Problems after cam install, help!
Problems after cam install, help! I'm in dire need of some help, as my car has me thoroughly confused in what is going on! It's a 99 Camaro SS with 93k miles. Stock heads. Mac mid-length headers, off-road Y-pipe, Flowmaster catback. Just did a cam swap with the El Toro cam (230/230 .613"/.591" 111 LSA 109 ICL), 7.425" pushrods, PSI LS1511ML springs, LS6 oil pump, and LS2 timing chain. I did the springs prior to the cam swap due to valve float from one of the stock springs. Car ran perfectly fine before the cam swap.
Now it has a really bad misfire according to Torque Pro on cylinder 6 and a some on cylinder 7 as well. Got the P0300 code immediately, and once got P0306 also for cylinder 6. If I try to drive the car, SES light flashes. The misfire isn't a false, you can watch the engine stutter and occasionally backfire. However, when I hold the throttle just out of idle, at a consistent RPM like 1,000 or 1,700, the misfires all go away and it sounds to be running flawlessly. I try to drive it with varying RPM and that's when I get the flashing SES light. Tried swapping injectors, coils, wires, and plugs for cylinder 6 and the problem remained there. Did a compression test that indicates a dead cylinder #6, but have no idea how it runs fine when at a consistent RPM above idle, especially when the car ran perfect before the cam swap. When you place your finger by the spark plug hole, without anything in it, the air coming out feels the same as a cylinder that doesn't indicate as dead. Swapped 7.425" pushrods with stock ones and still the same thing. My tuner took away some of the fuel at idle that was causing it to run really rich, and he is also as clueless as I am as to what the underlying problem is. He advised a cylinder leakdown test, so I suppose that will be next.
I am stumped and could use any help or advice I can get, please.
Now it has a really bad misfire according to Torque Pro on cylinder 6 and a some on cylinder 7 as well. Got the P0300 code immediately, and once got P0306 also for cylinder 6. If I try to drive the car, SES light flashes. The misfire isn't a false, you can watch the engine stutter and occasionally backfire. However, when I hold the throttle just out of idle, at a consistent RPM like 1,000 or 1,700, the misfires all go away and it sounds to be running flawlessly. I try to drive it with varying RPM and that's when I get the flashing SES light. Tried swapping injectors, coils, wires, and plugs for cylinder 6 and the problem remained there. Did a compression test that indicates a dead cylinder #6, but have no idea how it runs fine when at a consistent RPM above idle, especially when the car ran perfect before the cam swap. When you place your finger by the spark plug hole, without anything in it, the air coming out feels the same as a cylinder that doesn't indicate as dead. Swapped 7.425" pushrods with stock ones and still the same thing. My tuner took away some of the fuel at idle that was causing it to run really rich, and he is also as clueless as I am as to what the underlying problem is. He advised a cylinder leakdown test, so I suppose that will be next.
I am stumped and could use any help or advice I can get, please.
The PSI 1511 valve springs are excellent springs, however they set up light on the seat. You cam lift is pretty high. Have you measured the seat height of the valve springs to ensure you don't have coil bind or are not near it at full open?
I haven't had much time to work on the car in the last 2 weeks, but I just took the rockers off, aired up cylinder 6 from the spark plug hole, and air is exiting through the exhaust. Going to rent a boroscope in a bit. My guess thus far is either a bent valve, somewhow, or a jacked up valve seat. Any other suggestions?
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo Ok, so it was a bent exhaust valve. Found a good price on a good used set of 241s that I will be installing after I take the 853s off. My question being, what do I need to do to prevent bending another valve? Cam was installed dot to dot on the cam gear and crank gear, so it should be timed properly. Maybe I was ignorant in making the mistake of not checking pushrod length and went with the 7.425" others have used? This is my first cam swap, so please don't bash on me too hard...
TECH Fanatic
Joined: Aug 2004
Posts: 1,373
Likes: 4
From: Auckland, Nth Is, New Zealand.
Ok, so it was a bent exhaust valve. Found a good price on a good used set of 241s that I will be installing after I take the 853s off. My question being, what do I need to do to prevent bending another valve? Cam was installed dot to dot on the cam gear and crank gear, so it should be timed properly. Maybe I was ignorant in making the mistake of not checking pushrod length and went with the 7.425" others have used? This is my first cam swap, so please don't bash on me too hard...
241s get here tomorrow. Going to do a ptv clearance check and pushrod check. Before I do everything, I'm just trying to get an understanding of why this only happened on one single valve. Any input? Want to take all precautions to avoid this happening again. Pushrod length didn't seem to be an issue on any of the rest of the 15 valves. Going with GM MLS gaskets for the "new" 241s.
That cam when we installed it on my sons car was real tight on the intake valve. We retarded it 2 degrees with an adjustable timing gear for more clearance. You need to check piston to valve clearance with a light spring on 1 intake valve and 1 exhaust valve. Get 2 used lifters and take them apart and shim them up with washers until the are solid, then put them back together. Get a dial indicator and a stand and put it on the top of the rocker arm. Cycle the motor around and check clearance by moving the rocker by hand up and down. If its too close on either the intake or exhaust( less than .060 ) usually the other valve is a lot more like .120 or more. The adjustable timing set will alow you to move that clearance around so that you have more on one valve and less on the other.
