81 Malibu "Uncaged" Performance Therapy project thread

[NOT A TA]

Sunday I had some extra time while waiting for a SBC 400 to be be readied for decking so I did mine and took some pics for those that have never seen how it's done. This is not the latest, greatest, fancy machinery but gets the job done accurately.

Anyway "decking" the block involves machining the surfaces where the cylinder heads bolt on so that it's perfectly flat. In this case I took off about 10 thousandths of an inch. This is done by having the block move back and forth under the spinning head with a cutting bit in it. The block moves back and forth because the table it's sitting on moves rather than the rotating head. The process involves about a half dozen passes. The first pass very light to allow corrections to be made followed by passes where 1.5-2 thousandths are taken off with the last pass being made at a very slow table movement speed to get a nice final surface finish. Here's the basic steps involved....

First get a bud to help heave the block up onto the machine. There is a large bar that the main bearing journals rests on which is level with the cutting head. A bracket is bolted into the deck of the cylinder bank not being machined which gets an adjustable "foot" placed under it. Then a big file is used on the surface to be machined to pick off any lumps bumps or other abnormalities.



Next a straight edge is used to check for any warping. It's not unusual for a deck to have a bit of crown or bow but it's necessary to know before leveling the block



Then a very accurate level is used to level the block front to back and side to side. The adjustable foot is used for the side to side adjustment, and to make any minor front to back adjustment a piece of paper or two are used between the bar the block is sitting on and the main journal surface. There is fancy new equipment to level and rotate blocks but this is the basic old fashioned way, the new ones just make it easier for the machine operator. The block is not bolted solidly in place. It's just sitting there held only by it's own weight.



A very light first pass is made to check and make sure the deck is square with the cutting head in this case it was perfect! You can see that the cutting tool is just skimming the surface and touching both sides of the deck or grazing the surface from side to side like between the cylinders.



Then succeding passes are made and in the pic below you can see the bit is cutting almost the whole surface except a few small areas.



And then on the final pass which is done at a slow table movement rate the surface is done. After the final pass you get a bud to help pick up the block and flip it 180 degrees so you can do the other deck surface and start all over. File straight edge, level, light pass etc. If we're decking a block say 35 thousandths or something to raise the compression we would drill register holes in the deck to the correct depth ahead of milling and would also mill the ends where the intake manifold would sit. With my block since I was only taking off a little bit neither of these steps were necessary.

[deuce4935]

Now thats what I call getting hooked up!

[NOT A TA]

Originally Posted by deuce4935

Now thats what I call getting hooked up!

Oh ya! I would have just kept driving the Malibu with the stock 6 cylinder drivetrain if it wasn't for the contest and the machine shop.

Had to take a couple months off this project to get other non car stuff done, but I'm back on it! Scrounged around the machine shop and put together a set of Manley valves from miscellaneous leftovers. They are 2.02 intakes and 1.60 exhaust and are the correct length. Some new and some used so I cleaned up the used ones and polished the stems. Then "cut" the valves. Since the 1.6's are bigger than stock the heads will be cut later for new seats.

Cutting valves involves grinding the correct angle on the face that contacts the seat and then chamfering the top the stem and cutting the tip flat. For this engine 44.5 degrees is the angle of the face where it contacts the seat. Here's a pic of the machine we use. It's an older machine and we rotate the valve by hand to do the seat angle and the bevel on the tip. In the pic the valve is set for making the bevel on the tip which is done dry. The 44.5 angle on the head is made with the grinding stone on the other side of the machine and is done with lube that flows onto it while grinding. Forgot to get a pic of grinding the angle on the valve heads.

[NOT A TA]

With a set of valves ready now, it's time to check the valve guides. Shop technique for this is to put a valve through a guide and wiggle it to feel how much play there is. Then put a finger over one end of the guide, insert a valve stem till it hits the finger, then pull the valve out quickly to listen for a pop caused by the suction. After checking all of the ones in my heads we decided the valve guides wouldn't need to be replaced but needed a bit of work to tighten them up a bit. This is done with a "sipraler".

A spiraler cuts a groove into the inside of the guide without removing any metal. By deforming the metal it causes the inside diameter of the guide to be reduced and also allows path for lubrication. After the spiraler is run through the guide a ream which is the correct diameter for the valve being used is then run through the guide. Both tools are run down from the top and drop out the bottom so the head needs to be up on stands.

Pic below is a spiraler bit and a drill with a gear deduction so the work can be done at slow bit speeds. No pressure is used just the weight of the tool is enough. A couple drops of cutting lube are used during spiraling.



In the pic below you can see the grooves cut into the inside the valve guides by the spiraler and the ream being used to make the inside of the guide straight and the correct diameter. No more lube needs to be put in before reaming, whatever's left from spiraling can stay and is fine.

[NOT A TA]

The head I found to replace the cracked one already had stock size exhaust seats installed in it at some point so they needed to be removed before cutting both heads for the bigger exhaust seats that will be installed. Seat removal is done with a cutting bit on the drill press. The head is mounted and leveled then the old seat is cut till just a very small amount of it is left which then spins freely and can be removed.

Here's a couple pics showing the cutting bit that gets lined up on the bit guide which is inserted into the valve guide and then the old seat after cutting and removal.

[NOT A TA]

Since we were out of the correct size for the new exhaust seats (and it was a holiday weekend) I jumped over to working on the block a little. I had scored a set of breather tubes for the lifter galley out of an engine I was stripping for scrap at the shop a few weeks ago. Someone had blown up something and swapped all their good parts over to a new shortblock and left the old one with the tubes in it. They're not the fancy looking aluminum ones but will do the same job so they're perfect for my no budget build.

The block needs to be threaded in order to insert the tubes and plugs so while I was at it I threaded the end holes for plugs also. To thread the holes first a tapered reamer is used on a drill to chamfer the top of the hole so its easier to get the tap started. Then cut threads with the tap. Because these are tapered pipe thread the depth is checked on the first hole and then the tap is marked and the rest are tapped to the same depth.

Here's a pic of the reamer and tap . And then a pic of the vent tube and a plug. Bottom pic is the end of the block where plugs get installed.

[NOT A TA]

Since I was pressing wrist pins out of connecting rods at the shop I figured I'd get mine apart so they'd be ready for some work I want to do to them. The block had been bored to work with a slightly used set of .040 over forged pistons my buddy Mike at Mikes Automotive Machine in CT hooked me up with long before I moved south. It's been so long and with all the miscellaneous parts I've had and moves I made etc we figured we should double check the cylinder bores and pistons to be sure everything was going to work out cool. No sense taking the piston/rod assemblies apart if they wouldn't work. So here's a couple pics measuring things.



The cylinders came in at 4.041 and the pistons were around 4.0398+ so we'll be right in the ballpark of the recommended .0015+ gap recommended by TRW after the cylinders are honed. For the experienced/knowledgable guys I'm aware that these pistons were prone to cracking in the skirt curves when run too loose loose back in the day before they switched to the shorter skirts and I checked these. They were a gift so although they are an older design they're waaaay better than what I would have otherwise! Thanks Mike!

[NOT A TA]

For those that have never seen it done, this is how we remove stock style wrist pins from piston/connecting rod assemblies. (Later on in the thread I'll show how they're installed)

The pin is fitted with an interference fit in the top of the connecting rod and it takes a lot of force to push them out so a press is used. A support is placed under the side of the piston (different supports for different pistons) with a hollow base support below that to provide enough height to push the pin down. Then a tool that fits inside of the wrist pin with a shoulder that will push the pin is inserted. The tool is smaller in diameter than the pin so it will fit through the hole in the side of the piston. In the bottom pic the wrist pin is still stuck in one side of the piston but can be pulled out by hand. The "tight" fit is in the top of the connecting rod.

[NOT A TA]

Shops mark things that are supposed to go in a particular place,order, or match up with machined surfaces.The rods had markings from other shops on them (in this case stamped letters/numbers and indentation dots) so I lined them up in order and did them the way we do them in this shop because I may loose some of the other markings as I work on them. I zipped the lock side of each rod with a disc and etched a number in each with a dremel. You may be able to see the 7 etched in the rod on its side and dots on the bottom of some of them. After that I removed the caps and bolts so I can start grinding them.

[NOT A TA]

With the rods marked and disassembled it's time to start working on them. In this first step I'm using a carbide bit to grind away the ridge in the center of the side and blending into both ends. Care needs to be taken to keep rods even when viewing the sides not being ground and also not to remove too much material. The square "chunk" of metal at the top of the rod is left alone and will be ground a couple steps from now when I "balance" the rods. The bit in the tool is used for steel, the one on the bench for aluminum. The last person who used the air tool before me had been doing some welding repair work on aluminum heads.