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Old 07-11-2002, 08:30 PM
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Post 2 bolt vs. 4 bolt mains

Ive got small block 400 im planning on building up to be crazy. Its going to be a full floating roller engine, fully balanced and blueprinted and all forged with aluminum 5.7 rods, 2.08 dart aluminum heads. My problem is that im going to be putting a supercharger on the engine but Ive been told i need a 4-bolt to handle the beating. My problem is that my block is a 2-bolt. Will the 2-bolt hold up or should I get the block machined to a 4-bolt? Its going to be raced on weekends and driven daily. Any info will help, thanks
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Old 07-12-2002, 06:42 AM
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If you are going to supercharge the engine, you are going to have to make it into a 4 bolt. It sounds you are going to sink a lot of money. You might as well do everything right the first time instead of going back and keep fixing everything later.
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Old 07-13-2002, 05:18 AM
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I've heard that having a 2 bolt block machined to a 4 bolt and putting splayed 4 bolt main caps on it is actually stronger than using a stock 4 bolt block because the outside bolts go in at an angle instead of strait down. Learned that right here on this site. I agree with Andrew...if your gonna go as far as putting a blower on, you might as well not take any chances and do it right the first time. Good luck, HRS10
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Old 07-18-2002, 11:51 AM
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Would a studded 2 bolt work?? Ive been told by a few people that a stud kit would hold up. They say that the stud pulls from both sides instead of one side (like a bolt) making the assembly stronger. One person told me that they have built several 2 bolt blower motors and haven't had a problem. Whats your opinion??
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Old 07-18-2002, 02:48 PM
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Here is a little food for thought. I use to run a Automotive Machine Shop and I have taken a 350 SBC block and mounted the block in a bridge port and tapped out the mains too take 1/2 inch ARP studs,You also have to machine out the caps to take the 1/2 inch studs. I used the ARP studs for a B/B Chevy they are 1/2 inch, after you machine out the caps put the mains together and check the line bore on the mains. I have used these blocks for stock car motors and pulling tractor motors with NO problem.I even did this to a (307)block for a pulling tractor and as far as I know it is still alive and doing well. If you don't really want to go this far and really want a 400 4 bolt main block give me an E-Mail as my son has a 400/4 bolt main block For Sale. I will have to find out what he wants for it.
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Old 07-18-2002, 09:40 PM
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Stud it and don't worry about it. How many crank shafts do you see fail on the mains? They fail on the rods always. Spend the money on the rods and a good forged crank.
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Old 07-19-2002, 05:22 AM
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If you are truly going to blueprint the block,then you will be align boring it.So if that is the case,why not put the billet splayed caps on? If you are setting the block up in a Bridgeport to drill and tap the 10 holes from 7/16" up to 1/2",then I always prefer to just drill and tap 6 holes for the 4-bolt caps.Yes,it is more work to fit the billet caps to the block;But,like I said,if you are going to align bore the block anyway,why do it with 2-bolt caps instead of 4-bolt caps? Lastly,lets not forget about the fact that when you are done playing with this piece of iron,and you decide to get a new block,you can sell the 4-bolt block for a lot more money.
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Old 08-03-2002, 07:51 AM
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all of the above post have excellent ideas.
so far what I've seen and had experience with the 400 block would be shakey no matter what you do to it. Most of these things have been used and abused, gotten toasted a few times, frozen other times, pulled big trucks and driven by numbnuts until death. Keeping the bottom end together is one thing but when FI and carb engines split cyl walls frequently I think I would go with a 350 block and all of the block toughining tricks. Studs are mandantory especially the larger 1/2" ones. head studs too. o-ring the block for the blower too. head gaskets are probably going to be the biggest problem. there are solid copper gaskets available but for the street you will really have to seal these good as they do leak water around the edges sometimes. doesn't hurt anything if you keep the rad. filled. Turn up the wick on the blower drive for more hp...it's easy. psi = cubic hp & cubic torque. You don't realy even need super ported heads if can live with being a bit down on power. save your cash for a good set of alum heads and good valves. By the way you need a very large set of headers. more the better. forget 1 5/8 tubes. 1 3/4 or larger is better. Too much back pressure will blow gaskets. If you have 3" from the header back you won't be in overkill. use the biggest f... ng flowingest mufflers you can find.
One more thing..go over to Sears and get a package of shorts at least one size larger, then go to Wal-Mart or Sam's and get the biggest package of Pampers you can find. The shorts will allow you wear the pamper more comfortably. You will need them with the wick turned up on the blower!!

bentwings
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Old 08-03-2002, 02:22 PM
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"They say that the stud pulls from both sides instead of one side (like a bolt) making the assembly stronger." I'm not sure what you mean by this but I think the real advantage to studs is that you aren't twisting the stud when you torque it (unlike a bolt). Also you don't run the risk of damaging the main threads in the block if you frequently pull the caps (blown motor beating bearings to death). If you are going to align-bore anyway (you are) then go with splayed 4-bolt billet caps. If you've ever seen an engine that failed due to caps you'll know why. And give some thought to how much street driving you're actually going to do with aluminum rods. Sounds like a fun combination! What's it going in?

The Vandal
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