cal camara

I have noticed that from 1970 to 1975 the 454 specification are very similar. they all have the same bore, stroke, mains, rods, and valves dimentions. The cranks from 70-72 are forged steel and from 73-74 the are nodular (what is that). The heads vary a little with (73-74 having 113 cc heads), (72 113 cc's), (71 118 cc for the 425 hp, and 113 for the 71 365 hp motor), Since most of the specs are similar does that mean the HP diferances are primarily due to cams.



thanks

Gage

don't know where you are getting you info from, but I thought the 73 heads were 122cc. I hope you are right and I am wrong because I want as much comp as possible.

cal camara

I took my info from "chevrolet by the numbers" 1970-75 by alan colvin
cal

Neo Fender

HP ratings changed from Gross to Net during that time too.

Jughead

Decreasing compression too.

djcwardog

I'm not sure about the accuracy of your numbers. The heads in the 1973 are at least 119cc if not 122cc. The cams are different as well. I think mine is a #353040 with 0.440 lift and 210/210 duration at 0.050 lift. Tom's 73 website lists the seat-to-seat specs for this overwhelming power stick! I think the power drop from 1970 to 1971 was mostly in the way they report the power - net vs. gross along with a bit of a drop in CR. More drop in CR for 72. 73 saw better heads but a weaker cam and lower CR (8.25:1). 74 saw different heads and the end of the 454 in Corvettes - none in 75. In sum, if my stock motor were rated in 1970 gross specs it would have likely been a 454 350HP or some such...rather than the 454 275 HP it is in net HP.

Turbo-Jet

i think all LS5s had same cam. esentailly the same engine 70-72, except 1970 has higher compression

BigBlockk

Chevrolet reported gross HP numbers in '71. The LS6 had 425 Hp gross in '71. The bis performance drop between these years was due to the drop in compression.

1972 brought net power ratings. 1973 brought exhaust gas recirculation (I believe) and recalibrated ignition timings that ferther choked the engines.

1974 would be the end of the line for the big block.

1975 brought a 100 cid cut in engine size and catalitic converters.

The bark times.

BigBlockk

Later.....

zwede

71 engines were rated both gross and net. The LS5 was 365 gross hp and 275 net. This shows just how inflated the old gross numbers were...

LS-5 71

err.. 71 engines were rated at 365HP gross & 285HP net. 72 lowered the net to 270HP with no gross horse power figure.

Ironcross

A couple of other 454`s available were the LS6 in a Vette rated at 425HP and in a 70 Chevelle at 450HP because of a compression differential from 70-71 and the very potent and rare top of the line 454 LS7 which was only a over the counter service package engine that basically replaced the 427 L88 and ZR1`s of similar 550+HP but at a little less potential RPM`s due to the longer stroke. But still one hell of an engine.