Thread: aluminum heads / gaskets

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What do I need to know to change the intake gaskets on my 383 stroker with aluminum heads and intake? Any special materials or techniques?

The 'shop' installed the intake on the Summit longblock and it leaks vacuum.

So, I'm going to make a day of it, and swap hedders, intake gaskets, and distributor.

Make sure to get intake gaskets that are apropriate for your intake // heads combination.
For example, there is the " Early style " up to 1986, " Late style " 1986 & newer, IIRC.
I don't recall when the change was made.
Differences include bolt angles, locations, and number of bolts used.

Also Blue or Black RTV sealant or similar.

Have you done this before?
If not, I'm sure you can get very detailed & exact info here on CHR.
Great group!!

Just a thought here - did your shop square the block? Standard height is 9.025 and it's not uncommon for a block to be a titch out of square. You can take a couple thousands off with out much problem, but if they took the block below 9.020 and didn't shave the intake manifold it will be really difficult to get a good seal.

That said, if the block hasn't been cut or if it has and the manifold milled to match, I'd remove the intake and proceed as follows:

Lay a few rags in the lifter galley to catch fluids and woolie goobers. Clean the head and the engine block with acetone. (Goes without saying - please put on some safety goggles before using the acetone - I'd feel horrible if you got a splash in the eye and you'll really feel horrible!!) Remove the rags and clean any obvious little bits of gasket. Use some Gasgacinch or similar sealant on the heads and on head side only (none on the manifold side) of the gaskets – this is important – let the Gasgacinch dry until it’s no longer tacky and then set the gaskets on the heads. Do not use the rubber end seals that come with the gasket kit, rather a good RTV silicone sealer instead. I use black, but I’m not sure it matters – my dad swore by the blue RTV and he built a ton of “leak-free” engines. Put a good bead on each block end seal surface – make sure to overlap the intake gasket about ¼ inch at the four corners. I let this sit for a “full-cup-of-coffee” before setting the manifold.

Follow the instructions with your manifold for the sequence of tightening. I put a small blob of silicone on the eight inner bolts to prevent oil leaks (irritating if you forget and get a bit of oil pooling on your nice new manifold). Torque value for pre 1986 is 20-25 foot pounds. Vortec heads usually are good at 10-15 foot pounds – resist the temptation to over-tighten as it will squish the silicone out and you’ll be right back to square one.

Change your oil and you’re good to go!

Have fun,
Glenn

And don't forget to remove the grease rags from the lifter gallery! I know of a mechanic who left one in the engine once. The customer got a free rebuild. The shop owner was not happy.

Originally Posted by rumrumm

And don't forget to remove the grease rags from the lifter gallery! I know of a mechanic who left one in the engine once. The customer got a free rebuild. The shop owner was not happy.

Good instructions from Glenn! Not to hijack, but a good friend tells the story on himself - before painting his new intake glossy black to match the engine he ran a strip of duct tape over the machined surfaces to keep them clean, trimming the edges nice. A few days later they were all ready to assemble, and a buddy was assigned to hoist the intake and plant it square on the new gaskets. All buttoned up later, and after a bit ready for first fire. Cranked & cranked, never could get it to do anything. Quit in frustration a few times before they finally decided a few days later they were going to have to pull the intake. Yep, still taped, nice & tight, with nary a molecule of air getting into the cylinders. Talk about embarrassing!!

Okay - true confession time - I'm usually pretty conscientious about putting things back together and on one occasion, I got a friends '68 Firebird buttoned back up after replacing intake manifold gaskets (hmmm - sound familiar??). Well, I was wiping tools and I couldn't find a 1/2 inch combo box/open that I knew I had used. I hunted high and low and couldn't find it and then tried to remember where I had last used it and couldn't remember. In fact, I'd used a 1/2 x 9/16 to tighten the alternator. Then I started to worry and so I informed my friend that I couldn't find the wrench and we needed to pull the manifold off because I feared that the wrench was inside the lifter galley.

Long story short - pulled the manifold off and nothing. Now I was really getting upset and my buddy grabbed the coffee pot and two folding chairs. As I sat down, I felt something weird and discovered that the wrench was in my back pocket. We both laughed until I cried. I finished my coffee and then re-assembled the engine which fired and ran beautifully with the timing spot in the first crank.

I don't put tools in my back pocket anymore.........

I've told this one before, but it's just a reminder of things that can go wrong....
I was doing an engine swap, 302 Ford/C4 into an '83 Mitsubishi pickup. It was impossible to install the engine and transmission separately, so they had to go in as a unit. I was just gettin' ready to fire the motor off to break in the cam (Isky 270 mechanical) when I looked over at the little shelf on my toobox. There, resting comfortably, was the driveshaft that goes from the torque converter to the transmission pump. Everything had to be torn apart to pull the motor/trans, separate 'em and insert the shaft...... fuel lines, exhaust system, wiring, cooling system, etc. Doing something stupid like that will sure take your self confidence down a notch or two.

As far as aluminum heads, use only the head gasket recommended by the manufacturer of the heads. If the fire ring in the gasket stands proud, it can imprint a depressed circle of material (called Brinelling) into the cylinder head. While this should not be a problem on your present build, it could be a problem if you used the Brinelled heads on another build later. The heads would need to be shaved down to get rid of the Brinelled ring and get a smooth surface again. Better not to have to do that, use the correct gasket in the first place. The default gasket to use for a 350 Chevy block is Fel-Pro #1003 if you cannot get any info from the manufacturer. It uses a pre-flattened steel wire fire ring. Here's verbage from Airflow Research....

"Fel Pro #1003 for all aluminum heads up to 4.100 bore. Fel Pro #1034
should used for 4.100 or larger bore. Applications requiring steam holes (SBC 400 block) should use Fel Pro #1014. Late Model LT-1 reverse cool applications use GM gaskets or Fel-Pro #1074. AFR has removed the cooling passage between cylinders 1 & 3 and 5 & 7 to increase strength of the casting, do not drill these areas out in an attempt to find water jacketing."

Thanks much everyone.

Guess I should have mentioned, It's a Summit long block, and new air gap edelbrock intake.

There are some machine shop fellows on this site who disagree with what I'm going to say here, but for most of us fellows working on our motors at home, I recommend buttoning up the motor with all torque specs, then removing the intake to inspect the gaskets between the heads and intake. Without expensive equipment, that's the only way I know of witnessing that the gasket material is depressed and sealing all the way around each and every intake port. If you get an INTERNAL leak there, the motor will be pulling oily vapors into the cylinder every time the leak sees suction from the intake valve. You'll never find it by spraying ether or other materials that are used to find EXTERNAL leaks.

Pat and Jerry and other fellows who have access to high-buck equipment can engineer a motor build without sacrificing another set of intake gaskets, but us poor folks have to use other methods to insure that the motor is sealed up inside and outside.

The other recommendation I'll make is to use a high-rise, dual plane intake such as the Edelbrock Performer RPM or Weiand #8116 or the Holley 300-36. All three of those were patterned off the 1969 Z28 intake that was cast in aluminum by Winters for Chevrolet and will make more power on a street motor from idle to 6500 than any other manifold. Weiand changed the design of their Hi-rise and you can no longer buy the 8116 new, but if you find a used 8116 or Holley 300-36, buy it. I found 3 new 8116's for sale on Amazon a few months ago. I posted the info and they were gone in a day or so. There may be more of them languishing on shelves somewhere as new old stock (NOS). When you find 'em, buy 'em.

Edelbrock 7101 for early heads.
Weiand 8116 for early heads.
Holley 300-36 for early heads.
Edelbrock 7116 for L31 heads.
I would use an air gap intake ONLY if I lived in a hot climate. Cooler climes will like the non-air gap better in my opinion.

well yes .... and No... if you look at the old gaskets and intake they will tell the tail of the inprint if it is leaking sooo . then you should mock it up with old gaskets and check intake that the china rails are not bottom out .if you want to use a new set of gaskets thats up to you

China rails? Haven't heard that one.

As for climate, the car is destined for Georgia, unless I get a good offer.

[QUOTE=firebird77clone;464089]China rails? Haven't heard that one.............................. sorry china wall s as in the great wall of china the front in back of block that close in the lifter valley the thin part of the block that are like a rails or china wall ok

Originally Posted by pat mccarthy

well yes .... and No... if you look at the old gaskets and intake they will tell the tail of the inprint if it is leaking sooo . then you should mock it up with old gaskets and check intake that the china rails are not bottom out .if you want to use a new set of gaskets thats up to you

I agree Pat, and that will work fine until you take any kind of a cut on any of the pieces. If you are tearing the motor down to freshen it up without cutting any metal from the block, heads or intake, then yes, go by the imprint of the old intake gaskets.

who.s cutting any thing ? if the intake was leaking then the gasket he had on it will show it leaking and were and then you take intake to a guy like me. he will get it close . then recheck it BUT i been threw many many times on tall deck race engines and some short decks if way off. then it better to take the engine to the shop so it can be fitted to the block the guy checking and the guy cutting works out better if he is the only guy . that why most all engines i build leave with the intake on. if intake is bottom out on china walls the gasket will not show. most all times this holds intake up making for a hell of a leak. if ports are close the intake will not leak from port linement only. but if the intake is warped and would have to be a hell of alot then a clean up will help . angles can be off. i use a feeler set push the intake to the one side of the head intake face side then check air gap top bottom and front and back . but first shim up shim up the china wall