67 GT500 oil fill cap

[shelbydoug]

I have this cap, C5ZZ-6766-D EC-10,  but it is too large and hits the valve cover.

It can't be the right one?

Is there another, smaller diameter, with the breather tube that fits?

[Bob Gaines]

I have this cap, C5ZZ-6766-D EC-10,  but it is too large and hits the valve cover.

It can't be the right one?

Is there another, smaller diameter, with the breather tube that fits?

The cap with the nipple was not typically used on a GT500. Here is a link to the type of push on oil filler cap you need. https://www.npdlink.com/product/cap-oil-filler-and-breather/105518 They don't make a repro that has the exact correct trademark that you need however. FYI here is a link to the correct valve cover twist on cap.It is larger diameter compared to the smaller oil fill cap. https://www.npdlink.com/product/cap-oil-filler-and-breather/147069 . For those reading these are the typical caps used on non thermactor equipped 67 GT500.

[Bob Gaines]

The push on oil filler cap would only have the Fomoco script in the oval on extremely early cars. All others had the Autolite trademark. The twist on valve cover cap would have the Fomoco in block letter inside a rectangle on early cars and Autolite for the rest.

[shelbydoug]

The push on oil filler cap would only have the Fomoco script in the oval on extremely early cars. All others had the Autolite trademark. The twist on valve cover cap would have the Fomoco in block letter inside a rectangle on early cars and Autolite for the rest.

Good to know.

I'm creating my own problems again by attempting to have a functioning pcv system.

The 67 GT500 original system did not function. It was there for looks. It's like the original engineer didn't even understand how the system works?


I haven't investigated the possibility of putting the nipple cap on the twist in side and the "stock" non-nipple on the oil filler?

That may be a possibility though?


Even a judge could appreciate that?

I find that these engines run much better with a real functioning pcv.

[Bob Gaines]

The push on oil filler cap would only have the Fomoco script in the oval on extremely early cars. All others had the Autolite trademark. The twist on valve cover cap would have the Fomoco in block letter inside a rectangle on early cars and Autolite for the rest.

Good to know.

I'm creating my own problems again by attempting to have a functioning pcv system.

The 67 GT500 original system did not function. It was there for looks. It's like the original engineer didn't even understand how the system works?


I haven't investigated the possibility of putting the nipple cap on the twist in side and the "stock" non-nipple on the oil filler?

That may be a possibility though?


Even a judge could appreciate that?

I find that these engines run much better with a real functioning pcv.

A Shelby or Mustang concours judge typically appreciates a well historically done car. If you want the pcv to work best then run the hose to one of the pass side forward plugged vacuum ports on the intake and plug the nipple on the air cleaner base . If you want it concours historically correct no matter how inefficient run the hose to the air cleaner base . It is not a big deal to switch if you need to. The breather cap arrangement as you describe is farther off the mark in terms of originality (given the direction of your questions) and less efficient compared to the intake vacuum port.

[shelbydoug]

The hose from the pcv should go to an intake manifold vacuum port.

The hose from the oil filler cap, to the nipple on the air cleaner base plate.

It's a simple arrangement and maybe it wasn't done originally for a couple of reasons.

1) the 67 GT500 has the reputation for fouling spark plugs because of the 'supposed over carbonation'.  Adding the hose connection to the intake MIGHT have the tendency of siphoning oil out of the valve cover and adding further spark plug 'fouling complaints'.

2) there wasn't an oil filler cap with a hose nipple that was small enough to clear the valve cover.

Who knows for sure but the combination of the two and the California Air Resources Board's willingness to accept the 'production' connection kind of solved the problem.

The lack of a functioning pcv system would show it's effects on a 30,000 something engine and NO ONE built a car that would go 30,000 without major reworking back then anyway, so if you think about it, it's kind of a 'cheapskate SA no brainer' solution?