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Old 12-05-2004, 11:50 PM
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SBC400 options

Hey guys, I'm new to this forum and the world of gearheads.I own a 66 chevelle (nice driver) with the original old tired 283, th350 (not original), and 307 rear end. What I have in my garage is a (disassembled)SBC 400 out of my 77 blazer that blew a head gasket and cracked one head.At 110,000 miles it was rebuilt and bored out .30, then driven another 75,000 til it started to use oil and ultimately spewed steam.Would like to build it and use it in the chevelle after I have it either bored to .40 (new pistons) or just honed to use existing pistons (dished).
My objective is to increase the compression just enough to support a cam that will give me a noticeable lope yet idle nicely, create 300-350 HP, and not overheat. NOT A RACER. Which route would best serve to acheive this and what combinations of HEADS,CAM,PISTONS,CARBS might you suggest? Is this project doable? Or should I consider other options (crate motors,283 rebuild)? Any suggestions would be much appreciated as I have been visiting your site for some time and have come to relize the wealth of knowledge here is invaluable.
Bill

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Old 12-06-2004, 06:22 AM
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Bill,

I would have the 400 block checked and evaluated. If it was "spewing steam", that is a concern. Hopefully, it was just from the cracked head...probably an 882 casting.

As for compression, you will probably want to stay around 9:1 or a little higher. The mid-70s factory 400s, with a four barrel, put out a staggering 175 hp, with 8.5:1.
I'd suggest finding a decent set of 76cc heads and then decide on a piston-heads combination to get you to your desired compression.

As for a cam, a Comp Cams XE262 or XE268 might be considered.
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Old 12-06-2004, 09:18 AM
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A lot will depend on what your budget is and exactly what that 400 needs done to it. If you really want to use that 400, I would definitely have the block checked throughly by a competent machine shop before you make the decision to use it or not. If the block is ok to use without any major defects, by all means build it. Cubic inches make more torque which is what you will want in a heavy car with somewhat tall gears.

If I was to build a 400 for what you desire in that style of chassis, it would be along the lines of this article:http://www.chevyhiperformance.com/te...148_0306_406/.

You can use the stock 400 rods which would not require the small base circle cam but be sure and use ARP rod bolts in them and have them checked over. I would also substitute a 750 vac-sec in place of the Holley 750HP that was used. Whatever you decide, build the motor for torque and you will not be disappointed. Good luck!
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Old 12-09-2004, 12:01 AM
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400 rebuild

Nice article but a little to rich for my wallet. One of the cost saving steps I am considering is to have the block honed (provided it can safely be done) thereby saving my stock rods and .30 over pistons. I'm not sure if this is such a good idea, but if I'm going to spend money I'd like to spend it on some better breathing heads (my old head is cracked anyway)rather than the bottom end that appears to be in pretty good shape. Does anyone agree with this aproach or should I just go ahead and bore it to .40 and get new pistons? I am taking it in to a shop next week to determine weather either one of these options can safely be done, but any opinions or suggestions on this forum would be welcome.
BILL
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Old 12-09-2004, 01:44 AM
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If the motor has 75,000 miles on it I suspect there will be a fair amount of bore wear. I would suggest )assuming there are no deep scored in the bores) getting it bored to .040 as you mentioned, this will insure that your rings have a good life.
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Old 12-09-2004, 12:15 PM
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If its one thing you shouldn't spare money on its the bottom end. Thats your support system. You wouldn't spare money on the foundation of your house would you??
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Old 12-10-2004, 06:36 AM
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It most likely will need bored. The thrust angle of a stock 400 is a little more severe than than any other sbc due to the shorter rod and the long stroke. Definitely make sure you get the bottom end built right and have everything checked so you got the correct clearances. When I built my 400, I thought .030 over would clean it up but had to go .040 so get the pistons after you have the machine work done. Make sure when you get the pistons that they will allow you to run the octane you want with the heads you desire. 76cc heads will allow a flat-top and 64cc you will need a dished. Either combo will allow for street gas.
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Old 12-10-2004, 02:09 PM
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you don't have to increase the c.r. for the cam to sound good and run good.call nay cam company and they'll help you pick a cam.after that if you want a little better sound and perf. get a set of 1.6 rockers.the rockers will give your valve another .030" lift.they cause the valve to be opened sooner and stay open longer.like using mushroom lifters.before anyone goes crazy here i didn't say the cam change's but the mechanic's of the rocker.

if you look in the knowledge section here you'll see it explained better.
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