What are symptoms of #9 or #10 camshaft lobe wear?

[RICHTGP]

I've read some past postings about camshaft wear on #9 and#10 camshaft lobes. What were the symptoms? Thanks for any replies. :twitch:

[killinprixs]

sounds like a wrx... drone in the exhuast, valvetrain noise, loss of power, slightly lower compression in one cylinder, loose pushrods... anyone else?

[mfewtrail]

sounds like a wrx... drone in the exhuast, valvetrain noise, loss of power, slightly lower compression in one cylinder, loose pushrods... anyone else?

Besides those, worn lobes can cause backfiring.

[RICHTGP]

Mine just picked up a skip at idle. when taking one plug wire off at a time narrowed it to number 5 cylinder.
This is the only cylinder that did not change the rpm when plug wire pulled off. replaced plug and wire.
tested coil with spark tester at end of number 5 wire while running.  Had plenty of fire. Don't notice it skipping as bad at slight ly higher rpm. can also hear it "thumping at tailpipe.  :icon_cry: One other symptom I noticed was when going WOT from a stop it would accelerate goold but then make a muffled bump in the engine one time and then I would lose almost all power. does this every time under WOT.  :damnit1:Engine would still run but only about 2000 rpm. If I pushed throttle any at all it the rpms would drop and car would shut off if throotle pushed far enough. After about 30 seconds of it running this way it would magically go back to accelerating normally again. I wonder if it backfired and overboosted the engine causing the computer to stop acceleration. I have replaced just about everything on this engine and rebuilt the tranny. Thanks for all of your replies! I should also note that I have no problems at part throttle as I routinely go to work on the interstate at 95+ MPH.  SHHH!!!

[cobracmdr]

Have you replaced the ignition module, and not the coils the box....I have had weird stuff go on when that thing goes out.  On and the pfhh pfhh pfhh at idle is a normal tgp idle hahahah. They all do that a little bit.

Ken

[RICHTGP]

Yeah, I did replace all the coils and ignition module when I had the engine out. However, did go aftermarket. Read posts after replacing them saying not to go aftermarket so that could be a problem.

[R Dubya]

In my experience with a failed #10 lobe, the car would idle rough, seemingly indicating a failed ICM.  You could hear the boost come back into the engine bay when accelerating, it would accelerate, but would eventually fall on its face and sometimes even stall out while rolling.   I however had bent pushrods, and that made the diagnosis to that cylinder relatively easy.  Compression would obviously not be there if there was no cam lobe, but I'm not sure how much wear it would take to make a noticeable effect on driveability.  It's hard for me to give a concrete diagnosis, because I know I had crap Bosch injectors installed, and that they weren't working right either, so that could have complicated things. 

I removed the rear rocker cover and manually turned the engine, found that the lifter/pushrod asm was not moving the rocker.  You can always remove the pushrods to investigate, or  you can remove the LIM and check and compare lifter movement from cylinder to cylinder as well.  I wouldn't be surprised to find out the problem was with that injector or all of them?  Have you checked those?

If the cam has failed, it is possible to replace it without removing the engine, and although it would be recommended to replace main/rod bearings, it is not entirely necessary. 

[RICHTGP]

Hey, thanks for the last post. That is exactly what mine is doing. I had noticed before it got the noticeabel skip and exhaust pipe noise change that the car seemed to get extremely winded above 3000 rpm and the acceleration dropped way off above this rpm. Maybe the cam is causing that too. I have the factory injectors in the car that it came with. I do not have one of the GM factory fuel injector testers that allow you to watch preesure drop on each injector. Wish I did!  Well, I have kept the engine stock and have never gone into the motor other than to reseal it. Guess now I'll probably go with a more powerful cam and change the injectors as well. I wonder if I will get any power gain this way using the stock turbo?  Also, if anyone has any cam recommendations in terms of lift, duration and brand it would be very helpful.  The last question I have is what causes cam failure on these lobes and what will prevent this from happening to a new cam?  Thanks for everyone's advice and help. This forum is a life saver because the OBD 1 diagnostics suck on these cars. Service manual really not much help either!! :icon_biggrin:

[killinprixs]

i would just do a compression check and if its good i bet its the stock injectors.

[R Dubya]

in this case, you aren't necessarily looking for leak down on the injectors, you are really looking to find out if it is pulsing the way it should be.  a leak down test on these cars is simple.  simply remove the fuel rail/injector assembly from the LIM and pressurize the system, make sure the engine isn't hot obviously, and its probably a good idea to have an extinguisher nearby.  if the injectors drip, you know thats at least part of your problem, but as killinprixs said, if you are getting good compression its likely not the camshaft.

You could always ohm them all out to find out if there are any major differences in the resistance.  I do not know the proper numbers off hand, I believe it is no less than 12 ohms on any injector? someone confirm that please.

either way, good luck with figuring it out. 

[cobracmdr]

You can also get a fuel pressure gauge to check the injectors and make sure they hold pressure after key on for 2-3 minutes.  Should be around 40 psi if I remember correctly.

Ken

[RICHTGP]

Does anyone have any suggestions on which cam to use to get a little more power with the stock motor and turbo/ECM setup? Also need to know which injectors to get. Thanks for everyone's input.

[RICHTGP]

I'v spent a lot of time going through past posts over the years ont this forum to try to select a good cam replacement for my stock TGP. I saw mentioned a couple of Crane cams. One had 480 lift and 284 duration with 112 sep. Another choice was a 440 lift and 266 duration with 114 sep. Also recommended 26lb injectors and valve springs if I want to hit 6500 rpm. Do any of you have experience with these setups? Who makes the 26lb injectors recommended and what valve springs do I need?  Has anyone gotten their motor to run at 6500 rpm and be streetable with good idle?  So many questions and dreams of increasing performance but so small budget! Also who burns chips to make these perform better besides JeffM.  Also, depending on cams recommended, what is the best thermostat, 160 or 180. Thanks for anyone's input. :icon_confused:

[cobracmdr]

Ok I know you have  a lot questions and they are good ones.  Here are some simple answers:

Valve work. If you want to run a cam you should up the following on your heads:

LS1 Valve Springs 98 corvette (GM PN 12589774, 12 of them)
LS1 Shims 98 corvette (GM PN 12565118, 12 of them)
96 '3100 V6 valve spring retainers ( GM PN 10166344, 12 of them)
96 '3100 V6 valve key retainers (GM PN 10166345, only need 24 but get extras incase you drop them)
82' 2.8 V6 rocker arm studs and nuts (GM PN 476530 and 477212, need 12 but get extras again)

With this setup you will prevent valve float with that cam.  If you want to be extra sporty you can get some 95 3100 V6 1.6 ratio rocker arms (stamped steel kind).


Tuning, talk to Adam, Flybynite.  Working with him is always a pleasure and I learned how to tune my car myself eventually with his help.  At the very least he can hook you up with a tune to get started but you are going to have to go to moates.net and get the stuff to start datalogging your car and reflashing your chip to get it as good as a factory setup. 

Budget?  If you want to do anything performance wise be prepared to spend some $$.  Make a budget for how much you THINK it might cost to do it, then double it because that is what it will cost you in reality to do it right. 

Ken

[TGed]

82' 2.8 V6 rocker arm studs and nuts (GM PN 476530 and 477212, need 12 but get extras again)

Ken

Why those?  Stock style studs fit the 3100 1.6 rockers fine.