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-   -   400 sbc hp? (http://www.hotrodders.com/forum/400-sbc-hp-229825.html)

smith9300 02-21-2013 10:52 AM

400 sbc hp?
 
hey guys just seeing if i can kind get a rough estimate on hp/tq on the engine i am going to be building

400 sbc
stock bottom end with -22cc
vortec heads 64 cc
comp cam xe 256 max lift of .454
dont have intake yet but prb just a edlebrock
edlebrock 650 carb

just kinda wondering what i will end up with. ask for more info if needed ill try to answer but any and all comments appreciated. or if anybody has a similar build and there specs on it

vinniekq2 02-21-2013 10:58 AM

vortec heads are limited to mid 400s plus or minus.If you use a hydraulic flat tappet look closer to 400. You can use a 750 cfm carb of bigger,depending on application.You will have good low RPM torque with those heads

JohnMatt 02-22-2013 10:39 PM

My guess is 420hp 450tq maybe more torque but those are my guesses

smith9300 02-23-2013 02:21 AM

That seems pretty high to me with stock bottom end and just some new heads

jtz55 02-23-2013 07:12 AM

are u running headers or stock exhaust .I have and am currently running a similar setup 485 lift cam 5.7 rods .it is putting out alittle over 400 hp and 525 ft lbs very good street manors .have fun with your 400 they make tremendous off idle torque and will shred the belts off most street tires.

smith9300 02-23-2013 08:03 AM

Headers for sure but it going in an 85 2500 with 6 in lift andon 33 but what is the complete build u have would like to compare

vinniekq2 02-23-2013 08:16 AM

horse power
 
Quote:

Originally Posted by jtz55 (Post 1649567)
are u running headers or stock exhaust .I have and am currently running a similar setup 485 lift cam 5.7 rods .it is putting out alittle over 400 hp and 525 ft lbs very good street manors .have fun with your 400 they make tremendous off idle torque and will shred the belts off most street tires.

varified or estimated?

the 400 came with 265 hp plus or minus
using a decent upgrade in cam/manifold/carb/headers could net 50 plus hp
vortec heads are very good improvement over most heads,especially for moderate performance and low lift cams.
vortecs flow 230 plus CFM on the intake side
these heads would peak at 5500 rpm on a 400.the cam would need to be big enough to rev 5500 to take full advantage of these heads

may need exhaust port worlk

smith9300 02-23-2013 09:18 AM

Yea the cam I have now goes to 5200

jtz55 02-23-2013 10:28 AM

Vinnie its the same motor chp built a few years back called the impersonator .they claimed 425hp and 525 ft lbs .u can look it up just do a search on it .was june 2003.anyway I built mine to spec just a little bigger carb(mines a 800 )I know they inflate the numbers a little but guys in the know that have been in my car say that its pretty close so I would have to say alittle of verified and alittle estimated.

vinniekq2 02-23-2013 12:54 PM

varified
 
Quote:

Originally Posted by jtz55 (Post 1649631)
Vinnie its the same motor chp built a few years back called the impersonator .they claimed 425hp and 525 ft lbs .u can look it up just do a search on it .was june 2003.anyway I built mine to spec just a little bigger carb(mines a 800 )I know they inflate the numbers a little but guys in the know that have been in my car say that its pretty close so I would have to say alittle of verified and alittle estimated.

using equal or better parts Im sure its 100% Thanks for the answer

Mr. P-Body 02-23-2013 03:07 PM

I use Performance Trends Engine Analyzer "Pro". It's a decent simulator. We use it primarily to plot power curves and anticipate results from changes. As for the "peak" numbers, I've seen it anywhere from dead-on to 15% "high" based on engines that went to real dynos. So take the numbers with a "grain of salt". I'd be willing to say they're within 10%, reliably.

When I saw the XE256H cam listed, I realized the "guessing" going on was based on smaller engines or larger cams. I've used this cam in both small blocks and Pontiacs extensively. The 400 Chevy "likes" cams more like the Pontiac than the 350, IMO. This cam will have pretty much a "dead smooth" idle in a 400. Stock converter is fine.

I "assumed" Performer, as he mentions Edelbrock, and RPM isn't appropriate for this cam. The 650 carb IS a bit small, I agree. But with this cam, it works to the "curve" the 400 has. I also "assumed" 1 5/8" headers, "open".

Following are the numbers generated, using the real data for all the parts, 93 octane gasoline, 165 deg. test temp, (note the program assumes "perfect" air and timing).

Peak torque: 482 lb. ft. @ 3,500 RPM. Over 400 @ 2,000. Flat curve. Still made 440 @ 4,500.

Peak HP: 377 @ 4,500 RPM. 322 @ 3,500, 358 @ 5,000. Nose-dives after 5,000.

Calculating to 9.56:1 static compression and dynamic compression ratio of 7.60:1, and estimated vacuum at idle, 17.7". It doesn't "like" an aggressive spark curve until 4,000 (shows "spark knock" under that).

Based on all this, I'd say the torque numbers are a bit high, but HP numbers are a bit low. Having used that cam in several 400 Pontiacs with stock heads, the curves fall "in line" with an engine of this displacement. The Pontiac will make a little more torque and a little less HP, but the ranges are the same. For those unaware, the Pontiac and Chevy 400s are close enough in bore/stroke and volumetric efficiency at these speeds, the data is "good" for either. The longer rod and taller deck makes the Pontiac more of a "torque" engine, and the shorter rod and good heads make the Chevy more of a "HP" engine.

I would say this combination would be dynamite in a heavier car for "sporting use", not racing or serious performance. It might get pretty decent gas mileage, too. Even though I'm well known as a Pontiac "bigot", I'm not stupid about Chevys... (:- The 400 has SERIOUS potential when properly built.

If you want to "move the power up" just a bit, and still enjoy GOOD low-end, use XE262H instead. The 750 carb with that cam would really wake it up. 1 3/4" headers would be called for here.

Sounds like a nice street engine, either way!

Jim

jtz55 02-23-2013 03:44 PM

Quote:

Originally Posted by vinniekq2 (Post 1649694)
using equal or better parts Im sure its 100% Thanks for the answer

no problem Vinnie I should of stated that we were a little more of a complete rebuild than just a intake and a cam .with the kb pistons and 64 cc vortec heads the scr was at 9.5 .

don't know if the OP is upgrading the rods and pistons .the comp.on those stock 400's were about 8.5 with a dismal quench. heads were junk and a 2barrel carb,not exactly a big HP combo.think I recall f-bird saying he had a high HP version out of a 70 something chevy but cant remember what.

smith9300 02-23-2013 04:43 PM

Thanks a to Mr p that is a very good help but yea I have thought about getting that cam insTed and I prb will before its all over with


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