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406 build
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cmarr6
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Location: West Point, NE
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PostPosted: Fri Feb 08, 2013 6:45 pm    Post subject: 406 build Reply with quote

New to the site and a fairly new engine builder. Built some other motors but just kinda threw some parts together and hoped it worked, you know? First time I've really researched and tried to learn what all the various combonations can do. Looks like a great site. Read some other posts about some builds but didn't find just the right info. I am building a mild street motor to put in a 66 impala. Have been doing alot of research trying to find the right combonation. The motor is a .30 over SBC 400. Had the bottom all redone. Block cleaned and align honed, bored, crank turned (stock crank). Rods were checked out and were good. New pistons. Thats were I want to know what to do. before I go buttoning this thing up, do you think I need some flat top pistons or can I stick with the original style dished. I got a Summit 1103 cam and plan on getting some AFR heads or something like that. Will the dished pistons be alright or do I need some flat top pistons to bump up the CR? Or if I get a set of heads with a smaller CC will that do the job?
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Fri Feb 08, 2013 6:55 pm    Post subject: Reply with quote

For a mild street build flat tops might yield too much compression. Really depends on how hard you intend to push it.
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2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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cmarr6
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Location: West Point, NE
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PostPosted: Fri Feb 08, 2013 7:38 pm    Post subject: Reply with quote

Not planning on pushing it too hard. Just a sunday cruiser type of thing. Definitly not 1/4 mile stuff. Maybe do a smoky burnout now and then, you know. I've heard the 400, with the short rod and all doesn't like too many RPM'S anyway. Just concerned about the compression ratio being too low with the dished pistons. You think flat tops would be too high? I've read that stock compression ratio of a 400 was 8.5:1. Is that correct? Shouldn't I shoot for something a little better than that? What size of cumbustion chambered heads should I be looking at? I think the stock 400 head are like 76cc. Should I go with something smaller, like 64cc? Just need some advice on all of this. For the novice, it can be a little daunting learning all this stuff.
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clay
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PostPosted: Fri Feb 08, 2013 8:03 pm    Post subject: Reply with quote

To be sure you will need more information. You need to know how big the dish is. Also it would be nice to know how far down the piston is at t.d.c. Have you ever done any cc'ing? Don't worry at all if you haven't. It's pretty easy and you don't really need any fancy tools to get the accuracy you're looking for. I would absolutely do that before you buy heads. Since you already have pistons hopefully you can get heads that'll work. If you haven't done it before I'll be happy to walk you through the quick and dirty method I've used. Welcome to Smokemup! Clay
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Paul P
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Location: Townsend, Mass.
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1971 Chevrolet Chevelle

PostPosted: Fri Feb 08, 2013 8:14 pm    Post subject: Reply with quote

Getting snowed in here up in New England. Anyway. You are .030" over and have your choice of pistons so it should be relatively easy to set it up with any compression you want. I know basic flat tops with 72cc chambers are easily at 10:1 with -6.2cc valve reliefs. There is a good calculator on the site for the sign up fee of $5 it is worth it for a novice engine builder. There are a lot of dimensions in that you might not have thought of.
Welcome!
Paul

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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1972 Chevrolet Nova

PostPosted: Fri Feb 08, 2013 8:22 pm    Post subject: Reply with quote

Paul - I was under the impression he already had pistons.

Cmarr6 - Paul is right about the automath. Even if you do cc the cylinder and do the math there are several other features that are informative and the price is ridiculously low. Clay

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Paul P
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1971 Chevrolet Chevelle

PostPosted: Fri Feb 08, 2013 9:18 pm    Post subject: Reply with quote

clay wrote:
Paul - I was under the impression he already had pistons.

Cmarr6 - Paul is right about the automath. Even if you do cc the cylinder and do the math there are several other features that are informative and the price is ridiculously low. Clay


Maybe he could share the part number with us to help him out? I'm sure that we could get a pretty good idea of what would work for him.

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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cmarr6
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Location: West Point, NE
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PostPosted: Sat Feb 09, 2013 9:52 am    Post subject: Reply with quote

Already have pistons. They are the stock style dished pistons, one big dish accross the whole top surface. They are .30 over. Clay, I would love to know how to CC them. Fill me in on an easy method. By "how far down in the cylinder the piston is at TDC" are you talking about "Deck Height"? I am at the point now where there is no turning, back unless I want to tear it all down again, and I don't want to have to do that. Have been wondering about my choice of pistons all along, and want to make sure they will be alright before I go any further. I could still swap them out for something else without too much trouble at this point. It's not going to be a 1/4 miler, but I want to make sure it's not a dog after I get it all done.
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Big Dave
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PostPosted: Sat Feb 09, 2013 1:49 pm    Post subject: Reply with quote

Check out the car mags on line tech articles. They can show you how to CC a motor with a $100 kit you can buy from ProForm.

As to deck height you are in the 0.027" down in the hole range from the factory. But keep in mind no two motors are identical, it pays to measure what you have with a bridge and a dial indicator (another $100 bucks from Summit Tools).

I built a 406 (0.030 over SBC 400) and I used flat tops with 76 cc heads to make a pump gas friendly motor with aluminum heads for my '89 Caprice (still kept the 305 air cleaner lid). The aluminum heads help to keep you out of detonation which is another reason to pay the extra coin for them. I normally seek a smaller chamber but this isn't a race motor, so the bigger chamber made for an easier way to reach my desired goal.
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cmarr6
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PostPosted: Sat Feb 09, 2013 1:53 pm    Post subject: Reply with quote

I just did a CC of my #1 cylinder and I got 41cc's. Does this sound correct. I smeared the cylinder wall with some assembly lube to seal it and brought the piston to TDC. Leveled the motor and took a syringe and filled it up to the deck surface. It held 41 cc's.
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Sat Feb 09, 2013 5:34 pm    Post subject: Reply with quote

That is a serious dish. When you say stock style you mean cast piston? They don't have a part number on them? Most manufacturers provide that data. If not someone has posted the dish volume somewhere. That method does take all factors dish, down the hole volume and ring land if you have the rings on it. You will struggle to get 8:1 with 72cc heads. I used -41cc dish and 0 for the ring land piston to deck. I would try to go with a smaller dish and bigger chamber to unshroud the valves but that will not be possible as you already have the pistons. A 64cc head gets you to 8.33:1. This will be a low compression motor with a dish like that if it is a 41cc dish. Put a small blower on that thing should run well with that dish setup.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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1972 Chevrolet Nova

PostPosted: Sat Feb 09, 2013 11:35 pm    Post subject: Reply with quote

When you say you filled it up to the deck did you have a piece of plexiglass or lexan sealed to the deck surface? If not it will be very difficult to determine when the liquid is "level" with the deck. It actually won't be because of the miniscus effect. I usually cc with the piston down from t.d.c. because it lets the fluid flow easier and reduces air bubbles. You can pick any height such as 0.500" 02 1.000. If you don't have anything to measure the piston depth get a pair of digital calipers from Harbor Freight. They are dirt cheap and are actually pretty nice. Use a straightedge to span the cylinder and then set the piston down in the cylinder whatever distance you choose (subtracting the straightedge thickness). You'll use the quench "ring" for your measuring point and not the dish itself. Coat the cylinder / piston like you did to seal it and then use grease to seal your plate to the deck with the fill hole facing one side of the block. Then I set the engine so the fill hole is slightly higher instead of dead level. This makes filling easier as you don't have to fight air bubbles as much. Calculate what the theorectical volume would be with a completely flat piston at your height then subtract that from whatever you actually fill the cylinder with and that's your dish volume. Then yes you will need to know deck height at t.d.c. and that 's where the calipers and straightedge come in. Dave is right on - unless it has been decked the piston will be around the 0.025" range down in the hole. Once you have these numbers it's just a matter of the ratio of total volumes at b.d.c. (piston dish, deck clearance, gasket, cylinder volume, and chamber volume) vs. what's left at t.d.c. (all the previous volumes - cylinder volume). Sorry if it's confusing - it's late. If you have any more questions feel free to ask and I'll try to clarify. Clay
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cmarr6
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PostPosted: Sun Feb 10, 2013 8:52 am    Post subject: Reply with quote

I didn't have a peice of plexiglass or any thing. Just watched when it reached the top and started to leak out. Because of the miniscus effect it probably held more than the actual volume, but I figure it was pretty darn close. I don't have a part # or anything, but I can take a picture and show you. The dish is the entire top surface of the piston, probably 1/16 to 1/8 inch deep, excluding a raise ridge around the outside edge of the piston. Now you know why I was concerned about using these pistons. They are exactly like the stock pistons that I took out except .30 over. The 41cc is the entire cylinder volume, not just the dish, if I wasn't clear on that, but I would say the dish is probably half of that total volume. I did try to measure the piston depth at TDC with a caliper but couldn't get a very accurate measurement. I have a digital caliper but I was measuring to the inside of the dish. I will do it again and measure to the quench ring. Like I said, it is in completly stock configuration except that it is .30 over. Shouldn't the stock numbers be out there somewhere.
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cmarr6
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PostPosted: Sun Feb 10, 2013 9:10 am    Post subject: Reply with quote

Just found on another site, stock 400 pistons had a 22cc dish. I think that's about right judging by my measurements. Like I said, the entire cylinder volume @tdc was 41cc. Taking into account the miniscus effect, maybe 40cc. Can I make decent power with this setup if I get some good heads with a smallish combustion chamber and maybe get the heads milled and use a thin head gasket?
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clay
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PostPosted: Sun Feb 10, 2013 9:50 am    Post subject: Reply with quote

Stock numbers are out there but you don't have actual factory pistons. You have a replacement piston that while it looks like the factory piston it may or may not have the same dish volume. Looking around it appears the factory dish was around 21cc. If you add the volume of 0.025" deck clearance (5.5cc) you are still way short of the 41cc you measured. This is why I think you need to get the plexiglass and do it again. Going through and measuring everything is important so you know what you have. The listed compression ratios for stock 400's are for around a 76cc head but the factory heads varied somewhat so you don't know for sure. If you don't have a straightedge to bridge the cylinder I can see where you would have some trouble measuring piston depth because of the large chamfer on the piston edge. If you have any straightedge it will work - blade out of a carpenters square, etc. Just subtract whatever you measure the straightedge thickness from the total. This will also help you to be sure you are at t.d.c. as the pointer or balancer mark may not be dead on either. The indicator and bridge Dave mentioned make that easier or you can do it with a degree wheel and piston stop but you can do it with the straightedge and calipers - it just takes longer and is a little aggravating. Not being at true t.d.c. could affect the volume you are measuring also. Clay
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