question about knock after head/cam install
09-05-2009, 01:18 PM
#1
question about knock after head/cam install Well I just got my car back together, I have swapped in the custom cam and the prc heads, I also put a ported fast 92 with the ptm throttle body, UD pulley, 42 lb injectors, and katech rod bolts.
I sent the ecm to tsp for a mail order tune, that way I could run the car and check for problems before taking the car up for a dyno tune.
--first concern, the engine is noisy, no real noticable clacking or tapping, just noisy I swapped in a set of LS7 lifters with the new ls2 trays and am using comps 7.4 pushrods, I think I willl buy a pushrod length checker and verify that my length is correct, and check the lifters, (I assume that to check the lifter just push on the rod and make sure it compresses?) the cam I have is a 224/236 .610/.608 on a 114+4 I would not think the cam and heads would cause such a noise, TSP said that there would be a normal sewing maching noise but I dont know.
--second concern is that the engine runs super, and pulls like it did when it was stock with the 120shot. But the ses light comes on, it is giving me a knock sensor code, I removed the manifold, checked the harness, and found some bare wire I ended up soldering new wires to the connectors, I then ohmed the wires out and got .002 resistance, that is close to perfect So i know the harness is not bad, and I dont believe the knock sensors could have just magically went bad, So I am not sure whats up.
I did swap in a set of spohn solid motor mounts, could this be causing the knock sensors to pick up noise, or could they be picking up the valvetrain noise, I thought that knock sensors were only supposed to detect a certain frequency, I want to have these problems taken care of before I make the trek to TSP in lubbock, so I would appreciate any help or advice or experience on this. Where I am gonna start is removing the valve covers and checking the pushrod length and making sure that everything is oiling up top (oil pressure in car is never lower than 40 -ported&shimmed LS6 pump-) Thanks for any input fguys.
I sent the ecm to tsp for a mail order tune, that way I could run the car and check for problems before taking the car up for a dyno tune.
--first concern, the engine is noisy, no real noticable clacking or tapping, just noisy I swapped in a set of LS7 lifters with the new ls2 trays and am using comps 7.4 pushrods, I think I willl buy a pushrod length checker and verify that my length is correct, and check the lifters, (I assume that to check the lifter just push on the rod and make sure it compresses?) the cam I have is a 224/236 .610/.608 on a 114+4 I would not think the cam and heads would cause such a noise, TSP said that there would be a normal sewing maching noise but I dont know.
--second concern is that the engine runs super, and pulls like it did when it was stock with the 120shot. But the ses light comes on, it is giving me a knock sensor code, I removed the manifold, checked the harness, and found some bare wire I ended up soldering new wires to the connectors, I then ohmed the wires out and got .002 resistance, that is close to perfect So i know the harness is not bad, and I dont believe the knock sensors could have just magically went bad, So I am not sure whats up.
I did swap in a set of spohn solid motor mounts, could this be causing the knock sensors to pick up noise, or could they be picking up the valvetrain noise, I thought that knock sensors were only supposed to detect a certain frequency, I want to have these problems taken care of before I make the trek to TSP in lubbock, so I would appreciate any help or advice or experience on this. Where I am gonna start is removing the valve covers and checking the pushrod length and making sure that everything is oiling up top (oil pressure in car is never lower than 40 -ported&shimmed LS6 pump-) Thanks for any input fguys.
09-05-2009, 01:41 PM
#2
I would definitely check pushrod length for sure. LS7 lifters cups are taller than the stock LS1 lifters. I have never measured the difference personally but did see the LS7 lifters are taller then the stockers. From the info I have seen on here, the lifter cups on the LS7 is .05 taller then the stock LS1 lifters which will offset pushrod length. Also check to see how close your ypipe is to your undercarraige. If it is vibrating, that can set your knock sensors off, even though you have solids on there doesn't mean it still can't touch. I barely tapped a couple valves on my originally install on my stock block. My combo was a MS3(114LSA) with PRC 5.3s though but your cam has just as much lift, just not the duration. If your vavletrain is super loud then more than likely you need a different size pushrod bro.
09-06-2009, 06:28 PM
#6
scanner reads 2 codes,
1st po327 Knock sensor 1 circuit low
2nd something about mil pending on the knock sensor
everything worked perfect before the h/c swap, but when i put the tranny in I noticed I pinched the knock sensor harness, so I ended up pulling the harness, finding the damaged wire, and then soldering new wires to the connectors, then ohming the harness out and getting my readings of 002 which is just about perfect, hardly any resistance. I can buy the new knock sensor harness, but then I also have to buy 2 new knock sensors, because my car is an early 98 it has the clip style connectors and sensors, instead of the newer squeeze connectors. I dont want to spend 140 bucks on new harness, and sensors and then have the same problem. its got me stumped.
I did notice that the SES light would come on generally after a full throttle burst, but I havent done but 2 of them, because both times the ses light came on and I dont want to tear anything up. as of right now the only thing I know to do is pull the covers, and make sure that everything is getting oil, and then check pushrod length, also I will push on the pushrods and make sure that I am getting some compression out of the lifters, they should collapse some and then come back up right? if they dont collapse or if they stay down then I would imagine there is a problem, I hope not because they are brand new LS7 lifters with less than 10 miles on them. so once again any help or advice will greatly be appreciated and tried thanks again.
1st po327 Knock sensor 1 circuit low
2nd something about mil pending on the knock sensor
everything worked perfect before the h/c swap, but when i put the tranny in I noticed I pinched the knock sensor harness, so I ended up pulling the harness, finding the damaged wire, and then soldering new wires to the connectors, then ohming the harness out and getting my readings of 002 which is just about perfect, hardly any resistance. I can buy the new knock sensor harness, but then I also have to buy 2 new knock sensors, because my car is an early 98 it has the clip style connectors and sensors, instead of the newer squeeze connectors. I dont want to spend 140 bucks on new harness, and sensors and then have the same problem. its got me stumped.
I did notice that the SES light would come on generally after a full throttle burst, but I havent done but 2 of them, because both times the ses light came on and I dont want to tear anything up. as of right now the only thing I know to do is pull the covers, and make sure that everything is getting oil, and then check pushrod length, also I will push on the pushrods and make sure that I am getting some compression out of the lifters, they should collapse some and then come back up right? if they dont collapse or if they stay down then I would imagine there is a problem, I hope not because they are brand new LS7 lifters with less than 10 miles on them. so once again any help or advice will greatly be appreciated and tried thanks again.
09-06-2009, 06:55 PM
#7
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When my car threw that code, one of the sensors got water in it somehow (there is a tsb about this), so when we replaced both, a little RTV sealed it up for good.
That's my experience at the very least.
That's my experience at the very least.
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09-06-2009, 08:43 PM
#8
Little more info, I pulled the valve covers and started the car up checking for good oil on top end, everything looks good, oil coming out of the pushrods, splashing on the rockers, looks good.
I backed all the rockers off, and then removed about 4 rockers and pushed down on the pushrod to see if I could get any compression on the lifter and make sure that it is free, but Icould not move any of the ones I tried????????? maybe because the motor was still warm, or because I havent given them enough time to spring back up,,??? I really dunno about this one, I would have thought that when i pushed on the lifter I would get some kind of movement.
Still playing the safe route, gonna wait till tomorrow, and try to move the lifters again. see what goes on there, and then I will wait for my pushrod checker and be sure of that. Then i will be able to sleep knowing that the valvetrain is as it is supposed to be. Doing my best to find out what the heck is up with these stupid knock sensors.
I backed all the rockers off, and then removed about 4 rockers and pushed down on the pushrod to see if I could get any compression on the lifter and make sure that it is free, but Icould not move any of the ones I tried????????? maybe because the motor was still warm, or because I havent given them enough time to spring back up,,??? I really dunno about this one, I would have thought that when i pushed on the lifter I would get some kind of movement.
Still playing the safe route, gonna wait till tomorrow, and try to move the lifters again. see what goes on there, and then I will wait for my pushrod checker and be sure of that. Then i will be able to sleep knowing that the valvetrain is as it is supposed to be. Doing my best to find out what the heck is up with these stupid knock sensors.
09-06-2009, 09:59 PM
#9
TECH Resident
I have motor mounts machined out of solid aluminum, no knock problems, so I would say it's not the mounts. My lifter are noisy, and I have adjustable rockers, no knock problems. I think the problem is in your harness or sensors. It is posible to mess up the sensor when it was screwed into the block, the hex on the sensor can turn from the body, sensors are cheap, it might be worth a try to replace them.
