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Buick 455 differences


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Are there any significant differences between a '76 455 and a '71 455, other than the HEI distributor?

I'm working on cleaning up my father-in-laws mini car hoard. He is a long time BCA member. Amongst the cars are a '71 Electra 4 door hardtop and a '76 Electra 4 door hardtop. Both have 455 motors.I have this vague notion of keeping one of the engines and transmissions for a street rod or custom project in the future. Perhaps trying to wedge the 455 and 400 trans in the body of a '54 Roadmaster I have.

Thanks

Scott in Colorado

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I know the system can be somewhat "unsightly", but those systems aren't the big "performance killers" they were made out to be, back when the car was newer. Basically, you have the air pump itself, a "diverter valve" which sends the air to different places dependent upon some operational parameters, the check valve for each bank, the metal manifold which attaches to the exhaust manifold, AND "nozzles" which put the air deep into the exhaust passages of the exhaust manifold.

The check valves are there to keep the "hot" exhaust gases from migrating upstream from the divider manifold on the exhaust manifold. Should a check valve deteriorate, exhaust gasses can then easily get to the rubber hoses which take the air to the divider manifold, even melting the divider manifolds from the inside out. Reman pumps and new check valves are available in the aftermarket or in the restoration parts side of things. Many common parts between the various GM divisions, too.

Many people used to remove those systems all the time, back before a visual check for emissions hardware became a Texas State Inspection item. Not unusual to see pickup trucks with pipe plugs in the manifold holes. A quick check of the emissions decal would verify what had happened or not happened. GM's replacement exhaust manifolds were usually set-up for the air pump system, even if the vehicle didn't have one from the factory.

The ONE part many didn't know about is the nozzles in the exhaust manifold, held in by the divider manifold. They need to be removed, too, if they are there.

The air pump usually had it's own belt pulley groove on the water pump and crankshaft pulleys. Everything unbolts and can be removed. Key thing is to make it NOT look like it ever had an air pump system on it. GM has some "plugs" for the air pump holes in the manifolds, or used to have them in the parts book, which look quite a bit better than universal pipe plugs.

Might better check with your local state inspection station to see if "emissions hardware" is something they check for on that model year of vehicle . . . for good measure. If there are some failed parts, they'll probably need to be replaced.

Enjoy!

NTX5467

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NTX5467, Thanks for the explanation. I purchased a 73 Centurion with 50K miles. It has been sitting in dry storage since 99 and I thought it would be nice to get rid of the emissions junk as I bring it back to life. I will check with the local inspection station. Bob Smits

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Actually Willis, the Buick A.I.R. system was connected to the intake manifold and not the exhaust manifold(s). A much more sturdy system than the style than tended to rust out from the hot exhaust manifold gasses, a style that the lower cost Chevy's used. The Chevy style used, as you stated, spindly pipes connected to the exhaust to inject oxygen to the exhaust stream to "light off" unburned hydrocarbons. On the Buick system, one can block off the A.I.R. passages with a pipe cap, similar to the style used on natural gas pipes (black pipe) and remove the belt from the pump itself and the system is then disabled but can easily be reconnected should the owner wish.

Buick 455's, starting in 1972 and also in 350's beginning in 1973, used this style of A.I.R. A different intake manifold, with the proper passages, was utilized in those later years and can be ID'd by the cast-in passages located near the edges where the intake bolts to the heads.

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75-76 Buick 455s had updated structural (lifter valley) and oiling passage improvements incorporated into the castings.

Hence, they are preferred by 455 enthusiasts. Also, the 75-76 heads do not have

the A.I.R. heat passage holes that the 73 motors will have. I used a 73 Riviera 455 in my"LoadMaster"

51 Chevy panel truck & had to plug all those passages in order to allow the installation of aftermarket

intake manifold. As Brad pointed out above the 73 manifolds had tubular shaped passages cast in to them for the

nasty stuff to travel thru!

The 76 would be a better choice for a hot rod or street machine, in my opinion. Regardless of your choice

I have always incorporated the following into a 455 Buick build:

- upgrade the timing cover seal from "rope" to conventional neoprene seal (T/A Performance & elsewhere.)

- upgrade to newer style rear main seal (be sure to offset clock it 1/4" to assure a good seal.)

- buy the T/A Performance oil pump plate kit & the adjustable oil pressure fixture ( only a few bucks to remedy the wear

on the oil pump thrust side of the timing cover & you'll have gobs of adjustable oil pressure) Pack the oil pump with

Vaseline to assure good priming on initial start up.

- Teflon coated cam bearings that improve the oiling of the camshaft bearings. These require the cam bearing

installer to pay attention to the instructions for clocking them into position!

Lastly, whatever motor you use ….. use the pulleys that came on the motor originally to ensure correct belt line up.

A lot of 455 builders buy a pulley here & there or off of eBay and then realize there were some many variations in 455 configurations

they end up with a bunch of pulleys that bolt on, but don't line up!

mike<script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/1e3d64fe/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/1e3d64fe/background/helpers/prefilterHelper.js"></script><script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/1e3d64fe/background/helpers/prefilterHelper.js"></script>

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Someone can correct me if I'm wrong, but I think the only difference between the 1970 and 1971 versions of the 455 is that the 71 used dished pistons to lower the compression ration to allow use of the then new unleaded gasoline of lower octane. If one is doing a complete rebuild, then installation of new 1970 specific pistions into the 1971 engine should restore the higher compression. That would be my preference.

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The only advantage of the late 455's is the block thickness. 71 and later blocks have the enlarged oil passages already. 75 and 76 heads are good for use as door stops due to their open chambers, reducing compression even more.

And yes, 70 pistons have a smaller dish and will raise compression on an otherwise stock 71+ engine.

If you don't plan on doing any rebuild work on the engine you choose, then grab the 71. Or if you can get both, save the 76 short block.

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You might want to closely check the piston specs of any non-GM replacement pistons. In the middle 80s or possibly a little earlier, many replacement piston manufacturers started to "de-stroke" their pistons .020" to make them more compatible for the generally lower octane unleaded fuels of that time, before super unleaded gained a few more octane points. This means they changed the "compression distance" (between the centerline of the piston pin and the piston crown) to lower compression for better customer satisfaction with these lower-octane fuels. Otherwise, the pistons will look correct for their application.

Many replacement piston manufacturers will note this in their specs as "de-stroked _____ from stock".

Thanks for that information on the Buick A.I.R. System, Brad.

NTX5467

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  • 8 months later...

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