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351C 2V intake leak,
#1
Looking for a bit of insight as to why I am having issues getting this intake to seal to the block.
First a bit of history as to how I got to where I am.
My inlaw had he 73 restored and figured he'd finally put a 4 barrel and aluminum intake, chrome dress up kit on at the same time.
He had the parts installed on the motor by the person doing the restoration (I believe it was done by a different garage than the body shop).
Anyway, the person ordered a 4 barrel intake for a 351C, naturally they ordered the wrong one and got the 4V part instead of the 2V. He drove the car for the remainder of the summer, then ordered the right intake to be put on over the winter by me. I have put them on in the past on a couple Chevys and one windsor and never had a problem.
This Cleveland is confusing me.
As per the edelbrock instructions, I removed the valley pan (The 4V aluminum intake was installed with the valley pan left in) and used a nice layer of Ultra blue along the front and back of the block (I've never had an issue with blue before this). The intake gaskets I used were the "free set of edelbrock gaskets" that came with the new intake as a bonus.
After some spiritted driving, I noticed an oil leak coming from behind the intake pooling around the oil sending unit and eventually down the back of the block.
After doing some reading I here how terrible the blue is and I should use black or "the right stuff". I chose the right stuff. After a super cleaning job and making sure no oil is remotely near the sealing area, I put a nice bead on and the intake squishes it out evenly across the entire width. Letting it sit over night I go for a nice drive and see no oil, Hooray, it's fixed!!!! Smile
Then I decide to test the new intake and carb a bit, when I return the leak is back.Angry
Why is this happening, should I put the valley pan back in?
Why is there such pressure to be able to push "the right stuff out" after I read it was like super glue when installed?
There is a breather in the "add oil" driver side valve cover and a functioning PCV valve hosed in to the port on the base of the carb on the passenger valve cover.

Is it possible that this issue has been there a while but because the car was never driven "hard" before the carb/intake swap it was just never noticed until it has been hitting the higher RPM's?

My Inlaw is 73 years old and I'd say that he has been a "mature" driver with his car for the previous 10+years.

Bad rings be a possibility? I believe the engine hasn't been opened up since it left the assembly line. I am going to pull the oil sending unit and put a plug in for a quick test to make sure it's not coming from there (if it's possible).

What's my next step??? Huh
  Reply
#2
travisgm;83316 Wrote:Looking for a bit of insight as to why I am having issues getting this intake to seal to the block.
First a bit of history as to how I got to where I am.
My inlaw had he 73 restored and figured he'd finally put a 4 barrel and aluminum intake, chrome dress up kit on at the same time.
He had the parts installed on the motor by the person doing the restoration (I believe it was done by a different garage than the body shop).
Anyway, the person ordered a 4 barrel intake for a 351C, naturally they ordered the wrong one and got the 4V part instead of the 2V. He drove the car for the remainder of the summer, then ordered the right intake to be put on over the winter by me. I have put them on in the past on a couple Chevys and one windsor and never had a problem.
This Cleveland is confusing me.
As per the edelbrock instructions, I removed the valley pan (The 4V aluminum intake was installed with the valley pan left in) and used a nice layer of Ultra blue along the front and back of the block (I've never had an issue with blue before this). The intake gaskets I used were the "free set of edelbrock gaskets" that came with the new intake as a bonus.
After some spiritted driving, I noticed an oil leak coming from behind the intake pooling around the oil sending unit and eventually down the back of the block.
After doing some reading I here how terrible the blue is and I should use black or "the right stuff". I chose the right stuff. After a super cleaning job and making sure no oil is remotely near the sealing area, I put a nice bead on and the intake squishes it out evenly across the entire width. Letting it sit over night I go for a nice drive and see no oil, Hooray, it's fixed!!!! Smile
Then I decide to test the new intake and carb a bit, when I return the leak is back.Angry
Why is this happening, should I put the valley pan back in?
Why is there such pressure to be able to push "the right stuff out" after I read it was like super glue when installed?
There is a breather in the "add oil" driver side valve cover and a functioning PCV valve hosed in to the port on the base of the carb on the passenger valve cover.

Is it possible that this issue has been there a while but because the car was never driven "hard" before the carb/intake swap it was just never noticed until it has been hitting the higher RPM's?

My Inlaw is 73 years old and I'd say that he has been a "mature" driver with his car for the previous 10+years.

Bad rings be a possibility? I believe the engine hasn't been opened up since it left the assembly line. I am going to pull the oil sending unit and put a plug in for a quick test to make sure it's not coming from there (if it's possible).

What's my next step??? Huh

First time i put my intake on it leaked too on my 351 cleveland...I didnt use any valley pan..and even used the cheap cork gaskets front and back...But i used good fel pro gaskets going to the head...But first time i did it...I thought i put enough of the black on the front and back of the motor....Plenty in my mind...but no....I opened the intake back up and i could see mass spots it didnt touch...You got too put a real good amount on there...More than normal....wipe away the outside stuff before it dries of cource....I would double check it...once you pull the manifold you will see the spots your missed usualy....i did on mine.


Bad rings should not pull up oil outside the motor...Sending unit could be a issue...it spitting alot of oil?
  Reply
#3
It does spit a lot (in my mind anyway). The little "valley" where the sending unit is mounted, it is full after a 10-15 minute "aggressive" drive. Barely any when driving "normal".
I can't rule out for sure, but I doubt it's lack of sealant. put at least a 3/8" bead across the front and back, making sure to "push" it in to the corners where the head and block meet, then up a little on top of the intake gaskets. When I mounted the intake it pushed out evenly across and I then took my finger and smoothed it out, like you would to caulking around a tub or sink.
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#4
You should be able to see your source of the leak with a mirror.

I had a 71 M-code 351c that suffered from blow-by at anything past 4500 rpm. If you didn't have a really thick bead front and back, it would push oil out at the higher rpms. But you could drive for weeks keeping it in the 3000 range and never have a problem. Even with the pressure that engine developed, once I had things sealed up, it was fine. I should note I was using a factory spread-bore cast iron manifold.

You noted you have an Edelbrock aluminum intake. Have you checked to ensure it is not warped?
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#5
+1 on check for warpage. You should also do a compression leak down test just to verify you don't have any ring issues. Easy enough to do for the peace of mind.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
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#6
It's a brand new intake, anyone heard of a warped one from new?
  Reply
#7
No. But if you take it off again, a good metal strait edge will tell you.

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
  Reply
#8
Even if it is warped, it would have to be extreme for it not to seal against the silicone, wouldn't it?
I'm not against pulling it (for a 3rd time, getting quick at it now), I'd just like to make sure I have any new or better parts sitting there waiting, or a plan of attack, whether I need to put better gaskets, valley pan, etc...

If there was a warp in the intake, (which I'm not disputing at this time, just brainstorming because I'm at work now and won't see the car for a day or two) How is that much oil getting there so quick if it's really just a mist floating around in that area?
Would there be other signs on or around the ports/ gaskets around the ports that I should be looking for?
It has to be more than just along the back of the block I would think because it would have to be major for the the silicone not to seal it.
It strikes me odd that it would leak along the back of the block and not the front. I know I put more sealant along the back because it is hidden from view when opening the hood as compared to the front. The front has been bone dry everytime it's been driven. I would assume the bead along the front of the block is atleast a third smaller then what I applied to the rear.
What's the best intake gaskets to use upon reassembly? Exact PN's would be great (ball park price would be nice too).
So if it all looks good and square, I should use the new gaskets, put an even bigger bead along front and back, then reassemble?
  Reply
#9
easier than a leakdown test is to hook up a vacuum gauge. Worn rings will show as lower vacuum at idle say anywhere from 8-14 inches at a smooth idle. To verify open and close the throttle quickly and if the rings are worn it will drop to 0 and then come up to maybe 20 and then drop back down to where it was. A healthy engine will drop to 2 and come up to 25 or so.

Large cams will change the numbers to some degree.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
  Reply
#10
Engine is stock everything right from 73.
I did notice at any speed, getting on the throttle hard/quick, there is a stumble or hessitation . I just assumed it's the carb not being tuned just right. It's an edelbrock performer 600 I believe.
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