I'm gonna be doing my first stroker build and have some questions on the rotating assembly. The car is a street car with a little strip action, i have a stick and 4.11s. I have a good 350 block waiting for machine shop and have to order rotating assembly next. I really want to do a 3.875" stroke instead of a 3.75".

I priced out a few kits made by scat and sold by flatlanderracing.com. It seems i could get 3.875" forged 4340 crank, 6" H-beam or I beam forged rods, and forged mahl pistons with bearings for $1,400.

I could do a 3.75" stroke much cheaper and stay with scat 9000 cast crank, 6" I beam forged rods, forged flat tops for around $800.


questions:


Do i really need a forged crank for a street motor, or should i cheap out and go cast?
Unsure about I-beam rods or H-beam rods?
Is the extra cubics from 383ci to 396ci worth the extra $600 in cost?


I'm on a budget here but if the forged stuff is really alot stronger and i need it then I'll go that route. but at the same time that extra 600 bucks could go towards machine work.



this is my first real High Perf. small block so I'm still learning. I already have some protopline 200cc, 2.02, 64cc alum heads, and xs282s solid comp cam, 1.6 roller rockers, 750cfm speed demon, 1 7/8 headers. I want keep compression at or just under 11.1 and run a single plane intake.

Thanks for help

 

IMHO, if you are ever going to spray it, go forged. I assume you are not going to put a turbo or supercharger on with that compression. Street motor, I think you are fine with the economy route, make sure you have a machine shop balance the rotating assm.

 

Cheap rotating kits are generally externally balanced which is a no win situation. As for me I never do 3.750's

 

Look at it this way...everytime GM decided to up the HP in a motor they needed to warranty...they went forged. Why would we expect to make even more HP and only need a cast setup? Yes, cast have lived through lots of HP in the past...but these days the price difference isn't that bad. Stay away from any CAT branded junk or no name house brands. At least use Callies CompStar, SCAT or Eagle. Also go for an internal balanced setup because balancing some of the other stuff costs more than the crank did in the first place.


JIM

 

Looking at the cam specs shows that the intended power range is 2400-6800 RPM. That means you need a forged crank especially since you have a 4.11 rear end and can easily spin the engine to redline in any gear. That much RPM also means an internally balanced rotating assembly if you want the engine to live on the strip.

Talk with FlatLanderRacing about what you want to do with the kit you've chosen. Personally, I would go with H-beam rods for the added strength.

The extra cubic inches will make the engine easier to drive on the street (more torque in the lower RPM bands). Pump gas is going to be the biggest problem as you'll need at least 10.5:1 compression to compensate for the valve timing at lower RPM. Don't know exactly which kit you're looking at, but you're probably going to end up with over 11:1 CR with any machine work!

Good luck with your build!

 

you need to be careful when you do anything larger than a 3.750 stroke in a factory block especially with scat rods. they have larger rod bolts and there is a chance you could break into water when you have the block stroker clearanced

 

I build the 3.875's careful lower block grinding is OK. the 4 inch strokers with the big rod bolt ends requires half filling the block water jackets.

I don't advise 4 inch on any gm block. Save your money and buy the motown or darts and use a 4.125 stroker and make 441 or 447 ci

 

I have been considering purchasing a dart SHP block. they're about $1500 shipped and come with 4.125" bore which can be bored .060" safely, they have 350 crank journals, and are rated for 500-600hp. They are advertised as already ready for 3.75" stroke, but I talked with a builder at carisle who said he did a 4" stroke in a new dart SHP and it didn't need any clearancing!

 

so if I got the SHP block i would just need to final hone it and then I could assemble it without any other machine work? So i would use the 4.125" bore, 4.125" X 4" stroke or 4.125" x 3.875". i will call a few places tomorrow and ask about rotating asemblies.


the SHP block comes with 400 crank journals or 350.

 

You may want to check the main line and make sure its to the desired size, lifter bores may need honing and if you want a block with a 9.025 deck height that would be up to you whether to get it decked to zero or not.

All oil galley holes must be tapped with a tapered pipe tap.

 

Listen to Blockman, he knows these SHP blocks inside and out. You also may want to drop him a PM for a correctly prepped one.

 

So you went from budget stroked to forged 427? You can't let us spend ur money.

Though the gm race block 1 Oct seal at $1600 is pretty ready to go, finish hone, deck and clearance.

 

This is a link to a buddy in the process of building his engine using a preassembled 383 roller short block. Buying one this way can save some money and hassle in having machine work done. Mine is a 355 using the stock L83 forged crank and eagle H beam rods with forged floater pistons.
This is a link to see what he has done.
http://www.vettemod.com/forum/showthread.php?t=280

 

The fact that you are concerned with it NOW even before the build leads me to think you will always be concerned if you build it with the cast set up.
For the difference in cost it isn't worth the comfort and peace of mind the forged stuff will give you.
If you go with low end forged stuff (imports) I'd have the crank checked by the crank grinder for trueness and the rods for size. I've seen issues in those areas.
I've seen a large number of cranks that need turning to make the rod journals be made parallel with the mains.

 

Thats why I have been using the Callies rotators their journal sizing is spot on campared to the others mentioned, It would be hard for me to put a cast crank in an SHP block.

 

One thing that's normally true is you pay for what you get. Good stuff doesn't come cheap. Or the price would be higher. I've seen some poor stuff be imported and get used in builds. The entire engine is only as strong as the weakest part. If the RPM's are kept under control they last for the most part.
When you take into concideration the added cost of having the machine shop check everything and the comfort of knowing you have good parts and resale value of a car with an engine built good parts (take pics as it goes together ) evens out. To a point.
I suspect everyone on this forum is driving a highly desired car. I'd put an engine in befitting a corvette. I'm pulling out one Mondy that does not meet that level. Gonna build something special for it.
I have no machine shop costs so I guess it's easier for me to have that opinion.
Always balance a new build regardless of the parts you use. Balanced and proper clearences and basic mechanic experience or understanding and the outcome is usually good. A good machine shop is a must.
We made circle, back to line one, you get what you pay for.

 

Blockman recently did an SHP 383 for me with forged Callies internals and Mahls pistons. By the time your all said and done machining a GM block the SHP is not that much more money and you can do anything you want to it. I kept mine to a 383 to keep extra thick cylinder walls thereby minimizing cylinder distortion. I can't say enough good things about that block and blockmans work. The Callies stuff also seemed to be real good requiring no rework and it doesn't require a small base circle cam. Carl also balances everything himself as all the kits require some rework in balancing.

 

Why not go with the good 3.750 crank, offset grind it to get the stroke you want and go with small journal rods to help with the clearence issues.
Pistons may be a little high.
I understand the geometry of the long rod motor, but for a street driven engint I like a bit longer piston to help keep it stable as it begins to wear.

 

If your seeing pistons wear and have to use pistons with longer skirts I would say your doing something wrong or the pistons are not being fitted correctly!!!!

 

Dont cheap out, not worth it worrying everytime you really lean on the motor. Wait, save some more $ and do it once.