RPO engine code?
Thread Starter
Pro
Joined: Apr 2012
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From: USA
update
found this thread (i should have searched before)Quote:
Originally Posted by rvzio View Post
The base 350/300 has a 2 bolt main. Most folks have the original motors bored 30 over and while you at it put in 4 bolt mains..
Not in 69. The base 300 hp 350 in 1969 was a ZQ3 and not a L48. A ZQ3 is the code for the base engine and was a high compression (10.25:1) L48 and had 4 bolt mains. The lower CR/2 bolt L48 arrived in 1971. (note, there are many instances where people have discovered their L48 had 4 bolt mains from the factory - luck of the draw)
In 69 there were two 350's, the 300 hp ZQ3 and the 350 hp L46. The difference between them is essentially valve size, camshaft and pistons, so it is possible to upgrade a ZQ3 to a L46 spec. A SBC being a SBC you can also turn it into just about any engine spec you want.
Originally Posted by rvzio View Post
The base 350/300 has a 2 bolt main. Most folks have the original motors bored 30 over and while you at it put in 4 bolt mains..
Not in 69. The base 300 hp 350 in 1969 was a ZQ3 and not a L48. A ZQ3 is the code for the base engine and was a high compression (10.25:1) L48 and had 4 bolt mains. The lower CR/2 bolt L48 arrived in 1971. (note, there are many instances where people have discovered their L48 had 4 bolt mains from the factory - luck of the draw)
In 69 there were two 350's, the 300 hp ZQ3 and the 350 hp L46. The difference between them is essentially valve size, camshaft and pistons, so it is possible to upgrade a ZQ3 to a L46 spec. A SBC being a SBC you can also turn it into just about any engine spec you want.
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
Further..depending on how much of the car is lost to time....
Big block radiator?
Fan clutch?
Type of radiator..copper vs aluminum.
I know this is dumb (and its long gone) emission sticker.
all are clues to the origins.
Unkahal
Big block radiator?
Fan clutch?
Type of radiator..copper vs aluminum.
I know this is dumb (and its long gone) emission sticker.
all are clues to the origins.
Unkahal
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From: Virginia
Just curious, does it have a bright blue vinyl interior? Trim code 411.
http://corvettec3.ca/interior.htm
http://corvettec3.ca/interior.htm
Thread Starter
Pro
Joined: Apr 2012
Posts: 696
Likes: 193
From: USA
did....
Just curious, does it have a bright blue vinyl interior? Trim code 411.
http://corvettec3.ca/interior.htm
http://corvettec3.ca/interior.htm
nots no mo!!
Le Mans Master
Joined: Mar 2004
Posts: 7,450
Likes: 1,479
From: Little Rock AR
I have a loose ZQ3 in my garage now. 4 bolt main and cast flat tops. Decent 186 double hump heads with small valves. Pretty much an L-48 with smaller combustion chamber heads.
Last edited by stingr69; Feb 22, 2026 at 02:46 PM.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
found this thread (i should have searched before)Quote:
Originally Posted by rvzio View Post
The base 350/300 has a 2 bolt main. Most folks have the original motors bored 30 over and while you at it put in 4 bolt mains..
Not in 69. The base 300 hp 350 in 1969 was a ZQ3 and not a L48. A ZQ3 is the code for the base engine and was a high compression (10.25:1) L48 and had 4 bolt mains. The lower CR/2 bolt L48 arrived in 1971. (note, there are many instances where people have discovered their L48 had 4 bolt mains from the factory - luck of the draw)
In 69 there were two 350's, the 300 hp ZQ3 and the 350 hp L46. The difference between them is essentially valve size, camshaft and pistons, so it is possible to upgrade a ZQ3 to a L46 spec. A SBC being a SBC you can also turn it into just about any engine spec you want.
Originally Posted by rvzio View Post
The base 350/300 has a 2 bolt main. Most folks have the original motors bored 30 over and while you at it put in 4 bolt mains..
Not in 69. The base 300 hp 350 in 1969 was a ZQ3 and not a L48. A ZQ3 is the code for the base engine and was a high compression (10.25:1) L48 and had 4 bolt mains. The lower CR/2 bolt L48 arrived in 1971. (note, there are many instances where people have discovered their L48 had 4 bolt mains from the factory - luck of the draw)
In 69 there were two 350's, the 300 hp ZQ3 and the 350 hp L46. The difference between them is essentially valve size, camshaft and pistons, so it is possible to upgrade a ZQ3 to a L46 spec. A SBC being a SBC you can also turn it into just about any engine spec you want.
that ZQ3 / L48 contrast/comparison is Spot-On! ... you can corroborate very same data via downloading FREE specs for those years from GM Heritage center https://www.gmheritagecenter.com/gm-...tion-kits.html-add-
My GMC Sonoma also has OE ZQ3 package ... modern rpo ZQ3 is tilt-cruise control ... also has OE ZQ8 ... sport suspension (that works great!)
Last edited by jackson; Feb 14, 2020 at 04:56 PM.
Melting Slicks
Joined: May 2002
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From: Laporte, IN
The ZQ3 is the option code for base engine for 1969-1972. Then L48 was used as standard engine code for 1973-1980. "Z" codes denote packages, which may or may not include a particular engine. ZQ3 denoted the base Corvette with standard suspension, standard tires, standard engine
Suffix codes for a base engine in 1969
HY 350 Base 300 Rochester Q-jet & Manual Transmission
HZ 350 Base 300 Rochester Q-jet & Turbo Hydra-Matic
Suffix codes for a base engine in 1969
HY 350 Base 300 Rochester Q-jet & Manual Transmission
HZ 350 Base 300 Rochester Q-jet & Turbo Hydra-Matic
