SB Chevy intake end seals

[Ron Slabaugh]

Prior to building my 383 I'll bet I installed dozens of SB chevy intake manifolds. I always used the rubber end seals and NEVER had a leak.

My 383 runs AFR 195's and a Perf RPM intake. The layout does not lend itself to using the rubber end seals. I've used a thick bead of high temp black silicone instead, like many people do with success.

I'm almost embarassed to admit I'm pulling the intake for the third time due to the rear leaking oil. Can anyone recommed a sure-fire method of reassembling this thing to seal it up? The Fel-Pro intake gaskets for the 195's come with cork end seals that I could use. Also, what type of sealant is best?

Thanks in advance.

[the FLYER]

been a while fer me... my old method was ta get a small center punch and put 2 rows of dimples on the block and intake... seemed ta grab the seals better. i hear all the time about usin' silicone in place of seals... but i've yet ta try it... i've no experience concerning the cork seal usage...


best of luck to ya :)

[FunkyNova66]

I used the red high temp silicon and never had a leak whatsoever. Run a nice "bead" (like a nice thick weld) across the front and rear all the way to the felpro intake gaskets. Carefully set the intake straight down as close as possible on the first attempt. You can move slightly (side to side) to start the intake bolts but do NOT lift the manifold back up once you set it down.

Make sure the surface on both the manifold and block is clean of old silicon, oil, etc prior to doing this.

Good luck.

[Ron Slabaugh]

Maybe the intake does not fit the heads correctly due to block or heads being milled?

The heads are straight from AFR. The block decks were milled by a very competent machinist. He used a fixture that set up on the crankshaft and camshaft centerline. The decks are exactly square.

I would expect poor geometry to impact intake gasket sealing, which is fine. My problem is with oil leakage from the end seals.

Thank you for the thought though.

[bowtie0069]

I never use seals, just silicone. Are you sure it's the manifold and not some other source? I've had the plug on the rear of the deck area leak; the distributor can ooze oil past the gasket..........just a thought.

[Repointer]

Did it about 6 times in the last year. Always scrap real good with a razor and then clean with alcohol. Used the high temp red and made sure it was lined up on the first shot like Funky. I let the silicon "set" for about 10 minutes before installing the intake.

[the FLYER]

Did it about 6 times in the last year. Always scrap real good with a razor and then clean with alcohol. Used the high temp red and made sure it was lined up on the first shot like Funky. I let the silicon "set" for about 10 minutes before installing the intake.

didja do this 'cause ya had a leak or because of other reasons ??? i'm assuming yer manifold was always sealed, but had other reasons...


just clarifyin' fer the sake of yer advice on sealing ;)


respectfully,


the Rotten guy :D

[Repointer]

didja do this 'cause ya had a leak or because of other reasons ??? i'm assuming yer manifold was always sealed, but had other reasons...


just clarifyin' fer the sake of yer advice on sealing ;)


respectfully,


the Rotten guy :D

I guess that could be taken as I couldn't get it right huh.:awkward:;)

No, I put on the holley, victor, holley, holley, holley, and finally the air gap. A cam change, new heads, new manifold, all at different times...I been getting lots of practice.:D

[the FLYER]

heheheh yes, i remember readin' 'bout some of yer exploits :D just hoped Ron did too or it coulda been misunderstood :eek: :rolleyes: :D

HA !!! glad ya took it as humorus :D


have a Great Weekend !!!! :D

[chevynuts88]

Years ago I decked the block on my engine and planed the heads and had the same problem.All done by competent people.In order to make it seal properly they had to take some material off the sides of the intake.

[Pick]

I have a 383 with AFR 195's straight from the factory and an RPM AirGap. I did not use a gasket on the end walls, just a thick bead of UltraGray RTV - and mine leaked also. The front had a small leak and I stopped it completely by cleaning the surface as clean as I could get it, and then putting some RTV on my finger and running it back over the existing seal. I've done the same thing on the rear, and I've nearly stopped the leak, but I will still find a little oil escaping now and then. I'll pull the intake this winter and try again.

You ain't the lone ranger on this one.

[DriveWFO]

I use RTV as well and never had a problem. I lay a nice, thick bead on the front & rear walls and let it "skin" up for a few minutes. I first clean the walls with a razor blade scrapping tool and brake cleaner.

[kceb10]

I have never used the end seals, just silicone after you get the intake back together let it sit for a couple hours before you start it up so the silicone have time to completely dry should never leak

[Paul Wright]

As most have alluded to the trick is not being in a hurry and torquing down the intake too soon

The RTV has to stick to both surfaces and then partially cure. The reason is to have a springy preload.

When I worked in dyno we swapped intakes on a regular basis. With practice you can do a leak free intake swap in no time.
The RTV of choice is Red high temp. This was developed in conjunction with GM specs and works very well.

1. Both surfaces must be grease and oil free so the RTV sticks.

2. Lay down an even bead but not too much or too little. Test fit the intake and visualize the gap that has to be filled.

3. Set the intake on evenly and straight. You don't want to slide it around distrupting the bead. The bead should have an even convex bulge and no gaps....anywhere.

4. Install all the bolts engaging a few threads but don't tighten. Use a line up tool to hold the gaskets.

5. Wait for 20 minutes (depending on temp) so you get a partial cure. During this time you can smooth excess with a wet finger tip to get a nice convex radius. Think nice bathtub caulking.

6. Torque the bolts in sequence and in 3 steps.

7. After cure you can use a razor blade to trim excess, but if you've done it right there shouldn't be any. If it oozes on the outside then it oozing on the inside.

[Ron Slabaugh]

I have a 383 with AFR 195's straight from the factory and an RPM AirGap. I did not use a gasket on the end walls, just a thick bead of UltraGray RTV - and mine leaked also. The front had a small leak and I stopped it completely by cleaning the surface as clean as I could get it, and then putting some RTV on my finger and running it back over the existing seal. I've done the same thing on the rear, and I've nearly stopped the leak, but I will still find a little oil escaping now and then. I'll pull the intake this winter and try again.

You ain't the lone ranger on this one.

One thing I've noticed with the AFR heads is the distance between the manifold and block where the end seals would be is better than 1/4". I think the problem is getting the silicone to effectively bridge this distance. You need to start with a uncompressed bead of silicone 3/8" tall or taller. I waited a few minutes before installing the intake the last go-around and the bead of silicone seemed to grow shorter and wider.

[laser-red-nova]

I found the GM silicone from the dealer works the best.It is a little expensive compared to regular silicone but well worth it. It is alittle bit thicker also. My$.02

[stock z/28]

Hi,

Ron, if you have a real large gap that may be the problem as you said.

I have had similar problems with various after market cylinder heads and intake combos.

Its kind of a lot of work but I used the cork seals as templates and and cut some aluminum strips that I could attach with small countersunk allen screws. Of course I had to drill and tap the block and I used loctite flange sealer between the block and the strip and (I like the Ultra seal gray) silicone between the strip and the intake. This pretty well solved the problem, but it is a lot of screwing around.

Another issue I always worry about when I see an excessive gap is the distributor fit.


Good Luck

Jeff

[Ron Slabaugh]

I found the GM silicone from the dealer works the best.It is a little expensive compared to regular silicone but well worth it. It is alittle bit thicker also. My$.02

Ya know, you're not the first person to tell me that. Our fleet manager at work recommended the same thing. I'll see if they're open tomorrow.

[Ron Slabaugh]

Hi,

Ron, if you have a real large gap that may be the problem as you said.

I have had similar problems with various after market cylinder heads and intake combos.

Its kind of a lot of work but I used the cork seals as templates and and cut some aluminum strips that I could attach with small countersunk allen screws. Of course I had to drill and tap the block and I used loctite flange sealer between the block and the strip and (I like the Ultra seal gray) silicone between the strip and the intake. This pretty well solved the problem, but it is a lot of screwing around.

Another issue I always worry about when I see an excessive gap is the distributor fit.


Good Luck

Jeff

I'll give you credit for an innovative solution. I like it. However, I think I'll give the GM silicone a try. If it doesn't work maybe I'll break out the aluminum.

I checked distributor to oil pump shaft engagement during installation years ago. It wasn't ideal, but certainly not scary either.

I'm surprised that three of us on this thread alone have had problems with the excessive gap. I'm disappointed of the problems, but happy I'm not alone.

[Paul Wright]

Just how big is your gap?
If you have excessive gap the best solution is the aluminum shim that Jeff talked about. I've seen these used before on weird race combinations.

I think if you trace a cork end seal on a 1/4" aluminum plate and cut it in a band saw(maybe even a jig saw?) you could make a suitable spacer. Drill and counter sink some flush flat head allen head bolts. 10-24 may be the correct size. You'll have to check.

[Ron Slabaugh]

I measure the gap and it is under 1/4". The cork end seals measure around 1/8". Would it work to adhere these to the block with Gorilla snot and use a short bead of silicone to fill the remaining 1/8" gap?

[bowtie0069]

Just how big is your gap?

Sounds like a personal question to me! hehe.

I had an engine combo that had a huge gap--I tried stacking 2 corks and it still needed silicone to fill! It was time for a machine shop.

[Pick]

The gap on mine is about 3/16", maybe 7/32" in a spot or two. I'm sure it will seal when I redo it, I just didn't get the bead quite thick enough when I put the intake on. I will give the GM red a try though. Thanks for that tip.