sbc 350 rebuild questions

Forgot to mention the heads.  882's with a simple valve grind to clean up the faces and seats.  

mrp77:
My question deals with displacement.  I just rebuilt the 400 small block in my '77 Chevy.  I was in a hurry picking parts and wanted a very mild engine.  The cam I chose was a 214/224 @.050 with 443/465 lift.  I put a Perfomer intake on with a 600 cfm Holley.  Truck also has Summit headers and crappy 2 1/4 inch exhaust through glass packs. I know that the 50 more cubic inches make a difference in the performance but how much of a difference? With this set up should I have gone with a smaller cam?  The truck sees logging trails, mild mud, and a little towing.  Its a 1/2 ton with 33's and 4 inches of lift with a 350 th and full time 4x4

For wanting a very mild engine, you did not select a very mild cam. Plus, headers do not help matters here. When you see a dual profile cam like yours they extend the lift and duration of exhaust to get a few more RPM out of it top end at the expense of low end torque. They use a shorter duration and lift on intake to keep idle and low RPM response a little cleaner. Without knowing a little more about your truck (like axle ratio and CR) it is hard to say what cam would be better/best for your needs but I feel that you are too warm on cam now and I would guess that MPG is pretty poor at times too. With the right cam and exhaust that 400 SB could be a real stump puller at low and middle RPM and improve MPG a bit too. Another engine that can make good torque too is a 377 which is a 350 block, heads and pistons with a 400SB crank with mains turned down to fit in 350 saddles and using 400 rods too. The longer stroke boosts torque and increases compression ratio too and it can give a noticeable power bump. (BTW if you ever do this, you need to use a 400SB flywheel/flexplate and a 400SB harmonic damper too as 400 SB crank is externally balanced)  

so which stock heads have the 1.72 intake valve and small runners?  
STAND ON IT!!!

The headers were on the truck when I got it.  The cam choice was kind of a ordering parts and the guy threw a bunch of numbers at me so I picked what I thought was small.  Until I got this truck all I ever built and played with were 400 CID Pontiac motors that were in my GTO and my '71 Formula.  I had no intention of keeping them mild and used a Comp Cams 305h magnum in one and the other cam was even bigger so I was unsure what to use here.  I have no problem down sizing the cam after the summer but was curious as the engine does not even begin to lope and pulls well down low.  After I finally put my engine together I took time to look at cam specs and the cam I put in the truck is supposed to be in the 1800-4800 rpm range, which seemed ok.  I had MSD send a 5000 rpm limiter for my 6AL so I know the top range is ok.  I'm open to any suggestions as I want the best, most reliable real world performance I can achieve with what I have.  This is definately no high HP mud bogger or a rock crawler, and as I'm new to the 4x4 world I figure you guys can help out.  

I kinda know what you are talking about on hot cam on old motors. When you have a BB with high compression (11 to 1 or more) it acts differently on a cam than same engine with 8 or even 9 to 1 CR. (when I started driving, 9 to 1 was consider low and 11 to 1 or better was the norm for hi performance engines in new cars). Most drivers today do not realize some of the nasty motors that came out of Detroit in 60's and early 70's and know only of smogged SB's and BB's and do not realize that engine were completely different animals from what they have been exposed to. (there were some real beasts!)  Wild cams with big overlaps have reduced effective CR's at lower RPM's and higher theoretical CR's help make up for this will providing even more power when you "get on the cam" at higher RPM and was used a lot back then. By shear displacement you are going to have some torque at lower RPM with your 400SB and the short rods and long stroke help too here. But with a shorter cam with a duration of around 210 or so at .050 and with a asymmetrical lift (like competition cams uses) you could have even more low end and nice mid range too. Loosing the headers would help too because while headers can help upper mid range and top end, they can hurt mid range and bottom end because they let expanding exhaust gasses vent too quickly from cylinders at lower RPM's and less energy is transferred to crank. Ideally if great lower range torque is desired, you want exhaust pressure in cylinder to not drop too low before BDC. To me a SB400 could do some of its best work below 3500 RPM when setup properly and could easily be making over 200 HP at 3000 RPM too so that you would have some nice usable power that you would not have to wind up engine to get too. (if you can make about 375 ft lbs of torque at 3000 RPM that equals about 215 HP) This is why turbo diesel do so well, not because their HP is any stronger but because they make it at lower RPMs where it is better used with proper gearing.  

I appreciate the advice.  Pretty much my first try with a SB Chevy and a truck as well.  Definately a little different than the RA II and RA III's I'm used to. I already have a good amount of work in but changing a cam is nothing.  Block has a new crank, new rods, new bearings and rings, and new timing set.  That with a 5000 rpm limit and a little judgement I hope to make it last.  

5000 RPM (or a bit less) is a good sane limit for your 400SB in current state. The whole 400 SB concept was born to deliver higher torque at low and middle RPM to power heavy vehicles even with emission control in place, not as a high RPM/top end engine. One tip, make sure your cooling system is running 110 percent. 400SB's do not take overheating well and it can seriously damage it. (blown head gasket and cracked heads) Make sure you cooling system keeps it cool in any scenario (even if it means putting in a bigger radiator) as this will extend engine service life under heavy usage. If it every starts overheating on you, (say 215 and above) get out of throttle and get it to cool off. Better to be safe than sorry here. The reason for this temp limit is that 400SB has siamesed cylinders and limited coolant flow in place in block and head and when coolant get above 215 to 220 under heavy load the coolant can actually flash to steam in hot spots and create a gas pocket that lets surface get even hotter.  It is best to keep it below 200 or so and fairly steady in temp if possible. Do not use 160 Tstat as they reduce efficiency and increase condensation build up in oil because engine does not get warm enough to burn it off. 180 to 190 is about ideal here for a Tstat in this engine  

a 180 degree thermostat, 8 pound cap, and a refurbished 4 core.  Also a tranny cooler and a power steering cooler mounted off of the radiator so as to not impeded airflow.  I knew about the siamesed cylinders so I also made sure to go with a top of the line fel pro head gasket.  It hits 200 degrees and I start worrying.  

Nice to see another low pressure cap user. I have been using them for 20 years on new and old vehicles. Seems to really extend house life a lot. If you are not already doing so, I would suggest using 60/40 or 70/30 (antifreeze/water) coolant mixture. Contrary to popular belief, antifreeze absorbs more heat in liquid state and has a much lower surface tension (meaning when gas/steam bubble form, they disperse for easier) which means greater heat transfer. While it does take more energy to boil off a gallon of water (and this is where myth likely started) we do not cool with steam and as stated above,in a liquid state, glycol can absorb more heat energy.  Sometimes cars appear to run warmer with high levels of glycol but this is because it is more effective in removing heat from block and temp sensor reads coolant temps, not block temps. It also raises boil point of mixture too. A side benefit is that radiator stay clean like new for a very long time too. If you want to get exotic, you can run pure propylene glycol (non toxic antifreeze) as it freezes around minus 90 and boils around 344 in a 100% concentration (unlike Ethylene Glycol)  

chopperfreak2k1, what cam did you choose and how did it turn out?  

chops still hasn't finished it yet or gotten a cam...  
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