I know about his car (who doesn't ). And the nickname for it (by them, not by me) is the time bomb. I want to spray the crap out of mine, and not worry a bit about the bottom end. I cannot speak for what others choose to do, and it's not my place to sit in judgement of what someone else does. If Jason can get away with running the stock crank, then more power to him. It's not something I choose to do (nor would most others here building for max power I would guess).

My car is a pure street car, not a trailered race car that comes out when the weathers nice. It's gotta be able to drive to the track, lay down a serious number, and drive BACK home. Everytime. With the stock crank, when you want to run 12's, it's no big deal. Go bottom 11's and your pushing your luck. Spray your way into the 10's, and you are definately on borrowed time, and I personally don't want to spend the cash on machine work for a block that will more than likely be trash if the crank breaks. It's just plain common sense to upgrade the crank along with the rods and pistons. Sorry if my view on it doesn't mesh with yours. I'll betcha that if you duplicate that setup (ross pistons, Eagle H-beams, stock crank and ARP hardware), spray 300 on it time after time and DRIVE it (as in every day daily driver) then your going to be walking in short order, and I invite ANYONE to tell me different, but your going to have to provide a better reason than saying someone else did it, so it must be fine. Lucky, yes. very very lucky if it lives.

No flames intended to anyone with this post. Just another view..

Dave C.

 

The reason I posted about spending $400 is because I've been down that road with stock mains on my last 355 with about 450 rwhp and when I took the motor apart to do my 385 the Crankshaft was cracked and the rods and crank had been twisting tearing up both main & rod bearings. You may get away with 2-bolt mains but as I said before why take the chance especially if you are are going to the track once in a while.

 

Why I posted that, is because everyone seems to think that 4 bolt mains are a necessity no matter what.

As far as I'm concerned with my own motor, a forged bottom end with 2 stud mains will work just fine, and hold up constantly to a 200 shot while being daily driven.

 

Thought I would chime in here as I have some experience with nitrous on a 2-bolt.

My experience with a 2 bolt 327 has shown evidence of main cap movement while running a 175 shot on the engine. It was a basic stock crank & rods, forged pistons & stock 2 bolt block with stock fasteners. I was turning it to 7200, but the shorter stroke of the 327 should have lessened the loads significantly over a 350 or 383.

After driving the car for 1 year, (this was my daily driver w/ 4.56 gears) I pulled it apart for a new set of rings/bearings & the cap/block mating surface was shiny, meaning the caps were moving slightly. The caps were registered tight in the block when built, so this was not from improper clearances etc., but from lack of clamping force. It never broke, but was probably very close to failure. This combo was approximately 550HP.

I would strongly recommend that at least upgrade the bolts to ARP type fasteners or studs. Remember that this may require align honing due to the different bolt clamping forces running up your costs.

Remember fixing the damage always costs more in the long run than doing it right the first time.

 

there was some one running over a 1000 hp with a two bolt block.

 

Well put it this way.

If you break the bottom end, or spin a bearing it's going to cost you more than the conversion to a billet 4 bolt main assembly to fix. Lonnie has some good advice.

On that note, 500hp is about the limit for longevity on a 2-bolt bottom end with main studs in it. Spinning main bearings is not a good idea, but to get over 500hp (430rwhp) usually takes more money in the heads than most guys do. Spend the money up on top until it will make more power than the bottom end will handle.

IMHO if you have a forged crank you should have a set of steel main 4 bolt caps on your motor too. Why risk a $500+ crank, a $200 crank is one thing (and will hold the power of a 2 bolt setup just fine) but the more money you have to loose in the bottom end if it breaks means that the 4 bolt caps are needed more and more.

Boost and N2O require that the block and caps are actually stronger than a NA setup so make sure that you take that into account.

One thing I can't stress enough is the Lemming syndrome, where just because one guy does it everyone thinks it's a good idea. BTW Lemmings don't actually jump off a cliff together to their death. The population fluctuates from overpopulated to almost extinction in areas because of their breading, predators and lack of shelter. So even Lemmings are not that stupid to keep doing the same dumb thing another one does.


Bret

 

And I have a key to the elevator in your high school I can sell you for $10.

1000hp in a 2 bolt block without a 4 bolt main conversion is not going to last very long. Maybe 1 pass.

Bret

 

as Bret's post implies, there is no certain hp that will necessarily Anstantly mandate upgrading to stronger bottom end parts. But as you come closer and closer to the absolute elastic limit the service life of the weakest link becomes shorter and shorter. I don't know how long a stock 2-bolt setup would last with 1000hp in a drag race setting, but it wouldn't be long.

OTOH, I see a lot of people with billet 4-bolt splayed mains that don't "need" them. Still, better safe than sorry. There was some evidence of "movement" in the caps on my last teardown. The motor was in the low 700rwhp range and I was using straight 4-bolt iron caps. This years motor will have straight 4-bolt steel caps. Well see how it works. The guy who does my block work swears that straight bolt caps are better on modern production castings.

Rich Krause

 

I'm not EVEN going to touch this one....


SStrokerAce:

So what do those little suckers taste like? hehe. JJ

Dave C.

 

Smokey says it ain't about the lack of clamping force. The bearing ends try to move together when they absorb impacts through the rod.

 

Okay, now we're getting to what I wanted to know. This car is my commuter/daily driver so I want a wide powerband and I need to pass California emissions. I don't expect to ever make much more than 400 hp so I want to avoid spending for stuff like forged pistons/crank and 4 bolt mains if they are unnecessary. Thanks, guys.

 

You got me.



Good pistons and rods are usually a good idea. Rod bolts are a must so just make sure you pick your parts wisely.

 

I just researched this topic a week ago 4 bolts are need on stroker due to more leverage being put on the caps. As for your set up why not get them cost 300 bucks and they are really not that hard to put in your self if your going to spend 500+ on a crank, 500 bucks on pistions, 400 on some nice rods then only run 400 hp then imo you just wasted tons on cash on stuff you dont need. Leave forged stuff for the big boys(650+hp).

 

The splayed setup is stronger because the load is supported in 2 different planes instead of 1. This is why the LS1 used horizontal bolts in addition to the regular vertical bolts. A splayed bolt does what a horizontal bolt can do. The main objective is to keep the caps from moving at all.
With that being said, I would install them if you can afford it. If I ever break my motor, they will be installed, along with more cubes. So far there have been no problems
How about using a stock cast crank with 4 bolt mains? Bet it would work pretty good.
Note: Milodon makes ductile iron caps too.

 

Billet steel caps are the best way to go. The B.S. about them not expanding at the same rate is horses**t. The difference in expansion at 225deg (where the block never even gets too) is about .0002. I've pulled stock 4 bolt nodular iron caps off a high 400rwph car and they were litterally in 2 pieces. The 4 bolt blocks are better than the 2 bolt ones, but the best way to go is a 4 bolt billet steel cap.

A 4 bolt conversion is one of the more difficult things to machine. You need to have access to a line bore which is not a common tool. A line hone to finish off the line bore and a mill to get the new bolts holes into the block, so it's far from being a do-it-yourself job.

The RPM and HP are what is going to cause problems with the main bearing caps, not so much the stroke of the motor. If that was the case then a 400 would always have had 4 bolt mains. Since it also had a 3.75" stroke.

The best place to put the outer bolts on a 4 bolt conversion is the best place in that block for them. Splayed stuff works great on blocks with material out there for them, but sometimes straight studs are the way to go.

Bret