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Discussion Starter · #1 ·
I was at the machine shop and documented the beginning of my engine build. It's a 302 mexican block that I found locally. Looks like it's gonna have to be bored .030" over.

Question for you knowledgeable type:

I've heard that certain procedures are supposed to be done with the pistons in hand. I'm assuming it's final honing, not the initial boring, right?

In this case, the bores have some ridges and some surface rust, so I guess to determine how much to bore, they first have to do .030" over, see if there are no pitting (from the rust), if it's good, I order the pistons, and they do final honing with pistons in hand, right?

It doesn't make sense to me to do it otherwise, cause to order the pistons, I need to know final bore, so I can't order them before they bore, makes sense? Is this the way it's supposed to be?

I just want to make sure they're doing a good job...good ole anal me.


This is what I started with:


In the giant block washer:


washing done:


A trip thru the blaster machine:


And done:


 

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Luis, I am no expert, but you kind of answered your own Q'. Be careful with cylinder finishes and also overboring. Make sure each cylinder is measured and that they ALL are within tolerances. When my builder was looking for a vintage block, he needed to check the bores to insure that there was enough material to work with after cutting, honing and other machine work. You may want to make sure the deck surfaces are true. I am sure there are many other factors. Randy (Big foot) could probably help you quite a bit. He seems to know this as good as anyone.

Dan
 

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Nice block! You are correct with the overbore then piston order sequence. Honing is specific to the type of rings you will use. Moly, steel etc...which will require the crosshatch pattern to ring type. G.
 

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Correct way:
- Block is rough-bored (pistons not required)
- Pistons are brought to the same temperature as the block by being in the same area for 24 hours.
- Pistons are measured at the skirt in the location prescribed by the piston mfgr. and numbered.
- Block is honed to spec for each piston.

Almost any block will go .030" over. Seems like you can hardly get .010 or .020 pistons anymore. Sonic testing is a good idea if you are building a lot of HP as blocks can have thin spots in a cylinder. Not to worry though - you can typically run up to two sleeves in a bank if needed.

Note:
There are a lot of shops that don't believe in equalizing the temperatures, but those that build the big HP engines will almost ALL do it that way..

[ December 15, 2003, 07:52 PM: Message edited by: Big-Foot ]
 

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The remainder of your block preparation should include having it align honed and decked to square things up. It looks like this block was tumbled in a vibratory polisher which works over the surfaces pretty good - I would assume that they are going to hone the lifter bores. You might want to check to make sure this is on their list.

Before they turn the block back over to you, they will (or should) install new cam bearings and frost plugs. Request brass plugs. Few dollars more but they won't rot-out on you either..

I don't know how much HP you are planning on building, but you may want to have them install main studs prior to align honing and indexing the mains.
 

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Everything randy said is right on the money. If you are balancing the rotating assy, then bring them the rods and crank too, plus the bearings. They will do a mock-up and be able to determine the exact size to "zero-deck" the block. This is not nessesary, but it will help with the "quench effect of the flame travel" in the combustion chamber and that will help minimize and detonation. Also will bring up compression ratio. Make sure you know what your heads will give you with the piston of choise so you don't go beyond the limit of the fuel you plan on using. A good high perf machine shop should be able to guide you through and meet your goals without unneccesary procedures. Hope this helps Your Friend BenC
 

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Be SURE that you balance the rotating assembly, and be sure the shop uses a "torque plate" when they bore the cylinders. This is a plate bolted on top to simulate having a cylinder head bolted on: the head bolt tension distorts the block slightly, and if you don't use the torque plate, the cylinders won't be exactly round when the head is bolted on later.

Forrest
 

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Discussion Starter · #10 ·
Excellent info! Thanks guys.

Rickster:
I remember your post. I actually told the guy, "casually" about how they had left the old freeze plugs in "some guys'" (you) block. I don't think he'll get lazy when it's time to take them out after that comment.

Forrest:
Yes, I'm balancing. I will be there tomorrow morning for boring, I'll make sure they use the plate.

Randy and BenC:
You make good points, and actually my next question was about decking. He said he needed the parts in order to deck the block, and I can understand that if I want zero deck, but what if I want to deck the block to the minimum it takes to get it square? Then I would need the final deck height first in order to calculate the compression ratio in order to order the pistons, right?

If you say that I want zero deck, then I could calculate my CR, order the stuff and bring it over for them to deck. Is that what I want?

Also, one of the main caps has a dent on the bearing surface side, he said that align honing will take care of that, and I believe him, just want to make sure.

Randy:
Thanks for your advice. It wasn't a vibratory polosher, but a sandblaster. The block turns around and it's blasted that way. They are honing the lifter bores, and I will insist on brass plugs. They are also O-ringing the block (I'm putting a supercharger).

I will put main studs and a girdle, but, does it matter if they align hone with the existing bolts? or does it need to be align honed with the studs? what is the difference?

Also, what is "indexing the mains"?

Thanks for your help.
 

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Originally posted by LuisO:
Randy and BenC:
You make good points, and actually my next question was about decking. He said he needed the parts in order to deck the block, and I can understand that if I want zero deck, but what if I want to deck the block to the minimum it takes to get it square? Then I would need the final deck height first in order to calculate the compression ratio in order to order the pistons, right?

If you say that I want zero deck, then I could calculate my CR, order the stuff and bring it over for them to deck. Is that what I want?

Also, one of the main caps has a dent on the bearing surface side, he said that align honing will take care of that, and I believe him, just want to make sure.

Randy:
Thanks for your advice. It wasn't a vibratory polosher, but a sandblaster. The block turns around and it's blasted that way. They are honing the lifter bores, and I will insist on brass plugs. They are also O-ringing the block (I'm putting a supercharger).

I will put main studs and a girdle, but, does it matter if they align hone with the existing bolts? or does it need to be align honed with the studs? what is the difference?

Also, what is "indexing the mains"?

Thanks for your help.
He will have to have the crank, bearings, pistons, pins and rods before he can deck the block. I have seen some factory blocks that are already at zero and if they deck it further, you will have a problem. You want at least .040" from the top of the piston to the cylinder head.

Align honing is always best to be done with the type of clamping force the engine will be run with. Studs don't stress the block and main saddles the way that bolts do.

Indexing or Registering is where the main caps are peened or knurled - if needed - to fit into the recess of the block where they bolt on. This keeps the main caps from trying to walk around if they are only being held in place by the torque of the studs/bolts.

Make sure you have a good set of rod bolts installed prior to having them resized. Don't even think about skipping the rod resizing (also called rebuilding) if you are running used rods. I have never seen a rod with more than 500 miles on it that was not at least slightly egg-shaped on the big-end. They all get this way eventually, but you want it to happen while the rod and bearings have been married for a while. Put a set of new bearings in an egg-shaped hole and I will guaranty you trouble..

Also - Forrest is right about the deck-plates. Have the block at least honed with plates on it. Chebbies can get away without this because they have 5 headbolts per hole, but Fords (this is really dumb) decided to only use 4 headbolts per hole and the block distorts more. That's why SBF's eat headgaskets..
 

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I started into this post ready to offer all kinds of advice. There is none left to give, Luis you've got the goods already. Great info here. Gawd I love this forum.

Larry, this could be a handy post.

But now that I'm here I have to say SOMETHING...so...make sure they hone the lifter bores as Big-Foot suggested, this is often overlooked.

Also, it's almost unthinkable that anyone would do this anymore, but to save a few minutes, some shops used to knock the freeze plugs into the water galleys instead of pulling them out properly :eek: which obviously leads to problems. Hardly worth mentioning, except for the fact that it happened to a forum member last week!

AJ
 

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Discussion Starter · #14 ·
Thanks Randy! I'm using a brand new 347 stroker kit, so no worries about oval rods. So are you saying that when you "zero-deck", you leave no less than .040" deck height?

I was at the shop this morning. The guy was putting the block in the boring machine. I ask him, about the top table in the boring machine, if that's the torque plate...and he says "no, the owner didn't tell me to use the plate...we usually don't use it for stock motors" :eek:

So, he proceeds to apologize for the miscommunication, and goes to get the plate.

I see him ready to start bolting it up. I ask him, shouldn't you magnaflux the block before doing anything to it? He says, you're right, but I'm almost 100% sure this block is good, no cracks, they usually crack here and here...etc. While he's talking, he goes get the big magnet and the dusty powder, and starts checking the block thouroughly. Block is fine, no cracks.

He cleans the threads in the block, bolts the plate to the block and torques it.

He starts commenting how it looks like he may have to go .040" over. I ask him, you really think so? he says yeah, lots of rust and ridge.

I mean, I can see how it would be a pain to do .030" just to find out that it's not enough and then do .040", double work...but I still want to see if .030" is enough, don't wanna have thinner walls if I don't need it.

So I put my social engineer hat and tell the guy: "are you a partner in this operation?" he tells me no, he's just an employee. I say, oh, I thought you were a partner, I reach in my pocket, pull $60 and give it to him, I say, listen I appreciate you taking the time to show me how stuff works, and taking care to do this block right...I want this thing to be blueprinted, by the book...etc, etc.

I say, what about that bore, you think we gonna have to go .040"? he says...let's see, maybe .030" is enough. He starts with the worst looking cylinder, bores it .030"...and bam, it's perfect.

I already notice a change in attitude. He's forthcoming with racing and engine building stories...he tells me the place was a dump before he started working there...he wanted to buy it but it fell thru. This is an older guy (not a kid) and I can tell he's experienced, he just doesn't have the motivation to excel in what he's doing, so I have to provide said motivation.


The moral here...Stay on top of it if you want it done right!!! Don't be a jerk if you're gonna have your stuff done there...try to win the person, not antagonize it.

He's gonna flow the heads for me and smooth out the ridges from the CNC porting process. He's also going to determine combustion chamber volume so I can calculate comp ratio. Once I get the parts, I'll go there and watck LIKE A HAWK. I'll write down every measurement, every clearance. Time to have a phone chat with Randy and hit those books to see what to watch out for. ;)

I'll post some pics of the boring and magnaflux processes when I get home today.
 

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Discussion Starter · #15 ·
Originally posted by turbochicken:
Looks good, thanks for the pic's. I remember hearing lots of good things about the mexican blocks, and now I want one... could you refresh my memory on what years are best. Thanks in advance.
turbo
turbo: these were made during the late 60's early '70s, but I "think" they are all the same (meaning no difference between the years).
 

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What a great story. So true. When our home was being built over the winter of 2001 - 2002, I was the guy who showed up at 5:30 on the odd evening with a 12-pak ready to share with whoever was working on my house that day while we looked over the progress. This was in a development of 94 homes. All the guys knew me personally, while some other buyers never set foot on the property until the final inspection for their closing.

I still think that paid huge dividends in little details.

AJ
 

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I had my block hot tanked and then acid washed to remove as much rust as possible without damaging the threads. The machinist took my pistons, measured them, and bored/honed them to have the recommended .003 skirt clearance with torque plates (essential).

He aligned honed the mains with the main caps torqued.

He checked the deck height and then squared the deck both sides. They are now exactly the same.

I had the crank turned .010, nitrided, and balanced with the rest of the rotating assembly.

He also honed the lifter bores, installed the cam bearings and the welsh plug.

I also had him swap out the main bolts for ARP studs. I would suggest the same.

All this is not cheap. My total machining bill was $1400 which included a seasoned 460 block ($200).

2FAST
 

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Luis

Had my block done by a local machine shop and had a very similar experience to you. I visited a couple of shops before selecting this one and was impressed by the vintage parts (one offs) and race stuff in this shop. I live 10 minutes from the shop and had them call me once they were set up but before they did each machining operation. Not only did I learn a ton but I know exactly what dimensions my block was machined to. Worthe the extra money if you ask me.

BTW on the deck height. My stock decks were 0.038" different side to side, and were not square to the crank and cam bore. After machining the decks are equal, square and true. It cost more money but I feel it was worth it. I had mine decked to zero deck height. With a Fel Pro head gasket (0.038" compressed thickness) it is just about perfect. Getting the crown of the piston close to the quench area of the head results in a high amount of squish that causes turbulence in the chamber aiding combustion. The other advantage is that often detonation is triggered by air fuel mixture than gets 'trapped' in the quench area so it's much better to have the smallest possible space.
 

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LuisO and I have talked and I think he and his machine shop are on the right track. I advised Luis against running a High Volume oil pump with the hydraulic roller cam as they have a tendancy to eat up distributor and camshaft drive gears. I did offer to blueprint a pump for him if he chooses.

Block decking - This is something that requires the pistons that will be run in the block. I advised Luis to seek a negative deckheight of .003". This combined with .038" headgaskets will give him a little play on the .040" minimum between piston and head.

Is block decking really necessary?
Well, I think it is necessary in order to build a quality, well balanced engine. I have seen blocks that actually had a positive deck height on one end and a .030" negative deck height on the other end (this was on a small block Chevy 305). Most engines will be out .005 - .010" from what the specs are for deck height.

Is Align Honing really necessary?
As is decking, I think it is the only way to build a "true" block for your engine. The mainbearing holes may all be very close to perfect in size and shape, but are they all in alignment with each other? Are the maincaps registering to the block properly? If you have the align honing process done, you know that these things are "RIGHT".

My $.02 worth anyways...
 
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