1970 LS5 Intake Manifold Nipple

[Allen N.]

I ordered a 6272959 intake manifold nipple from GM Parts Giant. It has what appears to be a dichromate finish on it. Is this the correct finish that was on the original nipple?

Thanks,
Allen

[Allen N.]

Re: 1970 LS5 Intake Manifold Nipple

The original part number was 3838904.

Paragon sells one that has slits on the hose end to tighten it. You can see it at:
https://www.paragoncorvette.com/p-35...ld-nipple.aspx

There is the same part number on ebay which uses a wrench to install. You can see it at:

https://www.ebay.com/itm/Corvette-NEW-Intake-Manifold-Hot-Water-Heater-Hose-Fitting-1964-1980/172889811033?hash=item2841092859:g:sOoAAOSwVC1ZzLnS

Can someone tell me which one is the closest to the original design?

Thanks,
Allen

[Joe L.]

Re: 1970 LS5 Intake Manifold Nipple

The original part number was 3838904.

Paragon sells one that has slits on the hose end to tighten it. You can see it at:
https://www.paragoncorvette.com/p-35...ld-nipple.aspx

There is the same part number on ebay which uses a wrench to install. You can see it at:

https://www.ebay.com/itm/Corvette-NEW-Intake-Manifold-Hot-Water-Heater-Hose-Fitting-1964-1980/172889811033?hash=item2841092859:g:sOoAAOSwVC1ZzLnS

Can someone tell me which one is the closest to the original design?

Thanks,
Allen

Allen------


The paragon nipple is for the bypass between the manifold and water pump.

The eBay item you linked is close to the original heater hose nipple at the manifold. This one is closer:

https://www.ebay.com/itm/1959-1980-Corvette-Heater-Hose-Fitting/382429990964?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D50963%26meid%3D6f1b72dbf8cd4d099d4c1337bf60d65f%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D172889811033%26itm%3D382429990964&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A24a1e664-57bf-11e8-8053-74dbd180271a%7Cparentrq%3A60972b9a1630a888e47f88ddfffdb6d6%7Ciid%3A1

The original nipples were zinc plated with no chromate overplate.

[Allen N.]

Re: 1970 LS5 Intake Manifold Nipple

Joe,

Thank you so very much. I actually need both nipples, so I ordered one from each of the ones you recommended.

You are a tremendous asset to the NCRS.

Thanks,
Allen

[Patrick H.]

Re: 1970 LS5 Intake Manifold Nipple

The original nipples were zinc plated with no chromate overplate.

If it's dichromate (i.e. gold-ish) that is easy to remove and end up with a silver colored part.
If like most replacement parts, the underlying zinc is probably far shinier than an original part.

[Allen N.]

Re: 1970 LS5 Intake Manifold Nipple

I tried removing the dichromate. I first tried just wire wheeling, and it got a little lighter, but still gold looking. I then tried vinegar for two hours and saw no difference. I then tried muriatic acid for 30 minutes, and there was still little change. GM appears to use a very good dichromate.

[Ron G.]

Re: 1970 LS5 Intake Manifold Nipple

If my memory serves me right it is either natural or plated silver cadmium.

[Joe L.]

Re: 1970 LS5 Intake Manifold Nipple

If my memory serves me right it is either natural or plated silver cadmium.

Ron------

They were plated but I don't know if it was cadmium or zinc. Originals were dull, though.

These things are highly susceptible to corrosion and the plating seems to "disappear" rather quickly. They can be a major bitch to remove and replace.

For me, it's these exclusively:

http://performancesst.com/product.php?productid=28&cat=6&page=1

[Ron G.]

Re: 1970 LS5 Intake Manifold Nipple

Joe - then it was silver cadmium as that is always duller then zinc. Zinc is usually the brighter of the two silver finishes. - Ron

[Joe L.]

Re: 1970 LS5 Intake Manifold Nipple

Joe - then it was silver cadmium as that is always duller then zinc. Zinc is usually the brighter of the two silver finishes. - Ron

Ron-----


That's somewhat of a commonly held misconception. During my working days, I was involved in regulating industrial companies that discharged their industrial wastewater to the municipal wastewater system. Many were platers. I learned a lot about plating in the process. It turns out that either cadmium or zinc can be either dull or shiny. The difference between cadmium and zinc is very difficult to discern unless one has a cadmium and zinc plated piece side-by-side. Even then it's hard to see the difference. Cadmium is more durable than zinc, though.

MANY years ago I took minute scrapings of many "silver" plated Corvette parts and analyzed them in our laboratory using atomic absorption spectroscopy. Every one was zinc, not cadmium.

[Patrick H.]

Re: 1970 LS5 Intake Manifold Nipple

MANY years ago I took minute scrapings of many "silver" plated Corvette parts and analyzed them in our laboratory using atomic absorption spectroscopy. Every one was zinc, not cadmium.

John Hinckley said for years that few if any of the part on our cars were cadmium or black oxide. Both were too expensive for GM to use on a routine basis. Convincing anyone of this is a different matter, however.

[Ron G.]

[Joe L.]

Re: 1970 LS5 Intake Manifold Nipple

Patrick,

I have the great respect for John Hinckley and for anyone that worked on Corvettes or in the plant. However, like Joe Lucia, I also took original hardware from original cars to two or three different platers in Connecticut and the consensus was Black Oxide and silver cad. My opinion and experiences tells md a lot of parts for phosphate, Gray and black and other parts we’re clear zinc. I do know that Black Oxide is much more durable than phosphate and I agree with Joe L. that silver cadmium is much more durable than zinc. - Ron

Ron------


An example of black oxide finish are most of ARP bolts. Off-hand I can't think of a single part on a Corvette that was black-oxide-finished. There may be some but I can't think of it.