sep226

I'm rebuilding a 3vz motor for a friend, and I just got the heads back from the machine shop. Out of my own curiosity I asked them how they figure out what surface finish to go with and if they had a source for what manufacturers call for as I've looked in the FSM and I didnt see such a spec.Toyota doesnt cater to rebuilding and their engine overhaul section just tells you that if there is warpage more than 0.002" to just replace it. Anyways, the owner at the machineshop said they use the smoothest finish they have and that it works very well with ALL types of headgasket. I asked him if thats the case with graphite composite headgaskets and he said yes.

Now to complicate the story, the deck of the motor was pretty ˟˟˟˟ed up. Lot's of corrosion and pitting. I suspected it be warped because between a couple of the cylinders the old headgasket had been pushed away from the combustion chamber, compacted and become oval. I dont like to leave things to chance so I ordered a machinists flat bar and a set of decent feeler gauges. Sure enough there is warpage past the max limit. So now I need to strip the block down and get the block decked. I'm a bit lost here because I dont know if I should just take the machine shops word on how they are finishing the headgasket surfaces or if I should give them a spec. Based off what I've read online for composite headgaskets you typically want surface finish of 60-80 RA. At the same time I'm not finding specs from toyota in the FSM or online, and this shop is very reputable in the area that has been in business for 40 years so I'm tempted to believe what the owner is saying.

Anyways, I wanted to see what some of you thought about this. I know going to an MLS is an "upgrade" I can do it, but it's not my truck and to be quite frank I dont want to deal with it. I'd rather build it to OEM specs with OEM parts and call it a day knowing it will run for a 5 years minimum. The frame is rusted so there realistically no point in rebuilding the motor so it lasts another 20 years.

ZARTT

Hi:
While searching for the same information that you are, I ran across this site:
https://www.aa1car.com/library/gasket_failure.htm
Don't know if it will answer your questions, but it is surely informative.
As a guess, I would think that the roughness number needed would be more accurately quoted by the gasket mfgr. rather than Toyota.
Remember, they got it wrong in the first place.
Art.

swampedout

Guess theres not many engine builders on here...
i wish i could help

swampedout

I wouldnt be concerned with smoothness, though. Id be more concerned abt decking the block flat. If its a good shop, they should be giving you back a properly machined surface.
are you reassembling the motor?

sep226

I will be

sep226

thanks for sharing. I found a similar article but it didn’t go into this much detail. Very informative!

Andrew Parker

Sep226,
The 3VZ-E head gasket compression ring shape is not round because Toyota opened it up to clear the valves even though this engine is non-interference. You need to get a very straight edged steel ruler that has not been dropped on the garage floor. When you place this across the deck from corner to corner and across each cylinder and down the middle you will easily see .002". For the machine shop that I used, to get them to fly cut the deck correctly, I specified that I was using MLS head gaskets. LC-Engineering mentions a surface roughness of 25 microns for MLS but who has a profilometer to verify this? So the other option is to do this optically and that means reflectivity with as few surface imperfections as is possible. In order to accomplish what I had in store for my block I had the machine shop remove the bushings from the block and told them I would install them myself. I then took the cast iron tool rest from my drill press and I spray adhesive bonded wet/dry emery paper to the tool rests surface and lapped the block as a sequence of steps with different grits while applying liberal amounts of WD-40 to flush out the particles. I did this same procedure to the heads as well and as they are aluminum they get like a mirror finish fairly quickly. The key is to move the tool rest in a large figure eight motion along the length and width of the decks surface. If you do this religiously without any localized back and forth motion you will retain flatness over the entire surface. As you remove the machining marks from the fly cutter and reduce the sandpapers grit to finer grades you come to realize that the thinner areas of the block that makes up the surfaces between the cylinders has been cut further down by the machine shop than are the outer areas of the deck were there is more steel surrounding a given cylinder. This has to do with the dynamics involved with fly cutting a non-uniform steel surface and will be a bit different from cutting the aluminum heads. Toyota uses some very good steel alloy in these cast engine blocks and so the manner in which a machine shop cuts the deck may not be up to par with what is really needed. So as I lapped the block down I continued this process until the inner webs of steel between the cylinders cleaned up with the lapping process and the surface became uniform with the outer areas of the block. When I was finished the entire deck was flat and the fly cutter marks were gone. The GreenLee MLS head gaskets and the ARB head studs were installed and then the torquig of the studs and the one bolt ensued.

If you don't go with MLS then the composite gasket will be much more forgiving with having the fly cutter markings present in the deck surfaces. The area to pay particular attention to is a blind water gallery that is external to cylinders 1 and 6 but has the shortest distance to the compression ring in the HG. That is the area were my engines Felpro Composite head gasket had blistered into the gallery and failed as the coolant eventually found its way to the compression ring and the cylinder which had split as the gasket material was eroded away with a multitude of thermal cycles. Cylinder #6 is on the opposite corner of the block and it shares the same geometry as cylinder #1. I picked up my 4Runner in 2018 and it had 232K on it and by 235K the HG let go. The over heat was caught with in a minute of realizing but the semi floating pistons in the 3VZ-E do not tolerate much in the way of overheating before they join with the wrist pin and you will find they seize quite easily in the cast aluminum pistons. I had 3 of the 6 that were stuck and had to do a complete engine rebuild. Very glad I did as my rig literally runs circles around my Son's 1990 that is very overdue for the same treatment.