As you may know I blew the HG slightly on the rear bank, driver's side cylinder. Compression was 120 in that cylinder as opposed to ~170 across the other five. I subsequently have done probably 10-15 runs at 12psi, third and fourth gear pulls, including one in 4th almost completely to redline (as opposed to 6000 where I normally shift). I thought I heard/felt something a little weird at around 6400rpm in the run I did to redline, slight tonal and butt dyno change, but subsequent compression tests (two since the blowing of the HG) have revealed no changes. All appears OK.

I never did end up taking the car to the track sunday as I had hoped to. Axle problems (not the same problem as the shredded bearing on the passenger side) surfaced and I thought it best that I not push my luck.

For those that don't know I blew the HG while racing BriGuyMax's TT 350Z, got a little detonation while brake boosting for an as yet unknown reason and I think that's what did it. BriGuyMax's 350Z went 11.72 @ 120mph on 18" DRs on Sunday.

 

Wow, thats nice.

 

Any idea of who sell top quality HG for our DEK engine. I'll be rebuilding an engine this winter and while at it that would not be a bad idea to replace the HG.

 

Greddy's Grex fits. I believe that Mardi discovered that they have a layered design that you can take apart and make a thicker headgasket to lower compression as well. The Grex is made of copper.

 

What do you mean when you say it "fits"... is it made for the VQ30?

 

I ment to ask you, I thought a blow HG caused ALL cylinders on that side to be low, not just 1 cylinder?


Good to know it still runs.

 

I believe its made for the 350z, but matches up with the vq30. you might want to ask him about it.

More info
http://f.maxima.org/showthread.php?t=262688
http://f.maxima.org/showthread.php?postid=2040166
http://f.maxima.org/showthread.php?t=217159

Cliff Notes: After re-reading those threads, it seems like if you want to use copper, it will leak water and not be as streetable. In that last thread I think SR20DEN says that a good substitute is the stock vq35 head gasket, which is a little beefier.

 

There's different ways to blow a head gasket. You can blow it between the cylinder and a water jacket/passage (which I assume is what I did) which means you would consume some coolant, you could blow it between a cylinder and an oil passage which means you would consume some oil, you could blow it between both water and oil passage which would mean you'd consume both and also contaminate either your coolant or oil with the other substance, or both. You could blow it so bad that you get low compression in all the cylinders but I've never done that. I've blown two of them now, the first one was alot worse, front bank, right and left cylinders were both down at 50-60 compression, rest were around 180. This time around, just that one cylinder is down at 120, and the rest are still good at 170.

The little puffs of evaporated coolant coming out of my valve cover breather are what told me in an instant I'd popped another HG, but the fact that the car isn't idling super rough, or running rough, and that the power is still there and it's not getting any worse on 12psi tells me I can deal with this for a while until I decide whether or not I'm going to build a motor or what.

 

thanks for breaking it down

 

what about a cometic mls head gasket?

 

Never heard of it. I'll look into it. Have you got a website for it, if not I can google.

 

http://www.cometic.com/ a lot of honda guys run them

 

86.05 for each side so 172.10 total. Thats kinda expensive. I guess the ones from the factory are like 60-70 dollars for each one though.

 

Nissan factory MLS is stout. Control the tune and run ARP studs.

 

they are pretty tough from what i hear its worth the $$ if your pushing it

 

MLS Nissan 3.5 gaskets will work just fine.. If you can swap the heads... then 9 times out of 10, you can swap the gaskets. It's hard to bust a MLS gasket.. stock or aftermarket. Our QR25DE, making over 500hp, is on a stock Nissan MLS gasket.

Travis

 

But the 3.5 has a larger bore than my 3.0 does so that's not really an option unless I do a 3.5 swap.

 

I would check the head when you remove it, if you remove it. From tons of experience if you blow the Head Gasket and only one cylinder is not holding compression then the head is warped. About 50% of blown head gaskets are warped heads when checked in detail. Many dont check them and just put them back on.

Remember like Mardi said, Maximas use MLS gaskets, very hard to blow them since they are MLS, much easier on cars that use Graphite based gaskets.

Im still going to lean on warped head on your engine. The stock head bolts are Torque to Yield so they will strech on alot of boost. Thats where the ARPs come in with their 180,000 psi tensile strength.

Dixit

 

Are you saying that you are still running with a blown head gasket? Your a muh braver man than I, I would be changing that out with a quickness!

 

Yes that's what I'm saying. Changing the motor is easier than changing the head gasket in this car, but I'm tired of working on this thing it's all I've done all year, I'm going to enjoy the last couple weeks of snowless weather then park it and worry about it in the winter/spring. Compression is not changing and I'm making sure the coolant and oil levels stay where they shood.

 

Thats the problem though, coolant with no lubrication properties is going into your engine, wearing out your bearings. If your going to change it out though I say have fun.

 

That's true, point I hadn't thought of. With the tiny bit of coolant that is burning off though I doubt enough is getting down past the rings and into the mains to cause a problem. Lots of turbo people with less monitored setups run around with blown headgaskets for months or even years on end and don't even know it. If I hadn't totally grenaded one previously I would almost certainly not even know that I had a problem. I know one guy whos sister had a blown head gasket on her neon for two years and didn't get it changed until this summer lol.

I can get VQs for $250 at a local yard though so I'm not terribly concerned if I totally frag this motor, though obviously I'd rather not have to do the AAA thing.

 

Neil, Over the winter get a new one, take the heads off and put it back together using the ARP studs. Its easy to do, it just takes some time patience and a little more money. I have a set of 3.0 OE head gaskets if you need them.

YOU CAN DO IT!

 

Matt are you saying the 3.0 gaskets are MLS just like the 3.5 gaskets are? What's MLS stand for anyhow... multi layer ____ I assume.

 

We're talking about a difference of 2mm in bore size... The 3 liter is closed deck.. so there's plenty of seating area. The firing ring will seal on the deck.. it will work just fine.

Travis

 

Vq30 is open deck.

 

sorry.. I was thinking about the VG30.. But, it will still work.. a difference of 2mm isn't going to hurt anything.

 

3.0 is mls too, its good

 

Wouldn't that be a cool winter project... It can be done for under a grand, and then you wouldn't need 12 psi...

 

MLS means multi layer steel.

 

I'm going to richen it up to like 11.3 across the board this week and try 1 bar again for a few days and see what happens. I want to get to the track this coming weekend and hopefully put down some decent numbers so I'm going to test it out this week and see if it'll hold up.

 

Why would you go run 1 bar after what happend last week?????

 

Because I think it's the detonation that happened while brake boosting that caused the problem. I won't be doing that any more, and with the additional richness and race gas I don't think I'll have anything to worry about. If the headgasket can handle 12psi at this point without having any further problems I think that with the additional precautions I'll be taking 2psi more is not going to do anything worse than has already been done.

The more I drive it the more confident I get in the fact that it's not getting any worse. That combined with the fact that I'll probably be extremely tempted to push the boost back to 1 bar at the track when I'm there has me deciding that I should test it out close to home first before I drive all the way out there and try 1bar at the track for the first time.

 

I think the more important thing is probably doing another compression test after running at 1 bar for a short period of time. That would tell how well the motor's taking the power, if the numbers turns out well then why not run it at the track. Either way the motor would need to be replaced or fix sooner or later (hopefully later). Good luck with that and keep us updated.

Also just out of curiousity, its probably just the term "brake boosting" thats throwing me off but what exactly is it that you were doing? I hate to sound like a noob but I just wonder if it is something that is new to me or something I already knew but called it different.

 

Holding down the brake and gas pedal at the same time while cruising to build boost but maintain a constant speed. Takes lag out of the equation, so that when you release the brake and go WOT your already in boost.

 

Of course that's what I'd do I wouldn't just blindly do it and then drive 4 hours to the track without having checked to make sure the compression is still good. I've been checking the compression every other day. It only takes about 15 minutes.

 

Better than my Toyota over 20!





Sucks for me! Time for copper head gaskets LoL!

 

was that a 7mgte? if so those suck, both of my boys blew theirs @ 12psi in 2 months. but the hks stopper gasket for the 7m is tha bomb

 

3vz-fe, 3.0L v6.

 

oh word, i thought you were just showing 3 of the inline 6. i wasnt really paying attention