Why not to let your head be belt surfaced/sanded The subject head is a Mitsu 4G63T from an Evo VIII This head was in very good shape to start. The head was pulled due to a bottom end problem. It was not overheated. It was taken to another shop, NOT mine. The customer was told it was surfaced .003-.004 It was then run and the bottom end failed, Then came to my shop. The first thing I did was to check the thickness of the head. I know a belt surfaced head will not be parallel nor square along with not having the proper surface finish for a MLS head gasket. If you look at the 4 corners, you will see how the head gasket surface is not parallel to the valve cover rail. It is close, but still off This is the surface finish left by a belt sander This is how the surface looked after I milled appox .002 It did cut most of the surface, but it was still low at one corner, and it would happen to be right around the oil feed port to the head. I made another pass of about .002 This is how it looked. I made another .002 cut And was to this So one more pass to clean the gasket surface, and proper clamping force will be kept on the head gasket. I measured the head again, and it was 5.183 at all 4 corners When I cced a combustion chamber it was 44cc I also did oil port mod #1 before I surfaced the head. This head is now .002 below AREA min spec, but is still a useable head. ***I know here on V8Buick most have cast iron heads, the belt surface will still screw up your head gasket surface. A belt surface machine is fairly inexpensive as far as surfacing equipment goes and takes almost no training to use. With a cast iron head it may be ok to scuff the surface, but if you are trying to mill the head to rid of warp, I would advise to stay away of it. I had to correct a surface on a pair of Ford 400M heads once that were V'ed from a belt surfacer.
Some morons at a machine shop belt sanded the DZ302 block for my '69 Z/28. It all but took the numbers off the deck. I was pissed and asked them just what the F#@* they were thinking.
Smokey, You are lucky if thats all the damage they did. But on that specific block loosing the stamped numbers is a very costly mistake. When you had the short block, did you measure your piston to deck clearance? Its normally bad from the factory as far as tilt and equal depth at all 4 corners. The belt surface can make it worse, the leading edge grinds down more than the trailing edge of the block. There is also no way to index the head gasket surface to the mains. The belt surface is a horrid way to surface any critical surface, IMHO should only be used to flatten out (somewhat) exhaust manifolds.
I took the engine to a friend who went over everything they did and assembled it. He is a very experienced builder so I would hope he did things correctly. It's all together and on an engine stand.
Bet the surface finish looked a bit like this. If you start popping HG, even a composite, chances are better than even the block will have to come back apart and be milled.
/\/\/\ Thank You for the Email. Everyone should see what you sent me. Very informative. You do nice work, sir! I do plan on following your advice. I'm a part-timer at Visner, so the heads will be inspected by Dave. The block will be sent to whomever he recommends.
Smokey, Since you asked so nice, I went and posted that info. http://www.v8buick.com/showthread.php?295695-Belt-Surfaced-Block-Correction-Milling I hate seeing belt surfaced heads and blocks, to me It just shows a lack of detail in a decent machine shop. I know equipment is not cheap, but be upfront and understand what the equipment can do.
You are a little bit far from Engine Craft in Goodrich MI anyway, when Dave does a "numbers" block he loads it on the machine the opposite way that it is usually setup so he can stop or start(can't recall exactly how he explained it)so the numbers aren't milled off. He has all the main spacers for his mill to setup the deck square to the mains so no need to mock up the block and measure TDC on the 4 corners like some shops ask for, unless the rods are different lengths.(LOL) I hear you on the belt sander BS a friend of mine had a import intake for a sbc that the mounting port surfaces were warped and needed to be corrected. It was a pain in the arse trying to find the vacuum leak because the intake was sealed up top, the warp made it have a vacuum leak in the valley and was sucking oil from there! It was a Sunday and the only place opened was an auto parts store with a belt sander so he took it there. I told him I could fix it but would take a couple hours on my Bridgeport but he didn't want to wait. They ended up making it worse and I ended up fixing it on my mill, good thing they make thicker gaskets for the sbc because that belt sander POS took a lot off where material didn't need to be taken off. If a shop wants to belt sand critical surfaces with a belt sander find another shop, don't walk, run away from them. Derek
There's a shop near me still using the belt sanders. Their crank grinder was found to have the chucks off by .015" from each other. Worse is all the Serdi valve jobs I see that they only center the head to the pilot on ONE guide, then cut all 8...getting progressively worse and back to straight from the other head on the opposite valve. But hey, they only charge $125 for a valve job. People still go there to save a few bucks. Sad.
The belt surfacer is cheap to get... Less than $9k brand new to your door, Thats why shops use them, a decent CBN/PCD milling machine will start at $20 k and go up I wonder what Serdi machine they have I used one years back,it was about idiot proof, air float work head, that self centered with a live pilot set up. Great for production work. I hated it for the most part. I love the one I have, digital level and a dead pilot set up, runs the Serdi cutter blades and the common Souix pilots. $120 for the valve job is about the going rate around here for a basic V8 3 angle valve job. Or did you mean it is $120 to rebuild the heads, valve job and surface?
We have a Serdi at Visner. We just are in dire need of someone who can actually run it without screwing up expensive heads. . Know anyone? We had a real good guy, but circumstances made him stay in Minnesota. Our CNCs are all Fadals.
The Serdi machine actually locates the spindle off each guide as it goes, via a live pilot and fixed tooling, then locks in position before cutting. Leveling the head only needs to be close. That said, I've seen plenty of screwed up seat jobs off that, and virtually every other machine. The most scary thing about a belt sanded block is the prospect that it could then be bored off that surface. We cut the decks off the crank/cam centerlines parallel and true 90. That is then the datum line that the bores are referenced from. Some of the work getting done out there just scares me.
Yes, just to clarify; It only takes a few seconds to unlock the machines spindle to locate off the pilot and re-lock. There are shops that are too inept to locate the pilot on EACH hole, even if it only takes a few seconds per... Even decent equipment is wasted.
The belt sanders as I call them were ment to see how bad the surface is, not so much to resurface them.. You can never get equal amount of pressure across a belt sander.
You got that right. No matter the cost of the machine, it just takes an operator with no skill to make a mess of things. I've seen some of the best work come from the shops with the oldest, outdated machines and then some off he worst work come off brand new "state of the art" machines.
I've seen this first hand. We've had a couple guys who "knew what they were doing" fail at our shop. Billet heads are too costly for amateurs to mess up. We are actively looking for someone who can actually do the work.
