Need power, Chevy small block or big block??

Geo450racer:
wait you understand i have an edelbrock aluminum intake right?  yeah i know raising compprission will riquire higher grade fuel but im hoping for it to accept mid grade fuel like 89??? Im not going to overrev it so i guess ill stick to 400 for now but your saying just to add flat top pistons and cam and leave stock heads?

If it was my nickle I might change pistons but I would not worry about a head change. Stock heads will do fine as you are not supercharging it or racing it. Myself, I do not run 87 in anything here and have not for many years. I run 93 in warmer weather and 89 in winter months. When building a engine today I do not even consider 87 octane tolerance because I never use it. I have a engine on the stand that I am going to build next year that is going to be a bit of a experiment. I am going to stroke and bore a 305 .030 and make it a 334. I am going to shoot for 10.5 to 11 to one CR and it is going to be 93 octane or E85 only. It will be cammed to peak power before 5000 RPM too. The goal here it to make a motor that has good low and mid RPM response and torque for its size and good fuel efficiency too. With todays fuel prices it is cheaper to run better fuel in a engine designed for it that you fixate on 87 octane. With CR increase comes more power and improved efficiency. BTW, I have run my 89 burb on 93 year round for many many years with advanced baseline timing as well and it runs very good (better than it ever did with 87 when new) and averages MPG that it really has no business getting too.  

mudb8-.:
yep, ya can, although the stock heads are likely 882 castings, they are light and aren't worth putting money in.

I'd go with the stock pistons, 260 duration cam with a 112 lobe center and a set of heavy cast 64-68cc 327/350/ 194/150 iron heads with hard seats, steam holes drilled for the 400

why would chevy equip the blazer with "light" heads instead of heavy truck heads ins't this a truck motor?  but ins't ligher better?  why would you keep stock pistons? but yeah if i do swap on differnet heads i will drill the steam holes  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

The term light means a little thinner casting which they have been going to for a long time. As long as you do not start milling and porting them a lot or supercharging, the light casting is not a issue at all.  

the casting is thin, prone to heat and cracking, they survive just fine untill ya start making heat/horspower.

ya can find old heads cheap, theres nothing wrong with the stock pistons.  
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see me at robsoffroad.com

They will survive fine as long as you keep it cool. 400SB do not have full flow cooling anyway because of Siamesed cylinders and heads are the least of your worries. You need to take extra pains with cooling system in high HP apps moreso than worry about head type. A 400 SB is not a motor you want to overheat regardless of head type and people that have troubles with heads on them are not keeping them cool. Also if you run higher concentrations of antifreeze you will have less problems too because glycol has a lower surface tension and higher boil point (better heat transfer from block surfaces because of less hot surface steam/gas barriers) and absorbs more heat in a liquid state too. When we raced we used pure antifreeze and one problem we never had was anything cracked from heat.  

well my 400 never seems to run hot, around town it runs at 160 and in the desert with my foot in it, it runs 190 and never goes over 200 with that giant radiator and direct fan the motor is pretty well cooled, okay so here is my mod list then, flat top pistons in effort to raise comppresion(and efficency) hotter cam and that should be it, let me get you guys opionion , does it sound should like it should be healthy motor?  i know its nothing insane but with your experice what do you guys think??  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

Carb could be a little smaller but it will do I guess. On cam, it is better to error on the mild side than wild side. I would suggest a Competition Cams High Energy H260. I ran a few of these long ago and they played pretty well. Good idle with strong mid range and tops out at about 5000 RPM.  

in my 350's and a few 400's I use the crane 262-2nc.
with a mild/quick pollish on 186 and 041 cast heads, flat top keith black pistons, the 350's dyno'd a little over 325 hp with 600cfm carbs,

I never had any 400's dyno'd, I can tell ya though they had a bit more torque. one of the 400's is in a 73 nova that runs 14.3 in the quarter mile. with 3.08 gears th350 and 245x60-15 radials.  
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see me at robsoffroad.com

the 325 hp is that at the wheels or crank?  if that at the wheels then that not bad so how much do you guys expect out of my 400 with the mentioned mods? im hoping for at least 350 hp?  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

I feel these days that too many place more "value" on HP ratings than how engine is geared to load and its torque curve. As you staring increasing a engines output you do so by moving the torque peak and curve to a higher RPM (since HP is a function of torque and RPM) The potential problem here is that the net result can be LESS HP below 3000 RPM or so if you are not real careful. (a engine "rated" at 350 HP only has that amount when the RPM of the power peak) Myself I would rather have a engine that peaks its torque below 3000 RPM and HP well below 5000 RPM in a 4x4 SUV because this is usable power. This and proper gearing makes it all happen.  

it was a superflow dyno...
325hp @4500 and 390# @3500, starting out at 175hp @2500rpm and 360# ... 9.5cr 350ci, If ya think they aren't very strong cause its not on the ground, yer dead wrong...
I would expect a bit more from the 400ci with a good set of heads.

if you're after more than 350hp on the ground you'll be reaching into the 280-300 duration cam range, definately a set of high flow big valve heads, it'll have about the same torque as the small cam.... way up near 5000 rpms though.  
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but with 4:88 gears wouln'd they make up for some lost low end power from big valve high flow heads and hotter cam?  Also if i can't make big power without sacrificing low end power in a small block why not go to a big block?  how much power could i make out of a 454 with the previoulsy menitioned mods?  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

Geo450racer:
but with 4:88 gears wouln'd they make up for some lost low end power from big valve high flow heads and hotter cam?  Also if i can't make big power without sacrificing low end power why not go to a big block?  how much power could i make out of a 454 with the previoulsy menitioned mods?

Yes it would but with reduced torque also comes reduced efficiency so keep this in mind when you think about feeding it. They days I do not think about how much HP I can get be rather how much efficiency can be had. I just cannot see dumping any more money down tail pipe than I have too.  

give me rough estimate with the previously metioned mods on the 400 how much mpgs would you expect? since its highter compression shoudln't it give me better mpg than now, but  what do you think about big block power?  how much of a mpg hit would a big block do?  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

my guess is around 12-14 with a carb.
with the exception of a 427 I have the 454 is good for about 10mpg's, my 86 dually got about 6-8 till I put in a 6.5 turbo diesel.
the big blocks are much more spendy to play around with,

I was going through some old notes on the 383/400 combo's, GMPP has a roller cam #24502586 that has a duration @.050 that is 218 intake and 228 on the exhaust, (about a 275-280 advertised duration), lift is .560 on a 112 degree lobe center, with cleaned up iron vortec heads it should be able to make about 420 hp below 5500rpm and 450# between 3000-4500 rpm and 400#'s @2500. @9-9.5crs'
stepin up the compression and using big valve high flow heads it'll probably hit the 500# pound mark by 4500rpm and run close to 470hp at the cost of efficiency.  
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see me at robsoffroad.com