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How can I identify whether a 66 has the 425 HP or the 390 HP engine? Does the VIN identify the engines? Even if it did I still would like to check any visual engine characteristics to confirm. Some have suggested the tachometer may be different and if so that would certainly help identify what the car was when it left the factory.
I may have an opportunity to purchase a sweet survivor convertible. Problem is the owner is seriously ill and can't talk. So the wife owns it but knows little to nothing about it. She has no paperwork to speak of but the car has been owned by her husband for 30 + years. The car has been stored for about 5 years, under a car cover in the garage. Has not been started within that time period. It was running when he last parked it. But even if I could verify that it has the high HP version I would like to confirm that it’s an original 425 HP car so any help would be appreciated.
Last edited by Bosscar9er; 01-22-2019 at 06:35 AM.
Shy of having any real GM docs like the window sticker and POP your looking for clues that are very easy to reproduce. The first thing to check is the engine block is it in fact a 66 427 block? If yes then you can look at the stamp pad. That’s where someone who knows what they are looking at is for. You need to detrime if the stamp is a real factory line stamp or a fake. Then you can look else where’s through out the car for clues.
One indicator of a 425HP option engine is the special F-41 suspension as part of the HD hardware in the package, and that included the rear sway bar. Without the sway bar, it most likley a 390HP. Other experienced CF members may ad other details. Dennis
I thought all BB cars had rear sway bar? I think there may have been a diameter diff in the bar between the heavier F-41 suspension option, though.
Doug
I thought all BB cars had rear sway bar? I think there may have been a diameter diff in the bar between the heavier F-41 suspension option, though.
Doug
My read of my reference material indicates it was only on the 425HP cars. Maybe it's inaccurate. Someone will else should know the details. Dennis
All big block cars for 65-67 had a rear sway bar. The same rear bar for both standard and HD suspension. The rear spring for standard suspension for big block was the same as small block.
The front coil springs for big block engines with standard suspension were the same for both 390 and 425 HP. The coil springs for HD suspension were unique though.
All big blocks had to sway bars in front and rear. 425 horse have square port heads, four bolt main block, aluminum snowflake intake, Holley duel feed carburetor, 6500 rpm tech. 80 lb oil gauge. No way to tell for sure unless you have the original block or paperwork as stated above. Plenty of restamps out there.
Last edited by 65 Pro Vette; 01-22-2019 at 03:00 PM.
One indicator of a 425HP option engine is the special F-41 suspension as part of the HD hardware in the package, and that included the rear sway bar. Without the sway bar, it most likley a 390HP. Other experienced CF members may ad other details. Dennis
mine is a 390 hp w/sway bar. Does that mean it was an option? I thought all 66 427 had rear sway bar?
never mind. I just read the rest of the posts!
All big blocks had to sway bars in front and rear. 425 horse have square port heads, four bolt main block, aluminum snowflake intake, Holley duel feed carburetor, 6500 rpm tech. 80 lb oil gauge. No way to tell for sure unless you have the original block or paperwork as stated above. Plenty of restamps out there.
All that, and if you can see the sticker on the back of the instrument cluster it should have code LB on it in large red letters. Others will chime in with correct casting numbers for the block, heads and intake manifold. The stamp pad should have T followed by 4 digits with the month and day of engine assembly, then code IP, followed by "6" and the last 6 digits of the VIN. Don't know if any engines were assembled other than at Tonawanda, NY (the T)
All big blocks had to sway bars in front and rear. 425 horse have square port heads, four bolt main block, aluminum snowflake intake, Holley duel feed carburetor, 6500 rpm tech. 80 lb oil gauge. No way to tell for sure unless you have the original block or paperwork as stated above. Plenty of restamps out there.
Thanks so much. That's what I was looking for. And good to know if I purchased the car and tore the engine apart, I could check for the square port heads and 4 bolt main, but the 6500 RPM tach and 80 lb oil gauge are good indicators the chassis is a 425 HP. Not that someone couldn't swap those out but it's unlikely I'll look for the dual Holly carbs too. Where on the block would I find the two digit block numbers referenced by Tiger Joe?
I think all L72 4-bolt blocks have HIPERF on the 942 block. I think the L36 uses the 961 block which is a 2-bolt. I'd start to make sure it's a 942 block then find the HIPERF. Others can confirm, but you need to see 942 and HIPERF and a block casting date that makes sense with the production date of the car. In my opinion that 4-bolt 942 block is the secret sauce whether it's a go or no go if you want an L72. Anyway, should be easy to get the block casting number and determine if it's a 4-bolt. Intakes, carbs, etc are relatively easy to come by compared to the block.... and consequently cheaper. I think that HIPERF shows up in two locations on my L72 block. The HIPERF shows up on towards the back of the block.
I seem to recall the big P under the 942 is also for a performance block (4-bolt) designation. I wouldn't rely on what's stamped on the pad. Then again I read an old post where someone faked the block casting number.... Best wishes.
I think all L72 4-bolt blocks have HIPERF on the 942 block. I think the L36 uses the 961 block which is a 2-bolt. I'd start to make sure it's a 942 block then find the HIPERF. Others can confirm, but you need to see 942 and HIPERF and a block casting date that makes sense with the production date of the car. In my opinion that 4-bolt 942 block is the secret sauce whether it's a go or no go if you want an L72. Anyway, should be easy to get the block casting number and determine if it's a 4-bolt. Intakes, carbs, etc are relatively easy to come by compared to the block.... and consequently cheaper. I think that HIPERF shows up in two locations on my L72 block. The HIPERF shows up on towards the back of the block.
The 390hp motor also used the 942 block. But it was a two bolt main
01-22-2019, 06:35 AM
Big Block 427 how to ID the 425 HP?
Dennis
All that, and if you can see the sticker on the back of the instrument cluster it should have code LB on it in large red letters. Others will chime in with correct casting numbers for the block, heads and intake manifold. The stamp pad should have T followed by 4 digits with the month and day of engine assembly, then code IP, followed by "6" and the last 6 digits of the VIN. Don't know if any engines were assembled other than at Tonawanda, NY (the T)
