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| Username | Post: 406 ci sbc build -- Am I close? | |
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panhandle Contributor Posts 226 |
04-18-12 11:22 AM - Post#2216533
1957 Chevy 2 dr post 4:11 limited slip rearend 700R transmission 406 ci sbc Torque block bored & honed Eagle Crank Eagle 5.70 rods Speed-Pro flat top pistons Builder said compression can be dropped to around 10 to 1 with a thicker head gasket externally balanced Trick Flow heads 63cc with 180cc intakes Lunati Voodoo 227/233 @ .050 .489/.504 lift OR CompCams 230/230 @ .050 .480/.480 lift Weiand Stealth Air Strike intake Road Demon Jr 725 carb Holly HV fuel pump Doug's headers with 2 1/2" tubes w/ Flowmasters HEI ignition This setup will be strickly a street driven car and probably never see the track. It now has a 355 sbc and I just want something that has more power and torque on the street (FUN). Is there anything here that looks like it is not going to work and should be changed. Heads and intake will come off the 355. What's your educated guess on hp and torque. Thanks |
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grumpyvette Senior Chevytalk Moderator -- Performance Subject Matter Expert -- Posts 15641 
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04-18-12 01:26 PM - Post#2216562
assuming you get most of the listed components installed correctly,the only really obvious missing component required is a 3000rpm-3200rpm stall converter, without that a stock stall converter and either of those cams is not likely to work well. ID be guessing around 430hp/440 ft lbs at the flywheel, Id also suggest larger 195cc-200cc port heads with 69-74cc combustion chambers to get the compression correct, and allow the engine to breath over about 5500rpm
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panhandle Contributor Posts 226 |
04-18-12 02:26 PM - Post#2216579
Thanks, I forgot the stall converter, it's from Phonix transmission and I think it's a 2400 - 2600 stall. |
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MikeB Senior Member Posts 9388 
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04-18-12 02:35 PM - Post#2216583
“Builder said compression can be dropped to around 10 to 1 with a thicker head gasket” In a 400, you would probably need a .100” gasket to get 10:1 with a decked block and flat tops.  And a thicker gasket is not a good way to go, unless total quench is less than .050”. A better bet is to use D-dished pistons. “Trick Flow heads 63cc with 180cc intakes” So that’s what’s increasing compression! 70-72 cc would be better. Also, 195-200 intake runners would be a better fit for a 400 and a big cam. “Road Demon Jr 725 carb” Not for a cam as big as those you’ve listed. Doesn’t BG say the road Demon Jr. is for cams with less than 220 duration? I’d use a Holley 770 Street Avenger or an old school 750 #0-80508. Or even a BG Speed Demon. If you have to use those heads, buy a cam with around 220 duration and 112 LSA, and pistons with the biggest dishes you can find to get compression down to 9.5. Then go ahead and use a Road Demon 650 (not Jr.) or a Holley 650 or 670. Your existing stall converter should work well with that setup, especially with the 4.11 axle. Then be prepared to replace lots of rear tires. 
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Rick_L Honored Member Posts 24741 |
04-18-12 07:31 PM - Post#2216714
2-1/2" headers are way too big. You can't buy or build them anyway. 1-7/8" would do it. Not much loss with 1-3/4", which you can buy off the shelf. Even the 1-7/8" would be custom for your chassis. The rest of the advice is on the money. |
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greg_moreira Very Senior Member Posts 3262 |
04-18-12 08:33 PM - Post#2216738
yeah either the pistons or the heads need to go. As it stands, even if those flat tops have valve reliefs you should see a little better than 11.5:1 compression. You just cant get a thick enough head gasket in there to reduce compression to even 10.5:1 let alone 10:1. And even if you could.....this is no good for proper quench. As Mike said, youd need a .100 gasket at least to get compression in check(depending on valve reliefs and such) and that aint good. A 72cc head will bring you down to 10.5 with a .040 gasket. Really this would be best done with an 18cc dish piston and keeping your heads. The small chamber dish piston combo is the way to go vs huge chamber and flat tops or a huge gasket. If you meant 2.5 exhaust, then this will do. If you meant 2.5 primary tubes on your headers(which is how it came across)....this is a no no. Waaaaaaayy too much header. As Rick said 1 7/8 tops and Id gladly put a 1.75 on it. The combo is mild enough that a 1.75 will be fine and it will be an easy to get header. Use the lunati over that comp cam. |
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busterrm Contributor Posts 981 
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04-18-12 09:10 PM - Post#2216748
I agree with all the info up to now, 195-200 cc runnered heads with 72 cc chamber. You will need at least that much to be flowing enough at full lift. I calculated you'll need to get 14 cc dished pistons with a quench of .040 and you'll achieve almost 9.8 static compression, with the Lunati your dynamic will be about 8.09. If I might add that is a great cam from the Voodoo line, and yes I would choose Lunati over Comp Cams. Your stall will need to be at least 2800. I just finished a 370 with that cam and it works great with 2800 stall and 373 rear gear. A Holley HP 750 would work great in this case I think, at least a 750. I think for street 1.75 headers will be plenty enough for your combo.
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rumrumm "12th Year" Silver Supporting Member Posts 1784 
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04-19-12 05:22 AM - Post#2216808
yeah either the pistons or the heads need to go. As it stands, even if those flat tops have valve reliefs you should see a little better than 11.5:1 compression. A 72cc head will bring you down to 10.5 with a .040 gasket. Really this would be best done with an 18cc dish piston and keeping your heads. The small chamber dish piston combo is the way to go vs huge chamber and flat tops or a huge gasket. Use the lunati over that comp cam. I agree wholeheartedly with Rick on this. Take his advice.
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models916 Frequent Contributor Posts 1879 |
04-19-12 06:24 AM - Post#2216824
Try and stay with a 10" or smaller converter for the 700r4. Use a carbon clutch in it and the lock up will level it all out when you go cruising. 12" converters are known OD transmission killers. |
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panhandle Contributor Posts 226 |
04-19-12 06:31 AM - Post#2216827
Thanks guys, Looks like I need to buy different pistons for this build. I bought the block, crank, rods and pistons in a package purchase from a guy in Spokane, Washington. The Trick Flows will have to work for this build as they cost alot more than pistons. The 725 Road Demon Jr is the carb that I am using on the 355 right now. Looks like the Speed Demon is the correct carb. Which size would be correct? 650 or 750cfm. This engine probably will never see over 5800-6000 rpm on the street. |
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panhandle Contributor Posts 226 |
04-19-12 06:42 AM - Post#2216831
I will be using the Doug's headers that are already on the car which are 1 5/8". Most of what I have listed is already on the 355 engine. Picked up the 4:11 limited slip, roller rockers and 8 qt. pan with windage tray at the Portland swap meet last week. Was hoping most of the stuff could be used on the 406. Haven't gotten the cam yet so will go for the Lunadi and also a set of new pistons and probably a different carb. |
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greg_moreira Very Senior Member Posts 3262 |
04-19-12 08:35 AM - Post#2216864
Id try the carb before worrying about swapping it. It wouldnt be my very first pick but I can see it being plenty servicable with a little jetting and tuning. It definitely wouldnt be a priority to fit a new carb in the budget right now. What brand roller rockers did you get? New or used? There is some real garbage out there nowadays(like the proform or procomp or whatever they are). Lastly what valve springs are in those heads? Not sure what lunati reccomends but their reccomendation is always conservative. For that cam you want something that will provide 120 to as much as 130lbs on the seat and 310 to 325lbs open. Do not break the cam in with a spring that heavy. Use a softer spring and after breakin Id reccomend driving 5 or 10 miles with the soft springs in there but do not run it high rpms. Just normal cruising. You dont wanna risk floating the valves which will be a real possibility with the softer springs setup for breakin. After you drive just a few miles put the real spring in. If you use a dual spring....just remove the inner spring for breakin. That will adequately lower the spring pressure for breakin purposes. |
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panhandle Contributor Posts 226 |
04-19-12 10:09 AM - Post#2216899
I don't see any special spring poundage listed on the spec sheet that came with heads so I'm going to assume that the spring pressure is pretty close to stock specs. The heads were bought in 2001 and they now have about 7000 street miles on them. Will remove them from the 355 and have they checked out and then use them on the 406. |
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C10 Sleeper Valued Contributor Posts 3426 
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04-19-12 11:06 AM - Post#2216922
Don't forget the steam holes when you change the heads over to the 400 block.
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panhandle Contributor Posts 226 |
04-19-12 11:57 AM - Post#2216933
The Trick Flows are already drilled for use on the 400. |
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MikeB Senior Member Posts 9388
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04-19-12 01:45 PM - Post#2216968
Springs are critical, especially for the aggressive lobes on a Voodoo cam, and at the RPM range you listed. Also, you'll have more springs to choose from if the heads and valves can handle 1.750" to 1.800" installed height. Here's a good article on choosing springs. I'd recommend you read the first 3 pages. http://cranecams.com/userfiles/file/334-34 3.pdf Hope all those rotating parts are forged.  5800-6000 RPM is a lot for a 406 with 5.7" rods. To me, the beauty of big engines is they don't have to rev to be lots of fun on the street, where torque is king. 
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gotta56forme "8th Year"Silver Supporting Member Posts 3282 
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04-19-12 02:29 PM - Post#2216988
I haven't run the numbers, but a question for the more learned of you would be... considering that it sounds like he is going to have a high SCR, is he going to have a workable DCR with his chosen (for now) voodoo cam so that he will be able to run premium gas or below? I'm wondering if the parts choices are hinting at a high DCR and that it will be too high for pump-friendly gas based on what we seem to know right now...
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busterrm Contributor Posts 981
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04-19-12 09:35 PM - Post#2217136
I agree with the steam ports on the heads, have a machinist look at them and make sure they are correct. I also agree on the valve springs, make sure you have good quality and have strong spring pressures open and closed. One of the guys in my nova club cratered a set of aluminum heads because he used cheap springs with a Lunati Voodoo cam. I do agree with Greg, I would run it with the 725, of course you'd need to rejet it and adjust the powervalve and secondaries as Greg suggested. Also I would make sure you measure for the correct pushrods.
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busterrm Contributor Posts 981
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04-19-12 09:53 PM - Post#2217140
I haven't run the numbers, but a question for the more learned of you would be... considering that it sounds like he is going to have a high SCR, is he going to have a workable DCR with his chosen (for now) voodoo cam so that he will be able to run premium gas or below? I'm wondering if the parts choices are hinting at a high DCR and that it will be too high for pump-friendly gas based on what we seem to know right now... If the current heads are used 18 cc dished pistons are needed with a quench of .040. With that combination, Static will be about 10.06 with Dynamic of 8.33. If the heads are aluminum, he should be able to run pump gas.
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greg_moreira Very Senior Member Posts 3262 |
04-20-12 06:12 AM - Post#2217195
I haven't run the numbers, but a question for the more learned of you would be... considering that it sounds like he is going to have a high SCR, is he going to have a workable DCR with his chosen (for now) voodoo cam so that he will be able to run premium gas or below? I'm wondering if the parts choices are hinting at a high DCR and that it will be too high for pump-friendly gas based on what we seem to know right now... Just to talk about DCR for a second, remember that its only a guideline and not a guarantee. Cylinder filling hugely dictates what happens. If you had no cylinder filling at all, you couldnt create any cylinder pressure regaurdless of how high the compression ratio is. Even if it were 14:1 compression, compressing nothing 14 times still makes no cylinder pressure. On the reverse of that....even with low compression and a low calculated DCR, a blower/turbo motor can still build very high cylinder pressure. The cylinder pressure is a function of the blower/turbo filling the cylinder, regaurdless of how low the static and dynamic comp is. Even in terms of a naturally aspirated engine, the difference between 80% to 95% VE can make one engine more sensitive than the other even if they both have the same static and dynamic comp. So yeah there isnt really a clear cut line as to what DCR should really be. Only a decent general guideline for the average engine. With all that said though... if this combo stayed exactly as proposed, 11.5:1 or more compression definitely would not be safe to run with the lunati cam. But he did say he is now going to change pistons. If we use a piston that brings the compression down to 10:1 then Id have no worry about 10:1 comp with this camshaft. |
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panhandle Contributor Posts 226 |
04-20-12 06:49 AM - Post#2217203
Does anyone have a suggestion on which pistons I should purchase, such as make and part number with the 18cc dish? |
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panhandle Contributor Posts 226 |
04-20-12 06:58 AM - Post#2217205
As to the rpm range, I really have no idea what a 406 would peak out at. Whatever the transmission shifts at would be my top rpm and that would be a rare event. Haven't had a ticket in over 40 years and don't want to start now. |
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greg_moreira Very Senior Member Posts 3262 |
04-20-12 07:03 AM - Post#2217208
Does anyone have a suggestion on which pistons I should purchase, such as make and part number with the 18cc dish? SRP makes a good piston. Id use SRP-139625. Its a 21cc dish. With .040 quench, your heads, and those pistons compression will be 9.9X:1. Expect this engine to peak by 5500. Maybe even a hair sooner. It should rev a little beyond this if you choose to, but peak horsepower should fall close to 5500. And yes it will be a lot of fun. I knnow you said you wont race it, but if you did...it should run a solid 12.80 or better if the tuneup is good. |
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rumrumm "12th Year" Silver Supporting Member Posts 1784
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04-20-12 08:04 AM - Post#2217220
This will make a very good combination for you. You will probably have to run 91-92 octane gas, but you will like the power it will make. And it will be a street-friendly engine that you will not have to fight at stoplights or in heavy traffic.
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MikeB Senior Member Posts 9388
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04-20-12 08:54 AM - Post#2217245
Does anyone have a suggestion on which pistons I should purchase, such as make and part number with the 18cc dish? K-B 147 has 18cc dish. K-B 168 has 22cc dish. http://www.kb-silvolite.com/kb_car/performance.php... These are very nice hypereutectic pistons, but since they are designed to keep heat in the combustion chamber, top ring end gap must be set to approx .0065" per inch of bore, depending on engine usage. When I worked for a 383 builder 8-10 years ago, K-B hypers were our default pistons for street engines. We never had a single one fail in the 2-3 years I worked there.
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panhandle Contributor Posts 226 |
04-20-12 12:14 PM - Post#2217288
Looks like the Keith Black piston fits in closer to my imcome level. Could someone give me the specs that I would end up with the 18cc and the 22cc and your recomendations. |
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busterrm Contributor Posts 981
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04-20-12 09:40 PM - Post#2217467
Okay, I ran these on my calculator: ////// 18cc / 21cc / 22cc SCR / 10.24/ 9.95 / 9.85 DCR / 8.15 / 7.92 / 7.85 I think the 21cc pistons would give the best combo!
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panhandle Contributor Posts 226 |
04-21-12 06:33 AM - Post#2217518
Thanks everyone for your help. Looks like we have a plan. |
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greg_moreira Very Senior Member Posts 3262 |
04-21-12 08:52 AM - Post#2217550
Yeah those compression numbers will work out as posted above if you shoot for .040 quench. What this means is, once you have all the parts and are ready to mock up assembly..you gotta measure how far the piston is down in the hole at TDC. If your block is zero decked, use a .040 gasket to get your .040 quench. If your pistons are .020 in the hole for example, use as close as you can to a .020 shim gasket(.020 in the hole plus .020 gasket = .040 quench) And you dont have to split hairs here. If you end up at .038 or .041 or whatever....this is fine. No need to go to any great lengths if its not going to fall exactly at .040. Just get it close and those compression ratio figires posted above will be accurate. And yes the keith black hyper pistons will be fine for this app also. As mentioned, make SURE the top ring gap is set per keith black specs. The standard ring gap youd normally use will not work for this piston. They like the wider gap. No biggie. Just make sure your builder gets it right. Especially in years gone by those KB hyper pistons seemed to show up in dang near every street small block so if this builder has been around....im sure he will already be familiar with the ring gap deal |
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busterrm Contributor Posts 981
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04-21-12 07:22 PM - Post#2217708
Yeah those compression numbers will work out as posted above if you shoot for .040 quench. What this means is, once you have all the parts and are ready to mock up assembly..you gotta measure how far the piston is down in the hole at TDC. If your block is zero decked, use a .040 gasket to get your .040 quench. If your pistons are .020 in the hole for example, use as close as you can to a .020 shim gasket(.020 in the hole plus .020 gasket = .040 quench) And you dont have to split hairs here. If you end up at .038 or .041 or whatever....this is fine. No need to go to any great lengths if its not going to fall exactly at .040. Just get it close and those compression ratio figires posted above will be accurate. And yes the keith black hyper pistons will be fine for this app also. As mentioned, make SURE the top ring gap is set per keith black specs. The standard ring gap youd normally use will not work for this piston. They like the wider gap. No biggie. Just make sure your builder gets it right. Especially in years gone by those KB hyper pistons seemed to show up in dang near every street small block so if this builder has been around....im sure he will already be familiar with the ring gap deal I agree about the quench, its not rocket science. As long as your less than .045, that seems to be the cutoff to prevent detonation, but get as close to .040 as possible. The numbers I posted were figured at that quench factor. Oh yeah what length rod are you using? I figured the SCR and DCR with 5.7 rods. It may change minutely if they are 6.0 rods.
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busterrm Contributor Posts 981
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04-21-12 07:31 PM - Post#2217716
Here are calculations with 6.0 inch rods: ///////// 18cc// 21cc// 22cc SCR/// 10.24/ 9.85/ 9.85 DCR//// 8.12/ 7.89/ 7.81
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busterrm Contributor Posts 981
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04-21-12 10:26 PM - Post#2217754
I think with the 21cc pistons, this will be a great street combo with tons of power.
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panhandle Contributor Posts 226 |
04-22-12 07:47 AM - Post#2217844
Yes the rods are 5.7" in length. |
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MikeB Senior Member Posts 9388
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04-22-12 08:50 AM - Post#2217857
Even with quench at around .040", the near-10:1 compression may come into play and cause detonation at upper mid-range and high RPMs (where dynamic cylinder fill overshadows DCR). I'm just saying be prepared to run premium gas. Straying from conventional wisdom a bit, I'd shoot for closer to 9.5:1, even if quench was in the high 040s. Lingenfleter said his ideal was piston down the hole .005" + .038" gasket = .043" quench, but that anything under .050" wouldn't support detonation. Going by that theory gives you a little more room to play with. My 327 has .048" quench and runs fine on regular gas, even though its new, smaller cam has probably raised the DCR to 8.0 or maybe even a little more.
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DigiBen Forum Newbie Posts 1 
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 07-16-12 12:25 PM - Post#2248793
I acknowledge with the vapor slots on the leads, have a good look at them and create sure they are adequate. I also acknowledge on the device comes, create sure you have super quality and have powerful springtime demands start and shut. Most mentioned is already on the 355 motor.
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