Vortec intake manifold pitting

[Schurkey]

"Grey" RTV is not for filling gaps. It's for sealing two rigid pieces--one casting against another.

A sloppy gasketed joint is not a proper place for Grey.

https://4lowmagazine.com/rtv-colors-and-when-to-use-them/#:~:text=Black%20RTV%20can%20flex%2C%20allowing,exhaust%20and%20high%20heat%20applications.

 

[97-2door]

1. I'm concerned about the swirl-marks on the gasket surface. Did you use a Scotchbrite surface conditioning disc "cookie" to clean the gasket surface? Scotchbrite on a gasket surface is a Really Bad Idea. GM and other manufacturers specifically state not to do that. They'll wear into a cast-iron surface, they're really bad on soft metal like aluminum. And the 'active ingredients" in those Scotchbrite pads are aluminum oxide, titanium dioxide, and quartz silica, which gets EVERYWHERE including in your lungs. The abrasive dust inside an engine will destroy bearings and embed into aluminum pistons.

2. Yeah, I've used RTV to seal manifolds worse than that. But I have not used RTV to seal manifolds that use the "hard plastic/metal carrier and a silicone sealing bead" style of gasket. If this was me, I'd thoroughly clean the gasket surface, fill the pits with epoxy, and then sand the epoxy flat using sandpaper and a backing-pad for flatness.

I used one of the white 3M Roloc disks. It has a bunch of little “fingers” on it. I think they call it a bristle disc. Hopefully that wasn’t a mistake.

I think I’ll try to go the epoxy route, sand flat, then use the gel-pro gaskets I’ve got.

 

[Erik the Awful]

As a dealer technician, we used roloc discs on aluminum all the time, but you definitely need to be careful about which abrasiveness you use. If you use a brown roloc on aluminum, you're going to destroy your piece. We typically used red, and still we had to be careful with it. I believe the blue discs are softer for aluminum, but do your own research before you buy.

 

[97-2door]

I’m now wondering if I should get the fiber gaskets instead and roll with some RTV. The metal core Fel-Pro gaskets I currently have say to never use RTV with them. It’s also quite possible I’m overthinking this. Just really not liking the thought of possibly having to pull this again in the future…

Thanks for all the comments folks.

 

[Komet]

If you have the dry gaskets with the o-rings, I'd probably go the JB Weld route on just the big pitted area in the first picture so you get the right o-ring squish. Everything else I wouldn't worry about.

RTV and fiber gaskets would also be fine.

A carbide scraper would be my weapon of choice for cleaning gasket sealing surfaces. What I actually use is 6 razorblades because it's what I have. It takes quite a while but I have had 100% success with the end result and the guy doing the work has a low hourly rate.

 

[Schurkey]

As a dealer technician, we used roloc discs on aluminum all the time,

I learned about the surface conditioning discs at the Chevy dealership I was a service advisor for. The guys used a LOT of them, on everything.

I started using them when I moved to an independent shop, and on my own projects.

but you definitely need to be careful about which abrasiveness you use. If you use a brown roloc on aluminum, you're going to destroy your piece.

Brown was all I ever saw used, or saw for sale. Didn't know there were other colors until after I quit using them.

As said--GM specifically warns against their use. The abrasive material goes everywhere, including into the stalls next to the one where the disc is being used. Looking back on the situation, I think I know why there were so many problems with the transmissions that the Dealership overhauled. The guys would pull the valve bodies apart, and they'd cover 'em with shop rags, but while they were working on 'em, the guy in the stall next to them would be cleaning gasket surfaces with the "cookies". So the oily valve bodies had all sorts of abrasive dust dumped onto them.

I quit using them when the local machinist warned me against them. He said that gasket surfaces became "wavy", moreso on aluminum but even iron surfaces were affected. He could see the "waves" as the machine resurfaced the parts--the apparent depth of the cut would vary with the amount of material removed by the abrasive discs.

Eventually, I bought a couple of the "finger" style, but decades later, I've never actually used 'em. There's a couple in my tool box growing beards and using canes, they've never been used. I went back to scraping instead of abrading.

 

[Erik the Awful]

I've always known they can eat the part you're working on, so I've always tried to use them as minimally as possible. When it comes to removing hardened gaskets there's nothing better. I've had fossilized gaskets that a gasket scraper wouldn't touch, and at that point you're in danger of marring the aluminum just by brute force. A roloc works great in that situation.

You're right that they throw off a lot of abrasive particles. We were doing a lot of injector hose recalls and we used the rolocs to clean the baked-on gaskets off the intake manifold. We had plastic plugs that we put in the intake tracts.

 

[rebelyell]

Hi all. I'm in the process of putting a new crate engine in my 1997 Tahoe. I'm going with a stock 5.7 Vortec (L31), but I need to re-use the intake manifold from my old engine. The intake manifold was not leaking when I removed it. After cleaning it up, I noticed pitting around most of the ports, but especially around the front driver's side water port. I tried to get a few good pictures. I really don't have a good frame of reference, as I've never done this before. Is some pitting okay? The one corner around the water port definitely seems excessive, but I'd like to get some other opinions. I'm planning to use the Fel-Pro gaskets that are metal with black rubber molded on them. The Fel-Pro instructions say that if pitting is "severe" they recommend having the manifold re-surfaced. They state you can use epoxy. I just want to make sure I do this right the first time. If I need to get it resurfaced, I'm not even sure there is a machine shop near me (eastern NC) that I would trust to do this right. I guess I could try to find another manifold in a junk yard or eBay. Pictures I've looked at on eBay tend to have some pitting also. Really just looking for opinions on how bad this is and what my best options may be. Thanks in advance!

if what you're doing doesn't suit ya---

Kevin Blanks Performance
(434) 374-2188
6909 Highway Fifty Eight Clarksville, VA 23927

* not exactly Eastern NC but not so far either. For real race car blocks' lifter bore bushings, I've driven it from Eastern SC.
pretty much about 80 miles Due North of Raleigh, just across VA state line at Clarksville VA (call ahead; Blanks might even suggest someone closer to you).
VERY near South Boston Speedway.
Blanks' super clean machine shop can & does Anything and does work for top teams as well.
good luck with your project

 

[Supercharged111]

I too was scolded by a machinist for using the roloc discs on my block and heads. He said for a garage job use 320 grit on a block. My block's deck took on a whole different look after I followed my already roloc'd surface with 320 on a block. Much better looking. I'd do the same for this intake. I've had 100% success with silicone in this application myself on a much worse intake years ago, but I have grown partial to smearing JB weld in there and sanding flat. Seems it'd be an easier cleanup if a guy had to go back in there down the road.

 

[rebelyell]

I too was scolded by a machinist for using the roloc discs on my block and heads. He said for a garage job use 320 grit on a block. My block's deck took on a whole different look after I followed my already roloc'd surface with 320 on a block. Much better looking. I'd do the same for this intake. I've had 100% success with silicone in this application myself on a much worse intake years ago, but I have grown partial to smearing JB weld in there and sanding flat. Seems it'd be an easier cleanup if a guy had to go back in there down the road.

^^^this^^^
And instead of the "bad" biscuit roloc discs, years ago I switched to 3m "bristle discs" --- Far less aggressive. Yes, they cost more but results are worth it. Works for me, YMMV

https://www.3m.com/3M/en_US/p/d/b40064937/

https://multimedia.3m.com/mws/media/794141O/3m-roloc-application-guide.pdf

IIRC, white is Least aggressive