One other example here. Back in the 70s, gm had a 400 sbc. Block had same deck to crank centerline dimension as the LTx blocks. With the 3.750" stroke, the difference (for deck hgt. determination) from the 3.480" stroke, is .135". This is the difference from the std. 5.7" rod, with the 400 using a rod length of 5.565". Again, gm didn't violate the piston compression hgt. dimension, of the oem LTx engines. Just some more FFT, to support my prior post.

 

Stock LS1 rods are 6.098"

 

Along with the longer rod (appr. .40"), the LS block, comparing apples to apples, (by allowing for the negative deck hgt. of the LS block, and the positive deck hgt. of the LT block) has a taller deck dimension/allowance of .26". That leaves a diff of .14", doesn't it? This is offset, with the longer stroke and yes, shorter piston compression hgt. of the LS engine.

So, to answer the ? as to why the L(T) engine doesn't come with a 6" rod; it is a combo of shorter block hgt. and diff piston construction.

Ranting here...Is it really important/necessary (on a street engine especially), or is is more of the monkey see, monkey do syndrone, by insisting on comparing to high tech, sqeeze the last hundredth/horespower race engine? What rod length do the sb fords use? Do they make torque/power?

 

As Arnie suggests, more is made of this than is warranted. Talking about the theory is interesting and there may be some small advantages to certain rod ratios under a given set of conditions. But the rod ratios in sucessful engines really vary quite widely, indicating that there is no magic number.

Ford 454W stroker 4.187" stroke, 5.85" rod, 1.4:1 rod ratio

BBC 454 4.00", 6.13", 1.53:1

Chev 350 3.48", 5.7", 1.64:1

Ford 351W 3.50", 5.95", 1.70:1

Chev 283 3.00", 5.70", 1.80:1

Mopar 383 3.38" 6.35" 1.88:1

So, a 383 stroker with a 5.7 rod has a RR of 1.52 with a 5.7" rod and 1.60 with a 6" rod. Both kind of low but within the range of many other combos.

Rich Krause

 

Rich brings up a good point, in regards to the rod/stroke ratio being as, or even more important than the actual length of the rod itself. Although not a bad rod lgth./stroke ratio, the sb ford 289/302 had an oem 5.09" rod length. The stroker 302 (347) uses a 5.4" rod. This was, what I was referring to above. Anyway, the sbc/LT series engine has enjoyed the advantage of being a small, relatively lite package, which made it desireable, when it came time to wrap sheetmetal around it. The downside of this small/compact package, is a short block deck dimension.

You'd 'ave thot the engineers of the original sbc, could have added just a 1/4" to the deck surface. How much diff could that have made?