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?cc of '71 sb head c/n 3973487 ?


Well-known member
Dec 27, 2000
Florence, SC (Timmonsville SC)
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Anybody got a reference that approximates the combustion chamber volume of my stock, un-shaven sb heads? c/n 3973487, dates C 9 1 and C 10 1 (MAR 9 & 10 1971) Intake od = 1.94”, Exhaust od = 1.50”. I believe these were original to my base L48 270 hp 71 cpe which also had slightly dished pistons. I saw one reference where it showed pictures (but no c/n's) and it seemed mine looked like those reputed to be 69cc's. BTW, info at MorTec is great ... but does not provide desired detail.
Jack said:
BTW, info at MorTec is great ... but does not provide desired detail.

The MorTec site says they are 75cc. Isn't that what you were looking for?

brain fart

Thanks for info ... and my apology to MorTec ... just didn't see it/register last time I checked. MorTec also states these heads c/n 3973487 are used in LT1. However, by many other indications (i.e. cast crank, iron intake, small valves, 2"exhaust man, small balancer) mine is the base L48 (CJK on non-decked block)... and everything measured standard when I pulled it down for rebuild ... it really seemed the motor's not been into. Get this ... even the heads never had guidework ... and they didn't require guides/knurling. Also, my heads have pressed (not threaded) rocker studs ... I'd kinda expect screw-in studs on LT1 ... but I don't know. Well ... I do have a 50 ml volumetric buret ... but no buret clamp-stand nor headplate etc. I got the darn thing just to cc heads. Maybe I should go ahead and set it up ... at least just enough to estimate within 1-2 cc. I really want to know cc ... not so concerned whether heads are LT1 or station wagon.
Those heads were used on both the base and the LT1 in the 71 Vette. (Per the corvette Black Book). The differences in the heads would be the Valve Size, the LT1 would have the 2.02 intake and 1.60 exhaust while the base engine used 1.94 intake and 1.50 exhaust. The compression differences was due to the piston top and not the combustion chamber size.

Without actualy cc'ing the chambers I would have to say that they are 75cc.

CN 3973487 was used on some 71 and 72 Chevy 350 cuin applications. It?s identical to the ?461? head except for a new chamber design, a temp sender boss on the side, accessory holes on the front and the conical seat for the new plug design. The nominal combustion chamber displacement is 75.47 cc?s.

There are two ?versions? of this head: high-performance, with 2.02/1.60 valves, and low performance with 1.94/1.50 valves. The high-perf. unit was on LT1s and in taxi/police option passenger cars. The low perf. unit was on L48s in Corvettes and on engines in all other passenger car applications.

This head came with screwed-in studs and pushrod guide plates.

There is also another 71 head used in Corvettes and Z28s, CN 3986316 which is the same as ?487? except for a 76.18cc chamber.

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