Best Cylinder Heads for 1996 Z28 Camaro Question

What reasons did they give for your car needing the cylinder heads repaired? Charles

Here is the cars present situation suggesting that it needs a valve job:

The car has been running like crap since I purchased it 500 miles ago. It is missing on cylinder #3 and occasionally on #6. The cylinders are getting good spark from the opti and the injectors have been tested and are functioning properly. The fuel pressure for the line is fine and the fuel pump has been checked. The car has new plugs and plug wires and is wired correctly. The problem is that there is a funky vacuume pattern suggesting a valve problem. The car has 160,000 miles on it and is due for some major work.

What is a "funky" vacuum pattern, and why would you have your heads messed with over it?

Vacuum comes from the manifold, not the heads. If you have a vacuum leak, on a fuel injected engine, the RPM's will go higher then normal.

Have you had a compression test? If you can change the plugs you can test the compression on each cylinder.

Has the valve lash been checked? have the valve covers even been removed?

I hate to see someone suckered in to a head service when it is not needed. Your vaccum issues could all be EGR related. If the EGR pentle is clogged with carbon your engine will do everything from lose power, to misfire. Charles

Charles,

The mechanic who worked on the vehicle told me I needed a valve job. When I asked him how he knew I needed a valve job, he informed me that he had checked cylinder compress and that the cylinders were getting good compression, but that my vacuume was going up and down speradically. He insisted that it meant I needed a valve job. He said that he had not had an opportunity to take off the valve covers but that he was sure that the valves were my problem.

I, personally, have not had an opportunity to remove the valve covers to take a look at things. As you know, these engines are a pain in the @$$ to work on so its a full days work just to get the valve covers off. Before I tear everything down to get at the valve covers, I want to make sure I have everything I need to fix the problem once I confront it.

I appreciate your interest in my plight. Since fuel and spark have been checked and there doesn't appear to be a vacuum leak, what would you suggest I do next? Any advice would be appreciated. Also, if I do need to replace the valves, what heads/rockers/rods would you suggest for an upgrade?

Thanks, Nathaniel

Charles Bendig wrote:

Well, I am not the level of mechanic that Charles is, but even I know that if you had a valve problem causing missing, you would have a compression problem on the missing cylinders. The optispark IIRC is well known for causing symptoms like you describe if it's bad. I would certainly get a second opinion since it sounds to me like the mechanic is trying to rip you off or doesn't know what he is doing. As I understand it, the fact of a miss happening will cause the vacuum to jump around.

Ok, here's what you do. First, since you bought the car 500 miles ago, I'm assuming you have a comprehensive deductible on it. Lower it. REAL low; like $250 low. Second, find a different idiot mechanic who will tell you you need new heads, especially if he overprices it. Take that estimate, file a claim, and with your fat check, buy yourself the LT4 conversion kit(GM PART # pk12550630). Have a friendly mechanic install the goodies for you, and while your at it, take charles' advice and fix your EGR system. 160k is a good time to swap heads and rebuild the top half of the motor anyways; might as well make a good deal on a huge upgrade if you can afford the cost of the difference from the insurance.

Cy: Im far from the best, I just happen to do it more often then some here.

You would not believe the number of 1992 up GM vehicles with odd ball problems that lead to a mis-diagnosis because of one problem.

Very Often on cars & trucks with the 1992 up style electronic EGR Valve. The Pintle (the moving part inside) Gets clogged up with a chunk, or fleck of carbon. This hold the Pintle open, Thus keeping the EGR Valve Open all the time. This causes false/ghost trouble codes, the ECM will cycle vacuum switches, giving odd vacuum readings with a gage, and will cause miss-fire situations.

This year alone I have seen 20 cases of this issue, all in GM RWD vehicles with over 100,000 on them. The problem is found often enough that a few companies (Standard Motor Products, Help/Motormite and others) make a EGR gasket with screen. The Screen catches large carbon chunks or Flecks, and prevents them from hanging the pintle open.

Even some Ford engines have this problem (mostly 1993 up Trucks). Yet for a Mechanic who does not see this issue often, it can be hard to diagnose. I know a few master techs who were doing intake gaskets, fuel spiders, even new EGR valves trying to figure out why the cars and trucks would come back in a week or two with the same issue.

I was just fortunate enough to learn from there mistakes. Charles I take September 11th off work every year.

Alright folks,

Well the verdict is in... I took off the valve covers, examined all the springs and found that the cylinder 3 spring on the front valve had cracked near the base and was loose enough for me to spin it around with my fingers without alot of resistance. So its time for a valve job. Anyone want to chime in on the best cylinder head question?

BTW... thank you all for your feedback. I am going to take peoples advice and replace the EGR valve also.

-Nathaniel Gary - KQ6RT (NoMoreSpam) wrote:

.....or, you could just replace the valve spring.

Seriously, unless you have a broken valve you can't tell anything about the condition of the valves by looking under a valve cover. A compression test is what really tells the story.

Second of all, I wouldn't recommend anyone pull the heads off any fourth gen f body until it's time to drop the motor out and do a complete rebuild. I own a '96 Z28 myself and over the last five years I've taken apart about everything on the car there is to take apart. Pulling the heads off while the engine is in the car would be a nightmare of a job. There is a reason it cost so much.

I dropped the motor out the bottom of my car a few months ago, rebuilt it, and put it back in. I'm very familiar with everything you would have to do to pull the heads. It certainly can be done, but I wouldn't want to do it!

I would not pull the head because of a bad valve spring. They can be changed with the head in place. You use compressed air @ 80 psi to hold the valve in place while you change the spring.

A few companies make adapters for doing this that thread in the spark plug hole. I have a compression tester that the gage head removes from the hose, and has a Milton type M connector. If I remove the shader valve from it, I can use it to put compressed air in to a cylinder (the quick way to verify a valve, hole in piston or blowby).

At 160,000 miles, things like valve springs get weak. If you want to improve your engine, replace all 16 springs, go with roller tip rocker arms. Charles

How difficult can it be to change the heads? I've already removed the exhaust headers since I'm changing them out, and I'll have to take off the intake manifold. How much more difficult can it be to yank out the heads?

Charles Bendig wrote:

Gary,

How difficult is it to drop the engine out of the bottom and replace it? I can get a brand new engine for the car for $1750 at this place:

Since the car is high milage, do you think it would be worth it to trade it out? I just hate having to redo work when it is not necessary. I wouldn't want to change the heads or change out the springs only to find that my rings have 10,000 miles of life left on them. Thoughts anyone? BTW... thanks for all the input. I am learning alot.

Charles Bendig wrote:

Revision:

I was totally wr> Gary,

These links will explain the project in detail. This is what I used to do mine.

Gary

Heck just the LT1 AFR's are over $2,000 a pair from Jegs. Charles

How Difficult? For me not that hard. But then I have a Shop, with a Lift, a small (twin stage, single phase, 7&1/2HP motor) air compressor that will give me up to 200 PSI to bust lose bolts when need.

For you? Probably a royal nightmare with the engine in the car. Taking the engine out might be a bigger nightmare for you.

As for changing over to after market heads, your not going to gain much, even with headers & a after market intake. Not till you change the Cam. Yet if your going to change the cam, you might as well get the motor professionally built. Charles