# Generation III Internal Engine - bore and stroke combinations sbc bbc vs. gen III

01-08-2005, 01:46 PM
I want you guys to chime in on this topic. It seems to me that the ole' sbc and bbc have bigger bores and shorter strokes. Do ya'll think that the generation III bore and stroke combo's are better than the ole' sbc and bbc? The genIII engines have longer strokesand smaller bore (strokers). For example 382ci 3.90x4.0 inch stroke; 402 4.0 bore x 4.0 inch stroke: 427 4.125 x4.00. It seem to me the older sbc bbc have better bore x stroke combinations than the genIII engines. Chime in and give some pointers. Which will perform best :judge:

v8pwr
01-08-2005, 04:25 PM
I would point out the great cylinder heads of the genIII as the reason for the change in bore and stroke . From an OEM perspective why spin higher rpms when you can trade bore for increased stroke and make power everywhere in the rpm range .

Phil99vette
01-08-2005, 05:10 PM
4.200 x 4.000 = 443 cid good all motor
4.160 x 4.000 = 435 cid
4.160 x 4.125 = 449 cid
4.200 x 4.250 = 471 cid
4.200 x 3.620 = 401 cid high rev combo

Ratical
01-09-2005, 12:05 PM
4.200 x 4.000 = 443 cid good all motor
4.160 x 4.000 = 435 cid
4.160 x 4.125 = 449 cid
4.200 x 4.250 = 471 cid
4.200 x 3.620 = 401 cid high rev combo

In comparison some smallblock/bigblock combinations are:
4.500 x 4.50 = 572 cid
4.500 x 4.25 = 540 cid
4.250 x 4.00 = 454 cid
4.250 x 3.76 = 427 cid
4.030 x 3.75 = 383 cid
4.125 x 3.58 = 377 cid
4.125 x 3.75 = 400 cid
4.000 x 3.58 = 350 cid
4.000 x 3.31 = 327 cid

Another factor is the connecting rods.
A gen III comes stock with a 6.098 rod

Some old small block stock rod lengths were 5.7",(most engines) and 5.565"(400sb)

Big blocks used one length stock, 6.135".

I agree that the Gen III heads are the secret to their power. A stock LS1 head will outflow most aftermarket smallblock chevy heads out there. Most aftermarket big block chevy heads will flow more cfm than an LS1 head, but their low lift velocity numbers and swirl do not compare.

Now if only GM would make an aluminum Gen VII big block with LSx technology heads! :eek2:

PREDATOR-Z
01-09-2005, 12:24 PM
Now if only GM would make an aluminum Gen VII big block with LSx technology heads!

Gen 7 (ouch). 10 more years?/

No I vote for a LS2 Gen IV Z28 and a LS7 Gen V SS.:drool: