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Ok, I'm thinking I may not have the correct heads on my car. I have a 68 coupe that I bought already torn down. The engine had been rebuilt already. I know it's the original block because the VIN matches. Question is, what heads came on it? It's an early 68. Did the heads have accessory holes? Mine has the "double hump" heads with no accessory holes in them. I can work around that with bracket fittings if need be but what's got me is where does the temperature sending unit go? I can't find a hole on the side of the heads for one. And the only other two water holes are for the heater lines. My thermostat housing does not have a provision for the sending unit as there are no holes in it. Does it go in the thermostat housing? Thanks for the help.
On my 69 the sender is towards the front of the drivers side cylinder head. I have seen people install a T fitting in the heater hose connecting to the intake manifold. They then attached the sender to the T. This link may help you ID what heads you are workings with. http://outintheshop.com/faq/casting/heads.html
A pair of 3917291 for 300 and 350 hp; 3917292 350hp only.
...Did the heads have accessory holes?...
327 heads do not have accessory bracket mounting holes.
...where does the temperature sending unit go?...
Driver's side between #1 and #3 plugs. If you find a plug there, that head has been on the passenger's side at some point in it's life.
...My thermostat housing does not have a provision for the sending unit...
It's not supposed to mount the sending unit.
Pull a valve cover and check the casting number on a head. You cannot see the number with the valve cover on. While you're there, check the casting date.
If in your intake manifold you have two holes that are on the TOP FRONT horizontal surface ...one to the left of the thermostat mounting area and one to the right. The hole on the LEFT SIDE is where I would put the sending unit....IF...REPEAT...IF there are NO HOLES in the cylinder heads BETWEEN cylinder #1 and #3 like 'Easy Mike' mentioned.
The sending unit should never be installed into a thermostat housing.
Well, no luck finding any holes!!! I must have two passenger side heads on my motor. No provisions on the intake manifold either. I haven't pulled the valve covers yet to get the numbers, that's tonight hopefully. The only option I can think of doing is putting a thermostat housing on that has the provisions for a temp sensor? Any other thoughts???
not sure there is such a thing as a passenger side head, they both have the same part number. Can you post a picture of the front of the intake manifold and the side of both heads between the first two plug holes?
not sure there is such a thing as a passenger side head, they both have the same part number. Can you post a picture of the front of the intake manifold and the side of both heads between the first two plug holes?
No such thing as a 'passenger head'...or at least ..I ahve never come across a head that specifically had to be installed on ONE side of the engine ONLY.
Photos are really helpful.
I would like to see a photo of the top of your intake by the thermostat area.
If my memory serves me correctly..I believe that some early small blocks has no holes in the head by #1 and #3 cylinders....which would make it be the same on the passenger side and they would be cylinders #6 and #8. BUT what GM did was provide a hole for the temp sender in the top of the intake by the thermostat.
Once again...you SHOULD NOT put a temp sending in the thermostat housing...it is POINTLESS...because it will not read 'jack squat' until the coolant gets hot enough to OPEN up made allow coolant to touch the sensor....and if it did read something...it would NOT be accurate....so once again...POINTLESS.
Your original statement about wrong heads maybe correct. The 3782461 are earlier than 68 and worked with an intake that had an additional fitting on the front edge of the intake. This link shows bare 3782461 castings and there is no provision for a temperature sender. You may have to plumb it into the heater hose coming off the intake. http://www.enginelabs.com/news/quick...sting-numbers/
see the additional hole in this image next to the thermosat housing http://www.wernersparts.com/images/i...cs/WC%2091.JPG
The correct head for the 327/300 would be 3917291 and for the 327/350 3917292
OH YEAH...this is where the fun begins. If trying to maintain an original appearance...and I had to do something to this engine if it were in my shop. I have been trying to figure out what would be the least invasive modification....but not have some provision sticking out somewhere attracting your eye to it where the sending unit is installed.
If not having the correct casting numbered heads does not bother you.....I am caught between two ways. One....remove the intake and have it welded up so a hole can be drilled and tapped into it much like the photo shown in the last post. NOW...that is NOT where the wiring is designed to run...but it would be functional.
The next idea is pull the head if it was already re-worked and perfect....disassemble it and have a pad welded onto it so a hole can be drilled and tapped like it should be.
I do know some wicked epoxies can be used to create a pad...shape it ...drill it and tap it...so it would not require welding on the head itself. Due to the sending unit does not get tightened to the point that you chip your teeth doing it...Using an epoxy may work but the prep is important and if it were me...I would test it on another piece of cast iron and see that it would work before I did the head itself.
Then re-paint the head and re-assemble it and install it.
You can buy a thermostat housing that has one to two 1/2" NPT holes in it for problems like yours.
OBVIOUSLY you did not read this post.....putting a temp sending unit in the thermostat housing is POINTLESS.
Maybe YOU are not aware of it...but the REASON GM put NPT threads in a thermostat housing was for the specific temperature vacuum switches that operated components that used water temp to operate these switches,,,,,and NOT for temperature SENDING UNIT.
Or.....buy a new aluminum intake manifold that has provisions for mounting a water temp sensor. Note the blue anodized fitting just outboard of the T stat housing. I used a autometer sport comp mechanical guage. Very accurate. The stock sending unit/guage was marginal at best. Chalk that one up to GM just being cheap.
Last edited by Sunstroked; Aug 21, 2015 at 12:57 AM.
OR......drill and tap the area in the top of the intake where a sending unit would normally fit.....just DO NOT thread to FULL DEPTH in order to get a good thread sealing area.
Temperature Sending Unit???
No such thing as a 'passenger head'...or at least ..I ahve never come across a head that specifically had to be installed on ONE side of the engine ONLY.
