a main girdle or 4bolt conversion?

hi all,im building a 408w and im wondering if the 2 bolt block with a main girdle would be strong enough with a 200-300 shot of nitrous or would i have to convert the block to 4 bolt caps?
thanx

I'm not sure but I believe that the 4 bolt cap motors have thicker walls where the 4 bolts thread into. Just a thought. I myself have used the girdle's twice now.[img]/phpBB/images/smiles/icon_confused.gif[/img][img]/phpBB/images/smiles/icon_confused.gif[/img][img]/phpBB/images/smiles/icon_confused.gif[/img]

I'm utilizing ford motorsports billet aluminum (wish I would've went with steel, whatever), anyway, main stud girdle.
I ONLY pushed 577 hp last year, but have 610 this year. 418 cubes. 2 bolt main block. No problems whatsoever. Wing 'er to 7200 on a regular basis. (sometimes higher)..........[img]/phpBB/images/smiles/icon_rolleyes.gif[/img][img]/phpBB/images/smiles/icon_wink.gif[/img]
Haven't heard of many, (if any), 2 bolt mains coming apart.
Now, if you're adding 2-300 hp of juice, I can't swear that something won't come apart, but I know N/A it'll work......... My.002[img]/phpBB/images/smiles/icon_smile.gif[/img]
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I have been thinking about the same thing. I would like to add some insureance with a forged 418 or 408 in a good block to my curret setup (see MY CAR). I am a little concerned about the cast steel crank spinning at 7000 RPM that the new AFR 205 (ed curtis prepared)and 2" primary header (pro mustang)are going to require. If I was only running NA, I would not worry about the 2 bolt main with a stud gridle, but you all know the need to go faster, that's were the N20 comes in. Currently I am only spraying 100 shot and I would like to bump that to 250 shot. Should have thought about this a year ago.

I know you will need a block prior to 72 for the 4 bolt conversion. I am thinking about a sportsman block, then adding billet steel 4 bolt mains. I think this will handle about 1500 HP. Guys correct me if you think I am insane about that.

Mach....Wouldn't you be dollars ahead to go on and buy the M-6010-S351 for 1700.00 instead of the M-6010-A351 for 1200.00?

I know if your bank account is like mine, every dollar is precious....but, by the time you add the cost of new 4 bolt caps, the machine work to install them, you are going to be pretty close to the 1700.00 figure any way. Plus the A351 block only reccommended for .030" over bore verses .125" over bore for the S351.

Just my .02....and [img]/phpBB/images/smiles/icon_eek.gif[/img] not my money, I know.
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Just Smokein,

Roush racing has the A351 block listed for $845.00 so I was figuring it base on that. But I looked around today and everyone wants 1,200.00 like you said. If I can get the A block for the Roush price I will go that way.
Good point about the over bore. I talk with Ed Curtis the other day a he made 680 HP with the same setup that I am looking at. So I am think roughly 650 on motor and then a extra 250 of N2O. That would put me at 900 HP, so I would like a block that will handle 1000 hp. With that in mind do you think a 69 or 70 block converted to splayed 4 bolt mains would work.

If I am going to spent the money on an aftermarket block (DART or FPP) I will wait and build a turbo motor when the funding is there.

Jim

A buddy of mine pushed a 426ci 79' model block with a cut down 400 crank, Chrysler rods, and homemade main support into the 5's (5.92 @ 122) in the 1/8. This was using two stages of nitrous (around 350hp total) in a 3000lb coupe with a transbraked C4 and 3.73 gear. It had a 252/262 @ 0.050" solid roller and never saw over 6500 rpm. It used a WAY ported Victor Jr. and the old TFS Hi-Port heads that were ported about as big as they would go.

This was several years ago, but the engine held through two seasons of this abuse before he pulled it and sold it to another guy who ran it for a couple more to the tune of high 6's and low 7's (no bottle) using mildly ported World Products Iron Sr. heads.

Those 351W blocks are awfully strong. Their main webbing and bolts far exceed the power handling capacity of a 302, or small block Chevy. They use nice, beefy 1/2" main fasteners, where the Chevy and 302 just use 7/16" units. They hold up WELL. [img]/phpBB/images/smiles/icon_smile.gif[/img]

Good Luck!
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Just Smokein? hahahaha actually thats a cool name[img]/phpBB/images/smiles/icon_lol.gif[/img][img]/phpBB/images/smiles/icon_lol.gif[/img][img]/phpBB/images/smiles/icon_lol.gif[/img][img]/phpBB/images/smiles/icon_lol.gif[/img][img]/phpBB/images/smiles/icon_biggrin.gif[/img][img]/phpBB/images/smiles/icon_confused.gif[/img]

Any 351w block with a pre-74 prefix has the flat rails. These blocks are also about 10 lbs. heavier than a D4 or newer block and a bit stronger. As for holding up, all 351w blocks are strong, but at 900 hp you certainly have to consider how much you are willing to leave to chance[img]/phpBB/images/smiles/icon_rolleyes.gif[/img]

Steve

They better hold up, I'll keep you guys informed. As I should be cranking it up this week.

408w 600+ on motor +250shot[img]/phpBB/images/smiles/icon_eek.gif[/img][img]/phpBB/images/smiles/icon_eek.gif[/img]