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Old 09-21-2007, 11:45:29 PM   #1
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400 sb bored 40 over or a dart little m 434

I have been going back and forth and since I am in no hurry thought I would post to see what others thought. I have a 4 bolt 400 that had been decked, bored 30 over, the mains line bored and all the usual stuff. It had forged pistons and some dart replacement heads that had some mild porting with a fairly large hydraulic cam. The problem was that the cam wiped a few lobes (most likely due to the heavy springs and improper break in) and instead of being taken out of service was left in the car for some time. Needless to say it was driven hard and put away wet! Now some 10 years later I decide to tear it down with the wishful thinking I could reuse the pistons and such with out boring it any further. I knew it would need new bearings and such but instead the cylinder walls will need a 40 over to clean them up. I will now need a complete rotating assembly. I wouldn’t normally go 40 over on a 400 but the machine shop feels it will be fine since it will be used mostly on the street and will not be seeing any nitrous etc. I want to upgrade the heads to some AFR 210 with a hydraulic roller. I would like to keep the RPM at or below 7000. What I am going back and forth on is if I want to sink any money in this block when I could be putting it into say a dart block and turning it into say a 434. I know that the dart block with a forged crank / 4340 h beam rods and such would be much more expensive but the reliability and foundation for more would be there when and if I needed. On the other hand I have used plenty a stock cast cranks and less expensive parts and never had a problem running them hard on the street. This will be the first time I want to build some real power that wasn’t your average 400 – 450 horse engine. So what would you do, put it towards the dart or just polish the turd so to speak and build off it?
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Old 09-21-2007, 11:55:43 PM   #2
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if you have the $ go with the dart block you won't regret it.
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Old 09-22-2007, 12:38:48 AM   #3
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If you can swing it, I'd definitely go with the Dart block.
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Old 09-22-2007, 10:21:59 AM   #4
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Blocks have gotten so much better it's not even a decision to think of any more. If the money is there, the block is well worth it.

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Old 09-22-2007, 10:57:52 AM   #5
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ONLY because of what you say as far as it being just a street motor, I can see why you are fighting your head on the decision. Without a doubt the aftermarket block is the way to go for reliability. Especially if your looking at the 500-600+HP range. But a 400, hydraulic roller, little 210 heads,, you should top the 500-525 mark, but I doubt much more. The stock 400 casting will tolerate that. The 817 block is noted to be the softest of the three, and the 511 4bolt being the most desirable OF THE 4BOLT blocks. Not to be confused with a 509 casting fitted with billet splayed main caps. I'm sure you have heard the 400 main web deal. So it's all a gamble. Just is a matter of how much your willing to toss out there on the table in the hopes it survives.

IMO there is a huge difference in a street motor that may be capable of 500HP on demand, and how often that potential is really used. 99% of the hot street motors are cruised around tapping less than 10% of it's potential. That occasional stab at the throttle that is just to keep those pesky imports from buzzing around your head (like flies around a horses @$$,, I don't know what the attraction is there). Anyways, if you were considering track time a couple of dozen times a year, then there would be no question IMO, you NEED a stable, aftermarket platform to protect your investiment. But 100% on the street and not some foolish street racer... I'd be tempted to gamble on a production casting IF it sonic checks OK.
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Old 09-22-2007, 01:05:00 PM   #6
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He, He!!

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Old 09-24-2007, 02:57:15 AM   #7
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Marv you have such a way with words LOL. You are pretty much correct when you say this will pretty much be a street only motor. I don’t know if I will ever do any open track days but you never know. I would however do a few passes in the quarter, how many, well probably not a lot. I do want to have the ability to put miles on it whenever I want. More than just to the local hang out if you know what I mean. Money is always a concern since I have a lot of buying to do for the rest of the car. It may take more years than I want to finish it but I plan on only doing this once. It seems as if the 400 could do the job considering your example of using only 10% but it does have its limitations. You made mention to the heads being small. I am guessing that larger heads could be used with less cam duration to reach same objected horsepower? Will this also help make a fatter torque curve? This car will be heavy so I want to retain as much torque as possible in it’s prime operating range without killing the top end.
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Old 09-24-2007, 03:20:25 AM   #8
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Those AFR 210's out flow alot of heads that are bigger giving you flow and velocity. That will give you power and the torque you want for a mostly street driven car.
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Old 09-24-2007, 05:59:51 AM   #9
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Originally Posted by Marv D
. That occasional stab at the throttle that is just to keep those pesky imports from buzzing around your head (like flies around a horses @$$,, I don't know what the attraction is there). Anyways, .
Marv some folks might just thing your just to ole fashion get with the times my man..biuld a Ricer pierce your nose eyebrows and wear your pants down to your knees that is considered cool now a days..LMAO and don't forget ya! gotta have one of them tribal tattoo so you know what clan your from
the chicks dig that..
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Old 09-24-2007, 06:07:50 AM   #10
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i was in the same position as you... exept less cubes. ive got a 1992 4 bolt 350 short block. i was thinking of going with a scat rotating assembly, but i think ill test how strong my stock one is.

my motor will have around 450hp, it will never see past 7000rpm, but it will see 100 shot of nitrous. im going to bring the rods to school and polish them...

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Old 09-24-2007, 08:39:40 AM   #11
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I would surely go with the after market block if the money is there as there is better power to made just using a block that will be closer to blue print locations over a stock block.

We have seen lifter bores out as much as .025 on some GM blocks and with a flat tappet cam it not a big deal as the lifter is riding on a flat surface now by going to a roller cam and the lifter bores are off .025 and there off .025 from intake to exhaust not front to rear, Now your dealing with actuall lifter and cam center lines and and if ther off that changes the seat iming event a ton now times that by 16 lifters.

Thats why Joe Sherman has see up to 40 horse using a good after market block over a stock production block.
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Old 09-26-2007, 11:33:24 AM   #12
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Marv I was hoping you or someone else might shed some of their infinite wisdom on the larger heads vs. smaller cam duration I asked about. I know the larger heads have the potential to flow a lot more air and that they will make the biggest power. What I am not sure about is how larger is too large for a mostly street driven engine that rarely sees the right side of 6000. I was always led to believe that if the ports are to large and if you were using a single plane intake that unless it was turning enough RPM to take advantage of that set up, you would kill the low speed torque and have a much less usable combination. I am assuming that the air velocity would be slower causing much of this problem? I have heard that the new AFR eliminators were to help in both areas (more flow with a smaller runner)? I have a ton of what if question in regards to cam selection but I will start with the head vs. cam duration thing first. I just want to be able to have my cake and eat it too in regards to torque, horsepower, and 6500 / 7000 red line in a 3500+lb car driven on the street LOL
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Old 09-27-2007, 10:00:38 PM   #13
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I have a 400 509 block,bored over .060,with no issue,and it runs nitrous shot as well,cast crank,powdered rods,hyper pistons,comp cams hyd cam.510 lift ,with sportsman heads,air gap intake,750 d/p.
I'd save the money on the dart for something else.

like tires....
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