67 L79 intake bolts are black phosphate, right?

[Scott S.]

Re: 67 L79 intake bolts are black phosphate, right?

Scott,

Actually a mixture of zinc phosphate and black oxide will produce a browning effect. But the original was probably just black.

Take a look at this post:

https://www.forums.ncrs.org/showthre...phate&uid=7017

Within it is a Restorer Article on gray and black phosphate

Hi Jerry, thank you for the link and the article!

[Scott S.]

Re: 67 L79 intake bolts are black phosphate, right?

Forgot to mention Scott, the cluster screws on my 67 are also somewhat brown.

Mine were a nice brown, but I dipped them in the very mild "Evapo-Rust" solution, and all the brown came off. Now they're dark gray, about like my door hinge bolts look.

I liked that they were brown, it made them stand out just a bit from the black instrument cluster. I would like to make them brown again... like they were

[Joe R.]

Re: 67 L79 intake bolts are black phosphate, right?

Chuck -

Black oxide was a very costly premium finish for a fastener in the 60's; the only place I recall seeing it on a midyear is on the five exposed cluster screws.

John,

Well you need to look harder! Try the glove box for a look see! I can make you a list if you need to look farther!

JR

[Joe R.]

Re: 67 L79 intake bolts are black phosphate, right?

Yep, black oxide tends to look brown! When it rusts!

JR

[Domenic T.]

Re: 67 L79 intake bolts are black phosphate, right?

Well, actually you get double-dinged then. Once for washers, once for finish.

FYI, some use "AN" style washers as they're small enough to often hide under the bolt head yet still protect the aluminum.

http://www.speedwaymotors.com/Stainless-Steel-AN-Washers-Pack-of-50,4817.html

Patrick

Also the an washers come in 2 thicknesses. I use the thin stainless and they allow a smoth torque. They hide wonderfully as you stated.

DOM

[Thomas M.]

Re: 67 L79 intake bolts are black phosphate, right?

I have been searching the archives for info on restoring the intake manifold on my recently purchased 67 L79 and came across this thread which is close.
I plan to remove it this winter and would like to repaint/refinish the manifold and thermostat housing and the associated bolts.
Can anyone provide information on the best way to repaint the manifold and thermostat housing with a correct finish?
It appears from this thread that the bolts start black and then are painted silver?

Thanks
Tom

[John H.]

Re: 67 L79 intake bolts are black phosphate, right?

I have been searching the archives for info on restoring the intake manifold on my recently purchased 67 L79 and came across this thread which is close.
I plan to remove it this winter and would like to repaint/refinish the manifold and thermostat housing and the associated bolts.
Can anyone provide information on the best way to repaint the manifold and thermostat housing with a correct finish?
It appears from this thread that the bolts start black and then are painted silver?

Thanks
Tom

Tom -

I, for one, don't think the entire L-79 aluminum intake manifold was "painted", except for coverage along the edges (and the bolt heads) as a by-product of the painting of the head surface between the valve cover and the intake manifold. The cast iron thermostat housing was definitely painted.

[Thomas M.]

Re: 67 L79 intake bolts are black phosphate, right?

John

Thanks for your reply. I am surprised that this subject is so uncertian. Even at local shows there is are very strong opinions about the finish on a 67 L79 intake manifold.

I just purchased the NCRS Technical Information Manual & Judging Guide which states "The L79 350 hp engine uses an aluminum intake painted silver"
Under attachments, the manual goes on to say that the bolts are black phosphate and "may be painted silver during the intake painting process".

This last statement leaves the reader wondering if they mean the intake manifold was painted after instalation on the engine (which seems unlikely since no one has ever seen silver on surrounding surfaces) or the bolts are (sometimes) painted with the manifold prior to installation.

I am trying to determine the best paint to use.

Tom

[Gary B.]

Re: 67 L79 intake bolts are black phosphate, right?

Also the an washers come in 2 thicknesses. I use the thin stainless and they allow a smoth torque. They hide wonderfully as you stated.

DOM

Dom,

Can you tell us a vendor and part number for the thin AN stainless washers?

Thanks,

Gary

[Michael H.]

Re: 67 L79 intake bolts are black phosphate, right?

I agree with John Hinckley. The aluminum intake manifold was installed, unpainted. Once assembled to the engine, the area of the cyl head between the manifold and valve cover, and the thermostat housing and area, was sprayed with dull aluminum paint. This was not done with a small air brush. The over spray often nearly covered the inner sides of the valve covers and much if the front area around the thermostat.

Who do you suppose started all this silver (dull aluminum) paint stuff, anyway.

[Craig O.]

Re: 67 L79 intake bolts are black phosphate, right?

I just removed my 67 original aluminum intake the bolts are black (or a shade of ) head mark NAT with traces of silver on them also a dull silver on the intake runners only not the whole intake. note the intake is old and the amount and coverage is a guess. with gas and oil wiping over the years its hard to tell. one side of the head to block is almost bare steel and the other has some traces of silver. I plan on using LIC dull aluminum in a spray can to replicate these areas and on the thermostat housing.

[John D.]

Re: 67 L79 intake bolts are black phosphate, right?

Is there a part number for the intake manifold bolts ?

[Michael H.]

Re: 67 L79 intake bolts are black phosphate, right?

Is there a part number for the intake manifold bolts ?

John,

I've never been able to find a published part number for the intake manifold bolt. It may be in the GM standard parts section of the parts book but even if it is, we wouldn't know which of several bolts that match the physical description would be the same one that is used at the engine plant.

I agree with others on the "NAT" head marking and the black plating for 66 and 67. There may have been other head markings/vendors though.

[Thomas M.]

Re: 67 L79 intake bolts are black phosphate, right?

Thanks Michael

I remain perplexed by the definitive statement in the judging manual that states that the intake manifold is painted silver, with no further qualification other than the bolts may be painted silver.

Thanks
Tom

[Ken T.]

Re: 67 L79 intake bolts are black phosphate, right?

Yep, black oxide tends to look brown! When it rusts!

JR

Black oxide is great for a rust look.