I have a -66 mid-year corvette with a base 327" 4sp. engine. I understand all smallblocks prior to 1968 had "small" crank journals but what about main bearing caps, are the 300/350hp 327" two or four bolted in -66? I understand the basic differences between the 300hp and 350hp are cylinder heads, intake manifold and camshaft. Anything else?

Norwegian C2-fan

 

ALLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL 1967-earlier Chevy small blocks had small journal crankshafts and the main caps were 2bolt ONLY. The 4bolt caps on small blocks did not get manufactured until the very late 60s.

Now, just like everything else, there is always an exception to the rule. The 1967 Camaro, with the SS 350 option, had a 350 that was sort of a hybrid small block. It had features of both the 67-earlier small blocks as well as features of 68-later small blocks. THIS 350 WAS ONLY IN THE 67 SS 350 CAMARO! It had a large journal crank (like 68-later) and it still had the hole in the rear of the block for crankcase ventilation (same as 67-earlier small blocks). These 67 350 blocks are rather rare and desireable. By the way, this 67 350 block was only a 2 bolt version.

 

and pistons, 350HP had forged...... i'm pretty sure they had the steel crank/big balancer, i'm sure someone here will clarify

BTW: the rods are the week link in the early SB's (and even more so with the BB's)....... I wouldn't worry about not having 4 bolt mains, my cousin bought a new 2 bolt 68 Z-28 that was raced since day one (drag, both street and strip)...... it's seen 8500 RPMs many many times, no problemo.

 

Thank you all for the info, I learn something every day!!
Erik

 

Just as added info regarding "weak rods". Several years ago I built a SB420 for my boat. This was done before stroker cranks were readily available for SB400s. I had read articles about offset grinding the rod journals of a 400 crank down the the size of early, small journal 327s and then use small journal 327 rods. Well, I'm here to tell you it works! I bored a 400 .030 over and had the 400 crank rod journals turned from 2.10 to 2.00 and used a good, reconditioned set of small journal 327 rods (NOT 283 rods) with ARP Wavloc bolts. Presto, 420 cubic inches, .510 lift hyd cam, Trick Flow alum heads and it is a strong running SB engine!
My whole point here is that I have not had a failed rod or any other related problems (I must admit, this engine is limited to 6000 MAX). Years ago I had read a few articles about building such a stroker 400 in magazines such as HOTROD, and one day I thought I'd give it a try. It is true that today you can build 427 and 434inch motors from a stock block 400 and a 454 is possible with a World tall deck SB400 block (but for this kind of money a person could build a NICE 454BB). My method of building a 420SB was a very simple and inexpensive method of building a "poorboy" big inch engine to fit where a SB had originally been installed. Agreed, there is no substitute for cubic inches. So if you really want the big displacement engine, then go for a 454-496-502-572BB. But if there is a genuine need for staying with a SB, 400+cubic inches really makes a nice stump puller and my home built 420 with small journal rods is doing just fine!