Knock sensor on a '78 SBC 400?

[78 GMC Jimmy]

So I have a '78 SBC 400 motor. I think it might be pinging under load, but I'm not sure. Very loud engine/exhaust, so its hard to be sure. Is there a knock sensor on my motor? If so, where would it be and how do I confirm that its working? How would it retard the timing if there is no computer? Does it wire into the distributor module? Is there an aftermarket knock sensor kit with an idiot light that I can buy?

 

[Bent77]

yours will not have a factory knock sensor

The only aftermarket knock sensor I know of at the moment runs about $700.


What’s your total timing and what kind of fuel are you putting in it? Are you sure it doesn’t have a blown out exhaust donut?

 

[78 GMC Jimmy]

yours will not have a factory knock sensor

The only aftermarket knock sensor I know of at the moment runs about $700.


What’s your total timing and what kind of fuel are you putting in it? Are you sure it doesn’t have a blown out exhaust donut?

I replaced the headder gaskets and exhaust doughnuts a while back. For the timing, what do you recommend - 20?

 

[Bent77]

Depends on a lot of things. Compression, octane, driving style, elevation

What gas do you run in it?

 

[78 GMC Jimmy]

Depends on a lot of things. Compression, octane, driving style, elevation

What gas do you run in it?

Compression is 120 on number 1
Regular 87 octane fuel.
Sea level
Wide open throttle when possible.

 

[Bent77]

I typically run 36 total, but also use 91

 

[78 GMC Jimmy]

I have:

Vacuum gauge
Basic timing light

What the best way to set the timing? Should I set it to 16 with the light?

 

[Bent77]

You need to plug the vacuum advance and see how much timing it has at 3000 rpm

 

[78 GMC Jimmy]

You need to plug the vacuum advance and see how much timing it has at 3000 rpm

So check the current timing at 3K rpm with the vacuum advance plugged and then report back?

 

[Bent77]

So check the current timing at 3K rpm with the vacuum advance plugged and then report back?

See where’s it at yeah. If it’s much more than 36, that may be part of your issue