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1988 efi on a 77 block... Knock sensor?

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dirtwarrior17

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Some of you probably know i did a swap from an 88 stock 350 to a '77 heavily modified 355 strictly because of the high nickel content in the block and the amount of hp for the price- $1535.00 for 400+ hp and 425+ ft lbs on ebay. Got the swap done headers, intake, fuel system, and all efi components hooked up and running except the knock sensor. A '77 block has no knock sensor whole so I called the local chevy dealer and none of the techs know. Also called a few machine shops and got nothin. Where the hell can you put this thing on a '77?
 
Have you tried to use the water jacket drain holes in the block? I don't remember if they are the same size or not. If the knock sensor threads are bigger then the water jacket drain a machine shop could drill the hole out and retap it for the knock sensor threads.

Harley
 
knock sensor should go in the passenger side coolant drain plug hole. Fits fine on my 77 block. Only issue I had was the coolant temp sensor on the driverside. Needed a fitting to step up the size.(the hole and threads on my head were bigger than the sensor. But I have no idea what those heads are off of.
 
I tried the block drain whole on the oil pan rail and theres no threads....JB weld????????:confused:

The water jack whole is too small.
My dad wants to weld a couple spacers to the water jacket drain bolt and then weld a nut that fits the sensor on the spacer. I say the spacers will screw with the frequencies but maybe not...little help>:confused:

the motor doesn't want to run for more than 2 minutes without the sensor( think thats y its not runnin right) and i can't get it to a shop until i can get it to run. I think the sensor has to do with it idleing but im not sure. all other sensors are hooked up. I checked it at idle with a timing light and the timing goes from 12 in advance to 8 in advance in about 7 revolutions. Is that knock sensor or do i have bigger problems?

I know it retards timing when it senses detonation/ pinging but does it affect how the motor will run/idle?
 
what the f#@k is jb weld doing in there

from what i gather you just paid BIG BUCKfor a reman hp motor and there isnt a screw in plug just jbweld.:blush: if so take the thing back and say hell no not this.:mad: jbweld dosnt move like metel and will fall out under the expansion and contraction of the block. if its just up in the hole and not on the threds then its block filler and just pic out a little and thred in the sensor.

welding on cast takes vary skilled welder and special rod . and dosnt always hold up to the heat flukshuations.

sensor just needs to pick up the pinging of the predetination in the motor. some vehicles of other brands put them in other places. if need be move to a spot and lengthen the wire.

but i would be VARY concerend about the jbweld first .:confused: :blush:
 
the timing thing is that the wire for your timing advance is not disconnected. On my truck the wire is to the right of the brake booster along hte firewall. Brown wire with a weather proof connector. One wire by itself. Unplug that when you check the timing. Set the timing to 0. I had it a about 10 when I first installed my distributor, figuring, AH thats good enough, blew back through the TB and started a small engine fire(loose fuel line helped). Then I set it to like 2 degrees, had it at 0 but it moved when I shut off the truck, that didn't run well at all. At 0 its great.
 
lol
i was asking if should i jb it in... not that there was jb in it. If i saw that **** anywhere on my new motor i would have sent it back and gone somewhere else
 
the motor was just idleing with no rpm changes and should not have had to advance it at all, or should it?

I know what you mean with the engine fire. I almost blew my eyebrows off last night. I don't have my foot throttle connected because i don't have the $$$ right now for the adapter holley says i need so i was bent over the tbi with my hand on the throttle when it blew.
 
My dad wants to weld a couple spacers to the water jacket drain bolt and then weld a nut that fits the sensor on the spacer. I say the spacers will screw with the frequencies but maybe not...little help>:confused:
 
more info

now i understand about the jbweld. and the threads are pipe thread not regular nut bolt threads. possible lots of junk in there and need to be cleaned. but if you just recently got the motor thay should have removed and cleaned this area to remove sediment in the water jacket area and check over the threads and area . hope this helps
 
other place to put

i think you can put the sensor on the back side of the block in a web in the bell housing area if need be. drill and tap the hole. it just needs to pick up the pinging of predetination knock.
 
If you have a drain plug in the block the knock sensor should fit into the samr hole I used a 78 motor and mine screwed right in you may be able to get a hole above the oil filter, however it should run with out the knock sensor hooked up. The only thing that it does is tell the comp. to retard the timing I think in theory if you have it hooked up and it doesn't work your timing will not get retarded so if it's hooked up and not in the correct place it shouldn't matter as long as its not getting a false reading. :confused:
 
You just said water jacket drain bolt.

Thats where the sensor should go.

I've got a '68 block in mine, and it has the threaded coolant drain. I find it hard to believe yours isn't tapped. Got a digital camera so we can confirm you are looking in the right spot?

It's ABOVE the oil pan lip, just a bit closer (and higher up) to the front of the engine than where the starter "ends". Thats off the top of my head, its cold outside.

IIRC some marine applications used spacers to deaden the knock sensor signal. Some 4.3 applications had the sensor mounted to a plate or something, so there is obviously some variation in how they are mounted.

However, in GM 350 applications, they went into the passenger side block drain, so if there is a way to do it, thats how I'd do it.
 
thats the right whole. it would screw right in if it had threads. At the front of the pan on the passenger side with the pan lip real close to it. I got a digital camera but its a piece of **** and itd be so blurry you wouldn't be able to tell.

I think the wholes next to the filter are too small also but i haven't tried them yet.

As far as how it runs i think the motor might be pinging with no way to stop or retard it. Thats y it slows way down sometimes and timing changes. Its more likely that is the problem because the motor has 10:1 compression with a mix of 87 and 89 octane fuel in it. Add said it would run on 89 but not without the knock sensor.
 
It's not at the front of the pan, I'm not sure where you are talking about. If you look at the engine standing next to your passenger tire, and drew a line right through the center of the engine (from drivers side to passenger side) it would be close to the knock sensor location. You mention filter, sounds like the drivers side to me.

If the engine is pinging with the knock sensor, then the injection system is going to have some serious problems anyways.

If you run "against the knock sensor" as they say, you will kill performance and mileage, as the knock sensor circuit has a certain amount of retard for knock built in, and it will just keep your timing retarded all the time.

Maximum power is not usually found at "maximum advance" anyways, but it is hard to find where the best timing is for your engine without really spending a lot of time on it.
 
I mention oil filter because there is two holes for an oil cooler that might fit the sensor. somebody suggested it. the passenger side water jacket sounds like my best option but i can always extend the wire(already have on about every sensor). I think i will just weld a couple spacers and a nut to the bolt thats already in there and just use an open end to get it in and out.

The engine is pinging but the sensor isn't in it..... that's y i started this thread.


It will run fine on 91 but i think im done with 87 and 89 for about 200,000 miles or until my new motor decides it's done. Gonna b awhile i got over 60 psi in the pan... high volume oil pump. Gotta love a 75 dollar gas bill out of every pay check.:mad: I didn't build it for mileage tho. :cool1:

Ok i just figured this out. you have to read the first post to see what i am talking about. i didn't read your post right. The water jacket wholes are threaded but too small. there is a drain whole on the pan rail that fits the sensor but has no threads.
 
Picture

In that picture, the knock sensor location is almost directly underneath where the exhaust pipes for cylinders 2 and 8 merge. This is where the one you say is the wrong diameter is located?
 
Just to make sure we are all talking about the same plug here, I ran out in the -40 F weather to snap you a couple pictures :) Excuse the greasy engine, I haven't had the time to clean it up and paint it :crazy:

First picture is the plug, the second picture is the sensor installed on the other side. Make sure to use some anti-cease when you install it, or you'll have a heck of a time getting it out when it eventually quits working... You can see that the plug is just slightly past the dip stick tube, as a reference as to where it is :)

Untitled-1.jpg

Untitled-2.jpg
 
the knocking sound travels through steel and iron quite well so you can mount it almost anywhere on the engine but it has to have a good ground to the engine, so drill and tap a hole on a fuel pump block off plate and put it there.
 
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