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Cheap 4.375" Stroker BBC Build

10K views 8 replies 5 participants last post by  ericnova72 
#1 ·
The title may sound like an Oxymoron but here is what I have. A couple years back I wound up with a free 4.375" stroke forged Eagle Crank (long story). Last year I got a free, low hour 454 out of a boat with a broken block but good oval port open chamber heads (and rotating assembly, intake, sheet metal, etc). A couple of months ago I got a free 454 that had over 200,000 miles on it and has never been rebuilt. I also have a '72 Chevy K20 (bought for $100 from a neighboring rancher) with a worn out 350.

So right now I have $0 into all my parts. Obviously the cheapest route to get a running engine would be to bore the worn block .030" and build a mild 454. But, I kinda want to use the 4.375" crank (who wouldn't?) As you might be able to tell though, I am not a fan of laying out large sums of cash. To use the longer crank, the only extra money I would need to spend is for rods, pistons (might be extra, might not), and balancing.

This engine is going into a truck - not a race truck, just your average flatbed, cow feeding, pivot fixing, farm truck.



The engine will never need to rev above 5,000 RPM and might not even break 500 horsepower - therefore I think a set of I-beam rods will easily do the job. But which ones? From a clearance standpoint, should I use:

These Scat Rods?

Or these Eagle Rods?

So if I've got a 4.375" crank and 6.385" rods, what pistons do I need?

I would like to end up with the compression ratio right around 9:1 so I can burn the cheap 85 octane garbage they try to pass off as gas. Obviously cast pistons would suit my needs just fine, but are they available? And if not, what would be the cheapest forged pistons?
 
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#2 ·
Use the Scat rods. The machine screw fasteners will clear better than the conventional rod bolted Eagle rods.

Pistons will be the problem. I know of no cast pistons for the 4.375 stroke. Not many places stock a forged piston for the combo either.

I built a similar BBC this past spring. The customer decided to use off the shelf Mahle pistons for his c/ratio application.. $875 will make a real dent in the budget.. The MM rings are a real treat also..:thumbup:
 
#3 ·
Yeah, I was hoping to stay under $1000 for the finished rotating assembly.

I found THESE PISTONS MADE BY ICON

Thay say the top ring land is .32" down from the top. If I could mill about .07" off the top it would make it work out about right. That would leave .25" above the ring land - Is that enough?

If that would work, Summit Racing has those pistons for $470 and I could still run standard head gaskets. That would fit the budget nicely.
 
#4 ·
My math shows you would only need to mill .042" off the top of that piston to end up at zero deck in a 9.800" deck height standard block, which will put you at a near ideal quench figure of .041" with a gasket that thick.

Should be easily do-able. Of course, milling the piston because of rod and stroke moving it up the bore at TDC leaves less piston to valve clearance, so you'll need to check that and possibly need to mill the valve relief deeper.

Not knowing the true CC chamber volume of your heads I couldn't figure out the true compression ratio.
 
#5 ·
"so you'll need to check that and possibly need to mill the valve relief deeper."

Then you get into the problem with blowing a hole thru the intake valve relief into the top ring land. High compression 396 and 2307-2308 Fed-Mogul pistons were famous for this. :spank:

After all this machine shop labor. How much $ have you saved?
 
#6 ·
Like I said if I stay below $1000 on the rotating assembly I'll be alright. Money really isn't a problem, but the reason that I have a little extra money is because I don't like to spend it.

I'm certainly not going to run the most aggressive cam in the world either. I guess I need to figure out what cam I am going to run and then do some measuring on my heads to see how close the valve will get to the piston.

Any suggestions on cams? Good low end with a nice healthy mid range?

I was kinda thinking something similar to a Comp X4 262H but I would like some suggestions...
 
#7 ·
you are going to need a custom hydraulic roller cam for this 500 plus cube engine to rev out to 5,000 rpm. It will make 500 hp,,,,easy. Every corner you cut will cost you power. If you are cheap,then build the much cheaper 454,sell the stroker crank and lower the cost even more while making similar hp at or slightly above 5200 rpm.Either way the corporate diff will be a weak point consideration
 
#8 ·
I would sell the Eagle crank and with the money build a 454.

For one with a mark 4 block you will need to grind pan rails and bottoms of cylinders to clearance for the stroke. You will also have to get a stroker clearances oil pan.

Second some of those cranks are clearances for a 6.535 rod not a 6.385. Yes the counterweights can be cut down but than Mallory will be needed to balance it. You could have $700 in balancing.

The general never wanted that much stroke in a BBC. Just my 2 cents.
 
#9 ·
After thinking about it all, I agree with the last two posts....sell the "free" Eagle stroker crank and just do a 454 plus the overbore, it will cost you a lot less in the end than trying to use the "free" crank.....it won't seem so free once you add up the costs to actually use it. Forged pistons, special oil pan, piston mods, possible expensive balance, etc = $$$$

If you were looking for a big power mudrace or drag race engine then keeping the "free" crank would make more sense....but not for a budget deal for a farm beater.
 
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