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Old 09-11-2013, 09:07 PM
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Sbc 400

I bought a sbc 400 511 casting 2 bolt main double humped heads all stock lookin for some advice on improving top end would like to stay stock for the most part like crankshaft and bore what's a good cam, valves, springs, and lifters. Could I turn it into a roller motor with a stock crank and stock bore anybody got any tips on the build

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Old 09-11-2013, 09:52 PM
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If you take the engine apart and find out exactly what you have, there is no limit. Yes a roller cam can go in there.Camel bump heads did not come on that engine. To get the best match cam(depending on purpose) you need to know the compression ratio,piston deck height, and room for piston to valve clearance,,,
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Old 09-12-2013, 04:24 AM
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It's going in a 87 gmc truck short bed with a th350 behind it purpose just a hot rod I can drive around town then take to a strip and run a decent time nothing real fast it's goin to be my sons truck some day the motor came with a set of ram exhaust manifolds are they any good or should I switch to long or short tube headers and as far as the compression ratio piston deck height and piston to valve clearance ill got back to you on that if I wore to bore any suggestions on what size bore is good for a 400
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Old 09-12-2013, 07:47 AM
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Start by id'ing the cylinder heads you got. Look under a valve cover for the casting number. What is it?
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Old 09-12-2013, 08:11 AM
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Originally Posted by 87 gmc View Post
It's going in a 87 gmc truck short bed with a th350 behind it purpose just a hot rod I can drive around town then take to a strip and run a decent time nothing real fast it's goin to be my sons truck some day the motor came with a set of ram exhaust manifolds are they any good or should I switch to long or short tube headers and as far as the compression ratio piston deck height and piston to valve clearance ill got back to you on that if I wore to bore any suggestions on what size bore is good for a 400
There is no particular bore size to aim for.Only bore enuff to correct any wear,taper.& out of roundness.On the 400 block,less is better.
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Old 09-12-2013, 09:08 AM
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Barrel shaped bores

One thing to always watch out for is that the bores like to wear into barrel shapes due to the side-loading from such a short rod with such a long stroke and big bore. Check your cylinders, have it bored to straiten it out and bump yourself up to a 6" rod and pistons made for them. 400s love to run hot because the bores are siamesed. If it can be helped, don't bore it anything over .040. .030 is fine, even .040 is pushing it, anything more and those cylinder walls get very thin. They can distort, and it will always run hot.

Last edited by Speedshift_Sam; 09-12-2013 at 09:11 AM. Reason: Additional info
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Old 09-12-2013, 10:54 AM
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Start by id'ing the cylinder heads you got. Look under a valve cover for the casting number. What is it?
They are double humped heads but as far as casting numbers ill half to take a look
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Old 09-12-2013, 10:59 AM
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One thing to always watch out for is that the bores like to wear into barrel shapes due to the side-loading from such a short rod with such a long stroke and big bore. Check your cylinders, have it bored to straiten it out and bump yourself up to a 6" rod and pistons made for them. 400s love to run hot because the bores are siamesed. If it can be helped, don't bore it anything over .040. .030 is fine, even .040 is pushing it, anything more and those cylinder walls get very thin. They can distort, and it will always run hot.
The cylinder walls are good so it would be a good idea not to bore? Can I use a 6" rod and stock bore size pistons without having it bored?
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Old 09-12-2013, 11:56 AM
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Originally Posted by 87 gmc View Post
The cylinder walls are good so it would be a good idea not to bore? Can I use a 6" rod and stock bore size pistons without having it bored?
The cylinder walls have to be measured by dialbore guage to ck for taper & roundness,as well as measuring the pistons to be used to verify piston to wall clearance.These are things you can't see with the eye.The cylinders have to do more than look OK.They have to be the rite size & shape.The tools for taking these measurements are precision tools.If you don't have access to them,or,if you're not experienced in their use,I'd recommend taking the block to a machine shop to be cleaned,measured,& inspected.Yes,you can use stock bore size pistons with a 6" rod.Make sure you buy pistons with correct pin hgt for a 6" rod tho.You want a pin hgt of 1.125."

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Old 09-12-2013, 12:16 PM
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The cylinder walls have to be measured by dialbore guage to ck for taper & roundness,as well as measuring the pistons to be used to verify piston to wall clearance.These are things you can't see with the eye.The cylinders have to do more than look OK.They have to be the rite size & shape.The tools for taking these measurements are precision tools.If you don't have access to them,or,if you're not experienced in their use,I'd recommend taking the block to a machine shop to be cleaned,measured,& inspected.Yes,you can use stock bore size pistons with a 6" rod.Make sure you buy pistons with correct pin hgt for a 6" rod tho.You want a pin hgt of 1.125."
It's been cleaned and cylinders have been checked along with pistons crank and the heads have been cleaned too
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Old 09-12-2013, 12:20 PM
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I bought it with double humped heads good or bad idea to put them on or should I go with a different set of heads
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Old 09-12-2013, 12:27 PM
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Ok.I misunderstood.I thought you were goin by visual inspection only.Be aware that with 6" rods,your oil ring pak will be pass thru the wrist pin hole.You can also use a 5.7" rod to avoid this.Theres nothin wrong with a 6" setup.I just personally don't care for it.
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Old 09-12-2013, 12:33 PM
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Originally Posted by 87 gmc View Post
I bought it with double humped heads good or bad idea to put them on or should I go with a different set of heads
If i could,i would go with another head.Those are old & outdated.There are alot better options now.From Vortecs to very efficient aluminum heads of anything you could want.
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Old 09-12-2013, 12:39 PM
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I've built several 400's over the years and each one better than the last. Basic sbc rules apply, except they used a very short con rod due to the long stroke, because GM did not want to raise the pin height in the piston. I can understand they're thought here considering cheap cast production pistons, but this geometry really side loads the bottom of the bore. Secondly was the water passages were left out between the cylinders, (siemesed) differences being the small "steam holes" in the heads. If you have camel humps lets hope they were drilled. My opinion, ditch the 40 year old technology camel humps for a pair of vortecs, and drill the steam holes!! Use the longest con-rod possible, and pistons to match. Don't waste time and money hoping to stay with stock bore. If this motor has any miles at all machine the bores to true them up. .030 would be ideal for availability of pistons, and DO NOT excede .040! Don't go crazy with cam. Something like a comp 270 would still give decent low end and vacuum too. A decent radiator and shroud and I wouldn't expect maybe 5-10 degrees more than any other sbc. My last 400 actually runs exactly where my 350 was temp wise, same water pump and car. Regarding the heads, I switched from 64cc 202 camel humps (with lots of work done) to a cast iron aftermarket vortec style, and dropped 1/2 second off my 1/8 mile ET. These make big block torque so no need to try to spin it over 6000
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Old 09-12-2013, 02:31 PM
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Would aluminum heads help keep a 400 from running vs cast iron heads hold heat more than aluminum heads or does that matter
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