... as seems to be the case my 93's rear intake manifold rail seal is leaking, I'm planning on removing the manifold resealing the front and rear rails and installing new gaskets.

My questions are:

Why type of RTV should be used to seal the manifold rails? (I understand it should be an 1/8" bead towards the outside edge with an extra dab in the corners where all the gaskets come together.)

Do you re-use the manifold bolts or install new one's? If you re-use them what type of thread sealant is used?

Anything else to watch out for? Looks like an awful lot has to come off, I suppose the belt plus the alternator/ac braket - wonder if they will stay put will that bracket is off? How difficult is it to remove the injectors and fuel rails as one unit? Any tricks?

Thanks and Merry Christmas.

 

I would recommend Permatex "Right Stuff". My 93 Lt1's manifolds and countless others have been succesfully sealed with this. It isnt cheap, but oil leaks dont look good.

 

Ask Bogus, he did an article on c4guru on the LT1 intake.

I couldn't find it and I really need to do mine if time will only let me

 

 

And there's no need to replace the bolts. They don't torque to anywhere near the stretch limit. I replaced mine, but with stainless so only for aesthetics! No sealer is really needed but a little anti-seize wouldn't hurt, especially since they thread into aluminum.

 

This would be a GREAT opportunity to take DETAILED STEP BY STEP pictures and post on the forum as a tech tip. I too would appreciate that.

 

I did my inake gaskets last summer and here is a pic of my '95 intake just before re-installation. Yes, you need to take off alot of parts, so make little sticky notes for the different bolts, components, etc. If I didn't do this, I would have for sure forgotten where some of the stuff went....
1) wrap ties are excellent for holding back various AC and vacumm lines.
You want complete clearance when you lower the intake back down. Lower the intake straight down into place, you don't want to have to "slide" it, as this would screw up your RTV bead big time.
2) yes, as mentioned, use "The Right Stuff". It comes in a pressurized can, so there is no tube squeezing involved.
3) clean, clean, clean the front and rear mating surfaces. You don't want any residual oil anywhere near the RTV sealant. Scuff up the front and rear mating surfaces(intake and block) using course grit sandpaper. This give the RTV something to bite into. Others on Forum will recommend "dimpling" these surfaces with a punch or small drill bit. Your choice here.....
4) You can reuse your old intake bolts, as they are not a high torque bolt, so they should not be stressed out!! Just chase them to get any crap out of them. Use anit-seeze on your intake bolts before re-installing. Use correct torque and bolt torque sequence. Definately advisable to re-torque after a couple days or so of driving, as settleing will occur....
5) Remove the fuel rail and injectors as 1 unit, and place on windshield. When re-installing, coat the O-rings with oil or vasilene. This will help them slide right back in....
6) Easy job, really, just time consuming.

 

Thanks!

I only remember to take step by step detailed pictures about 75% through any given job. I have done most all Corvette repairs but NO PICTURES... I'll get better!

 

I use laquor thinner to clean the grease off.
At the rear of the manifold when sealing it up,make sure you don't break the bead ,one continues line.
At the rear I would lay the bead down like a snake and another on top of it.Let it set up of a minute or two before you set the manifold down on it.The back will leak easier then the front.

 

Wow thanks so much Mike that's good information. The service manuals are great but you always have questions about some of the process, and you guys are there to fill that gap. Thx.

I saved that picture, funny if it weren't for the newer seats that looks like what mine will look like next week. Heck I even have those saw horses. <grin>

How heavy is the manifold? Yeah I figured so much on the surface contact method, if you have to be extremely careful on the bead to ensure none get inside, I can certainly see why you want a straight on mating. Yeah I pre-read the procedure it was last week but I think it said to torque them all in sequence to like 12Nm then in sequence the full torque (which I forget at the moment).

If I remember correctly the injectors just press in, it's the rail end that has the clips? So it would just lifting them free of their mounts. I like the picture that gives me a much better idea. Good thing I have all new hoses and vacuum manifold and valve, they should be easily disconnected and not be brittle and fragile as they were.

Yeah I've got a couple major jobs pictured just no time to document it. And I have this job and the evaporator - accumulator that needs to be replaced. So this is going to be a fun couple of months ahead.

As always thanks.

 

The right stuff in a can, I guess I'll just have to try it to see out the bead is delivered sounds interesting.

Guy's this is all great info, thanks.

 

I have the tech tip for C4 Guru... I just need to upload it...

However, a trick - drill the intake and block walls with random small dimples. This will give the RTV a chance to grab something.

Also, I use Copper RTV.

 

I pulled my intake out 4 times over the yrs. I used permatex blue twice and once with permatex gray and I have also use GM stuffs. I nerver have any leaks problem. I like permatex blue and or GM stuffs. They cure faster the permatex gray.

 

I noticed you mentioned removing the injectors and fuel rail. This is not necessary if you're only R&R'ing the manifold. I've never removed them unless there was another reason for doing so. Also, the manifold is not heavy at all since it's aluminum.

 

The right stuff is very good stuff! You cannot go wrong with it.Since Ive began using it some years back,I will not use anything else these days.Its more money but still cheaper than the gasket kits and etc thats required for the repairs.I use them on my other GM cars/vans when i did repairs that required sealer and it has never leaked,ever.I used a average intake sealer once in the past,I forget the name and it leaked within 2 years on the engine intake manifold.I was pizzed.

Also,be sure to lube your injector O rings with oil/lube before pressing them back into the manifold bungs.If any O rings look damaged,replace them all and lube before install.

 

i used gentle taps with a center punch myself.

many people have installed the gaskets "dry" (no RTV), but i used a thin smear of black RTV around the ports. without the RTV i could never get a good seal.

 

Chris, can you explain more about how the FI rails don't have to be removed when R&R'ing the intake gasket and sealant?

This is the first I've heard to put gasket sealant along the intake gaskets, is that true? Service manual only talks about extended the 3/16 bead from along the aft/rear rails up 1/2" onto the intake gasket (basically that sounds like the extra dab in the corners my rebuilding manual talks about).

 

I don't use any sealer on the gaskets themselves. I had my manifold off two or three times w/o ever pulling the rails. I never removed them until I had to to put them onto the ported manifold. I don't even remove the TB unless there's another reason for doing so.

 

 

my use of a sealer on the gaskets goes against what the manual, and what everyone has advised me. the only theory i have regarding the cause of my problem is that my head or intake surfaces are slightly out of true. i could not see any warpage via my high-tech steel straightedge and light combo.

twice i have installed dry, and both times i get leakage at the middle of the driver side bank. (spraying starter fluid along the interface would bog the engine.)

i checked bolt torque countless times without avail. not willing to invest more time in problem solving, and definitely not willing to pull the heads for inspection, i just smeared sealer onto the gaskets with my finger - just a very thin film. i figured if the sealer did not goop out into the ports it would not hurt. now everything seals fine...