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I just swapped out my stock cam for a custom ground Twin Turbo cam and went from zero knock to having lots of Knock.
I'm wondering if it's a valve to piston clearence issue..
Im seeing the knock when leaving a dead stop, in the 800 to 1600 rpm range at light throttle and in the 3,400 and up range at wide open.. ive also noticed a ticking sound that increases with RPMs.. I had been assuming its from the Dual valve springs but now I'm starting to wonder.
The Tune is spot on so that's not the cause of the knock.
No, stock lifters are still in there. Wouldn't it be at all rpm and a constant knock if it was a valve clearance issue? I really would like to avoid pulling the if I can.
You just saved me from pulling the heads to check 👍 so if you don't think it's a PTV issue, what would cause all this knock? The tune is verry conservative. Could this all be false knock from the new cam and dual springs? Im seeing the knock in HP Tuners, I do all my own tuning.
I'm seeing knock in my HP Tuners logs.
Up to 10 degrees at one point. Getting knock from 800 to 1800rpm when leaving a dead stop at light throttle. And knock at WOT around 2,400 to 4,400. I can't hear any knock though. AFR and timing are both verry conservative.
I can't imagine ptv clearance with that cam. My Titan 4 had in the neighborhood of .080" ptv with stock pistons. Get a bore scope and take a look to be sure, mine is a cheap eBay version and it works well for that sort of thing. When I had my cam out, I taped mine to a dowel and fed it in the cam opening and could read the numbers on the lifter rollers.
If you valves are hitting the pistons hard enough for the knock sensors to pick it up the engine would not run. Check you air intake temp and coolant temp sensors readings.
Still chasing this knock issue. I decided to check / swap out the lifters to rule out a damaged lifter, they all looked like new. No noticeable wear.
Piston to valve clearance is fine.
I decided to replace the knock sensors and harness while I was in there as well. Also went with a .060 gasket to drop the compression a bit.
Hope to have it back together and test run it tonight.
If the knock is unchanged I think at this point all I can do is top off with some 112 to see if it goes away. If not, the sensors are getting desensitized a bit. I'm over this false knock BS
Did you retune for the cam swap? Surely you didn't swap from a stock cam on a boosted motor and not retune. What timing/AFR where the knock is shown at WOT? If its from 3400 and up and not just at tip in, some of that is likely real knock.
Still chasing this knock issue. I decided to check / swap out the lifters to rule out a damaged lifter, they all looked like new. No noticeable wear.
Piston to valve clearance is fine.
I decided to replace the knock sensors and harness while I was in there as well. Also went with a .060 gasket to drop the compression a bit.
Hope to have it back together and test run it tonight.
If the knock is unchanged I think at this point all I can do is top off with some 112 to see if it goes away. If not, the sensors are getting desensitized a bit. I'm over this false knock BS
Chased false knock on a build recently and it ended up being the transmission was chewing itself up and the knock sensors were picking it up. Hopefully your issue is nothing like mine was.
Knocking/detonation/pinging is pre ignition. Usually caused by too much compression, too little quench, or both.
What is the dynamic compression with the new cam? Anything above 8.5'ish can be a problem.
You changed the head gaskets to something thicker. Yes, it decreased static compression a smidgen. Unfortunately, it increased your quench by a significant amount - and that's a bad thing.
Did you happen to measure piston height while the heads were off? The stock height is listed as .008" (but it could be more or less). With a stock .052 gasket, you'd have a theoretical .044 quench area. Which is a little more than ideal. Now your quench is about .052'ish. This alone will increase detonation. You probably would have been better with a .047'ish gasket.
All is Good! 😁 no more knock! , left the tune unchanged and it ran pretty good. It must have been one of the lifters. I dialed in a rough ve table and once the wide open throttle AFR's were on point I added some timing back into it. She deffinetly picked up some power in boost from the new cam!
06-10-2019, 07:41 PM
Valve to piston clearance issue? 
