400 build torque and power guestimation

[400smallblock]

im putting a 400 small block in my truck. im thinking it will be in the 375 hp/400-425 torque range. not looking for 600 hp.want a torque engine at 200-4500 rpm. right where it can be used without major mods to everything else.im using a vortec l31 heads, a procomp dual plane aluminum intake, comp cams 268h hydraulic cam,218@.05 on I/e and ..455 lift in I/E,stock style dished pistons.shortblock already has been running.stock rods,on summits website i came in at 8.8:1 compression. 600 vacum secondary holley carb. summit headers. i think they are 1.625 dia, and 2.5"duals with flowmaster mufflers exiting in front of rear wheels.i sure love these 400sb engines-wide torque curve at low rpm. gets the old heap movin. what you guys think?

[Blue Rat]

I came up with what you supplied an guessing on the head numbers with 315 HP.

[68GMCCustom]

more compression (9.25-9.50:1) and lift (.495-.525)....but that's just me.

[mud.man.rj]

I agree, about 315-320hp, to low of compression and did you drill steam holes in heads to match 400 block, won't heat up off idle but will cruisin slow if you didn't. More cam with more compression would really bring it all together as mentioned.

[Blue Rat]

For kicks, ran it with 10.5 which would be in the area of flat tops. Put in a 12-212-2 CC hyd. An a 64cc head with 2.02/1.6 an 750 Holley. Came up little over 350 HP.

[mud.man.rj]

Nice work Blue Rat, I think he wants more, which costs more like always. Full roller rockers and cyl head porting with a port match will help a bit more but still not 400hp yet, I guess turbo, blower or NOS.

[Blue Rat]

Change intakes to single plane with better heads with big valves an pocket porting an a 12-246-3 an it's little over 400 HP. That is what my simulator is showing.

[68GMCCustom]

Originally Posted by mud.man.rj

Nice work Blue Rat, I think he wants more, which costs more like always. Full roller rockers and cyl head porting with a port match will help a bit more but still not 400hp yet, I guess turbo, blower or NOS.

....that's why I really like the bigger LSx motors. 400hp is a cake walk.

[chevyrestoguy]

Originally Posted by 68GMCCustom

more compression (9.25-9.50:1) and lift (.495-.525)....but that's just me.

Definitely. Run a Fel-Pro 1095 shim gasket and it'll help with what you've got. You'll be around 9.15 to 9.25:1 with that alone. A little extra compression makes a world of difference on torque, and that 400 will love it. Here's a cam that would go great with the parts you already have:
http://www.lunatipower.com/Product.aspx?id=1983

Originally Posted by 68GMCCustom

....that's why I really like the bigger LSx motors. 400hp is a cake walk.

LS engines are awesome. They make EASY cheap horsepower, get great fuel mileage, and they don't leak! And they're getting cheaper, too. I have seen the little 4.8 motors with low mileage going less than $800 complete with computer, wire harness and all the accessories. The 5.3 and 6.0 motors are cooler, but the 4.8 is great for someone looking to make 350 horsepower and get 20 mpg.

[mud.man.rj]

The only problem with the single plane intake is the only difference is from 5,000 rpm up but below that an airgap or Rpm intake will kick it;s butt down the road to at least 5,000 where every day driving is most of the time.

[400smallblock]

wow those #s are a surprise. not as high as i would want for power. what about torque #s,thats what im really after.the heads are not on engine yet.i pulled a set of 993 heads off it. the vortecs are 906 castings. how much do you think i would gain by 1.6 rockers? about .030 lift. i would have to put screw in studs and guideplates, and regular 1.6 rockers to do this as i dont think antone makes aligning 1.6 rockers. i have a comp cams 292 magnum(244 degrees at .05-.500 lift) i had in another 400. it ran good in that motor. how much power would the 400 make with it? i still want to keep my torque curve in the 200-4500 range? would this cam move it up too much?

[jjzepplin]

I am not sure of my horsepower or torque but my 400 is .30 over , flat tops, stock heads-opened up to 2.02's and cc'd mild porting, 1.6 rockers, air gap intake, 675cfm holley truck avenger, accel hei, and this thing is screamin for the last 10 years. (all arp bolts holding it together) Stock rods and crank. I used marine steel head gaskets to bump the compression a bit. I also plumbed coolant to the back of the engine as this seemed to be a weak point of circulation.

[400smallblock]

zeplin, what cam are you running?

[jjzepplin]

I have a Comp Cams 4x4 extreme. I would have to look back at the specs. It is very streetable and as good vacuum. No real noticeable lump. I have always had good luck with Competition Cams. I had stock "y" pipes at first but just installed Hooker Comps and 2.5" exhaust. Have not run it yet but looking forward to it. I have a 700r4 and she would easily spin both 36" Swampers before. So those little Goodyears are gonna have trouble keeping up.

[ctandc]

Originally Posted by chevyrestoguy

Definitely. Run a Fel-Pro 1095 shim gasket and it'll help with what you've got. You'll be around 9.15 to 9.25:1 with that alone. A little extra compression makes a world of difference on torque, and that 400 will love it. Here's a cam that would go great with the parts you already have:
http://www.lunatipower.com/Product.aspx?id=1983



LS engines are awesome. They make EASY cheap horsepower, get great fuel mileage, and they don't leak! And they're getting cheaper, too. I have seen the little 4.8 motors with low mileage going less than $800 complete with computer, wire harness and all the accessories. The 5.3 and 6.0 motors are cooler, but the 4.8 is great for someone looking to make 350 horsepower and get 20 mpg.

Wish they could be had for that out here.

They are always missing the harness / sensor etc, and that all adds up quick.

[GMR-PERFORMANCE]

FOr what its worth take a look at a dart SHP block. Read my thread on my 408.. I have a virgin bore 400 block with a not matching #3 cap. If you add up the machine cost to do a block correctly, then look at the SHP you will be suprised at the upgrades you get.

Marv told me up front to buy an SHP , well I was lucky and only threw away a small amount of money. But really with them they need to be line honed to ensure your crank is not going to get bound up and run for thousands of miles trouble free.

Adding boring, decking, line hone ( or maybe line bore ) it adds up very fast. A dart block is something that I would look at as an investment up front.

For what its worth I cannot give away the 509 block I have here.. LOL too funny really.

Maybe Marv will tell you about his that peeled the deck off of one side..

[mud.man.rj]

Originally Posted by 400smallblock

wow those #s are a surprise. not as high as i would want for power. what about torque #s,thats what im really after.the heads are not on engine yet.i pulled a set of 993 heads off it. the vortecs are 906 castings. how much do you think i would gain by 1.6 rockers? about .030 lift. i would have to put screw in studs and guideplates, and regular 1.6 rockers to do this as i dont think antone makes aligning 1.6 rockers. i have a comp cams 292 magnum(244 degrees at .05-.500 lift) i had in another 400. it ran good in that motor. how much power would the 400 make with it? i still want to keep my torque curve in the 200-4500 range? would this cam move it up too much?

The 292 is a fairly big cam I think in the 2,500 up to oover 6,000 range, have used them in cars that weigh a lot less, usually use a 268/274 range cmp cam. One saving grace is cubic inches, since a 292 seems a big big in a 350 it really drops about one size for a 400, cubic inches make the cam seem a bit smaller so in the 280 range, so will work alright for Hp but still a bit big with low compression. If you can use the thinner head gasket as mentioned and get the comp in the mid 9's range the cam will still work. A bit of a stall or manual trans will make it work even better. Nothing like a 400, great for torque and will still spin up like a 350/383, nice. If you use 1.6 rockers then the cam steps up between 2 cam sizes and should use the correct pushrods (which a lot don't) to correct geometry fo top of valve stem. I would stick with the 1.5's especially if actually using the 292 cam. Don't want it to be all top end and a dog at bottom. Don't need studs or guide plates yet. But the bigger the lift and stronger the valve springs the more stress it puts on the press in studs.

[Marv D]

Just remember, with stock vortecs your limited to .47 lift before you start smacking retainers into the top of the valve guides. The Vortec style is a good head,, but IMPO the stock GM castings are all but door stops. Some 15 years out of production , and a light weight casting to begin with,,, most need just as much rebuilding as a set of early double hump heads. Much like Steve said,, your SO much better off looking to the aftermarket for small block stuf these days. But it costs,,, HOWEVER... The cost of destruction in a failed main cap, block, valve keeper, rod / bolt,, it's just getting scary with some parts being reconditiioned 3 and 5 and 15 times now.

That said,,,, the 400 eats 0.050" duration like a semi eats fuel! Myself if your set on using the combination you have,,, well you know your leaving a good 150HP on the table. Big HP numbers takes torque and RPM!!! The motor you described isn't going to make big HP numbers because it is going to be all done by 4000. That small cam may limit bragging rights in HP, but I really think the combination is going to make up for it in all around GRUNT to pull the horns off the devil himself, and do it in a very DRIVABLE RPM range.
TORQUE is where it's at in a big heavy street driven truck. 400 pound feet of torque at 4000rpm is only 305 HP. Don't sound like much do it. Neither does 400-450 # at 3000rpm,, which is only 225-250HP. But you need to realize that 450# twisting on the driveshaft, the thing that ACCELERATES the truck. You will not have the fastest truck out there for sure,, but I think it will be fun to drive, and will be a work horse!!!

I used the Edelbrock version of the Vortecs (the 170cc Etecs) in a 406 in a buddys 74 Nova budget bracket racer. At 3200 pounds it went 11.0's at 118 footbraking. I built the tow motor for my 94 4x4 I tow with,, it's just a 383 with RHS iron vortecs,, it pulls my 12,000 pound race trailer around faster than I care to pull a 12000 pound trailer!!!

Point I'm getting at is if you want FAST,,,well I'd sure look for alternatives. So don't get carried away doing a lot of 'fixin' to a old csting that just isn't worth it.

But that's just my 2¢,,, what do I know.

[Captainfab]

Several years ago we built a SB400 for my son's 4x4. We used a stock rebuilt shortblock, with dished pistons. Added a set of new Vortec heads with Comp 981 springs, screw in studs and guideplates. For a cam we went with a Comp XE4262, Extreme 4x4 cam. The intake was a Performer RPM, topped with a 3310 Holley 750 carb, and a HEI distributor. I was really surprised at how well that engine ran. For a big heavy truck, that thing would get with it. After my son wrecked the 4x4, we dropped that engine into his '85 IROC with a 3000 stall and a TH350, 3.73 gear and ran a mid 12 quarter.

[400smallblock]

marv. what you wrote is exactly what i wanted to hear. i know a street engine for a "normally" driven vehicle needs low end torque,2000rpm to 4500 rpm. right in the sb400 wheelhouse. i did some more research on other hot rod sites and im satisfied with my planned package. should make at least 400 # from 2000 to 4000. thats what im after,a torquey street ehgine.a bone stock 400sb in 1970 had 265 horsepower and 400 # torque at 2400 rpm.right where a 4000 lb truck can use it and have some fun but still be drivable. you guys estimate my setup at around 325 horsepower. thats ok. the low end torque will be there with no stall speed converters and such. i did that dance before with my old 71 truck and a 400 with that 292 comp cams magnum. ran good. but that stall speed coverter got old after a while.thanks wpold it be worth trying a 3310 holley 750? i have a 1850 600 holley i was gonna run on it. summit racings carb calculator says i only need 600 cfm if im turning the 400 to 4500 rpm?

[GMR-PERFORMANCE]

600 is enough carb for the street. Again TQ is what you are after. It will respond quick , have great drivablity in the low range. A small convertor is no issue at all on the street, and will work wonders for getting the engine to not stall when you drop it in gear, or lurch forward.

Will be a bunch of big inch stroker engines with small cams. They do not produce big hp but the low end tq comes in fast and they are a blast to run.

[Marv D]

When we talk 406's I always love to throw these pictures out there,, This is my buddy's 74 Nova,, stock GM 3951509 casting,, with a bunch of quality machine work, but stock 2bolt mains, (actually sleeved #2 cylinder because it wouldn't clean up at +.030 Zero decked, torque plate honed, yada yada yada....)
Edelbrock E-tec heads (170cc version) Comp XE294 flat tappet cam with 1.6 Crane roller rockers, Edelbrock Vortec Air-gap, and a Prosystems 780cfm carb, Supercomp 1.3/4" headers, Hughes TH350 Street-strip trans and a Jeggs 3500 stall convertor. Drove it 100miles to Speedworld, slapped on the slicks, went 11's , changed back to the street tires and drove it home (usually)


HOLY CRAP thats a big picture,, here's a link instead

but also have to show this one,,,,,, After a few changes (afr heads and a bit more cam and running 10.4's) this is what #7 hole looked like when we took the head off... after one of the KN Hyper-you-cracked-it pistons decided to return to the sand from whence it came . Dana enjoyed abusing that motor for 3-4 years before it gave up,, but in reality that is like only a couple thousand miles



We didn't take the piston out,, it was GONE!! no evidence of it other than a pile of sand in the bottom of the pan. and a piece of one side wraped around the pin. Hyper-u-cracked-it's are like pyrex when they go, there into a couple hundred billion pieces in milliseconds. And don't ya just love the way she tied the rods in a nice neat "X" at the bottom of the bore. It was an expensive day

As a fyi,, we salvaged one head, intake carb and headers and 5 pairs of roller lifters. The other head took $650 in aluminum repair and fixin (valves, seats, weldin and such)..
The block, crank, rods, (I refuse to re-use the rods after this), balance of the pistons,, Lunati 50124 billet roller cam, and 3 pairs of Lunati solid rollers were instant scrap.

Parts suppliers simply LOVE them stock 400 blocks and hypereutectic pistons LOL

[GMR-PERFORMANCE]

That XE 294 cam is so close to the howards I run that its not funny. thats in my 408 ,...along with 11.2 comp single plane high rise intake, FORGED CP pistons ( ha ha ) with the dart block 4340 stuff in the bottom. and away you go.. If that wont get it done the two stage cheater system will always be ready to go...

[Marv D]

You better pill it up and get some stickeys if your gonna hang with the big dawgs Steve,,

[GMR-PERFORMANCE]

All in the works. Marv baby steps, WAAAAY different than my old race cars, those all where full boggy set ups. Never have to worry about DQ LOL ...

Have the new MSD power grid on the way looking forward to setting everything up with the lap top.