Solved. Intake Manifold Question: What's the hex bolt for?!?

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phaetn
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Your car is a: 1974 Fiat Spider 1800
Location: Ottawa, ON Canada

Solved. Intake Manifold Question: What's the hex bolt for?!?

Post by phaetn »

Later this week I am going to go and pick up a ’74 Spider that I bought on Thursday. It is getting a crack/hole in the exhaust manifold welded and then it’s good to go to take home.

Right now my concern is that I see a bit of coolant pooling on the intake manifold, between the intakes for cylinders 2 and 3. I also see that there is a bolt with a u-shaped loop threaded into the manifold around that spot and I wonder what it’s for.

Image

Could it be for some type of thermostat? I don’t see a sender wire from it. I am wondering if the coolant could be leaking from there. Is there a coolant passage within the intake at all?

For more clarity, here's a pic from Midwest Bayless of the oem equipment in isolation:
Image

What is the purpose for the removable hex bolt (item #1). What can be put in there in its stead?
What is the purpose for the passage (item #2?)

Excuse my oily engine. I *know* it’s not clean, and I’ll get around to replacing gaskets and having surfaces planed at a machine shop to stop the oil leaks at some point – maybe next winter. Right now I just want to get it out, drive it around for a bit and see what really needs attention before getting deeper into the engine. I’ll perform a leak down test once I buy the gauges later this week as cylinder #1 is reading lower than the others.

In the meantime, the mechanic is going to pressure test the cooling system but I’m still wondering what’s around that might cause the coolant to pool there. I didn’t see any hoses right there that would drip onto that area, but I really don’t know the engine well enough since it’s not yet in my garage.

I looked at the oil on the dipstick and there’s no evidence of coolant in it so I think that would rule out a head gasket leak.

Thanks for any input!
Last edited by phaetn on Tue Apr 08, 2014 12:18 pm, edited 1 time in total.
1974 CS1
32/36 DFEV; CompuTronix ign.
9.8:1 c/r; 40/80 intake cam w/ Isky springs
Vicks' SS header & adj. cam pulleys
A/R's progressive coils, Koni Yellow dampers
205/50-15s on CD-66 style rims
Momo wheel, Corbeau seats w/ 5 pt belt
pics and HD vids
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aj81spider
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Your car is a: 1974 Fiat 124 Spider
Location: Chelmsford, MA

Re: Intake Manifold Question: What's the hex bolt for?!?

Post by aj81spider »

It's the thermovalve for your emissions system. I have a 74 and went down this path ahead of you!

http://www.fiatspider.com/f08/viewtopic ... 38#p191138

It can be removed and plugged, and coolant can definitely come from there!

http://www.fiatspider.com/f08/viewtopic ... 67#p203867
A.J.

1974 Fiat 124 Spider
2006 Corvette
1981 Spider 2000 (sold 2013 - never should have sold that car)
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phaetn
Patron 2018
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Posts: 575
Joined: Thu Jan 02, 2014 7:42 pm
Your car is a: 1974 Fiat Spider 1800
Location: Ottawa, ON Canada

Re: Intake Manifold Question: What's the hex bolt for?!?

Post by phaetn »

Excellent - thank you so much! I had searched for a good two hours under the terms "intake manifold" but never saw the posts you have indicated. Very helpful - thank you!

This board is awesome!! :)
1974 CS1
32/36 DFEV; CompuTronix ign.
9.8:1 c/r; 40/80 intake cam w/ Isky springs
Vicks' SS header & adj. cam pulleys
A/R's progressive coils, Koni Yellow dampers
205/50-15s on CD-66 style rims
Momo wheel, Corbeau seats w/ 5 pt belt
pics and HD vids
jetboy

Re: Solved. Intake Manifold Question: What's the hex bolt for?!?

Post by jetboy »

nice, i was wondering what the heck mine was as well -
now ill just plug it.

edit: its an 18 mm plug 1.5
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