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Discussion Starter #1
Currently in the process of installing new intake gaskets on my '82 mustang (below) since oil is seeping out the rear gasket.

What's the best way to seal the ends of the intake without the end gaskets pushing out during installation? What type of sealer is best to use on the ends. I have the intake off and just waiting for the gaskets to arrive through Summit. I used a silicone sealer last time on the ends without using the end gaskets because I was told to just use silicone on the ends to avoid the hassle but I think I was mis-informed last time!
 

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Currently in the process of installing new intake gaskets on my '82 mustang (below) since oil is seeping out the rear gasket.

What's the best way to seal the ends of the intake without the end gaskets pushing out during installation? What type of sealer is best to use on the ends. I have the intake off and just waiting for the gaskets to arrive through Summit. I used a silicone sealer last time on the ends without using the end gaskets because I was told to just use silicone on the ends to avoid the hassle but I think I was mis-informed last time!
Nope, you were informed correctly, just make sure you run a healthy bead (at least as big as the gasket that you are replacing it with) and then run your finger along the seam to smoosh it back into the seam after you get the intake on.
 

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I have never had to run my finger down the bead after isntalling the intake. If you need some clearance around the distributor, let it cure, then cut it away with a blade. You can also paint it if it's the right stuff (gray) and it becomes invisible.

What I've always had decent "luck" with is just running a bead of GRAY (semi-hardening) funny-cone (or silly-cone, whatever you call it), let it skin over a little, then use some long 5/16" bolts with the heads removed as guides to set the intake down squarely. Once the silicone is compressed a little DON'T move the intake forward or back. You get one shot.

The keys are: cleanliness. Clean the bottom of the intake. Clean the block mating surfaces. I use sandpaper to get ALL of the old gasket goop off, then some acetone and a towel (lint-free of course...T-shirt works well since I tend to ruin them in short order anyway) to wipe the surfaces perfectly clean. Silicone will not stick to the tiniest bit of oil, gas, methanol, etc. It needs to be bare metal...and the 60 grit helps rough it up a little so the funnycone will "bite" to it.

Gray silicone works well for this. It's less flexible once cured. It also expands just like any other silicone...so if it's applied properly, it will acutally expand inside and squishes a little outside the gap you're trying to seal up, which tends to hold better. I've used Orange, Blue, Black, and Copper...they all worked ok but after a while they get loose from the constant pulses inside the running engine (crankcase pressure). Of course we run methanol which complicates things a little but thus far the gray had worked excellent. Actually the intake is a bit hard to remove when freshening up...the stuff just sticks better and gets a little harder. The one downside is that you don't want it to be starting to harden while dropping the intake on. It needs to be slightly "skinned" but nowhere near hard. About 5 minutes after application is all you have..it hardens pretty fast but takes a while to fully cure. Handles the heat just fine as best I can tell. Most of our stuff never gets over 220-230° anyway.
 

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Whenever I do an intake and get GOOD lasting results where customers don't come back for leaks, I CLEAN THE HOLY SCHITT out of BOTH surfaces SUPER DRY, the intake and block!

Then I snake a 5/16 inch bead of RTV on the ends and go around the coolant ports on BOTH sides of the gasket with a nice THIN THIN layer of RTV, then set the intake on it, and put in 4 bolts finger tight and let it sit 2 hours before screwing with it again.

After 2 hours I go through the tightening sequence three times, I go through it once to get proper torque on all bolts and on EACH BOLT i use Permatex THREAD SEALER (non hardening), and after abotu one hour I do it again, then 30 minutes later I do it again and I get 100% perfect compression and sealing on my intakes.
 

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+1 on the other posts. CLEAN. Good bead. Set in-place with just a few pounds torque and let it semi-cure before final and repeated torquing. I wait over-night if possible, so I'm actually compressing the half-cured silicone. The beads will take 2-4 days to fully cure all the way through. I've never had a leak with that method. BTW - if you cut the heads off 4 cheap bolts to use as guides when placing, you won't fudge the beads.

David
 

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use some long 5/16" bolts with the heads removed as guides to set the intake down squarely. .

How does this work? The bolts on an intake screwed in on an angle, am I right? How do you set the intake down on them?
 

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If i recall correctly, the intake bolts are straight up, ARP offers an intake stud kit, install the studs, your RTV both ends & slip the intake over the ARP studs, tighten her down following the right sequence, foolproof!
 

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Discussion Starter #8
How does this work? The bolts on an intake screwed in on an angle, am I right? How do you set the intake down on them?

You're thinking of a Chevy intake. They are on an angle like you mentioned.
 

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Discussion Starter #9
So you guys say I should use RTV gray silicone (semi-hardening) for the ends? How long after I have everything back together should I wait to fire up the engine? A day or so afterwards?

BTW, silly me forgot to drain some of the coolant out before removing the intake and now I have to change the oil again because anti-freeze spilled out of the water passage from the heads into the lifter gally, which most likely made it's way to the oil pan I'm sure....Grrrrr!
 

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Discussion Starter #11
Ok, have a few more questions. My gaskets arrived today but they are not exactly like the old ones. For one, the port size is bigger and there is a missing hole in the center of the gasket (where the two center bolts are).
The package says they are for 1.40 x 2.25 ports and all 260, 289-351w ('62-89) including TFS, GT-40, N heads. The ports sizes are taller than the ports on my heads ('74 351w). Can I still use them or do they need to go back?

Second, I got the Fel-Pro black composite type. What side goes towards the block...the smooth glossy back side or flat gray side?
 

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Sounds like you got some 1262 R's. Those 2.25's are for fairly large port heads. I believe they are also .090 thick compared to the normal .060 thick gaskets. I went with the 2.10 x 1.28's on mine this time. I run a set of iron World Products heads with 180 cc intake runners out of the box. There was just a little on one side and the top of the intake runner that needed to be removed to fit the gaskets. The intake is requiring more grinding to port match but it was cast to be port matched.

These are what I am running. Felpro Q 1262, 2.10 x 1.28, .060, no exhaust gas cross overs.


That hole or missing hole in the middle is for the exhaust gas crossover. Neither my heads or intake have that passage open. There is a special biscuit that comes with some intake gaskets to block that if your heads have that open. A regular gasket will burn through I think.

If you put the silicone on your ends in one afternoon I would let it cure over night. I have used red RTV on the ends for years. Dry fit the intake first with your side gaskets to see how much gap you have. You want your silicone bead to be about as wide as the block faces and about twice as high as the gap so that it will spread out when you place the manifold. Both the intake surface and block surface should be clean and dry. I use B12 on a rag to make sure there is no oil on the surfaces.

Once you set the intake down don't wiggle it around a lot. Get your bolts in and torqued down fairly quick. Next morning, re-torque your intake bolts again.

Since you are asking these questions I thought I would add that you need to make sure that you put the front side to the front on your gaskets. And some are labelled manifold side versus head side as well. Sorry, was thinking of head gaskets. Some of the intakes do have a manifold side versus head side though. Your intake may have the water passages blocked on the back. Back on the silicone thing, I paint a very thin film of silicone around the water ports on the intake and the heads for extra safety.

Felpro 1250, biscuits but no gravy, LOL. 2.00 x 1.20 port size, .060 thick.
 

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Discussion Starter #13
Yes, those are the part # I received today. SO I guess they are going to have to go back...damn it. I think I need the QMS 90361 or the QMS 90116 for the stock port size and exhaust crossover ports.
 

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You would use 90116s if your manifold has 16 bolts or 12. The early heads have 16, and if the manifold has 12 be sure to plug the extra holes by the water jackets with silicone so they don't turn into rust pits in-case you want to use a 16-bot intake some day. You can use 1250s, which are a bit over-sized (especially for stock 289/302/5.0), but have the option of blocking the heat crossover. I always block the crossover unless I expect extended sub-zero temps on a daily driver. The intense heat causes carb heat issues and reduced performance after warm-up in more 'normal' weather, even with EFI. Depending on your manifold, it may take an extra 30 seconds to 2 minutes to fully warm.

As a general guide to port sizes (various castings have random actual dimensions) and performance gaskets to compare how they stack:

  • 289/302/5.0/late 351W - 1.80 x .9
  • Cobra & Explorer GT40/GT40P - 1.87 x 1.05
  • '69-'74 351W - 1.97 x 1.18
  • Fel-Pro 1250 - 2.00 x 1.20
  • Fel-Pro 1262 - 2.10 x 1.28
  • Fel-Pro 1262R - 2.25 x 1.40
The 1250s (and equivalents from Victor, Mr. Gasket, Flatout, SCE, ROL, etc.) are used in ported stock heads, and aftermarket up to AFR185, TW170 and similar. The 1262s are for AFR205, TW190FAC and similar. 1262R is only for big-port race heads, and are usually modified during custom porting. As Hottarod already stated, they are also thicker to get better sealing around the relatively thin edges.

FWIW, classic SBF ports from 289s to 5.0 HO run in the 120-125cc range, with the early 351W and GT40s in the 135-140cc area. Considering that stock GT40s can slightly out-flow stock 351W heads even with their slightly smaller ports and valves simply shows how airflow does not rely on big holes, but well-shaped ones. HTH

David
 

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best way I found is Permtex #2 around coolant holes , for ends sand the manifold/block rail .RTV bead for ends . no skinnig over , this lets it act as a glue .
RTV on gaskets act as a lube . will let the gasket slide/move
 

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Discussion Starter #16
best way I found is Permtex #2 around coolant holes , for ends sand the manifold/block rail .RTV bead for ends . no skinnig over , this lets it act as a glue .
RTV on gaskets act as a lube . will let the gasket slide/move
That's what I did. I used RTV super blue sealant though. I was going to use gray but they didn't have any left so it was either RTV red, blue, black or super blue...lol. I got the intake on last night and torqued down to 25 ft/lbs. All I have to do today is install carb, dizzy and the other odds and ends plus change the oil because I forgot to drain some coolant out before I started this project.

Hottarod, I took my old gaskets to the parts store to match up with the new ones. I needed the 90361 set. The 90116 set has slightly different shaped water passage ports.

Since I had oil seeping out the back before, was I losing much vacuum or performance? It was like that for a long time and didnt seem to hurt anything. I just now finally felt like going through the hassle of getting it fixed..lol
 

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Since I had oil seeping out the back before, was I losing much vacuum or performance? It was like that for a long time and didnt seem to hurt anything. I just now finally felt like going through the hassle of getting it fixed..lol
NONE more than likley...just makin a mess
 
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