Knock System

[O-Gauge Steamer]

OK, so....

Crawled under it and discovered the holes referenced are 7/16-20 in size.

7/16" = 0.4375"
5/16" = 0.3125"
Delta = 0.1250" giving 0.0625" as a side wall for a thread adaptor. Not enough material to hold a thread. Even if I locked the thread together with Loctite 680 spherical retaining compound...

If I were to tap drill for a 1/2-20 thread that would then give 0.09375" for a side wall. Might work. The threaded boss up by the number 6 cylinder, same size... Problem, of course, is that there is no way I can get that done. Would have to pull the upper control arm (not easy, it is a LA) and would need access to a quality lathe to make the adaptor.

So, back to the drawing board...

 

[kastein]

I might be wrong but for some reason I always thought the knock sensor was screwed into the back of the cylinder head. I have seen the sensor bolted to the driver side of the block under the manifolds but thought it was the renix coolant temp sensor.

 

[CobraMarty]

would this work?

http://www.cranecams.com/product/cart.php?m=product_detail&p=25916

 

[kastein]

interesting idea, but IIRC those 7/16 holes are 7/16-14 coarse, not -20 fine.

 

[CobraMarty]

interesting idea, but IIRC those 7/16 holes are 7/16-14 coarse, not -20 fine.

Sure now you tell me, back to my searching.

 

[Talyn]

Good enough for the Factory, good enough for me!

That is where I would put it.

 

[Talyn]

I might be wrong but for some reason I always thought the knock sensor was screwed into the back of the cylinder head. I have seen the sensor bolted to the driver side of the block under the manifolds but thought it was the renix coolant temp sensor.

The coolant temp sensor is more toward the front where a block drain plug is.

 

[O-Gauge Steamer]

Just FYI, I checked the threads using a tap. It is a conundrum, yes? I can go recheck it but the fine thread tap ran to the bottom of the bore.

For information only:
http://http://www.parker.com/portal...tid=1769&vgnextcat=P5ON+-+HEX+HEAD+PLUG&Wtky=

This give the flavour of what I may need to build. Yes, I know this is a pipe adaptor. But the photo is valid for the idea.

Or, what do you all think of taking a 7/16-20 Shoulder Bolt, cutting the head off, turn down the shoulder to 8mm and then thread it? Basically make a two thread stud out of it. Then 680 Loktite it into the block. I think this may be the better solution. Less expensive at any rate...

 

[CobraMarty]

A 7/16-20 set screw 1.5"long with a socket/allen on the end. Turn down or grind down half and thread with 5/16-18. Make a double ended threaded stud.

 

[CobraMarty]

These should still work. Sorry for the large pic, can't resize.

 

[kastein]

Just FYI, I checked the threads using a tap. It is a conundrum, yes? I can go recheck it but the fine thread tap ran to the bottom of the bore.

For information only:
http://http://www.parker.com/portal...tid=1769&vgnextcat=P5ON+-+HEX+HEAD+PLUG&Wtky=

This give the flavour of what I may need to build. Yes, I know this is a pipe adaptor. But the photo is valid for the idea.

Or, what do you all think of taking a 7/16-20 Shoulder Bolt, cutting the head off, turn down the shoulder to 8mm and then thread it? Basically make a two thread stud out of it. Then 680 Loktite it into the block. I think this may be the better solution. Less expensive at any rate...

There is a good chance I am wrong... I ran taps down every hole I need to use on the old block from my 91 while cleaning it up a few weeks ago, and don't own any fine thread ones, so maybe I misremembered or missed those holes.

 

[O-Gauge Steamer]

Well, it is a strange beasty this Heep o'mine. I am referencing the hole just aft of the bottom aft engine mount bolt location. It has a very nice flat spot on the block...

If I do have to machine an adpator and it sort of looks like I will, this project just went on indefinite hold due to yet another Surprise From Life. Tires and an MC for the Wife's POS Ford.

Don't get me wrong here, I like Fords. Just not Her Ford. Another grand out of pocket. Between her and the Kid ($7,608 in the last month), I will never get this Heep finished.

Think I should just give up and sell it on to someone who can finish it? What do you think it may bring? Sorry for the dump, I have just pulled the three remaining strands of hair I had out.

 

[jeeptec]

the Renix knock sensor is located on the left (drivers side) it would be the 2nd red circled hole alond the oil pan rail. that is in the middle of the block along the pan rail.

 

[O-Gauge Steamer]

I'll go look. I will also attempt to take a photo as the block in my Heep appears to be different from the 2000 that Talyn posted up.

If we were to number the circled holes as 1 - 5 from left to right on the manifold side of the block...
1) Will need to be investigated.
2) Has the bolt for the belt tensioner bracket in it. The bracket is not stock, it came with the Supercharger. But I believe it to use the original bolt location. But I will double check it. It may also be a larger than I can use hole as well.
3) Engine mount bolt location.
4) Another 7/16-20.
5) Buried behind the exhaust so is unusable.

Plus, I have another hole that looks just like the number 3. It just aft of that location.

Interesting eh? It appears that perhaps Jeep changed the block more than we thought.
Renix, Early HO, Late HO and WJ/TJ?

We do know that the block was changed to permit the A/C and Alternator moves on the latest incarnation and it now appears to be other, more subtle, variations. Could be wrong though...

But, it is all moot points as I have been stopped by reality. As I no longer have access to a lathe, I would have to use a Machine Shop and as of now and the foreseeable future, this will be the case. I must needs help the Kid finish his LAST SEMESTER.

Then, he can just get thrown to the wolves.

My Kid, when he was about 12, asked my to explain "conscripted forces" as we were watching some show on the History Channel. I explained it this way:

Imagine. Imagine you are in a sleigh traveling through the woods in the dead of Winter. Imagine that everyone is in the sleigh. Also imagine, that you are being pursued by a pack of ravenous Wolves. Every now and then, the Old Guy In Charge grabs an 18 year old and tosses him out of the sleigh and feeds him to the Wolves in order to hold them off.

That is Conscription. It is also a reasonable explanation of the "throw to the Wolves" expression...

 

[kastein]

My stock setup uses hole 1 instead of hole 2 for the tensioner, iirc. Not completely sure on this.

The first hole along the bottom skirt of the block is used by a cable clamp for the upstream o2 sensor harness on 91-99 iirc. I know it is on 94, 96, and 98 at the very least. Of course you could simply wire tie the harness to the knock sensor instead.

I know both the tensioner mount bolt and the o2 harness clamp bolt are 9/16 head, and I am 100% certain I ran a tap down them, which means they are 3/8-16NC. Bet mcmaster has 3/8 to 5/16 adapter studs... and if not, get a 3/8 bolt with a smooth shank, then chuck it up in a drill press and "turn" it down to 5/16, then run a die over it.

 

[CobraMarty]

My turn at the pictures, Just went out in the heat to take these just for you guys.
Drivers side, I guess the exhaust gave it away.
Sorry that they are so big, cell phone pics.

1st Pic- 1st and 2nd holes- 1st hole used for the O2 sensor wire clamp, 2nd hole for the motor mount
2nd Pic- 2nd and 3rd holes- 2nd for the motor mount, 3rd open
3rd pic- 3rd hole with 7/16-14 bolt- only 'threads in' 1-1.5 threads. Hole is 7/16-20-- This is the best/only place to mount the knock sensor.

 

[CobraMarty]

My turn at the pictures, Just went out in the heat to take these just for you guys.
Drivers side, I guess the exhaust gave it away.
Sorry that they are so big, cell phone pics.

1st Pic- 1st and 2nd holes- 1st hole used for the O2 sensor wire clamp, 2nd hole for the motor mount
2nd Pic- 2nd and 3rd holes- 2nd for the motor mount, 3rd open
3rd pic- 3rd hole with 7/16-14 bolt- only 'threads in' 1-1.5 threads. Hole is 7/16-20-- This is the best/only place to mount the knock sensor.

Sorry about that, here are the resized pictures.

 

[offroadordnance]

Has it already been considered to adapt a steel freeze plug?

 

[kastein]

are you sure you didn't just try to thread a bolt into a super crusty rusty hole? Try a tap, if it doesn't go in nicely, you're right, if it does go in with only a little resistance, the hole was just too rusty to thread the coarse bolt into.

edit: I'm gonna go check mine now

edit2: the '91 block in the basement, a -14 tap will go in a good half dozen turns. the '98 block in the yard appears to be fine thread however...

 

[O-Gauge Steamer]

edit2: the '91 block in the basement, a -14 tap will go in a good half dozen turns. the '98 block in the yard appears to be fine thread however...

Strange, eh? Differences in the blocks.

And, as to why the Engineers decided to make an apparently useless change is anyone's guess. Factory assembly tooling perhaps? Wish I knew someone who built thesee things...

I will go look at the location with the cable clamp. At this point it may be OK, who knows? Worth a look and thanks for that!

If I can't get this done on a dime, it is not going to happen. I just found out that I will be actively supporting the Kid as his part time job is not going to cover the rent increase starting in August. If he would just learn to live under a bridge and stop eating... And, of course, if he does not find a placement by Graduation, I will have him under my roof again. Betcha he still eats then too...

If I do make a "custom stud", it will have the proper 8mm on the small end. Not 5/16. I mean, if you have to make a part anyway, why not make it to fit? Chuck it into a drill press? meh. Last resort that. Would rather spend the money at a machine shop as the stud will need to be hardened. All studs are hardened as part of the manufacturing process. I know. I can case harden it in a bucket of oil, but I can't control the temperature properly.

Kastein, glad you checked out your 98 block as I was beginning to wonder just what is under the bonnet in my Heep...

I mean, I am crazy (own two Jeeps, 5 decades apart in age) and perhaps senile, but it is comforting to know I am not wrong on this wierd issue.

Was really beginning to wonder.

Todays simply useless information.

When attaching parts to an aluminium structure, you can apply about twice the torque to a nut on a stud than you can a bolt directly in the aluminium. The aluminium changes state (at the molecular level) by the application of the friction of the bolt as compared to the pure shear load of the stud.

Also, threads in aluminium should, IMO, never be cut. They should be rolled. Uses a different tap style and diameter hole. A rolled thread will have greater holding capabilities. All production produced bolts/studs have rolled threads.

In steel, maximum bolt strength is achieved at one diameter. This is why nuts are as thick as the bolt diameter they fit. The exception is the jam nut.

When installing hardware in an aircraft, a minimum of three threads must be showing out of the nut as those threads are tapered so the full diameter is not available for torque. The maximum is five threads.

Told you it was useless information...