350 Block Question

[ogsRULE]

Hi, I am feeling just semi competent right now! I am installing my motor and I am stumped by this port in the motor. I was convinced it was for the water temp sending unit, but three trips to the parts store reveals no fit. It is a bit smaller than 1/2 pipe and bigger than 3/8ths. I figured out there is provision for this unit on the manifold, but just blank on what this port is for? (I know I'm gonna feel stupid!)

Thanks,

Scottie

[fattyarbuckle]

it is for temp sender, it can be plugged and installed in the intake also.

[ogsRULE]

Thanks, this just seems so strange since it does not fit either of the senders available for 80-85 blocks: 3/8 NPT and 1/2 NPT. Any body know the size of this hole?

Scottie

[storm9c1]

Yep, temp sensor. Should be 3/8" NPT.

The 1/2" was only used on the older blocks. Not sure why it wouldn't be one of those two sizes. Could be a QA problem if this is a reman.

[ogsRULE]

Thanks I'll go back to the builder.

Scottie

[burnin oil]

Yes it is the temp sender. My new motor has it plugged and and I installed the sender in the eddy intake. It sits right under the upper radiator hose. I got the plug at home depot in the plumbing section. When the new instrument panel is finished I will move it back to the head. Different sender will fit the stock location.

[Marv D]

... or a brass bushing and your existing temp sender will fit.
Remember the late 90's Vortec motors has one sender for the computer, another for the dash gauge.

The temp sender uses the GROUND of the sender to relay the signal back to the gauge/computer. Make sure you have a good engine ground, and I'd suggest you insert it DRY into the head,,, I try to resist the temptation to use teflon tape and such that can be detremental to the GROUND. Brass fittings do a really great job at sealing without any tape / sealing compounds.

[dwcsr]

GM had a brain fart and used metric plugs on some engines. I think its a 16mmx1.5 or 18mm x 1.5 pipe plug not straight thread

[storm9c1]

Originally Posted by Marv D

I'd suggest you insert it DRY into the head,,, I try to resist the temptation to use teflon tape and such that can be detremental to the GROUND. Brass fittings do a really great job at sealing without any tape / sealing compounds.

Partially true IMHO. Yes, brass does a good job of sealing. I've also had them leak without using tremendous torque. It can go either way.

Teflon tape will not affect ground. The Teflon only fills the voids. There is enough metal-to-metal contact to shave off the tape around 90% of the fitting.

The only exception to this would be for knock sensors on modern engines. Tape can affect the those since these connections are more mechanical to the block than electrical.

If you still don't believe me, scroll to the last page of this document. They tested sensor readings with and without tape.

http://www.lbfun.com/warehouse/tech_...eCF-Thread.pdf

[storm9c1]

Originally Posted by dwcsr

GM had a brain fart and used metric plugs on some engines. I think its a 16mmx1.5 or 18mm x 1.5 pipe plug not straight thread

Really? Ohhhh-kay. That's a new one on me. Maybe a modern block? Because all of the older blocks used SAE sizes.

[burnin oil]

I have found that brass seals perfectly as Marv says. Now the problem is in pipe style fittings that are tappered. One cut to big or small and it will leak like hell. I had this exact issue when installing an onboard air tank in my 5500. None of the fittings would seal.

The bushing works as long as you have the small sensor and a big hole. I have the opposite problem

[Marv D]

Originally Posted by burnin oil

The bushing works as long as you have the small sensor and a big hole. I have the opposite problem

hahaha sounds like someone is trying to fit a Automerter temp gauge in a LS1 head?. Can you believe you have to buy a special temp sensor from Autometer just for the LS heads!!! what a $21 crock of extra cash-flow!

Storm,, Wasn't trying to target teflon tape specifically,, just saying brass into iron and you really don't need anything. I've seen guys tap the pipe threads too deep with the tapered tap to loosey-Goosey, and then try to use 15 wraps of teflon tape to 'take up the space' . Then wonder why the gauge doesn't work. There are a myriad of sealing compounds and ideas,, none of them are 'good' for a electrical connection. But I do agree, Teflon tape (2 wraps like your supposed to do) is probably the least offensive to making ground. It only takes what,,,,,, 1/16 square inch of solid contact to make good ground.

[burnin oil]

Originally Posted by Marv D

hahaha sounds like someone is trying to fit a Automerter temp gauge in a LS1 head?. Can you believe you have to buy a special temp sensor from Autometer just for the LS heads!!! what a $21 crock of extra cash-flow!

Storm,, Wasn't trying to target teflon tape specifically,, just saying brass into iron and you really don't need anything. I've seen guys tap the pipe threads too deep with the tapered tap to loosey-Goosey, and then try to use 15 wraps of teflon tape to 'take up the space' . Then wonder why the gauge doesn't work. There are a myriad of sealing compounds and ideas,, none of them are 'good' for a electrical connection. But I do agree, Teflon tape (2 wraps like your supposed to do) is probably the least offensive to making ground. It only takes what,,,,,, 1/16 square inch of solid contact to make good ground.

No New alum heads for my 400sb have the small sender hole. My new autometers do have the small sender. Just have to get around to finishing my new cluster. Have ya seen the oil pressure gauge for the LS? That one looks like a PITA!

[gulfcoast66]

Originally Posted by marv d

... Or a brass bushing and your existing temp sender will fit.
Remember the late 90's vortec motors has one sender for the computer, another for the dash gauge.

The temp sender uses the ground of the sender to relay the signal back to the gauge/computer. Make sure you have a good engine ground, and i'd suggest you insert it dry into the head,,, i try to resist the temptation to use teflon tape and such that can be detremental to the ground. Brass fittings do a really great job at sealing without any tape / sealing compounds.

x2..

[gulfcoast66]

I have 1998 vortec l-31 heads, I bought one of those cheap kits from advance auto, oil water and temp gauges to get the right brass bushing for my temp gauge.

[gulfcoast66]

Pic

[LONGHAIR]

That is not a "block" question