I have to replace the valve covers 149k is a long time for the originals.

I see plastic covers advertised and was wondering about them.

Does anyone have experience using plastic as replacements for the OEM's?

Thanks

Welcome to the forum.

I'd definitely stick to OEM for this. This isn't a job you want to do twice due to plastic cracking due to heat.

Arent our OEM ones plastic already?

I was just at the auto shop and asked the mechanic. He said that the valve covers ARE plastic. I just didn't know. thanks

My first reaction to seeing this thread was ... well there isn't an emoji for it on this site, LOL. Plastic??? WTH ????
After a bit of google and reading, seems everyone does it .. and has been for years - even huge diesel trucks have plastic valve covers and oil pans. They claim that they are 'better' because they are lighter, and can be molded as one solid piece to replace 3-4 multi piece systems. Other benefits include parts consolidation, cost savings, durability, reduced warping, corrosion resistance, more sound dampening, reduced weight, and improved fuel economy.
This from an article in a C.A.F.E. report in 2010: "It’s no longer unusual to open a hood and find plastic air-intake manifolds, valve covers, fuel rails, water pump housings, HVAC systems, brake fluid reservoirs, electronic throttle controls, engine covers, filtration systems, and other powertrain parts".
So I reckon if it's OK for a dump truck engine, it's probably no worry for a car engine.

Thanks for the reply. I found much the same thing. Now I have to figure out of @$50 cover sets are that much different from the @$300 sets. No real place to get the answer so far.

I would still follow the advice from Ilya. I'm not sure an aftermarket valve cover is the best thing. This (like most repairs on our cars) will be a mini-nightmare of a chore. I wouldn't want to do it twice because a part that is 'supposed' to fit might not seat properly and have to be replaced in a year. There are places like Infinitipartsonline . com that usually have OEM parts at a nice discount, but I doubt there is any place to buy them at a price that will match aftermarket parts. And buying used OEM parts can also fail much earlier than expected.
I usually buy my own OEM parts and pay the labor for the dealer to install. I usually save about half what the dealer charges for the parts.

Thanks Larz.

Wow, did not realize the OEM stuff was plastic. Learned something new.

If you change the valve covers and gaskets yourself, be sure and set aside a whole day to do it and start early in the morning (8-9am or so). You have to take out the intake, upper and lower plenum, and unplug most of the engine harness. That takes an hour or two if you have never done it before and are making a lot of notes along the way. The main two things you need to keep track of are keeping bolts for each thing separate and marked for what they are, and also note how each one of the spark plugs is plugged in. You dont want to swap two plugs.
Start the project early in the morning so that when you are halfway through and have the old covers off, you can get your new gasket set in the new covers with some RTV and then you can go do other stuff and go to lunch while the RTV dries. Then you can come back in the early afternoon and put it all back together.
It is not a hard job, just takes a long time.

I would also recommend changing some hoses while you are there. At the very least buy some with a plan to replace them as you will probably break one or two while removing the valve covers due to their age. The large vacuum line that goes between the covers was hard as a rock on mine and the only way to get it off was the break it off.


Z1 Motorsports sells both left and right OEM covers and gaskets for $380. I was going to post a link but apparently their site wont let me copy the URL.
Search their site for: "OEM VQ35DE / HR Valve Covers and Gaskets Package"
The hoses you need are: "Z1 Silicone PCV Hose Kit"

Thanks for the very detailed reply. I learned a long time ago that I am the absolutely wrong person to repair ANYTHING!

Do you have experience with aftermarket covers? They cost substantially less.

Thanks in advance.

I have never used any new covers yet, only replaced the gaskets. I have been through 4-5 valve cover gasket replacements, just replaced them a couple months ago for this most recent time. Covers still look good for me at 159,000 miles. Probably because they get removed every 15k miles or so and cleaned when the gaskets are replaced.

Our engine's PCV system is very inadequate and going above 6-6.5k RPMs or so will cause it to basically fail to function at all. The gist is that the PCV system in our cars does not seem to suck enough at high RPMs and will not maintain the necessary vacuum pressure. Taking the engine up past 7k RPM for more than a second will usually cause a small blowout of a gasket, as will revving hard before the engine is 100% warmed up and the whole block is fully saturated with the heat. Just because you hit "normal engine temp" within a couple minutes does not mean the engine is ready to be driven hard. You have to wait at least 10-15 minutes of driving before the block is saturated enough and everything is warmed properly. The problem is worse in the winter because it takes much longer for the engine to saturate. Hence why I usually replace every 15k miles... Im sure there is a good "winter is coming" joke in there somewhere. Anyway. None of that really matters to you but I know someone was going to ask how come I have had so many gasket replacements.


I wouldnt really worry much about the quality of the plastic in an aftermarket cover, Im sure it is just fine. The one thing I would worry about is whether the aftermarket cover comes with the proper gaskets around each spark plug tube, and whether they are fitted right. You dont want to buy an aftermarket cover and then find out you have to buy the gaskets for those separately, because you cant buy them separately. The OEM covers come with gaskets around each spark plug tube, and the gaskets you buy are not these gaskets. You cannot buy the spark plug tube gaskets. If those ever fail, you must buy a whole new cover to get replacements. I would hope any aftermarket valve cover would know to have these gaskets as they are mandatory, but you never really know.
The way you know whether one of these gaskets has failed is if you find any oil in the spark plug tube locations. If you do, the cover must be replaced. If you see oil on the engine block around the valve cover, most likely you can just get a new main valve cover gasket and replace that as this is what normally fails due to high revving.

I replaced the gaskets on my old ‘07 M45 with 239k on it. I used OEM gaskets and reused the OEM plastic valve covers with no issues. Modern plastics are great. You don’t need to replace them.

Sounds like you got lucky, I'm 119K and my passenger side valve cover has two of the o-rings bad, they leak oil into the spark plug hole..gonna just RTV around the seals and call it a day