Hex allen plug FI coolant passage

[Yves]

I prepare some winter project, one of my project is to rebuild my spare FI 1500 head.
What it the size of hex allen plug are you using to block the coolant passage of FI head?

Yves

 

[Dr.Jeff]

I took a slightly different approach. Rather than just plug the holes, I used those holes to add guide pins to locate the intake manifold. That allowed me to "port match" the manifold to the head with it always going back on in the same location and port alignment. To do this I tapped the holes to match some stainless steel bolts with the heads cut off. Naturally these locating pins also act to plug the coolant passages. Here is how it looks:

 

[dllubin]

I prepare some winter project, one of my project is to rebuild my spare FI 1500 head.
What it the size of hex allen plug are you using to block the coolant passage of FI head?

View attachment 37238

Yves

I tapped my carb head for M8 x 1.25 and installed set screws using Rectorseal on the threads.

 

[JimD]

Bernice lent me an M8 tap and gave me 2 stainless set screws to match many years ago. Here is the thread where I discuss installing the "plugs". It is also linked in the Engine section of the BOX.

 

[Yves]

Thanks folks, look like everybody agree with M8-1.25.

Jim, thanks for the details with your link... Super!

Yves

 

[Dr.Jeff]

In answer to your original question, I neglected to mention that the SS bolts I used to make the locating pins were also M8 (1.25) size.

 

[Yves]

Jeff,
Yes good idea for the guide pins to locate the intake manifold.
I like.

 

[ted83x]

I thought about making additional mounting studs, but ended up just using some set screws to block the coolant. Still think it might be a good idea to make additional mounting studs.

 

[Dr.Jeff]

I thought about making additional mounting studs, but ended up just using some set screws to block the coolant. Still think it might be a good idea to make additional mounting studs.

Are you referring to actual clamping (bolts/studs) mounts vs the 'guide' pins? I hadn't thought of that, interesting idea. Especially for my turbo engine to help avoid pressure leaks at the manifold gaskets. I made insulators to go between the head and intake runners, so two sets of gaskets there. Boost leaks are a fairly common issue with turbos and the whole SOHC's shared manifold mounting arrangement it isn't ideal for preventing leaks (the exhaust manifold to head interface is another concern). Something for me to consider, it would be easy to replace the blank pins with actual threaded studs and nuts.

 

[ted83x]

Yes the factory mounting is less than ideal, and the the location of those holes lines up with a flat spot on the after market manifold that I have. So those two holes could be used for mounting studs.
Some of my mounting studs are long, and I have a short piece of thick wall tubing between the manifold and the clamping nut, a a washer might not stay flat under load or over time and lose some of it's clamping. This also makes it a little easier to reach those nuts.

 

[Dr.Jeff]

those holes lines up with a flat spot on the after market manifold that I have.

As you can see in the pic I posted, the stock FI manifold runners have a small area there where a nut might fit. But it isn't quite flat all the way around it so I'd have to mill it a bit to make pads for the retainer nut. Definitely something to consider.