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Old 02-11-2008, 03:37 PM
pal pal is offline
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another 400sb help thread

hey guys, i need some advice on my 400 sb. i have a 1972 4 bolt (i know 2 bolt is better) this engine has a fairly fresh rebuild on it. i think the pistons are the old heavy TRW's, L3276 .030. they are deep dish. stock rods. i was going to use some small chamber double humps, but that deal never happened. a friend gave me a 69 327 i was going to use the heads off of. last night when i pulled them i found out they are 75 cc chambers, 1971 3973487 heads. they do not have the 2.02 valves in them. with a tape measure (crude) they measure between 1 15/16 and 2 inch. my problem is that this build is coming to an end and $$ is being spent on all the little stuff. if i use these 487 heads, is my engine going to be a real dog? my chassis wieght is 2200-2500 lbs., M-21, rear gear un-decided, 1 3/4"x18" primary tube, with 3 1/2" collectors, and a 4x2 intake with 94's built by the dickster over on the HAMB. i have not selected a cam at this point, and could use some help there as well. i like solids and would like to use one even knowing that this is a low RPM engine. i dont need a radical idle, but since it is a old school type hot rod, it still needs some of that hotrod sound. i dont want to use vortec's, because of my old vette covers and the intake i have, plus money. so will the heads i have work, or am i pissing up a rope? thanks, pal

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Old 02-11-2008, 04:08 PM
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Depending on whether or not you want to mill the heads, you will be around 9:1 compression. The Lunati solid 40155 cam will work OK for your solid sound and won't kill the torque. I'd use 1-5/8" headers if I were building it.

tom
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Old 02-11-2008, 04:39 PM
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thanks tom, the 9.1 will come with milling, or thats what you estimate it without milling? sounds better than i thought. i was thinking those pistons and 75 cc heads would give me low 8. something CR. i will look up the cam. one thing i did not mention was, this roadster is just a now and then take it out and raise a little hell, not a drag or street racer. pal
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Old 02-12-2008, 08:31 AM
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Pal I'm showing 7.7 to 1 compression with 30 cc dish pistons factoring in at least .010 in the hole , 5.56 rods, 4.20 gasket, .039 crushed gasket ,75cc heads, and a stock 4.125 bore.

I always use a calculated program like this one:
http://kb-silvolite.com/calc.php?action=comp

If you went with some flat top pistons and a 3.75 rod it would give ya around 9.5 to 1 and a better squish than those factory slugs. and make sure ya drill the steam holes in any heads ya throw on the 400.

just my .02cents
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Old 02-12-2008, 09:20 AM
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You'll have to check the depth and diameter of the dish. If I figure a .135" dish and the valve reliefs, I get around 15cc, which gives 8.9:1. I figured a .020" deck height and 9cc for the head gasket and 76cc for the heads. Deck the heads .010"-.015" and you are at 9:1.

tom
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Old 02-12-2008, 10:32 AM
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if i remember right, the part number on thede pistons indicate a 25 or 26 cc dish. it was once figured to be 9.4-9.5:1 CR with 64cc heads. does this sound right? if so, and i use the 75cc heads the CR will be way down in the 8's. it sound as if its going to be a real dog.
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Old 02-12-2008, 10:41 AM
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If they are 26cc, mill the heads to 72cc (.030"), 0 deck the block and you will be at 8.8:1 or so.

Or get a piston more designed for what you want (with less dish).

tom
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Old 02-12-2008, 11:16 AM
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I would keep the larger chamber heads and replace pistons and deck the block. I f you went with the speed pro flattops at 6cc for valve relief and 0 decked the block that would give you 10.27to1.

I correct my first post of 7 t0 1
i put in the wrong stroke. (DUH)

Im assuming you would go .030 on the bore to make a 406

heres 75cc heads with 26cc pistons and .020 on the deck your current set up---- 8.29:1
same set up with 64cc heads------------------------------ 9.07:1
same set up with milling the heads to 72cc----------------- 8.49:1

changing to flat top pistons and leaving the block at .020 deck with your current 75cc heads----9.84 to 1
changing to flatops and 0 decking the block with your current 75cc heads-------- 10.27 to 1

I think if money permits the last choice is what I would do, look on ebay or
at some speed shops online , pistons can be had at around $225 plus 100 for rings, and 5.7 scat rods are around 230. and then you will have a more reliable set up with alot more power and better quench.

Last edited by 66sedanman; 02-12-2008 at 11:17 AM. Reason: wrong info
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Old 02-12-2008, 12:35 PM
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okay that helps a lot. i will leave block as is, because its was re-built in the near past,and because of money at this time. what i am thinking is to mill the 75cc heads and run with the 8.49:1 CR. i will watch for some nice 64cc heads in the near future. how does that sound? now to have my cake and eat it to, what should i do for cam choice? as i have said, i want a solid. if i purchase a cam, lifters and springs suitable for my set up an future 64cc heads, can i get away with it for awhile on the 75cc heads? i rather not buy 2 cams. thanks, pal
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Old 02-13-2008, 12:07 AM
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use Lunati number 401A3LUN camshaft. This a nice nice "UDHarold" (Ultradyne Cams) street mechanical cam grind {01-UF15-UF16-12}. Will run sweet with your setup on the street. Easy to live with. Nice idle and overall smooth street power. Will work with your 487's and any new head you decide to go with.
Doesn't need anything special for the valvetrain. Lunati #73943 stock diameter performance springs @1.70"-1.72" installed height will work just fine.
Crane Cams # 113841 F-278-2 is near identical and another very good choice for your plans.

Lunati 401A3LUN

Crane F-278-2 113841
You won't be disappointed with either choice.

Last edited by F-BIRD'88; 02-13-2008 at 12:15 AM.
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Old 02-13-2008, 11:05 AM
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this is all very helpfull information and i appreciate the time its taking to help me. last night i did a little checking, and have TRW L2376 .030 over pistons. also i am going to re-ring and bearing the engine. so i will be taking the block in to booil and check everthing. the pistons are 24cc dish and are .025 down in the cylinder. what should i do as far as decking the block? at the least it needs a clean-up. i quess what i am asking is if i deck the block and mill the heads down (how much) will my CR become decent? still have tight budget to work with, but i want it to be right when done. how does the idle sound on that lunati cam? thanks, pal
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Old 02-13-2008, 01:00 PM
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I have read about guys having these pistons cut as flattops and then running 5.7 rods wich you can pick up super cheap. look here http://speedtalk.com/forum/viewtopic...3f7a7fc34d4b76

with that setup you have now 24cc dish and .025 in the hole youll have 8.35 to 1 with the 75cc heads

with just 0 decking youll have 8.72 to 1

with o decking and using 64 cc heads youd have 9.6 to 1

I would look into having the pistons cut down, just curious on the cost
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Old 02-16-2008, 09:22 AM
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there has been alot of very good advice given here. i decided not to work with the unknown. i tore the rest of the short block down and yes its a recent rebuild, but it shows signs of neglect and detionation. so i have it at the machine shop now, and will know what i have or dont have to work with this coming week. i met with 3 shops and really felt comfortable with the one i decided on. after a full cleaning and inspection, decisions can be made. they do recomend a "true deck", i guess thats a zero deck? also they claim that my heads can be angle cut for whatever cc i want. they build and race there own stuff plus have a engine dyno. there thoughts on this engine if all checks out are; true deck the block, angle mill the 75cc heads to 64cc, and use flat top pistons. i will see how everything checks out before macking any decisions about a cam. thanks, pal
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Old 02-16-2008, 10:37 AM
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With 64cc heads and flat top pistons and a 0 deck height.....
Your cr will be 11.5:1. Way way way too friggin high for pump gas.

for a 400SBC that runs on pump gas-----

pick 64cc heads with a dished piston (-18 to -22cc dish volume)

or 76cc heads and flat tops
One or the other or you will have excessive compression ratio and big problems running on pump gas.

True ing the decks is not the same thing as "O decking the block"

If you want to run a (-7cc) flat top piston and your #487 heads on pump gas.
Have the block decks cut just enough to straighten them up (flat and true to the crank C/L front to back. (.005" to .008" cut)

Mill the heads just enough (.010") to straighten their decks (73cc finished volume) no angle mill required.
Your cr will be 9.87:1 on a .030"+ bore 400. Just right for 92 octane gas.

Last edited by F-BIRD'88; 02-16-2008 at 10:49 AM.
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Old 02-16-2008, 11:59 AM
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Yea listen to F-Bird ^^^^^^^^^^^^^^^^^^^^^^^^

Cant run a flat top in a 406 with 64 cc heads on pump gas. 11.5to1 like he said .

I would have them clean up you heads to like 75cc have them zero deck the block and with the flat tops you will be at 10.2 to 1 running on super unleaded.
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