead, he says they get smeared due to the angle that the intake gets pulled down as it torques. maybe if the intake surface was lubricated it wouldn't grab & smear? i dunno

there'll be phantoms, there'll be fires on the road... and the white man dancing
Last edited by tinman351 on July 30th, 2012, 9:53 am, edited 1 time in total.
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Joined: June 23rd, 2010, 4:42 am

July 30th, 2012, 5:38 am #9

I have run into this lean issue before and when I increase the jet size the miss goes away. Also by looking at the spark plugs they look like they are running in a lean condition. With the oil in the intake runners I believe I have a vacuum leak which is drawing in both air and oil. I built the motor two years ago and it seems that I can change the gaskets and it will run fine for a awhile but then the leak will come back. I can't recall which rings I got other than they were a moly ring. I greatly appreciate the help.

Thanks,

Hawkxr7
Ok so what jet sizes and what carb?

What trans? If auto put a vacuum pump on the vacuum modulator and check for a leaky diaphragm.

When you said I changed gaskets, the problem goes away. Is this the intake manifold? A good machine shop will be able to remove material off the top portion of the intake verses the bottom, thus eliminating a potential gap. A taper cut if you will, the amount removed is minimal, like .001 bottom and .010 top.

This may not be practical but a two piece manifold will help determine where the oil is coming from. I have cut the lower portion off my Holley strip dom manifold and made a separate lower piece to isolate my oil problem similar to yours.
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Joined: May 20th, 2005, 4:48 pm

July 30th, 2012, 8:55 am #10

If the heads have been milled correctly, and it was only a clean up than no need to cut the intake. A minor port miss match can be cleaned up with a die grinder. Most likely the guides and seals need some attention.

If indeed miss alignment is an issue adding extra material is only going to make it worse. Since this is a dual plane, I believe, use the old gasket as a guide for the alignment.What piston rings you running? Why do you suspect a lean miss?
Usually in 40 years, all of this stuff has been cut to death....

Brent Lykins
B2 Motorsports, LLC






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