69 L36 intake finish

[Greg L.]

I read on some forum a while back that during the muscle car era a standard foundry practice for removing casting sand from intake manifolds was to blast them with steel shot. This comment was made by a gentleman that in fact work in a foundry during this time.

This being said, I'm now wondering if a re-skined intake is in fact incorrect and that it originaly would have had more of a shot peened surface?

Any thoughts?

[Joe L.]

Re: 69 L36 intake finish

Greg-----

I've never seen an original aluminum manifold that appeared to have been blasted with steel shot. For one thing, I think that steel shot blasting of the soft aluminum would leave a VERY definite and observable finish characteristics.

Every original aluminum manifold of the period that I have seen has a quite smooth finish. Many were painted with aluminum paint, too. All aluminum manifolds of the period were cast by Winters Foundry of Canton, OH. So, unless the foundryman who commented on the steel shot blasting actually worked there, I don't see how he would necessarily know the practices of that foundry.

[Greg L.]

Re: 69 L36 intake finish *NM*

[Greg L.]

Re: 69 L36 intake finish

Thanks Joe,

The guy never said where he worked but I just assumed that it was a foundry that supplied GM seeing as it was a GM forum that I was on.

Anyways, I'm just trying to get a reasonable solution for restoring my intake and was thinking that if what this guy said is true then I'd just clean it up real good and then get it lightly shot blasted...might not be the way to go though.

My last resort will be to either clean it up with aluminum cleaner and use it as is or send it out for a re-skin. I really hate sending out any of my original parts though in case they get lost or I get something else in return!

I had this manifold sandblasted back in the eighties before I knew better so I figured that the damage was done so I did a light blast on it yesterday at home. Then I lightly went over it with a soft brass brush to knock down some of the sand marks and bring a slight shine to it. I think it looks "okay" but it has the color of an original alternator and not the bright aluminum that you often see in pictures.

I guess my biggest problem is that since I don't have an original to compare it too, I don't know what I can do to properly restore it.

Other than sending it out, can anyone suggest what will work to cosmeticaly restore this thing?

Thanks again.

[John H.]

Re: 69 L36 intake finish

Castings fresh out of the mold went onto a "shake-out table" conveyor, which literally "shook" them to dislodge the core sand in the internal passages, and operators with air hammers went after the really stubborn stuff.

[Joe L.]

Re: 69 L36 intake finish

John------

I observed that exact operation several years ago at the GM Defiance, OH gray iron foundry. In this case, it was GM 60 degree V-6 blocks. They made quite a racket on the conveyor as the sand was being shaken out. I'd love to get back in that place. I could spend a whole day or, even, days watching the foundry operations. I'd like to spend just as much time in the nodular iron foundry next door to the gray iron foundry.

I love castings. They have more "character" than any other component of the cars.

[Art A.]

Re: 69 L36 intake finish

Joe, both my sons live near Cadillac Michigan and not to far from them is one of the major sources of the sand for casting sand. I could arrange a tour if you would like.

Art

[Joe L.]

Re: 69 L36 intake finish

Art-----

Thanks very much for the offer. You can be sure you'll hear from me whenever I get a trip planned to Ohio. Could be sooner than you might think.

[Patrick H.]

Re: 69 L36 intake finish

Joe,

Cadillac, Michigan is nowhere near Ohio. Having been to both locations in the not too distant past, I can attest to that.

Hey Art, I wouldn't mind joining Joe on that day.

Patrick