1965 - Bb

[Ewing M.]

what was the approximate first VIN BB serial number in 1965
& what approximate VIN did HP rating switch from 450 to 425?????????????

[Clem Z.]

Re: 1965 - Bb

what was the approximate first VIN BB serial number in 1965
& what approximate VIN did HP rating switch from 450 to 425?????????????

mine was built in march for a april 16 factory delivery was VIN 114271 and your second question happened to the 66 BB not 65

[Ewing M.]

Re: 1965 - Bb

i thought the 65 came out at 450 hp then was derated to 425 for insurance purposes, sorry ! now that i think of it, guess you are correct

[Tom H.]

Re: 1965 - Bb

I have an old 65 judging manual that states the 396 first appeared around VIN # 13000.

[John D.]

Re: 1965 - Bb

i thought the 65 came out at 450 hp then was derated to 425 for insurance purposes, sorry ! now that i think of it, guess you are correct

Ewing, In 66 I bought a new red 66 BB conv off the show room floor. It had a 425Hp decal on the black air cleaner lid. I think it was black?
Anyhow one of the mechanics at Grabiak Chevrolet where old Clem hung out said to me. "Do you know the 425 decal is a fake". I said what do you mean fake. Then he peeled the 425HP decal off and under neath was a 450 HP decal. I was impressed as I recall.
So Clem is right.
JD

[Joe L.]

Re: 1965 - Bb

i thought the 65 came out at 450 hp then was derated to 425 for insurance purposes, sorry ! now that i think of it, guess you are correct

Ewing------


As clem mentioned, all 1965 L-78 were rated at 425 hp and the air cleaners were so-labeled.

It was early 1966 that used the 450 hp rating. My guess has always been that what happened was that since the cubic inch displacement was going up, someone at GM figured that they should not leave the HP rating the same as the 1965 smaller cubic inch rating. So, they upped it to 450. For whatever reason, they "backed-off" very quickly and returned the rating to 425.

Intrinsically, the L-72 should have had a higher horsepower rating than the L-78. They were, basically, the exact same engines except the L-72 had 31 more cubic inches.

Some theorize that the reason for the lowering of advertised HP had something to do with insurance. However, I don't think so. There was never any insurance "break-point" that I am aware of for HP. In other words, if the car was rated at 425 HP or 450 HP, I don't think there would have been any difference in insurability or insurance premiums. With either rating getting insurance was going to be difficult and was going to cost a lot.

[John H.]

Re: 1965 - Bb

Some theorize that the reason for the lowering of advertised HP had something to do with insurance. However, I don't think so. There was never any insurance "break-point" that I am aware of for HP. In other words, if the car was rated at 425 HP or 450 HP, I don't think there would have been any difference in insurability or insurance premiums. With either rating getting insurance was going to be difficult and was going to cost a lot.

Joe -

The ECR (#73000) that stop-ordered the higher-horsepower air cleaner stickers on all '66 solid-lifter big-blocks (and the L-36) on all car lines and replaced them with the down-rated stickers stated as the reason, "Management Direction". That could cover lots of ground.

[Bill M.]

Re: 1965 - Bb

Intrinsically, the L-72 should have had a higher horsepower rating than the L-78. They were, basically, the exact same engines except the L-72 had 31 more cubic inches.

Joe:

There was a difference. The 425/396 was lashed at 0.020/0.024. The 425/427 was lashed at 0.024/0.028. I'm assuming that the 450/427 was lashed at at 0.020/0.024.

That doesn't explain the hydraulic cam engine going from 400 to 390, but the 390 pulled peak power at a lower rpm. If the engines were identical, then the test procedure changed. You won't get a lower rated HP speed for just a lower torque curve overall; the torque curve has to change SHAPE.

Did both changes drop it from 450 at 6400 to 425 at 5600. Maybe.

I think the valve lash was revised on the solid cam engine because it had such poor part-throttle low-end torque. I'm guessing that the the '65 396 3.36:1 standard rear gear was revised to 3.55:1 standard for the solid-cam 427 for the same reason.

That's my theory and I'm sticking to it!

Bill

[Twan B.]

Re: 1965 - Bb

Question......

Did the BB replace the fueli in '65 ore was the fueli avalible for '65 thru?

Gr, Twan

[Wayne M.]

Re: 1965 - Bb

Question......

Did the BB replace the fueli in '65 ore was the fueli avalible for '65 thru?

Gr, Twan

According to GM literature, the 396 was to replace the L76 (365hp), but both it and the L84 were produced to the end of production, so in effect, it didn't replace any other engine option.