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Old 03-23-2012, 04:12 AM
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Wanting to build a 406 sbc

Hey everyone,
I've got a 400 SBC in my 85 Camaro right now, I'm wanting to pull the motor out and rebuild it as soon as I have some time and a little extra cash. I'd like to plan the motor out a little ahead of time so I can have everything lined up.
Was wondering what everyones input would be on this build. Anyone out there done this? What rotating assembly were used, heads, cam, intake? Specs would be nice, and what kind of power you were able to make. Also, any tips on items or parts not to over look would be greatly appreciated! This will be my first complete tear down and rebuild so I don't want to get too out of hand. I'm thinking around 500HP would be a great weekend street/strip car. I'm 19 and am looking to build a car I can have some fun with.
Thanks in advance!
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Old 03-23-2012, 04:34 AM
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read this.

http://www.chevyhiperformance.com/te...d/viewall.html
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Old 03-23-2012, 10:00 AM
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not sure as to what you mean by a little extra cash. but you will soon find out that 500hp doesn't come from a little extra cash. i have a 87' camaro that i have already completed and they dont handle that kind of power without a lot of modification. with that kind of power you are going to snap those small 7.5" ring and pinion gears in a hurry, i know i did within the first 3 weeks i had my motor in. then i ended spending 3200.00 on a 12bolt moser rear for the car. not to mention that the factory 700r4 can't handle that kind of power either. i ended up going with Monster transmissions for a beefed up 700r4 (1400.00+400 for the stall), but when you take the 3.06 first gear and the 4.10's i have in the car, first gear was kinda a pain in the butt. since then i have replaced it with a ATI th350 with upgraded 2.75 first gear. then you will also have to weld the subframe together otherwise you will twist the body, you will also have to change the radiator and fan as the factory one sucks. i would say that i ended up having around 8000.00 into things other than the motor, just to have the car handle 500+hp.

currently i'm running a 561hp/527tq 385cid, and i would say between the motor, trans, and car i have between 16,000-18,000 into it.

just to give you an idea
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Old 03-23-2012, 11:41 AM
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Great article, thank you.

Also, I happen to already have a 12bolt rear end sporting 4.10's from when I bought the car, it came with a beefed up 700R4. Also with electric fans to help keep it cool, I know the 400's get real hot real quick, especially if you're driving like you stole it . I suppose looking after sub frame and thinking about swapping out transmissions is something I strongly need to consider then.
Thanks for the input! Anything helps!
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Old 03-23-2012, 11:49 AM
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All good info, also be careful not to get caught up in the horse power numbers. A 500 hp streeter is a lot of hp and as said costs a LOT of money for the engine and drive train. You are very wise to plan your engine build ahead of time, a lot of guy's don't do that and they end up with a bunch of parts that just won't work together.

The best advice I can give you is to build the best STREETABLE engine suited for your application with the budget you have....and be happy with whatever horse power level you achieve. Of course you won't know that until it's dyno'd, there's another $500 or so. I'm sorry, I don't know the exact web site name but it's something like "Ryan's car page" you might google it, LOTS of builds on there with the dyno results....worth a look and enjoy the fun and satisfaction of building your own engine.
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Old 03-25-2012, 07:56 AM
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X2 on what 327NUT said, i didn't think i would end up spending that kind of money on mine. and to give you an idea on how much i spent on my dyno-test & tune = $880.00 but that was for all day, they played with the tuning and ran it about 10 times. but it was well worth it since i'm sure me tuning it in my back garage i wouldn't have gotten those numbers.
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Old 03-25-2012, 08:18 PM
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Alright guys, I'll make sure to beware of the extra costs that come along and try not to get too ahead of myself, Lol. And I'll definitely have to get a dyno done. There aren't a whole lot of shops around here that are reputable for high performance applications.
I'm thinking of picking up a second 400 block that I can have all the machining done. Try to get that ready, rather then take my engine out and not be able to drive it while I'm building an engine.
When I take it to have it machined, what do I need to have done exactly? This is one place I can't quite understand. I know it's going to need to be bored, honed and decked. Is this all that needs to be done? How do I know what specs I need to have everything done to? I believe I understand boring. But I'm not totally sure about decking. Is there anyone that can dumb this down a bit for me?
Thanks everyone. The knowledge is always appreciated!
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Old 03-25-2012, 09:38 PM
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When you take your block in to have this done, the machinest will pretty much tell you what you will need to have done to it. Boring is just that, you are boring out the cylinders to cut away any grooves or imperfections in the cylinder walls. Honing puts a cross-hatched rough surface on the cylinder walls to help the piston rings break in (kinda like you scuff a surface before you paint it to help it adhere). Decking is where the top side of the block is shaved down because it levels the surface back out plus gives a perfect surface for a new set of head gaskets to seal to.

Since 400 blocks don't come in 4bolt, they only came from the factory with 2bolt mains, I would buy a set of aftermarket 400 splayed 4bolt mains and then when you have your machinest do yor work they can also drill and tap the holes for the splayed main caps.
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Old 03-25-2012, 09:44 PM
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Quote:
Originally Posted by White85Camaro
Alright guys, I'll make sure to beware of the extra costs that come along and try not to get too ahead of myself, Lol. And I'll definitely have to get a dyno done. There aren't a whole lot of shops around here that are reputable for high performance applications.
I'm thinking of picking up a second 400 block that I can have all the machining done. Try to get that ready, rather then take my engine out and not be able to drive it while I'm building an engine.
When I take it to have it machined, what do I need to have done exactly? This is one place I can't quite understand. I know it's going to need to be bored, honed and decked. Is this all that needs to be done? How do I know what specs I need to have everything done to? I believe I understand boring. But I'm not totally sure about decking. Is there anyone that can dumb this down a bit for me?
Thanks everyone. The knowledge is always appreciated!
First of all, stick with the stock crank. They are reliable and should be considered high quality and a bench mark to grade other cranks. Unless you spend big bucks on a high quality aftermarket crank (which is NOT Eagle or Scat), then you are pressing your luck.

What to do with the block?

Yes, bore and hone to get you +.040".

You should strongly consider align honing your block. This ensures the main bearing caps/bores are perfectly in line and straight and centered under the cylinder bores. This is not really a big deal for 400-ish HP engines, but as desired power levels increase this becomes necessary.

Decking is taking material off the top of the block (where the heads sit). If you just tell the machine shop, "oh yeah, deck the block too" they will probably just take .010" off to ensure the surface is nice and flat. Most of the guys here like to get the block to what is called "zero deck". In other words the pistons at TDC come up exactly to the deck (they are not down in the hole or coming out of the top). From there you chose the proper head gasket to achieve 2 things: (a) desired compression ratio (b) proper squish and quench (aim for around .040-.045").

To get the block at zero deck height takes extra time (read MONEY) by the machinist as he will have to assemble the short block and take measurements at cylinders 1,2,7 and 8 (aka each corner) to figure out how much material to cut. The added benefit here is that now you get a flat surface AND a straight/level surface (where as blindly milling off .010" is flat, but is it even with the bore of the mains? This leads to some cylinders with higher or lower compression ratios).

Keep in mind that if you get your crank reground and polished it probably won't be exactly 3.75" stroke. Also if you recondition your rods they are also likely to not be 5.565" in length. So again, all the more reason why the machinist must take the effort to assemble the shortblock to take measurements.

GM knew a thing or two about squish. Engines left the factory with around .040-.046" squish (.025" deck clearance + .015-.021" head gasket). There is a ton of articles about this topic, so I will let you google that. Here are some numbers though.

Deck clearance = Block Height - Reciprocating Height

Stock block height of a SBC is 9.025" (measured from center of main bearing to deck)

To get total height of your rotating assembly (measured from center of main bearing to top of piston -> does not include dish/dome):
Reciprocating Height = Crank Stroke Radius + Rod Length + Compression Height of Piston


Here are some examples:
==============

350SBC Example:
Crank Stroke Radius: 3.48" / 2 = 1.74"
Rod Length: 5.7"
Compression Height of Piston: 1.560" (rebuilder special pistons are often 1.540" to allow more leeway for decking and head gasket selection)
1.74" + 5.7" + 1.560" = 9.000" Reciprocating Height
9.025" - 9.000" = .025" deck clearance

400SBC Example:
Crank Stroke Radius: 3.75" / 2 = 1.875"
Rod Length: 5.565"
Compression Height of Piston: 1.560" (rebuilder special pistons are often 1.540" to allow more leeway for decking and head gasket selection)
1.875" + 5.565" + 1.560" = 9.000" Reciprocating Height
9.025" - 9.000" = .025" deck clearance
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Old 03-25-2012, 11:38 PM
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Just to clarify, the '70-'71 or maybe even '72 400 sbc had 4 bolt mains and as mentioned in many other posts and forums are known to be weaker than the 2 bolt. Like said above if you want a nearly bullet proof lower end have billet steel splayed 4 bolt main caps installed.
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Old 03-26-2012, 08:56 AM
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Quote:
Originally Posted by 327NUT
Just to clarify, the '70-'71 or maybe even '72 400 sbc had 4 bolt mains and as mentioned in many other posts and forums are known to be weaker than the 2 bolt. Like said above if you want a nearly bullet proof lower end have billet steel splayed 4 bolt main caps installed.



wow i completely forgot about them, i gues they just are seen that much anymore, but of coarse even finding a 400 block today can be a feat.
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Old 03-26-2012, 02:10 PM
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Awesome guys, this is really great! It's totally starting to make sense. Everything I've been reading about boring, honing and decking tries to explain so much at once it gets overwhelming. I know my block is a 2 bolt main, and finding 4 bolts is almost impossible to find. I found main caps for 70 bucks on summit to convert my 2 bolt to a 4 bolt. Shouldn't be too bad to have done then!
Thanks everyone!
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Old 03-27-2012, 12:22 AM
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400 4 bolt main?

So I've posted an ad in my city looking to see if I can find another 400 block that will be usable for a 406 build. I've got a reply from someone with a block that still has the original heads, cam, intake and rotating assembly. It apparently has been sitting in warm, dry storage for 20+ years. The casting number is 3951511. When I look it up it shows, 70-73 4 bolt main. I know it's been said that the 4 bolt mains are weaker. Seeing how I'd like to build a street motor with limited strip use. Would this be suffice? Would putting ARP main caps on it make a difference at all? Or would it just be in my best interest to stick with a 2 bolt doing the ARP mains?
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Old 03-27-2012, 06:21 AM
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I think you'd be better off using a DART SHP block instead of the OEM block. The DART blocks are stronger, have better cooling, primary oiling of the mains, blind water jacket head bolt holes, and 4 bolt mains.
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Old 03-27-2012, 04:19 PM
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He said it's going to be a street motor, doesn't need a Dart block for what he's looking for. Yes, the 511 block will be just fine......after you have it checked at the machine shop. ARP doesn't make main caps, they make bolts only.

If you use the ARP main bolts or studs you will have to have the main bearing saddles align honed because the ARP fasteners create more clamping force to reach "bolt stretch" or the proper "torque value" for that specific bolt/stud. This basically warps or distorts the main cap which requires them to be align honed to make them round again and bring them back into tolerance. For a street motor you could re-use the stock bolts if you're going to keep the power reasonable.....me, I use the studs and align hone, then you can do anything you want.
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