I have put in a 5.7 Vortec into my '87 IROC and am running a Vortec TPI base, but noticed that the back of the base wasn't sitting flat. After looking a little more I noticed that the fitting that the oil pressure sender goes into is too tall and is keeping the base from sitting flush. It is hitting on the driver's side rear flange where the runner attaches.

Went to the hardware store and picked up a 1/8 to 1/4 90* elbow, since that is what I have used in previous small blocks, but it wouldn't fit into the block. Little more research and the threads in the block are m10-1.0 and the sender is 1/4npt.

So what do I do now? I have looked all over the web and can't seem to find the elbow I need to give me the clearance needed to make the base fit.

 

Buy a tap & Die set, SAE and Metric. Make your own elbow from a small piece of pipe stock? Tough situation lol- let me know what you did, I'm interested!

 

Have a tap and die set but I really don't want to tap a hole into the block since the engine is in the car and I would run the risk of shavings getting in there.

My father in law knows a guy with a lathe so he's going to try and turn down the shaft on the factory elbow and thread it for me. If that doesn't work I will grease up the tap and hope no shavings fall into the block.

 

Looked all over the place for an elbow or a way to make an elbow, but in the end I ended up having my existing piece turned down and new threads put on.



This is the old setup that was on the motor.




After having the piece turned on a lathe and new threads added.

 

I am surprised the block isn't 1/8 NPT... my L31 is. I had the same Vortec TPI base interference, so I just plugged the china rail with a 1/8 NPT plug, and used the 1/4 NPT port just above the oil filter.

It looks like your adapter is now "too short" and the body will interfere more than just a 1/8" NPT (or whatever) pipe... I'd figure a 2" pipe to clear the intake + a 90* fitting would work.

 

After having it turned down and new threads cut it fit just fine with no interference.

 

My 89 was 1/8 NPT...fwiw....but glad to see you got it!

 

I've never run into this issue before. Every other sb chevy I've worked on has been 1/8 npt. Even my machinist thought it was odd.

 

I'm glad you figured it out, but I'm confused why the sender is there on a TPI. Was the car not originally a TPI engine? My 89 had a 305 TPI in it and the oil sensor was down by the oil filter. I had a square headed plug in the top location where you mounted your sensor. When I did my engine swap, I used a block out of a Suburban, so it had the opposite locations for the oil pressure sensor. When I went to buy a new sensor, most every person tried to sell me the smaller threaded sensor, so I can understand why your machinist thought it was odd. I guess using the port near the oil filter is an unusual location for most SBC blocks.

 

The engine is out of a '98 Tahoe and that is what they did on the vortec truck engines. My '00 k2500 gmc has the same engine and the sender unit is the same. Odd for gm to change the thread but that's how it goes lol!