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O/T Chevy intake leak !!!!

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Paul Shuler

02-02-2006 13:48:17




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Three years ago I built a small block 400 to drop in my old 86 Chevy. I put an aluminum air gap Edelbrock intake on it. I have had it off now two times for leaking where it meets the cast iron block behind the distributer. One time the parts place said to install without the gaskets just useing RVT. That lasted a few months. Then they said to use the gaskets and no RVT. Lasted a year. The last time I used both. About every two months or so it starts leaking again and I retorque the bolts and it stops it for a while. I don't want to crack that alum intake though. I have seen a lot of talk on here about stop leak products and pepper per Hugh. Would any of this stuff be a good / bad idea for this problem. Sorry for long post. Just tired of stepping in antifreeze.
Paul

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Dellbertt

02-03-2006 07:41:12




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
More knowledge posted than I have but I will say this. In my hotrod days, I had trouble with every Edelbrock I tried to use.



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Brownie 45

02-03-2006 05:40:57




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
Might try calling Fel-pro or one of the other gasket manufacturers to see if they have any ideas.



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Ron in Nebr

02-02-2006 18:36:08




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
Allan and the others are right- if it's leaking antifreeze it's the gasket between the intake and the head. Your description of "behind the distributor" was probably what got you the advice to just use RTV, since those valley gaskets often can be and are replaced with RTV.

But, NEVER use just RTV between the manifold and the head, especially around the intake ports. Gasoline turns RTV to a gell. I always just put a smear of RTV around the waterjacket openings with my fingertip and use nothing around the ports on the gasket.

Getting back to your problem, sounds to me like one of two things- either mismatched due to faulty machine work(in which case it "should" leak at other spots too). Lay a straightedge along the machined area of both the head and manifold and check for a low spot...Either that, or else you could possibly have a bad intake manifold casting- either poorly machined from Edelbrock(the straightedge would show that) or even a pourus casting that lets antifreeze "seep" through the aluminum.

Another thing, not sure if the Air Gap manifold has it, but some race aluminum intakes have a water outlet port at the rear flange surface to allow external water plumbing. If yours has this(I doubt it) the plug there could be leaking.

If it was me and there was nothing visibly wrong, I'd swap on another intake(you probably have the stock one lying around) and see if that cures the problem.

One final thought...since these are "redone heads", Check and see if one of the rear intake bolts isn't drilled clear through into the waterjacket...I doubt this is the case too, but ya never know...a dab of sealer on the bolt threads would cure that.

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Magman

02-02-2006 18:19:35




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
I put a 350 4 bolt main in my 88 chevy about 6 years ago and I have a simelar problem but mine leaks oil into the 1st two cylinders. So If your sure thats what it is and its not a hose or bad heater core maybe some teflon sealer around the threads of the bolts one of mine in front was drawing a little up through the bolt and I took it out and sealed it and it went away. JON



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Hermit

02-02-2006 17:41:21




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
You might want to try painting an indicator dye or ink on the manifold and pressing it against the heads. There may be a high point on the manifold hitting a high point on a head. Combined with the different expansion rates of the manifold and heads, a gasket and/or sealant may start leaking over time through shearing action as the engine heats up. Make sure you use a sealant that stays flexible at high temps.

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Mike S 806/H

02-02-2006 17:05:21




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
I have built alot of Big Block Chevys, Use Permatex Ultra Black RVT Put a 1/4 inch bead on the block and use your finger and smooth a thin coat on the intake also be sure the surfaces are CLEAN! use brake cleaner on a rag I have never had one leak, Also dont run the engine for 24 hours, let the RVT to cure



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r4etired

02-02-2006 16:21:29




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
I've have the dealer replace the intake gasket on my 97 chev pickup w/350 twice, once at about 55000 and again at 170000, Both times it leaked anti freeze on the shop floor, both times I would use Bar,s leak for about 10000 miles before I would spend the 600.00 to have it changed.Both times it started to leak it had set out in 10 below temp.Shop foreman said it was very common after a very cold night. I work on Farmalls pay for my Chevy work.

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Allan in NE

02-02-2006 14:29:24




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
Paul,

Just some ideas:

There is no antifreeze back at that valley gasket; just oil splash.

So, if you are getting antifreeze it has to be coming from one of the head/manifold runners at the side gaskets. Is it always at the same corner?

Are you torquing it down in a circle starting at the center? That aluminum bends like crazy.

Did you plane the block or heads? That will change the angle of approach on the intake. Are they the right heads?

Are you sure that the intake isn't warped?

Allan

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Paul Shuler

02-02-2006 15:22:12




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 Re: O/T Chevy intake leak !!!! in reply to Allan in NE, 02-02-2006 14:29:24  
Hi Allen, I didn't plain the block but it has new cast iron heads on it. Here is a photo of the motor when I finished it. I had a lot of problems with the machine shop. When it came back it was all jacked up with a ridge at the bottom of some of the cylinders. After much fighting with the machine shop found out the poor guy had a brain tumor and he didn't last 6 weeks. That explained the problems he was having. Had to have a lot of stuff redone on it. But it runs like a scalded dog. I just hate leaks.

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Allan in NE

02-03-2006 03:32:28




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 15:22:12  
Hi Paul,

Are those new heads 400 heads? 400 heads are totally different from all other small block heads and do not interchange, even tho others will bolt on. Same way with the head gaskets.

Those 400s are my favorite engine. Wouldn't trade one fer a trainload of big blocks.

Your engine looks sweet. I can just about feel it pull by lookin' at it! :>)

Allan



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Paul Shuler

02-03-2006 14:42:54




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 Re: O/T Chevy intake leak !!!! in reply to Allan in NE, 02-03-2006 03:32:28  
Yes they are new heads. And they are 400 heads. They had to have these small steam holes drilled in them. The machine shop ruined the first set by drilling them at the wrong angle.



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JACKKADE

02-02-2006 14:08:21




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
It may now be time to call the mfg (Edlebrock) for their recommendations. I think I would trust them to know better than the counter man at the parts store.



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BillyinStoughton

02-02-2006 14:04:07




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
While I guess a Chevy isn't a Farmall...I can't even count the number of SBC manifolds (both cast iron and aluminum) I've installed since my high school years. What I have done in the past is use the manifold end gaskets, but put a coat of quality RTV (Fel-Pro gray) to the underside of the gasket, install the gasket and allow it to "tack" into place. Now before setting the manifold, apply a good quantity of the same RTV to the top of that same gasket, and also into the corners where the end gasket meets the manifold gasket...give that a couple of minutes to set up and then drop that manifold on (being careful not to slide the manifold on any of the gasket surfaces).

This has always worked for me regardless of application, whether it be the 210HP farm truck or the 538 HP mini-rod.

I do find one interesting statement though...you say your are "tired of stepping in antifreeze". These end gaskets are only in place to keep the oil from the lifter valley from leaking out from under the manifold. If you have water coming from under that particular gasket, you have more problems than you may know. If indeed it is antifreeze you are stepping in, it may pay to do a little bit more investigation into the origin of the leak. A bad manifold lip gasket (either front or rear) will only lead to an oil leak.

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Paul Shuler

02-02-2006 15:14:49




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 Re: O/T Chevy intake leak !!!! in reply to BillyinStoughton, 02-02-2006 14:04:07  
You are right that it is more in the left hand corner {if looking at the motor} where the manifold meets the head. I got to tell you it's driving me nuts. I have been very careful to start in the middle and torque it per Edelbrock instructions and I did the rvt thing just like you said. Still leaks a cup full out overnight. I thank you all for your replys.
Paul



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Janicholson

02-02-2006 14:00:30




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
Milling heads can alter the sealing surfaces angle and distance. I would pull the manifold and look closely at the gasket (with a mic if possible) and look for uneven pressure applied at the gasket. (the manafold might be inaccurate as well).
If it is crooked, careful (minimal)angle milling/planeing of the manifold will do the trick.
Experience talking here.
JimN



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lee

02-02-2006 16:57:46




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 Re: O/T Chevy intake leak !!!! in reply to Janicholson, 02-02-2006 14:00:30  
I would second the notion that possibly the fit-up is to blame although sealing a manifold can be tricky business even with good fit-up. Lots of guys use the RTV across the valley rails. If you are using cork I would not use RTV but probably a hi-tack type adhesive cement and only very thin coat and only after checking to be sure the amount of squeeze (gap) is correct, too much/too little can be problematic. If using neoprene or silicone molded rail gaskets I'd put those in dry and pristine clean no oil, no hi-tack or sillycone. But your problem is really with the two manifold gaskets as that's where the water passage is so you need a good set of gaskets and I would hi-tack spray adhesive those a very thin coat allowed to nearly dry before very careful and precise placement on the heads and if there are any bolts running straight in i'd use long bolts with heads cut off or pins to guide the manifold straight down into place. Then you got to torque it slow and careful and bring it down int final position. manifolds can be a PITA. I've done my share. Worst I ever did was a Ford V6 3.0 I think took 3 tries to get her done then wrecked it two months later so don't know if strike 3 held or not. My problem was corks squezing out.

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VOLfarmall

02-02-2006 14:00:06




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 Re: O/T Chevy intake leak !!!! in reply to Paul Shuler, 02-02-2006 13:48:17  
Use fel-pro gaskets and use RTV in the corners don't over tighten I have had the same set up on a 454 for 9 years with no problems. I learned about fel-pro gaskets dirt track racing nothing else comes close.



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