V1 Coolant Overflow Feed

[Iwanttogofast]

Does anyone know the thread diameter and pitch of the ported bolt in the cylinder head next to the CTS that feeds the coolant overflow line? LSJ engine...



There are no markings on the bolt head at all. At first glance, I was sure that it was going to be 7/16-20UNF. But it's not. Then I thought maybe it is M10-1.5. Wrong again. It's like a 1/4-18NPT, but straight thread. ? I have something in mind that I want to do, but I've got to figure out if this is some special, goofy thread...

 

[Desert Sasqwatch]

M10-1.50 is the course metric thread. Is it a M10-1.25 fine metric thread. Doubt this is an SAE size bolt on the Ecotec engine.

 

[Gtstorey]

It’s an m14x1.5 on the LNF, if it’s the same as what think you are talking about.

 

[Iwanttogofast]

M10-1.50 is the course metric thread. Is it a M10-1.25 fine metric thread. Doubt this is an SAE size bolt on the Ecotec engine.

You are correct. I thought that I had typed M10-1.25, but my keyboard missed the "2". But, yeah... it's not 10mm or 7/16". It's very, very close to 1/4-18NPT but a straight thread. ???

 

[Ross]

Time for a new $9 thread pitch tool?
Oops, that had british withworthless threads. Here is a SAE and Metric one.

 

[Iwanttogofast]

Time for a new $9 thread pitch tool?
Oops, that had british withworthless threads. Here is a SAE and Metric one.

I've got a complete gauge set for internal and external threads - SAE & metric, coarse and fine threads. It's not a standard thread. It would be like a 7/16-18, which doesn't exist. I may just pass on what I was gonna do. Thanks anyway!!

 

[Iwanttogofast]

I just found out that there IS a 7/16-18UNS thread!! Never heard of it before. I don't think it's worth the trouble to do what I was gonna do, though. Why in the hell wouldn't they just use a standard metric thread?

 

[Gtstorey]

Pipe threads can be straight or tapered in the same basic diameter and pitch. The straight threads would normally requires a gasket to seal.

A 1/4-18 Straight thread has a nominal diameter of around 0.54"=13.7mm and a pitch of 18threads per inch=.0556"=1.411mm. Pretty close to M14x1.5.

Double Banjos and bolt washers,14 X 1.5 Thread. Bolt head 19mm. line 10mm ID | eBay

 

[Iwanttogofast]

I forgot to reply back a couple of weeks ago about this thread size issue. It turned out to be M10-1.0 extra fine thread.

When I originally checked the bolt with my M10-1.0 external thread gauge, the gauge had a piece of a burr in it - which is why it didn't feel right. I found the burr, removed it, checked it a 2nd time and it threaded very smoothly. So, for any other LSJ owners - it is definitely M10-1.0 extra fine thread.