I have a dilemma. I have put an ACCEL DFI fuel injection system in my 67. It has an air-gap style manifold with a single threaded port for temp sensor, and that is filled with the ACCEL DFI temp sensor.

I also have the 67 console gauges that includes a temp gauge. The gauge expects the sensor to have old-style GM resistance curve, and the new sensor for the DFI has different specs and is incompatible with the gauge.

I can see two options here:

1. Use the signal from the new sensor to drive a new temp gauge (and maybe just swap the guts of the gauge I have with new internals).

2. Find a compatible old-style sensor that has 3/8 npt threads so I can thread it into the AFR head port that is available.

The trouble I have with option 1, is that I don't know the specs of the new sensor, what gauge would be compatible with it, and how I might swap the new gauge internals into the location of the current temp gauge in the console (maybe using the old gauges face plate).

With option 2, I haven't been able to find an old-style sensor with a 3/8 npt thread (they were 1/2 npt in the old days).

Anyone face this problem before and find a solution?

Thanks,

Mitch

 

The attached is pertaining to a 69, but I believe the only difference between the 67 and 68/69 sending unit is in the way the wire attaches. Coolant Temperature Sending Unit. - Team Camaro Tech

 

Thanks for the pointers. The discussion on 'fine tuning' your sending circuit + gauge was really interesting. I'll probably need that, because the gauge (before I had EFI and did have a proper 1/2 inch port in my intake), always read too high.

I found a 3/8 NPT male to 1/2 inch NPT female adapter in town. I may try that and put the sender in the head. Note, I called AFR (who make my AFR 195 heads) and they say the port in the head is an NPS (not NPT) thread. Never heard of that before in my life, but I have a 3/8 NPT plug in there right now and it seemed to thread in OK and isn't leaking (at least with thread sealer). Trouble is I can't use thread sealer on my one-wire sender because it needs a good connection to ground through the threads. I might risk leaks without it. I suppose I could run a ground wire from the case/threads of the sender to a good ground on the firewall/head. Decisions, decisions.

I'm also considering tapping a 1/2 NPT port into my coolant crossover passage.

 

I was going to suggest trying an adapter, but I'm not sure then if the probe on the sending unit will be "in" the coolant the same as when it's hanging inside the head.
Both NPT and NPS threads are "National Pipe", but the NPT are Tapered threads, NPS are Straight cut threads (hence the T and S).