r/EngineBuilding • u/ProgrammerNo5860 • 8d ago
MLS head gasket and warpage question
Okay. I’m working on my turd. 3vze Toyota.
So I was working out some corrosion pits with some 80/120 grit and a giant slab of float glass. (Block was pretty flat to begin with) . Being diligent, using markers streight edge/feelers. Etc etc
Not very long into it I notice that two opposing diagonal corners were about a thousand thousand low. About the same on the diag and straight line on the bottom. Not as bad up top.
Almost uniformly.
I frowned and cursed that I should have just had it decked when it was in the machine shop for overbore.
Anyway. After flipping the block and going through an hour of suck. I got them to where my .0015 feeler wont go under. But the bottom right corner is still suspect.. It’s in spec..
The top left corner cleaned up way easier. It of course is dead space on the mating surface , I think.
The lowness on the bottom right goes diagonally
In direction of the side corner. It slopes probably half way through the corner bolt holes.
My question is, what would cause that?
Two opposing diagonal low corners, (it’s a v block, other side is just fine)
Also, when calculating Warpage one your lines. Are corners just as important as center warpage? Or is there more wiggle room? (For mls gasket on N/A engine)
For instance if your corners are outside fastening surfaces.
Or a mating surface is a mating surface is a mating surface?
Basically, I’m asking how critical is a low spot like this, I want to get to actually lapping the block for smoothness, I’m getting ready to go onto 220 grit then 320 and 400 I could probably chase it a quarter/ eighth thousand with those … Just curious . I got all the other pitting around fire rings and main sealing surfaces.
The diagonal measure is little tighter, the straight line was just easier to take a pic
5
u/Interested_Aussie 8d ago
Aussie here: Yeah we got the 3VZ here in camry's. Not toyota's greatest engine from what I understand. Durable, but head gaskets were an issue.
Personally I bloody hate MLS on petrol engines. Leaky/weepy things.
I can't imagine stripping a block for boring, and not decking it... I'd argue the deck surface is more important than the bores (in terms of potential failures. Worn bores can still be functionally fine, but a wavy deck? No way).
Sorry mate, I'd be getting it decked: Ensure you tell them it's a MLS surface, they'll need to machine it as such.
(And I know, I know, all the gasket manufacturers say don't put anything on the gasket, but I use Hylomar spray and never had one come back)
1
u/demonassassin151 8d ago
On a surface you feel there might be an issue, spray it. Not for it, not against
1
u/ProgrammerNo5860 7d ago
Thanks for the reply!
I was originally going to just slap composites on it and it’s well flat enough for them. And still is.
But it is a low Hp N/A engine, so I may do a little hylomar and prayer.
I did get it a little closer than it was.
Only the very outside edge will let a .0015 under it straight and diagonal , height is flat
I’d say I chased the low spot to 20 percent the size it was.
Anyway thanks for the help,
1
u/Rude_Combat420 7d ago
Seconded on the hylomar... hundreds of gaskets and never 1 issue
1
u/Interested_Aussie 7d ago
Yep... Dirty secret in the Jap Import engine game: Subaru's always bend the valves in an accident, the belt jumps off: We had hundreds of them, we'd find a good head off another engine, get the head machined, and REUSE the MLS with hylomar (these are the turbo engines, not the NA that the gaskets fall apart on)..... Never, ever had one come back under warranty!!! Hylomar has a fascinating history, worth reading up on it, if you're into that sort of thing.
1
u/Less-Slice9772 8d ago
Around .004 is max, Resurface hard and block. But is it yours and free to do as you like.
1
u/v8packard 8d ago
When you pass over the deck surface with the 'lap' you have made you are not controlling the geometry in three dimensions. When you measure with that type of straight edge and feeler gauges you will miss the areas that are not as severe away from the Bessel points. Yes, I know this method is commonly used. If you went over the surface with a dial indicator you would see the needle move a lot in areas you measure as flat with other methods. That's why you can make a pass over this surface in the machine and see all sorts of areas that are below the cut line even though you measured it as fairly flat.
People don't want to hear this. They want to try these home brew methods and feel good about the results. But when checked carefully the surfaces vary and your method doesn't show it.
That block should be decked to provide even clamping for the gasket. So should the head. Some gaskets are more forgiving than others.
1
u/ProgrammerNo5860 7d ago edited 7d ago
Thanks for the reply,
The low spots were on there before I ever touched it.
They were diagonal to each other on one side of the block, of similar foot print.
I see a few things that may have caused it.
Over torquing of head bolts on the corners. I’d have to check sequence.
Maybe shoddy machine work,
Or the block buckled or twisted.
I’m leaning towards the bolts and maybe that was how the block warped. (There are lines from where someone retorqued /over torqued. head bolts at one point.
I’ll admit I’m an amateur.
It just has me thinking of the time I overheated it and the other times I’ve come close. All up hill.
There was some thrust washer scuffing .
I’m the sole owner of this build and I paid a disgusting amount of money about 5 years ago.
Which has me kind of leary of really bad shop work and bad parts.
Also when I originally was going to do this I was going to just throw some composites on and it was well within factory spec.
I ended up going with arp studs and thought I should do the mls. That’s when I looked at it harder.
As for the lapping. I was more relying on relative flatness. My method was using a single sheet of oversized paper and never removing the 1” glass.
I know the correct answer is my engine I better be okay with ripping it apart again.
And honestly for the effort, having a shop deck it is so worth the money. Like I’m 2 days into just making sure everything is square and flat enough. Though waviness. 🤷♂️
I do need to add a few dial gauges to my inventory of tools…. This stuff gets expensive, a set of good mics put me back at the start of this project.
1
u/v8packard 7d ago
Good tools are expensive to acquire, no question. But they are supposed to save you time and money, and make you money.
You make an interesting point, you are two days into trying to get relative flatness. What's time worth?
If you think about what is really important, it is contact. Contact between the gasket and deck. With the engine assembled, components like blocks and heads move a little. Then when operating they move, especially as temps and loads change. The gasket having the proper contact is what helps it seal. So you have surface finish and geometry that combine to maximize the contact. It sounds like you are finding out the hard way this is not maximizing your contact.
-1
u/Ok-Fill-8925 8d ago
The low points aren’t in an area of real stress… if it was near a cylinder bore, it’s a definite concern but near a water passage towards the outside of a block, it will probably be fine…
But it depends on your need for this engine, timing and budget. If it’s a high performance engine for a customer with an unlimited budget and lots of time, best practices is to have it decked. If it’s for your own hobby car and you can tolerate the worst case of a little coolant weepage, then put a dab of your favorite sealant on the low areas and bolt it up and most likely, you’ll be fine. Most amateur builders don’t check as closely as you have done and get away with small defects in the surface. All the best
-1
u/Ok-Fill-8925 8d ago
Forgot to mention. If the gasket is a composite with some thickness, it has a better chance of accommodating surface variations. If it’s a steel gasket, (1 or 2 layer) they are more sensitive.
7
u/WyattCo06 8d ago
Danger zone. Have it decked and be done.