1991 350 TBI motor, factory location of the knock sensor is directly in front of the nose cone of the starter, which will interfere with the block hugger headers I'll be installing. According to JTR, the knock sensor can be located nearly "anywhere", even in the tranny bellhousing, and they show one installed as part of the motor mount parts.

Any reason I shouldn't just weld a fitting onto either the motor mounts or onto the fuel pump block off plate?

Anyone got a better/preffered location?

TIA...

I dont know about your motor, but when I installed TPI on my old-style (56?-85) block, I put the knock sensor in one of the coolant plugs in the side of the block. They're allen-head setscrews and both sides of the block have one. If thats not your case, I would put it in the fuel pump block off plate

Try back of the top of block. That's where my 4.3 one was mounted.
Jay

no,no,no,no,no,,,did I say never! the blocks harmonics change from engine size to engine size(5.0-5.7)and numbers of cylinders, use the right one in the factory location...or else.
That said ....we are all rodders of one nature or another, if ya feel like experimenting with your junk have at it. Just remember the knock sensor is used as one of the parameters for your ignition timing...late gm's run lean to produce heat( for optimum thermal efficiency) and achieve best economy and stoicimetric (sp?) ratio.
change the type and location of the sensor and you could risk damaging your engine. CAVEAT EMPTOR...BUYER BEWARE
L8TR SCOTT

I'm gonna bring this back to the top, as I've got the same problem.

Mine was in the same place as Woodys and since I am using block huggers also, I moved it to the other side of the block(driver side). It is real close to the headers on this side and has melted. It's not even hooked up now.

As I understand, the job of the knock sensor is to increase the timing as the rpms go up and to retard it if it detects knock. I don't think this will harm the motor, you will just lose horsepower in the upper rpms.

I did see a guy one time that had what looked like a 90 degree gas pipe fitting screwed in there and the sensor screwed into that, so that it cleared the headers. Do you think the sensor will still act normally like this?

Surely someone has a cool pirate fix for this.

The JTR book I have shows it incorporated into the motor mount, which is where I will likely install mine too, welding a pipe-nut onto the mount for the knock sensor to fit in.

Option C for me was to install it into the passenger side fitting where a temp sender might go....not sure that would clear the huggers tho, so waiting until I've got more fitted up before committing to that.

JTR states that location is not as important as everyone likes to think, and that it not necessarily be in with the coolant passages. IMO, anything on the block, like the fuel pump block off plate, would be fine, my option B.

Originally posted by woody
The JTR book I have shows it incorporated into the motor mount, which is where I will likely install mine too, welding a pipe-nut onto the mount for the knock sensor to fit in.

Option C for me was to install it into the passenger side fitting where a temp sender might go....not sure that would clear the huggers tho, so waiting until I've got more fitted up before committing to that.

JTR states that location is not as important as everyone likes to think, and that it not necessarily be in with the coolant passages. IMO, anything on the block, like the fuel pump block off plate, would be fine, my option B.

That sounds good to me. Your option C was my option A. It worked for a few months, but melted the sensor to the point of no return. I guess I'll buy a new one and put it on the fuel pump block off plate and see what happens.

I'm going to say that you are right about it really not mattering that much, because a buddy of mine told me that he knew a guy that was having problems with his knock sensor and after replacing everything within reason, found out that it was his suspension that was causing the problem. He had used tractor joints and there was so much play in them that the sensor would pick up the clunking noise as knock and retard his motor.

my JTR book also says you can move it.

they also recommend the mounting boss for the manual-clutch

linkage postion. This is just slightly above the oil filter mounting

location.



My buddy recently bought some block huggers from

Sanderson.... they were the style (CC3) I think that really

hug-tight next to the block. he returned them for the

clearance issue with the knock sensor. 96 TBI motor)

and instead bought another set from Sanderson (CC1)

I think that don't hug quite as close to the block.

these however are going to be close to the frame slightly.

they are the shortest blockhuggers on the market at only

4" tall from flange to collector.

--Sherpa

Go to www.jimsperformance.com.... he has a knock sensor that has either pipe or standard thread dont remeber I think that it is 9/16" and then you can put in in your head.... This works ask TPI Jeep that is what he did.

The knock sensor location is not too critical (except)...

The placement goal is to read sound (knock) as a frequency transmitted from the pistons/rod/crank to the iron of the block. Place it closer to the crank bearings and it senses (hears) better. Place it in contact with the iron and it senses better (no dampening from water or other isolator).

It is best located:
Snugged to the iron block or head (deadheaded contact to iron in the bottom of a threaded boss).
Placed along the centerline of the crankshaft outside the block's crank support webbing (direct iron path from crank to sensor).

Remember the goal of the knock sensor is to protect the piston from detonation failure (erosion and burn) and to protect the rod & main bearings from impact failure (any guess if this helps determine the best placement). Place it on the head and it is likely dampened by a water jacket (and who cares if an iron head suffers mild detonation, it's the piston that will rattle & burn). The further away from the crank, the more likely the sensor will read other noise (valvetrain & geartrain) as false knock (quick route to low performance).

If you cannot find a crank centerline boss (motor mount or other hole) away from the header, then look for a blind accessory hole that is backed by webbing in the block, or a blind hole near (but not into) the water jacket (the knock sensor reads best off the end of the sensor, not the threaded sides). Drilling and tapping the web off the rear main web (opposite the starter mount) is another option (better than some but can hear false knock gear noise if you run a manual trans).

HTH

Happy Trails!

BigJeepinYJ said it, go to www.jimsperformance.com email him, he offers a knock sensor that has a 3/8" coarse thread fitting, so you can screw it into any 3/8" bolt hole on the block or heads.. mine is mounted on the back of the pass side head. They cost about the same as a standard sensor... but do not mount it on a 90 or and other pipe fitting.

HTH

Ed,

The factory location on the bottom of the block in front of the starter is in a water jacket, so the water jackets have no effect on it. Don't belive me pull the sensor and stick a screwdriver in the hole to break loose any build up and walla, water!

Some people think you cannot mount it in the head or run solid lift cams due to valvetrain noise, this it false, the valvetrain rotates at half the speed of the engine so the harmonics of the valvetrain will not be consistant with engine speed so any noise produced by them will not give false readings to the ECU.

Mounting on the bellhousing will not work, the harmonics are not transmitted effectivly between the block and the bellhousing.. much less different materail types..

:D

I ran into the same problem when I put block-huggers on. I just used a 90 degree iron pipe fitting in the original mounting hole and that moved the sensor enough to clear. I haven't noticed any problems with this set up after a year of running that way.

Originally posted by EricFJ40
I ran into the same problem when I put block-huggers on. I just used a 90 degree iron pipe fitting in the original mounting hole and that moved the sensor enough to clear. I haven't noticed any problems with this set up after a year of running that way.

Your probably getting a less sensitive feedback to the ECM, but on a stock motor with very few mods, the factory fuel and spark map is almost perfect so only in extreme oddball conditions would you get a knock that would require the ECM to retard the timing, but with a desenstized sensor like that you are open to more less noticable knocks that would probably not be audible by the driver but could still be doing internal damage.

Food for thought!