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Discussion Starter · #1 ·
I just tore down a Chevy 350 engine and I'm about to bring it to a machine shop to get cleaned up. I'm starting to make my 'wishlist' for the setup and configuration I want for the engine (pistons, heads, rods, intake, etc.). I am a little lost on what my starting point should be however. I know the piston and head choice depends on the compression ratio I am aiming. But I can't calculate my compression ratio without knowing my deck height, and how can I measure my deck height without having my pistons already, but I don't wanna buy any pistons yet until I know my deck height to calculate my compression ratio! I know that might sound a little confusing but I just don't know where my starting point should be. Should I buy a set of pistons. then measure deck height, and then buy matching heads to adjust the compression ratio later?


Thanks in advance,
Mario.
 

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Race it, Don't rice it!
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The best thing to do wait untill you get the block back from the machine shop.
If they want the pistons for the an over bore then that will be your first purchase and the ywill tell you what you need if you ask em.

The chances of the block needing decked is close to 100% so the shop will probably plan for a 9.005.
 

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Discussion Starter · #3 ·
Thanks for the quick response, I'm going to bring it to the machine shop sometime this week. I'm getting a little anxious haha.
 

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Race it, Don't rice it!
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You basic plan of attack will always be put your desired goals on paper.
Put together a list of parts to reach that goal
If you need to adjust for budgeting reasons now is the time for that.
Once you have the parts list and a plan of attack take yout parts to the shop and talk to them about your plan. Listen carefully to them but remember they are just another opinion and not the only way to do things.
Post here or make your final plans and decisions and move forward.
 

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Race it, Don't rice it!
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These things are fun and exciting and the feeling of accomplishment will reward to greatly. These things take time and thought. That's why not everyone builds engines and why there's an art to it. However don't let your self cut corners and make assumptions. Doing so will surely never end up in your favor. Patientience no matter how hard to come by will be your best friend.
 

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Race it, Don't rice it!
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Is there a reliable way to calculate deck clearance without having the pistons on hand?

GM specs them at 9.000 on the blue prints so most calculations are based on that but that's assumed and not verified as an industry standard. Some shops like 9.005 to give room for a clean up when the engine needs overhauled again. You'll see that more in racing when engines are used up quickly and you wanna get several refreshes out of the block. It's still not a bad practice even for a street ride though.

There are so many pieces that go into this that tiny differences start to add up. That's why you cannot assume anything. When you buy the crank, rods, and pistons each will have it's own sizing tolerance. In reality the tolerance can be +/- .001 so now your DH can fall any where from 8.997 to 9.003 so you can't really know until parts are in hand and verified for sizing but the goal usually 9.000.
 

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Discussion Starter · #8 ·
I am a little confused when you say some shops like 9.005. I thought that if there were resurfacing a deck the deck height measurement would go down so its essentially getting shorter from being grinded down?
 

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GM block are production pieces where good enough to get out the door is all they reach for so GM blocks can range from 9.000 to 9.035 with 9.020-9.025 be more average. The deck is almost never square with the cam tunnel either.
 

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Discussion Starter · #10 ·
Ahhh gotcha I understand now. Thanks for the help, once I bring the engine to the shop I'll post my ideal setup and see what you guys think of it.
 

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A popular term the shop might use is "squaring up". That basically means the decks, bores and mains are all machined square to the cam tunnel.
 

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Race it, Don't rice it!
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Ahhh gotcha I understand now. Thanks for the help, once I bring the engine to the shop I'll post my ideal setup and see what you guys think of it.
Keep in mind your going to get all kinds of differing opinions. They are worth about what you paid for them so I'd advise you not get to caught up in them.
If you can find someone you can communicate with and you trust that's worth more than a 1000 opinions.
 

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Discussion Starter · #13 ·
A popular term the shop might use is "squaring up". That basically means the decks, bores and mains are all machined square to the cam tunnel.
Is there an average price I can compare my machine shop's prices to for these services? When I called they told me for them to bore the cylinders, hone the block, deck the block, wash, put in freeze plugs etc. it would cost $500. And for balancing the rotating assembly they quoting me to around $250. Are these reasonable prices? I'm NJ if that matters at all.
 

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Race it, Don't rice it!
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Is there an average price I can compare my machine shop's prices to for these services? When I called they told me for them to bore the cylinders, hone the block, deck the block, wash, put in freeze plugs etc. it would cost $500. And for balancing the rotating assembly they quoting me to around $250. Are these reasonable prices? I'm NJ if that matters at all.
That's what my shop is getting too. Shop prices are kinda based on quality. Carl at CNC blocks in NE is likely wanting $1500 but the work he does is impeccable and likely within .00001 whicj is good when you make 800hp at 8000rpm for hours and hours at a time but for a street car I think you quoted price is pretty good.
My shop bases the balance job on the time it takes so it's usually around $175 for me because I do the static weights my self like matching pistons, pins, rings, rods big and small ends before it gets there so they only need to put it on the machine and measure, then drill the crank and remeasure.
 

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Machine work varies in price all over the country. what I pay here in farm country is a lot less than I would pay in the metropolitan Seattle area of WA. state. It is more important to find a shop and machinist you can trust than paying less for a mediocre job. Check around your area and look at comments from folks who use them. Ask your friends, look at BBB stats and talk to the machinist about your build. Make your machinist your best friend... people go out of their way to do things right for friends.
 

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Discussion Starter · #16 ·
That's what my shop is getting too.
My shop bases the balance job on the time it takes so it's usually around $175 for me because I do the static weights my self like matching pistons, pins, rings, rods big and small ends before it gets there so they only need to put it on the machine and measure, then drill the crank and remeasure.

Is it difficult to match the static weight yourself? I've never done anything like that before but from what I can tell its not too difficult as long as you have a scale.
 

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It is not difficult but it is time consuming and if you get it wrong - well it's your mistake.
The most complex part is weighing the big and small ends of your connecting rods.
 

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No it's not.
I use a gram scale and just measure everything and mark it, then I mix and match to get all the bearings, all the rods, all the piston, pins, rings to add up to the same number within 1 gram.
Then I take the lightest one and lay it aside and start with the heaviest one and remove materials in variety of ways to get it to match the lightest one. I continue that process for all 8 sets then I double check them for accuracy.
 

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Race it, Don't rice it!
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It is not difficult but it is time consuming and if you get it wrong - well it's your mistake.
The most complex part is weighing the big and small ends of your connecting rods.
The shop is going to do that no matter what because the crank machine is likely matched to the rod for calibration. There's no real need to do that your self.
All the shops I know any way farm it out to a crank specific shop. Maybe it's different in your area. That shop should also verify your accuracy and check them for themselve and if it's all on size then you have saved the shop about an hours labor.
 

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1st thing to decide on is,what vehicle is it going into,how much power are you looking for,& what will it's main usage be?
 
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