Buick 455 Question?

Since I made my decision to go with a Buick 455 in my car, new questions arise. I know there was a dramatic drop in HP in the 455 in the early '70s. Im just not sure which year it was. Ive got a line on two 1971 455's and am just trying to make sure thats not the year of declining muscle in these motors. Can anyone help me out here? Thanks. Steve

If you can, get a Buick 455 that matches the year your car was made. I am not sure if its possible to tell with Buick, from the serial numbers. I know it is with Pontiacs and generally not with Olds.

The power decline you talk about was largely on paper.
Up to 1970, the power ratings were SAE 'gross', where all the power robbing accessories such as exhaust, water pumps air cleaners were not installed. There was also a LOT of advertising and fiction involved in their publication.
In 1971, GM went to SAE 'net' where the power was measured as installed in the car, with all equipment attached. This process is much more accurate.
Therefore, the 370 hp 1970 455 is not accurate and is likely almost identical to the 250 hp 1971 455.
There were 2 differences, though. 1971 and later had hardened valve seats, suitable for unleaded gas. Earlier engines will last longer if you use a lead suppliment.
Also, compression ratios dropped in 1971. You lost about 4% of power for every 1 point in compression dropped, but it will run better on todays gas.
Many high compression engines from the '60's will rattle like 6 lug nuts in a coffee can even on our premium unleaded today.

Finally, even a lower power 455 can really be boosted by some simple bolt on parts and careful tuning.

Thank you MagicRat-To many people do not understand the HP rating change

I would say 1972 is the last good year for the 455. After that, compression and horsepower really dropped and it probably isn't worth the $$ to fix it up. A 1971 455 should be strong enough.

Thanks again everyone. Hopefully will have some pics in a couple weeks. Steve

Actually the ratings changed from gross to net in 1972. You may remember that the mopar hemi was in its last year in 71 and it was still rated at 425. The LS6 chevelle was down slightly to 425 from 450. In the Buicks power dropped from 360 to 330 in the GS cars and to 270 in 1972. With muscle cars the difference between net and gross is about 50-60 hp. In 72 Buick and Mopar motors had EGR because they were particularly dirty and that dropped the power even more. FYI Buick engineers invented the EGR system that was copied by other manufactures and became the standard design of EGR.

1971 is a good year for a Buick motor because their were some revisions in the oiling system. They came with dished pistons to reduce compression to 8.5:1, so you can easily regain compression by switching pistons.

1976 was the only bad year due to the heads. They had smaller valves. The good thing about 76 motors is that they came stock with HEI.

there were several hp/torque drops from 71 to 76. the 1970 motor was the highest rated big block buick ever put out (370hp / 510tq) but it only lasted one year.

the drop between 70 and 71 was due to buick reducing the compression ratio from 10.0 (or the 10.5 option motor in the 70 GS) to 8.5 which buick used for all of their 455's until 75 when they slashed it to 7.9 . the 71 motors ranged from 315hp / 450tq to 345hp / 460tq. any 430 from 67 to 69 would be better with the 69 motor having 360hp / 475tq.

otoh, their biggest cam came on the stage 1 455 motors @ .490 / .490 while the 67-69 430's had the best rocker ratio with 1.59 or 1.6 . the 455's all came with a 1.55 ratio. i mention this because other than the dia of the bore the parts on the 430 and 455 are pretty much interchangeable.

1971 is a good year for a Buick motor because their were some revisions in the oiling system.
agreed, but any 430/455 should still have it's oiling system bored out if it's going to be used for a performance ap.
buick power production == greeeaaaatttt!
buick lubrication == crap

The LS6 chevelle was down slightly to 425 from 450.
CR drop from 11.25 to 9.0 . sickening innit?

ps - all of the spec info is from a 1983 edition of "Petersen's Big Book of Auto Repair" and i know that not all of the options are listed in it (it only notes stage 1 parts for 73-74)

the NHRA web site is also useful although they list 10:1 motors in 74 (wrong) and don't have any data for 73 at all

Actually the ratings changed from gross to net in 1972. You may remember that the mopar hemi was in its last year in 71 and it was still rated at 425. The LS6 chevelle was down slightly to 425 from 450. In the Buicks power dropped from 360 to 330 in the GS cars and to 270 in 1972. With muscle cars the difference between net and gross is about 50-60 hp. In 72 Buick and Mopar motors had EGR because they were particularly dirty and that dropped the power even more. FYI Buick engineers invented the EGR system that was copied by other manufactures and became the standard design of EGR.

1971 is a good year for a Buick motor because their were some revisions in the oiling system. They came with dished pistons to reduce compression to 8.5:1, so you can easily regain compression by switching pistons.

1976 was the only bad year due to the heads. They had smaller valves. The good thing about 76 motors is that they came stock with HEI.

First of all egr valves don't really affect max hp numbers as they are not operational under full throttle.

Gross hp to net hp can be as much a 1/3 in some cases

I would work on any Buick 455 except the 76 year. the 76 years heads were poor castings. (In 1976 though the 455 used HEI distributers.) Of the years 70-71, are the best choices, and the 72 is good, but that doesent mean I would discount those made between 73 and 75. Alot of people go crazy talking about HP. That sensationtion that places your back into your seat under acceleration is produced by torque. This Motor is all about torque, and in my opinion, thats how this motor should be looked at. Yes horspower and torque are related, the difference is Torque is the motors potential power. You really dont have to put the RPMs into the stratosphere to achieve a powerful Buick nor should you need to go with crazy gear ratios or Compression ratios. My words here are not Gospel, and there are guys that have made successful high revving high compression Buicks, all I am saying this is a different animal than a small block Chevy.

PS. Thats just my opinion, another thing you can do use the rear main seal application for a 76' cadillac 500cui its a modern neoprene seal opposed to the rope seal used by Buick.

There is a plate and spring set out there(made by milodin? sold at napa.) that places the bottom of the oil gears against steel intead of the original aluminum plate used by buick on the timing cover(it allows work on the oil pump without dismanteling the motor). One reason This Buick has a poor reputation in its oiling is that this original aluminum plate is soft and becomes scored by the oil pump gears,the new steel plate eliminates this problem improving oil pressure. Poston and TA Buick offer complete timing covers, and oil pump gear kits.(offering longer gears.)(the timing covers house the Oil pump gears, distributer and part of the water pump, they are cast aluminum.)

All this talk of horsepower and torque, if you're rebuilding an engine, is completely irrelevant. You can build whatever you like. The ehad castings can affect the ultimate outcome if they're too "small" or too "big".
The big Buick is an excellent torque engine. The biggest advantage in a street car, is the weight (lack of) over other large-displacement families. It is advised, if planning to rev it past 6,000 RPM, block braces and oiling upgrades are mandetory. Poston has excellent stuff, as does T/A Performance. I like the looks of that Poston open-plenum intake.
I have one customer running a cute G-body (the '80 or '81 Century model with the big back window) in the mid-6s (1/8 mile). Not bad for a heavy car, but he DOES have valve spring and cam bearing issues from time to time. The block is actually TOO thin, and any significant over-heating can cause so much flex, the cam bearings eat themselves up.
All in all, any year 430 or 455 is a good one, provided you pick the right parts to make power in the range you intend to use it.