4 bolt mains or stud girdle

[Scremn]

I had purchased a 3.58 forged crank,but sold it and deciced to buy
a 4.00 forged crank.I wanted some opinions on the bottom end. Should
i install four bolt mains,which I can purchase from a friend or use two
bolt mains with studs and stud girdle.The car is mainly a street car and
for car shows.It will go to the track on occasion.My Demon is a 4-speed
and rpm will probably will not exceed 6500.The car has 4:56 gears in it
at the moment with 30 in tall tires. I plan on installing 4:30 gears this
spring.I am going to be running a street roller in the car.Thanks for your
input.

[Maco]

The 4 bolt mains should be enough for your application...........All the best Maco

[MrChemist]

Could we get a little more info, projected hp, any nitrous use? Just from what I have read, I would say use the girdle. A few people have said that installing the 4 bolt main kit can actually weaken the block .

If this is a true street combo (<500 hp and <6500 RPM) you really don’t have to have either, just studs would suffice…but if it were me, I personally think a little over kill on the bottom end is a good thing (just to be safe). I believe the girdle makes the block good to about 600 hp. Good luck with your buil

[dave571]

Originally Posted by MrChemist

If this is a true street combo (<500 hp and <6500 RPM) you really don’t have to have either,

I agree


Small blocks aren't well known for cap walk or anything like that.
With the long stroke you will have high piston velocity, and rod upgrades are probably more important (assuming you haven't done so already

[BJSracing]

I'm with what is being said already.

[turbododge]

I have done the 4 bolt conversion, and it is not a good thing. I think the downsides far exceed the benefits. Your combo really shouldn't need it. If you get hot enough to need 4 bolts, really should be into a race block anyway, to get all the strengthening.

[5spdcuda]

The problem with putting 4 bolt mains in a production 2 bolt main block is that the two extra outboard bolts have to go into an area of the main web that wasn't designed for them. There just isn't a lot of meat there. Considering how you describe the intended use, I would use a set of ARP studs with the stock caps and not worry about it. The increased piston speed with the stroker is something to consider, as was noted high quality light weight pistons, pins, and rods should be used.

[djswwg]

All good advice here, to which I will add a bit of mine, for what it's worth. Piston speed at 6500 rpm with a 4" stroke will be way over 4000 f/m and you have a manual shift trans. Lots of stress is gonna be on those main caps as you bang thru the gears! Use a girdle, here's why. No machining is required, and you are basically tying the whole bottom of the block together with a hard steel plate. As 5spdcuda says, the xtra bolts go into a "light" area of the block, so why weaken it further by drilling out material for the bolts? Not a good idea. Get a good girdle kit and you should have a strong enough bottom end for what you're doing................djs

[jelsr]

I gotta go along with the girdle also. The biggest problem with the long armed crank is trying to twist the block under big torque numbers. The girdle would help this by making the block assy more rigid as well as the advantages already mentioned.

[djswwg]

another thing you may want to consider is a partial block fill. don't go crazy, especially on a street motor, just fill to the bottom of the frost plug holes to help stiffen up the bottom end................djs

[Maco]

Great idea, I never thought of that......Maco