LS-5 vs. LS-4 - what's the difference??
03-01-2003, 03:25 PM
#2
Le Mans Master
Re: LS-5 vs. LS-4 - what's the difference?? (SuperFast80)
The most obvious is the compression ratio. The LS4 was basicly a lower compression LS5 designed to run on low-lead fuel during the lead phase-out years. I am sure there are a few more sublte changes.
03-01-2003, 04:01 PM
#3
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Re: LS-5 vs. LS-4 - what's the difference?? (silvervetteman)
The `71-`72 LS5's had their cr reduced for use with unleaded. The LS4 replaced it in `73. I think the major difference was a milder cam in the LS4, though it's hp rating was 5 hp higher than the last LS5.
03-01-2003, 04:42 PM
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Re: LS-5 vs. LS-4 - what's the difference?? (SuperFast80)
The biggest difference between lets say a 72 LS-5 and a 73 LS-4 is the bottom end of the engines, The LS-5 still had a forged crank, while all the LS-4's to the best of my knowlwdge were cast, although I've seen one article that said to the contrary (manuals only forged for LS-4) but I haven't seen anyone on this board pull a forged crank out of an LS-4 yet. The 72 LS-5 was at 8.5:1 compression, LS-4 was 8.25:1 (probably for Nox control along with the EGR, LS-5's didn't have EGR valves LS-4's did). Some of the LS-5's did have 4 bolt mains (rare) all LS-4's were 2 bolt. I believe the 72 LS-5 was rated at 270hp/390 torque, 73 LS-5 was 275hp/395 torque, I believe the advantage was either due the cold air induction (doubt it since air is fed to the engine on a dyno), or the 049 heads for the 73 which are one of the better large oval port production heads, Chevy High Performance has their flow numbers up on their site (my guess as to the difference, since 74 had a different head casting).
:cheers:
Pat Kunz
:cheers:
Pat Kunz
03-01-2003, 05:56 PM
#5
Race Director
Re: LS-5 vs. LS-4 - what's the difference?? (SuperFast80)
I asked this same question on the NCRS board awhile back. Joe Lucia over there gave a good response ( http://www.ncrs.org/forum/archive5.cgi?review=8175 ). Here is the basics of his response:
1) All 70-74 Corvette 454 cid engines were two bolt main configuration EXCEPT 1971 LS-6;
2) Most, if not all, 70-72 Corvette 454 cid engines used a forged steel crankshaft. There may have been some exceptions, though, with those using a cast nodular iron crankshaft;
3) All 73-74 Corvette 454 cid engines used a cast nodular iron crankshaft; (note: Chevy lit indicates that the LS4 with manual trans used forged crank, tom73)
4) All 70-74 Corvettes with 454 cid engines, except 71 LS-6, used the same size intake and exhaust valves which, as I recall, were 2.06" intake and 1.72" exhaust.
5) 1970 LS-5 cylinder heads were unique to that year. For 1971-72 LS-5 engines, although different castings were used for each year, the cylinder heads were, essentially, the same. 1973 and 1974 LS-4 engines used cylinder heads specific to each year which were different for each year. As I recall, all 1970-72 LS-5 engines used cylinder heads which had about the same intake and exhaust port volumes. 73-74 LS-4 cylinder heads had smaller intake and exhaust ports, although I believe that 73 and 74 were about the same. All cylinder heads, except 71 LS-6, were cast iron material. 70-72 cylinder heads did not use induction hardened exhaust valve seats, including the valve seat inserts used on 71 LS-6 aluminum heads. 73-74 LS-4 cylinder heads used induction hardened exhaust valve seats;
6) All 70-72 LS-5 engines used the same camshaft, GM #3883986, which was also used on 66-69 L-36 427 engines. 1973 and 1974 LS-4 engines used a different camshaft, GM #353040, which was the same for both years. This camshaft was an "emissions profile" camshaft;
7) All 70-74 454 LS-4 and LS-5 engines used the same connecting rods which were forged steel with 3/8", knurled shank rod bolts;
(8) All 70-74 LS-4 and LS-5 engines used cast aluminum pistons. The piston dome configuration was unique to each specific year, however, even though compression ratios may have been the same (72-74). 1970 LS-5 used 10.25:1 compression ratio; 1971 LS-5 used 8.5:1 compression ratio; 1972 LS-5 used 8.25:1 compression ratio; 1973-74 LS-4 used 8.25:1 compression ratio.
9) All 1970-74 Corvettes with 454 cid engine used the same oil pan, including LS-6;
10) 70-72 LS-5 engines used unique-to-each-year cast iron intake manifolds. However, all of the manifolds were similar. 73-74 LS-4 intake manifolds were also cast iron but had smaller port size to match the 73-74 cylinder heads. 73-74 manifolds also incorporated provisions for EGR.
11) All 70-74 Corvettes with 454 cid engines used the same side-specific exhaust manifold castings. 1971 with LS-6 and all 73-74 LS-4 manifolds were drilled and tapped for A.I.R. fittings.
12) All 70-74 Corvettes with 454 used the same valve springs except the 73-74 exhaust valve springs which were shorter to accomodate the rotators used during those years.
13) All 70-74 Corvettes with LS-5/LS-4 engines and manual transmissions used a 14" cast nodular iron flywheel with an 11" clutch. LS-6 used a 14" flywheel with a special dual disc clutch;
14) All 70-74 Corvettes with LS-5/LS-4 used the same oil pump
15) 1970-72 with LS-5 used the CCS (controlled combustion system) exhaust emissions control system. All 1971 LS-6 and all 73-74 LS-4 used the AIR (air injection reactor system) exhaust emissions control system.
tom...
[Modified by Tom73, 5:01 PM 3/1/2003]
1) All 70-74 Corvette 454 cid engines were two bolt main configuration EXCEPT 1971 LS-6;
2) Most, if not all, 70-72 Corvette 454 cid engines used a forged steel crankshaft. There may have been some exceptions, though, with those using a cast nodular iron crankshaft;
3) All 73-74 Corvette 454 cid engines used a cast nodular iron crankshaft; (note: Chevy lit indicates that the LS4 with manual trans used forged crank, tom73)
4) All 70-74 Corvettes with 454 cid engines, except 71 LS-6, used the same size intake and exhaust valves which, as I recall, were 2.06" intake and 1.72" exhaust.
5) 1970 LS-5 cylinder heads were unique to that year. For 1971-72 LS-5 engines, although different castings were used for each year, the cylinder heads were, essentially, the same. 1973 and 1974 LS-4 engines used cylinder heads specific to each year which were different for each year. As I recall, all 1970-72 LS-5 engines used cylinder heads which had about the same intake and exhaust port volumes. 73-74 LS-4 cylinder heads had smaller intake and exhaust ports, although I believe that 73 and 74 were about the same. All cylinder heads, except 71 LS-6, were cast iron material. 70-72 cylinder heads did not use induction hardened exhaust valve seats, including the valve seat inserts used on 71 LS-6 aluminum heads. 73-74 LS-4 cylinder heads used induction hardened exhaust valve seats;
6) All 70-72 LS-5 engines used the same camshaft, GM #3883986, which was also used on 66-69 L-36 427 engines. 1973 and 1974 LS-4 engines used a different camshaft, GM #353040, which was the same for both years. This camshaft was an "emissions profile" camshaft;
7) All 70-74 454 LS-4 and LS-5 engines used the same connecting rods which were forged steel with 3/8", knurled shank rod bolts;
(8) All 70-74 LS-4 and LS-5 engines used cast aluminum pistons. The piston dome configuration was unique to each specific year, however, even though compression ratios may have been the same (72-74). 1970 LS-5 used 10.25:1 compression ratio; 1971 LS-5 used 8.5:1 compression ratio; 1972 LS-5 used 8.25:1 compression ratio; 1973-74 LS-4 used 8.25:1 compression ratio.
9) All 1970-74 Corvettes with 454 cid engine used the same oil pan, including LS-6;
10) 70-72 LS-5 engines used unique-to-each-year cast iron intake manifolds. However, all of the manifolds were similar. 73-74 LS-4 intake manifolds were also cast iron but had smaller port size to match the 73-74 cylinder heads. 73-74 manifolds also incorporated provisions for EGR.
11) All 70-74 Corvettes with 454 cid engines used the same side-specific exhaust manifold castings. 1971 with LS-6 and all 73-74 LS-4 manifolds were drilled and tapped for A.I.R. fittings.
12) All 70-74 Corvettes with 454 used the same valve springs except the 73-74 exhaust valve springs which were shorter to accomodate the rotators used during those years.
13) All 70-74 Corvettes with LS-5/LS-4 engines and manual transmissions used a 14" cast nodular iron flywheel with an 11" clutch. LS-6 used a 14" flywheel with a special dual disc clutch;
14) All 70-74 Corvettes with LS-5/LS-4 used the same oil pump
15) 1970-72 with LS-5 used the CCS (controlled combustion system) exhaust emissions control system. All 1971 LS-6 and all 73-74 LS-4 used the AIR (air injection reactor system) exhaust emissions control system.
tom...
[Modified by Tom73, 5:01 PM 3/1/2003]
