Removing emissions from 73 to make 71

Does anyone know if there is any difference between my 1973 455 block (1973 Centurion) and say a 1971 455 block ?

If I just replace the intake manifold with one from a 71 and take all the emission stuff off. Will my engine block be the same as a 71 ? I know the heads are different but will it hurt my engine to simply replace the manifold and nix the smog stuff ?

Thanks

Gary

 

I don't believe there would be any problems with doing that. You may need to reset the carb idle screws.

Don't toss all that emissions stuff out! There are some folks out there who are looking for those pieces because of their state inspection requirements. Who know, some day you might want an air pump...
:laugh:

Of course, it is possible to leave all that emissions stuff in there, but bypass it all so that it looks stock/original... :Brow:

 

The intake probly won't work. The '71 did not have the AIR holes, and '72-'74 did. Block will use a different head gasket, due to cooling differences.

Head will interchange w/o problems.

Jim

 

Gary, do a search on 455 intake manifolds, I'm not sure which ones interchange now...I remember some discussion about covering up the AIR holes, but don't recall the details about which gasket worked with what intake/head.

Autozone following (different) valley pan gaskets for '71 and '73 455s,

FELPRO INTAKE MANIFOLD GASKET for a 1971 BUICK CENTURION
Unit Price: $23.99
Part No.: MS96005

FELPRO INTAKE MANIFOLD GASKET for a 1973 BUICK CENTURION
Unit Price: $17.99
Part No.: MS96014

 

Gary,

James is correct. The AIR holes will need to be tapped and pluged to make the earlier manifold work. You'll still have the same choke plate problem we spoke of earlier. Best bet is a '67-'69 430 intake. No direct port to exaust gases and uses the '71 and earlier bathtub gasket. You will need to pull the heads to keep the filings from dropping into the exaust valves. Not sure if this will pick up any real power. If the smog polizi catch you doing this they will be pis_ed.

Jim

 

Regarding the 430 intake. only advantage is no direct exhaust to be sealed ? What is the bathtup gasket for? Is it 2 bolt or 3 bolt ?

SO the heads must come off ? Just on the left side right ? If I take the heads off, I might as well just rebuild the whole thing. Ihve never done that before. I have replaced head gaskets on a chevy before but thats it. Other than that I have replaced cams and manifolds on SB chevys, but Im not sure about rebuilding it. I just rebuilt a Quadrajet perfectly. Is it much harder than that to rebuild the engine ??? hehe. .. I have swapped engines before. I need a crane and a stand. Oh no what am I doing ???? I just got married 3 months ago. Im not sure if our relationship is strong enough to withstand the strain of an engine overhaul. He he ....

What do I plug the air holes in the head with ? Can I just use epoxy ? JB weld.. Like I did on the Carb plugs ??

We dont have emissions testing here.

Thanks

Gary

 

What did you do to the heads to refresh them? Would you recommend polishing the passageways and on the intake too?

 

Gary,

Rebuilding the heads is a machine shop thing. They will add the plugs into the AIR holes at that time. If this is a high milage motor, you may find weak cyclinders after reassy. The bathtub gasket is the only intake gasket available at the parts counter. T/A does sell the Chevy type gasket which eliminates the bathtub.

Do not have them excessively mill the heads. It will screw up the valve train geometry (we all just loved geometry class). The rest is basic mechanics, sounds like you possess the skills to do this. If you go whole hog and rebuild everything, have the machine shop assemble the lower end. Follow the threads on bringing up the oil pressure and break in like any other new engine.

Hope it helps, good luck.

Jim