Intake Gasket Replacement

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Ginger

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Written by kawamatt2


Well after 100,000 miles and seeing some wierd antifreeze like build-up on the inside of my oil fill tube i figured it was about time to replace the notoriously leak prone vortec 350 intake gaskets. To start with, this has been by far the most involved piece of maintenance i have done to this truck. I had never done anything this involved either. So basically short of what little info i could find on the internet i was flying blind. I will add though that my father helped me out through the whole process and he has worked on an engine or two.

So, to begin. As i have found through some interweb research intake gasket failure is a common problem for the 88'-98' style chevy 350. Characteristics of a leaky intake gasket are usually a milky oil, falling coolant level, white smoke, or in my case a redish build-up inside the oil fill tube. To replace the intake gaskets the concensus is to use Felpro gasket set MS98000T. This set comes with the two instake gaskets, upper intake plenum gasket, throttle body gasket, fuel injector assembly gasket, fuel line o-rings where they attach to the manifold, valve cover gasket, and what i think was a distributor gasket. There may have been other parts included but i can't recall because i probably didn't use them. I purchased my gasket set from rockauto.com and it was about $65 shipped. While i had it apart i decided to go ahead and replace the thermostat, cap, rotor, and radiator cap. So once you have all this you are ready to tackle this job.

First off, don't get too overwhelmed with the mess of wires that greet you after you pop the hood.
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What i chose to do first was to take off the upper and lower fan shrouds and drain the radiator. Have a couple of buckets or one big one handy because the **** will drain from two or three different spots in front the drivers tire.


Next, take off the air filter assembly and tube to the throttle body.
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Go ahead and remove the upper radiator hose and the thermo and thermo elbow. I also unscrewed the egr tube at this point.

That done, i chose to unbolt the throttle and cruise cables. There is a bracket on the a/c compressor and the upper intake.
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Now you can start to unplug all the sensors and stuff related to the intake. It would probably be a good idea to take pictures of each connector and where it came from but i'm fairly certain no two connectors will interchange. I only took so many pics to help remember the routing of all the wires.
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It is at this point that i would like to address the issue that seems to be so common with the heater hose quick disconnect. Below is a picture of the quick disconnect fitting.
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As you can see there is a plastic liner inside the metal fitting. This plastic degrades over time and pulling out the hose often times shatters or in some way degrades it to the point that it will leak upon re-assembly. The problem lies in the removal of the fitting from the intake. The fitting has what looks like either thread lock or sealant on its threads into the intake and is notorious for breaking the threads off inside the intake requiring the user to drill out the remaining fitting and retapping to .5" pipe tap. I foolishly rushed the tear down process before thinking of my options and went ahead and pulled the hose out of the fitting. I had the choice when re-assembling to try and put the hose back in the fitting hoping it wouldn't leak and try and remove the fitting from the intake. I was almost positive that i would break the fitting and this wasn't an option. My truck is my only means of transportation and it had to be able to get me 400 miles back from my parents house to where i live 2 days later. SO, with all that said, if i were to do this again in the same situation where i couldn't afford any down-time for broken parts other than what is required for intake replacement i would leave the fitting in the intake and cut the hose about a foot back from the intake.
Once the hose is cut you can remove the intake leaving the quick disconnect and section of hose still attached. When re-assembling i would use one of these to reconnect the section of cut hose.
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I actually already had this intalled in that hose but as i said earlier i rushed dis-assembly and never even thought to remove the hose from one of the ends and leave the quick disconnect alone as opposed to removing the quick disconnect from the intake. So this is my recommendation for dealing with the GM quick disconnect.

Now moving on, i went ahead and unplugged the three plugs from the a/c compressor and unbolted it. You can then just lay it back onto the passenger side inner fender like so.
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At this point i marked the plug wires and removed them from the cap and removed the cap from the distibutor.
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I then continued to unplug wiring harness **** from the intake and remove the brackets that hold the wiring harness up off the intake. I also remove this ground wire from the front of the block on the passenger side so i could get a little more slack in the harness for when i would need to tie it up out of the way.
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Go ahead and unplug the big connector for the fuel injector pod and protect it somehow. I used a ziplock back to put the connector in and stuffed a rag down into the pod. You can also disconnect the fuel line at the back of the intake. (Note: It helps to get up in the bay and sit on the core support to reach some things.)
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Ginger

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You can pull the fuel lines out of the injector pod once they are loose from the lines running up behind the engine. Be careful to not loose all the orings and such. I think there are two orings a washer and a spacer for each line. You can go ahead and put them back down into the holes in the pod. Re-assembly with them on the actual lines i don't think is possible.
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At this point i had all the sensors disconnected and tied up the main wiring harness to get it out of the way. I went ahead and pulled off the upper intake plenum. I did this in the truck for two reasons. One, so i could better see the distributor and mark its location correctly, and two, to try to cut down on the bulkiness of pulling the lower intake out.
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Now you need to go ahead and mark the distrbutor. You need to make a minimum of two marks. One need to be from the rotor to the distributor. This mark will help you when you go to re-install to get the distributor teeth to line with the cam teeth the way it came out. The other mark you need to make is from the actually distributor shaft to the intake. This mark is so that you can re-isntall the distributor in the block with out advancing or retarding the timing by having it turned slightly. Unfortunately i don't have any pics of this as it was a pain to just see back there much less take a picture. Any questions on this just post up.

Once these marks are made you can go ahead and remove the distributor by loosening the hold down bolt. Note that the bolt doesn't need to come all the way out. Once loose enough you can slide back the hold down tab and the distributor will lift right out. You can follow this with removal of the coil and its mounting bracket.

Now, you are going to have to loosen the a/c and power steering pump bracket and slide it forward to get access to all the intake bolts. There are two bolts and a stud with nut on it on front of the bracket around where the a/c pump mounts. This pics shows those three.
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There is also a bolt on front of the bracket that is below the power steering pulley and two the passenger side that must be removed. I unfortunately did not get a pic of this bolt.
Now there is also a bolt that just needs LOOSENED slightly on the back of the bracket. It is picture below. The bolt i speak of is the one on the right closest to the header. It holds down a bracket that is attached to the a/c bracket but this little bracket is notched so you don't have to completely remove the bolt, only loosed it so that bracket can slide.
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There is one last nut that needs to be removed in order for the a/c bracket to come from the block and slide forward. It is accesible from under the truck. It is near the front of the bracket under the power steering pulley. Here is a pic of it.
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as a side note, that bolt that is above the one i am pointing to is the lower bolt on the front of the bracket that i mentioned earlier.

Once all these are either removed or loose you should be able to slide the whole bracket out about 4 or 5 inches. This will be enough to get to the intake bolt that was hidden.
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Now go ahead and remove your passenger valve cover. It has to be done to get the intake back in.
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You'll also notice that i removed the alternator. I did this to give me a little more room to manuever and work in the engine bay. It is probably not necessary.

Go ahead and remove the 8 intake bolts. For my truck which is a 99' classic, all the bolts were the same length but you should lay them out in the correct orientation until you know for sure all yours are the same length. Then rip that damn intake off. This was actually easier said than done. That rtv they put on factory really had mine stuck down the the block. I ended up getting a pry bar and prying it up from the thermostat housing. I know this probably wasn't the best way but i didn't have a slide hammer and didn't know what else to do.
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Now you can start cleaning the mounting surfaces and soaking up any antifreeze that may be down in the valley.

Once you have everything clean to your standards its time to get ready to re-isntall the intake with the new gaskets. The felpro gaskets that i mentioned earlier are non-directional so either one can be installed on either side. They come with little aligment dowels molded into the frame of the gasket so no rtv is need to hold them to the heads before installation of the intake. Once you have your gaskets layed on the heads and your intake ready to be re-installed you can go ahead and make your fat beads with the rtv of the front and back of the engine.
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And heres my, "oh **** what have i gotten myself into" face right before i pulled off the intake earlier.
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When you have you rtv on the front and back of the block you'll pretty quickly want to go ahead and set the intake down on the engine trying to line it up perfectly the first time. Well i didn't hit it right the first time. When re-installing you have to be careful and make sure the edge of the intake gets up under the drivers valve over so it will sit flush on the heads and block. I didn't realize this at first and then tried to slide the intake around once i had set it down on the engine. This really smeared the rtv. Well back off it came to wipe down the block and redo the rtv and try again. This time i did it right and it dropped right in. The 8 bolts should be torqued to 11 ft-lbs as per fel-pro instructions in a criss-cross pattern.
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Now the hard part is pretty much over. The rest of the job is pretty much just a reverse of taking it all apart. Re-install your distributor making sure to line up the marks and install on the correct tooth so the rotor is in the same spot as when you took it out. Then put back on the upper intake plenum with your new big oring around the injector pod. Then re-install you coil and bracket and slide your a/c bracket back into place and reinstall or retighten all the bolts and nuts you previously loosened. I chose not to re-install the two brackets that held the main wiring harness up off the intake. Both of these brackets were back around the coil and distributor. They were a ***** to get off and i couldn't see that they really did anything. Now go ahead and start reconnecting all the sensors and bring the a/c pump back back into place and bolted up. Bolt up the throttle and cruise cable brackets and reconnect to the throttle body. Install thermostat and reconnect any coolant hoses previously disconnected. Re-install fan shroud and fan belt. You should probably wait a few hours to let the rtv begin to set up. It took me about 3 hours more to button everything back up after installing the intake so i figured the rtv had cured enough. You can go ahead at this point and change any fluids necessary, oil for example.

I went ahead and tried to fire the truck up. To my surprise it started right up. The heat from the engine should cure the rtv pretty quickly and its seal is not really a pressure seal or anything so i wasn't worried about that. Initially there were no leaks and everything was working fine. I proceeded to catiously take it for a spin around the block to bring the engine up to operating tempurature. Everything was going great. I was amazed that my reinstalled quick disconnect hose was holding pressure but it was. Well i get back to the house and pull in the driveway and notice a drip before i can even get the hood up. With my heart in my throat i pop the hood expecting the worst. Luckily i had just forgotten to tighten a hose clamp on one of the water pump bypass hoses. The hose in this picture actually. I had put on screw down clamps as opposed to re-using the stock clamps.
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Tightening that clamp up quelled the leak and i was good to go. I let it cool over night and topped off the radiator and overflow tank in the mornin. I think it took about 2 gallons to reach the correct level. The real test came the next day (which happened to be yesterday) in the form of a 400 mile highway drive back to where i live.

With apprehensions i set out on my trip back home. The truck performed wonderfully and fortunately i must have reinstalled the distributor the same way it came out because i had no knocking which would have probably been present had i accidentally advanced timing, nor did i notice any power loss from accidentally retarding timing. No check engine lights either.

This whole job took my father and i the better part of two days to complete. I am sure a more experienced mechanic could have it done in a matter of hours but we wanted to document everything and take our time. I can't thank him enough for the help. I would recommend having a buddy on hand when you do this job. Its alot easier for someone to just hand you things when your knee deep in the engine bay than having to climb out and get ****.

If anyone has any questions just post up. I posted most of my pics but i have a few more than i didn't so if you have a specific question about a step just let me know. And good luck with your install.
 

Crunk

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this is a good write-up, i used this thread as a helpful tool when i did my intake gasket swap even though mines a non-vortec 350.
 

hquick

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A good way to get the intake lined up first time is to get 2 or 4 - 8mm x 75mm (or thereabouts) bolts, cut the heads off and just lightly screw them into the heads.
These will then guide the manifold into exactly the right position. Then just remove the bolts and put the correct bolts in.

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NacIK

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Howard, every time I see one of your pictures of your intake I want to buy one. Your installs just look so well done and clean. Someone can only tell it is not stock because I looks so nice.
 
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