How To Tell 68 Big Block???

[Larry S.]

It is a 1968 convertible - SN 117XX. Presently there it has a 1965 small block and a 19?? four speed transmission. How can I tell if this car came with a big block??? Presently there is a big block radiator and radiator support in car, which makes me think it was a big block.

Is there any way to tell if it was an automatic or 4 speed??? I suspect it was (is) a four speed.

Thanks!!!

[Shannon Burgess]

Re: How To Tell 68 Big Block???

An original 4-speed car will have the welded in crossmember for the transmission mount. An A/T car will have a bolt-in removable crossmember.

Other big block clues would be a rear sway bay, caps on the differential side yokes instead of u-bolts, the tach redline (5600 or 6500 for big block).

Shannon

[Kevin Whiteley]

Re: How To Tell 68 Big Block???

There is no fool-proof method to detect if a 68 was a big-block car originally. It wasn't until 72 that Chevrolet started regularly putting in a code for the original engine. Shannon provided some easy ways to tell, although those items can be duplicated.

The odds are that if the radiator, radiator support, tachometer (red line) and other items indicate a "big-block", it probably is. But Caveat Emptor!

[Jack H.]

Well said, Kevin! *NM*

[Dick W.]

Re: How To Tell 68 Big Block???

Big block radiator core is 26 1/2", should have rear sway bar, tach red line(depending on which hp see judging guide), rear axle half shafts have machined caps to retain u joint on differential end vs u straps on s.b.

[Larry S.]

Re: How To Tell 68 Big Block???

Thanks for the info!!!