Okay, here's the deal. Picking up a bare 400 SB for $150. Has the main caps bolted to it.

A- do I need to have it aligned honed if I use a new crank in it?

B-How fast can a nodular cast crank be spun before endurance becomes an issue? Is 6500 RPM practical?

C- If you had to choose between the lightness of Hyp. Pistons, or the rugged strength of forged slugs, which would you choose? Remember, I'm talking 6500 RPM here.

D- Are there rod bolt clearance problems with the cam if 5.7 or 6.0 inch rods are used? How do I correct this, and on which pistons do they become a practical problem.

About how much would it cost at a machine shop if I were to get a rotating assembly internally balanced? What's the average rate? Mind you, if I went internal, I would be used the forged crank, 5.7 or 6.0 inch rods, and Hyp. or Forged pistons.

Thanks,
Slow Iroc

 

the main saddles can be out of align. This is not the same issue as the crank being straight. A straight edge across the mains will tell.

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B-How fast can a nodular cast crank be spun before endurance becomes an issue? Is 6500 RPM practical?

It can probably live as high as 7000. I know stock 400 cranks that go 65 everyday. The question is will you be making HP up there or just twisting it?

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C- If you had to choose between the lightness of Hyp. Pistons, or the rugged strength of forged slugs, which would you choose? Remember, I'm talking 6500 RPM here.

Price is the main factor.
Been there done that. I had a set of KBs with 5.7 rods and 1/16 inch top ring in the last 400 (i forget the number I think it is a KB135). It will take you several weeks to file fit the top ring for the KBs. It requires about .032" clearance. They are about 235 bucks from summit. A SRP piston will weigh about 100 grams less and use a pin that is about 40 grams lighter. They need a top ring gap of about 020" and are 465 bucks.

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D- Are there rod bolt clearance problems with the cam if 5.7 or 6.0 inch rods are used? How do I correct this, and on which pistons do they become a practical problem.

There are always rod bolt to cam lobe clearance problems on 400s on rod numbers 2 and 6. Use an I beam rod with cap screws and it is not an issue.

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About how much would it cost at a machine shop if I were to get a rotating assembly internally balanced? What's the average rate? Mind you, if I went internal, I would be used the forged crank, 5.7 or 6.0 inch rods, and Hyp. or Forged pistons.

Most combinations can be internally balanced with either 5.7 or 6 inch. I think it would be easier to do with lighter parts (less heavy metal). I just spent 125 to get a 400 externally bal. There is really no reason to go internal unless you already have the flywheel and harmonic balancer for internal.

Externally balanced versions of these parts can be purchased for less than the cost of the mallory metal that you will need to go internal.

 

jcb, I wouldn'y trust stock connecting rods to 7000 rpm... remember that 400 rods are weaker around the journal - they had to machine more off to make it clear the block. ARP connecting rod studs will help some, but I wouldnd trust those rods past 6000 rpm.

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."

 

You must align hone whenever you switch to studs and away from regular cap bolts.

Cast cranks have been blessed to 450+ HP, 7000 RPM duty in circle-track racing on many, many occasions. It's the rods and the rod fasteners that seem to be the weak link. If you are going to nitrous this engine, however, consider a better crank. http://www.dallasexportsales.com has many deals for cranks that range from $150 to $500 that will support many levels of performance, up to 750 HP.

------------------
Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.

 

I would not use stock rods for any performance mod. But i have seen it done. The guy uses stock bottom ends and 250+ hp nos shot and it lives.

I do agree in concept that align hone should be done when studs are installed. But I don't think it is required. I have seen many combinations that did not hone after stud install and it works fine. ARP recomends it but I don't think CP does (they also make main stud kits that I have used).

I just called the machine shop where i got my block work done and they said they do not automatically alignhone when studs are used. But that I should check the clearance with plastigauge. Told them I was going to mic everything and they still said I should check with plastigauge. I really don't understand why they feel that way, but i am hoping that this 2K shortblock is the last for a while sooo....


[This message has been edited by jcb999 (edited April 09, 2001).]

 

A-no. Its not absolutely necessary when doing studs vs. bolts either, but checking the cap alignment just to be sure couldnt hurt. Thats why most places recommend it. When changing rod bolts in any case, honing them is a good idea because rarely do they line up right after changing bolts.

B-I think they covered it. Is this a once in a while deal, or are you going to run a supercharger and keep it there all day long?

C-Cost is always an issue, so is the power adder question. If you have any thoughts of using NOS, a turbo, or a supercharger, dont waste time with the hyperglass pistons. They dont take well to fuel problems.

D-Since you are changing rods, and talking about 6500rpm, go with an aftermarket rod with cap bolts.