Ok so I got my new pulley on (3.4) and it seems im having some knock issue when the intake pipe gets heat soaked.. Seems when the intake gets above 75 or so, at full throttle, randomly i will get between 2 and 6.5* of KR.. What can I do to eliminate this..

The car has full custom exhaust from headers back and a fender well intake. Iridium equivalent 104s (I actually think this is the issue because before I swapped pulleys I went from autolite 104s to the iridium equivalent and was getting 1-1.5* just from the plug swap alone) and the pcm is tuned by milzy..

I also wonder if its possible for the PCM to revert itself back to stock settings??

Should I go back to the autolite 104s, the copper ones or should I just go to the 103s? Or should I try a PCM from ZZP or something instead??

Any help greatly appreciated.. Thanks.

Oh, the car has a 180* tstat but the car never gets above 180 anyway..

 

If it's very specifically linked to temperature, you ideally modify the tune to have it pull that timing out at those higher temps. With that said, 75 degree IAT is not very hot, and permanently pulling that much timing is going to make it a real dog all summer.

TBH, you dont really have a lot of knock reducing mods so KR isnt totally unexpected. Best course of action is to add more mods.

If you were at 1 and now are at 6 with just a plug change. I'd swap back. These engines seem to really like copper plugs.

Not without someone re-flashing it. It is possible all the fuel trims zero'd if you unplugged the battery, but if the fuel trims are having to pull it that far, it needs a retune anyways.

Definitely no to 103s, that's way too cold. Even the 104s are on the cold side for that few mods.

I dont think switching vendor pcms is the issue either. If this is real KR and assuming no maintenance issues, all a tune is going to do is permanently take that timing back out. Unless the Milzy pcm is commanding crazy high base timing, a 6 degree drop is a ton and will probably put you near single digits of actual timing.

I'd swap back plugs, check for maintenance issue, check to see if its real KR, and then either:
-pulley up
-add more mods to directly reduce knock

 

You have ways to monitor stuff right? What are your fuel trims like currently?

I want to make sure you aren't also running super lean with this KR

 

Autolite 104's work pretty good on a 3.4 pulley (if it's an L67, not a top swap). What are your plugs gapped at? I think mine were around .055 but that's been a while ago.

That being said, I had upwards of 9* of KR on a 3.4 pulley with your same mods (minus headers, had a Plog and 3" downpipe), plus I had a ported TB and ported blower.

Ported the heads and it dropped to 1* on hot days. You may need to add rockers, a cam, ported heads, or an IC to run that pulley or smaller.

 

Certainly 104s work, but it seems like people get better longevity out of 605s with few bolt ons (and given the already short life of copper can be a notable benefit).

I think with 104s being 2 heat ranges colder than stock, that any 3.4" setup is going to be at the outer limits of this plugs range as it's not really making that much more power / heat than stock. If they're on a daily driver that spends most of it's time out of WOT, you run the risk of fouling up the plugs early.

 

Alright, thanks guys. I thought any KR at all could be damaging. I def feel a little better now tho. Guess Ill do the rockers first or how bad is the cam to do. I would certainly prefer the cam over rockers.

And yea, these engines do not like anything but copper plugs. Wow! Its hitting about 2.5 with blips of 5-6 randomly.

Im still gonna get the fuel trim readings but its been raining all day and I just cleaned it.

I have the plugs gapped at .055

 

KR itself isnt damaging. It's just a measure of how much timing the pcm had to pull to get it to stop knocking. The problem is (especially the more power you add and the more KR you have) is how fast its able to detect the knock and pull that timing out since it has to happen for the pcm to detect it and at thousands of rpm, a lot of cycles can occur in a very short period of time. As we've seen numerous times on the 3800, it doesn't do a great job as all of those with chunked pistons can attest to.


Rockers are very easy, it's a few hour job. Very little has to be removed to get the valve covers off and then you're there.

A cam sucks due to FWD. You can visually look and see where the cam sits, just above the balancer. Now imagine pulling a shaft the length of the engine out of there. Other fun parts include pulling and reinstalling the balancer and changing springs.

No doubt a cam is way better for power, it's just a tough job.