440cid LA

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G

Guitar Jones

aka Angry Johnny
Joined
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Here's the deal. I have a siamese bore R3 block, 59 degree 4 bolt mains. It can be bored up to 4.22. While I'm not going to go that far I figure I can get an off the shelf piston blank for a .060 over 400 Chevy small block and a good race ring package. That would put the bore at 4.185. With a 4 inch stroke I'm looking at 440 cubic inches of LA rat stomping power :D.

By upgrading my W5's to a 2.08 intake I figure I should be able to make close to 700 HP with it. What I'm not sure about is the cast stroker crank. I may want to go steel on this. I'm collecting some parts now (already got a set of Eagle H beam 3D rods and the block) but I need to back half the car first so I can get a good size tire under it and a four link.
 
sounds nice!!!!! that is something i could consider to do! understand your need for a fourling since i only have a 340 and its fully capable of making long black lines on the asphalt att 30mph.. and with souch a great engine your planing it needs to be strong running!
 
something you might consider is the rod ratiowith this setup you are about 1.04:1 and most consider 1.50:1 to be the minimum acceptable ratio

This list show different ratios. Most pro engine builders think that 1.50 is the shortest to go. The smaller the ratio, the more side loading of the piston to cylinder wall. Performance wise, the longer strokes are alleged to produce more power. But that is always debated.
Click to expand...

if wanted I have some excellent articles on the subjeect
 
OUTLAW said:
something you might consider is the rod ratiowith this setup you are about 1.04:1 and most consider 1.50:1 to be the minimum acceptable ratio
Click to expand...

The rod/stroke ratio for his combo would be 6.123"/4" or 1.53.

Sounds like a killer combo to me. I love how easy it is to get 400+ cubes out of the Mopar LA blocks. :supz:
 
:scratch: The bore size has nothing to do with the chart in the link you posted. That chart talks about the relationship between length of the connecting rod and the stroke.

But yes, there is also a relationship between the bore and the stroke for a given displacement. Typically though, you want this ratio close to 1:1 for the best compromise between low end torque and the ability to also make power at higher rpm.
 
I never read the list cuv it came from a ford site and there are lots of factors to concider but I was only drawing a comparison on the most basic level which is bore/stroke =rod ratio and 1.5 is concidered barely acceptable on the low side.

Short Rod -- Min Rod/Stroke Ratio -- 1.60 Max Rod/Stroke Ratio -- 1.80

Long Rod -- Min Rod/Stroke Ratio -- 1.81 Max Rod/Stroke Ratio -- 2.00

Any ratio's exceeding these boundaries are at this moment labeled "design screw-ups" and not worth considering until valid data supports it.
Jerry Stahl - Stahl Headers
Click to expand...

read this http://sybertek.us/archive/engines/rod_length.htm
 
All of that is a bunch of speculation and conjecture. Not even worth considering. Bore size has nothing to do with piston speed or loading, the length of the rod and the crankshaft stroke are the contributing factors. It has been said however that over square engines aren't as good, in other words engines with longer strokes than bore size, this isn't the case here but in actuality that doesn't matter much either as they are being produced now anyway. Think of the 318 with a 4" stroke. The bore is smaller than the stroke, you get the idea. These engines produce power too. In fact an engine doesn't really care a whole lot as to how it gets it's cubic inches as long as it gets them.

There is a whole other argument on piston speed, side loading, and an engines tendency to detonate that is to be considered with rod length and stroke, but the jury is still out on that as well. Different spark curves and octane requirements may be all that is necessary there.

So I guess all those Pro Stock 4.625 bore 3.69 stroke engines aren't any good either huh?
 
I think you're only partially right. The causes of the forces are rod length and stroke. The effects are side loading of the piston (wear and horsepower loss), pisaton speed, and dwell and stability of the piston at TDC. Piston design is set by rod length and deck height. A long rod leaves the piston at TDC slightly longer, and a faster piston speed at 1/2 stroke, but down sides are shorter skirt, less ring stability, more piston rock at TDC, and heavier bobweight. A short rod gives a taller, more stable piston (les rock, better ring stability), less mass (the shorter rod, steel vs. aluminum of a piston skirt), less side loading(less wear and parasitic loss) and faster overall piston speed. This is how I understand it. My books are at home, so I cant say that's gospel. I do know, the only factors I really concern myself with (for street/strip engines) are bobweight (less is always better for durablility and power), side loading (you can wear a short piston/long rod out in a year, and if the block is special, that's a lot of repairs) that causes wear, heat, and takes power away from the crank. I also like tight quench if I can get it, so I dont like short pistons for that. I also think to say "it means nothing" is not really right. The size of the bore spreads out the forces of side loading, therefore making it less of an impact. I aslo think W5s will not be enough unless they really move some air. I am defiantely NOT the guy to preach about the W series heads tho. I've never used them personally. I think to make the levels you're tyalking about, you'll need 300+ cfm on the intake side. I dont hink the W5s can do that, but I may be mistaken there. Cool idea tho..The "auto math handbook" is a great explainer of this stuff.
 
You're right, you don't know about the W5's they already flow 305 at .650 with a 2.02 valve. You are right about bore size, side loading short and long rods and all that, at least that's the general theoretical consencus but in application I think it matters little if any. Certainly not to the point where it would wear out in a year, something else is wrong there.

If you want some reading on this a recent Hot Rod magazine issue did a test on short stroke big bore engines vs the same size long stroke small bore engine. What did they find you ask? The engine doesn't know the big bore short stroke combo is supposed to be better. I think they got a difference of 8 horsepower.
 
I agree, it's mostly things that if looked at seperately, dont make much sense to look at. But, at that level of "R&D", they might be something to look at. The engine in question was a Chevy, and there was nothing wrogn other than a very short custom piston. It was back in the late 80s, and aftermarket blocks were big $$ even for chevies, so this rotating assembly went into 3 different blocks in 4 years. It was a 427 CI in a 400 block, IIRC. (the theory was the 400s couldnt be bored over .030 safely) It did run like crazy tho, and was also used with 150 plate. It made him a LOT of money back then.
In terms of long/vs short, etc. The main thing is, what are you doing with it. An IMSA car will want to keep a higher piston speed, and can thanks to the transmissions and tracks. A street car will not need big rpms, but definately wants time for the pressure to build on the top of the piston for more immediate torque, and wants the mid stroke faster for better cylinder filling with big cams/bigger ports anf lower rpms. It's just an area I wouldnt ignore if you are going to the level you're ralking about, that's all. I'd still run the little "V-8" emblems and a ton of muffler..maybe paint it Mopar Lt Blue..lol
 
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