I failed at my fist attempt. I had a large internal oil leak to the ports. Engine is a 1957 283 with early 1959 Corvette heads. This time I am using Felpro 1256 gaskets. Some questions- China wall seal- Right Stuff black or grey? Or something else? First time I used Right Stuff black 1 minute and wonder if it set up too quickly before I got the intake torqued down. Plan to use 90 minute this time. Gasgacinch or hi tach to hold the gasket in place? Block and intake see to be at the correct angles to each other. Thanks
Well, I always use Felpro gaskets to the heads and something like Ultra Black on the ends. Never had one leak that I can think of. I have had a couple where the intake was pitted some around the water passages so also used a little of that black stuff around those ports.
I am speculating that the right stuff 1 minute set up enough that it held the intake so it didn’t torque down totally.
That would be my guess as well. Takes a bit to get it tightened down so 1 minute seems way too quick to set up.
If intake or block cut /milled a thicker intake gasket needed , usually .060 -.080 thou,,, some times a .120 . Good steady bead on china & in corner where head & intake meet. Start all bolts , then proceed to torque Right stuff or Gray , Black
The 90 minute right stuff only comes in the small tube- 1 or 2 to get the job done? Is black or grey better?
To verify that the fit is correct and that you don’t need thicker gaskets, you can set it on dry and make sure it appears that where it seals to the block isn’t holding it too far away from the heads.
In my experience when an intake leaks it’s because something isn’t right, not square, bolt holes not lined up, heads skimmed etc. Put some gaskets on and place the intake on, use a feeler gauge to check for squareness. Look down the bolt holes and make sure the bolts aren’t going to bind on the edges. Look down the ports with a mirror or endoscope and check they line up.
Came to say the same as @guthriesmith and @Oneball. Check fit dry, using everything you can to make sure head and intake surfaces are square and aligned. There are different thicknesses of gasket to raise or lower the installed height, but if the intake and head surfaces aren't parallel you are going to have issues. There are formulas for shaving the intake when the block is decked or heads surfaced, but most don't have those numbers at hand. Had a friend build a OT v8 with the decks cut more than normal. It required the intake to be machined and fitted due to the heads sitting lower and closer. Don't expect a thick gasket to seal a wedge, but a thin shim style will be less forgiving.
And while this probably is not the case...but just in case it is...if you're using the How to Rebuild you SBC book...note the listed torque spec contained within the book at 20 ft-lbs is wrong. It should be 30-35 ft-lbs. Don't ask me how I know, or how many leaking intake manifold gaskets I had before I figured that out!
I do have that book, I can’t remember what I used as a torque value. 30-35 with aluminum intakes as well? I wonder if this was the issue for me as well?
I torque them down, then torque them again after some run time. They settle in and are able to be snugged down again. I do the same with exhaust manifolds/header flanges.
Unless your intake ports have been enlarged & even then a 1256 has very large ports that probably won't match your components very well . Either the heads &/or the manifold have been milled excessively or the assembly procedure is wrong if they have a valley / port leak . How did you determine that you needed double thick , oversize gaskets?
Is there a PCV valve or at least breathers so your not building pressure ? I still dimple the top of the China wall and the intake to help hold in the sealeant just like I used to do 40 years ago when the trick was to use the rubber end pieces and 3m weather stripping adhesive to hold them in. I use black right stuff these days and never have any issues. Its got to be clean and have some texture . I still use a little silicone around the water ports if there is any pitting or issues it cant hurt really .
I think the 1256 is for stock ports? I am running an oil fill on the front and the rear of the block has a pcv plumbed to the front of the carburetor. The engine has the stock oil baffle can.
I use Felpro intake gaskets and toss the China wall pieces. I run a 1/4" bead of Ultra Black gasket maker along both China walls with a little extra at each corner to ensure the corner seals. I carefully locate the intake and get all the bolts started, then tighten them down lightly as I work around the pattern until they're all snug. Then cinch them down tight after that. Honestly I've never used a torque wrench on a SBC or BBC intake manifold and never had a leak once I abandoned the China wall gaskets decades ago. I also never start the engine up the same day I install new gaskets. I let the gasket sealer cure overnight before starting the engine.
Do you have the large or small oil baffle in the valley? If you have the long one which came on 2 barrels intake and not the short one it will inter with the intake sealing. You have two choice's find a small one or take a hammer and flatten it so the intake will fit flat. Try setting the intake on without gaskets if Rich’s you have interference with the oil baffle. Don’t leave it Out or it will leak oil out the road draft tube or the vent to breather if you have a PVC system like crazy. Here is a picture of the short version. I figured it out in 1959.
Yes, it's the front and rear walls of the block. A term used for many decades by hotrodders as in "the great wall of China". Do a Google search for "China Wall" SBC, BBC and tons of replies to look at. " Product Description Reher-Morrison’s intake manifold end rail spacers are CNC machined from 6061-T6 aluminum. These spacers fill the gap between the bottom of the intake manifold and the top of the lifter valley at the front and rear of the block. (This area of the lifter valley is sometimes referred to as the “china wall”.)"
Throwing this out there to make sure folks understand the consequences of milling different components. 1. If intake has been cut/milled but the block or heads have not, then you'll probably need thicker gaskets to make up for the material that was lost in the cut on the intake. Otherwise it will sit too low and you may have some port mismatches. 2. If the heads have been milled, or the block decked the result is that the heads sit lower, and consequently closer together. In this case if you have an uncut intake you either need to use thinner gaskets or have the intake cut accordingly, as a stock width intake will sit higher on the heads.
Well I have to tell you, as a kid I obtain a tunnel ram with two 500 CFMs bolted onto my 327, cut a hold in my 56 Chevy hood and hook everything up. Ran like crap, so with my idiot friends (as my Pop would say) helping still no luck. After about three days of screwing around the "Old Man" step into the garage to see what the problem was. I started it up for him and he spray a little oil in around where the intake meets the heads. Sure enough, I did not have everything tighten up. Follow the advice as given and you will have no problems.
^^^^ Yep, spraying carb cleaner at idle and hearing the engine respond = leak. An old follow up trick is to hit the area with a bit of silicone (which gets vacuumed into the leak), then shut off the engine and let it cure.
^^^^^ Double check this. Make sure the intake manifold is not hitting the oil baffle in the lifter valley.
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