455 Performance Specs

[Guest]

I'm rebuilding a 74 455 stock motor to as close to the 70 Stage 1 specs as possible. The only changes over stock as of now are Edelbrock aluminum manifold and performer carb, hemi-killer or similar cam, and stage 1 headers. I'd like to see her turn 400hp or so give or take. I know that there was a change in heads for the after 72 years, resulting in the lower compression. What do I need to do to the heads in order to make them flow to the 70 specs or how else would I get that higher compression resulting in the higher horsepower? Your advice has always been very helpful and I appreciate your expertise in advance. Have a nice day.<P>------------------<BR>67 Skylark 455

[The Old Guy]

The heads were not the only thing that changed the compression. The pistons had a deeper dish than the 70 pistons which was a good part of the lower compression. You can purchase the higher compression pistons from TA performance or Poston Enterprises

[Guest]

i highly recommend that you check out <A HREF="http://www.buickgsca.com/" TARGET=_blank>http://www.buickgsca.com/</A> <P>they have a bulletin board where there is a great deal of performance knowlege about the last buick v8's. i think you will find that you cannot just deck the block and heads, you will need either pop-up pistons with your stock heads, or a set of earlier heads and pistons.<P>allan

[Guest]

I RAN A 71 BLOCK AND STOCK PISTONS WITH 70 HEADS POSTON 113 CAM, TA SP1 INTAKE AND POSTON HEADERS. THIS WAS AN EXCELLENT COMBO FOR THE STREET AS YOU COULD RUN ANY GRADE OF FUEL WITH NO WORRIES ABOUT DETONATION. ASK 430 OWNERS ABOUT DETONATION. BETWEEN ME AND A FREIND OF MINE WE HOLED OR BROKE RING LANDS ON ABOUT 6 430 PISTONS.

[Guest]

I'm not certain about the differences bewteen the post '72 heads and the '68 to '72 Buick big block heads. Please correct me if I am wrong about this, but I believe that heads from the '68 & '69 430 motors, and the 1970, '71 & '72 455 motors are all but identical. My understanding is that compression ratio was lowered in 1971 and '72 strictly with a piston change. I know this to be true for the Buick 350.<P>As far as detonation with a stock 430 motor is concerned, these engines came with a 10.25:1 compression ratio, which was pretty healthy even back in the days of 102 octane. There is NO WAY you could run this engine on the street today burning 92 octane fuel without drastically altering the timing, or using octane boost with every fill up.<P>I would talk to T/A Performance about what your goals are before I did anything on one of these engines. It is sure what I plan to do with my 350 rebuild... unless I snag a '68 Electra on the cheap that's been at our local Goodwill. If that happens then I will be able to post with a little more firsthand knowledge about building a 430 for street use.<P>Matthew

[Guest]

again, if they ever get the board working over there, the buickgsca.com website's board is the best place to ask this.<P>to answer the last post-<BR>the chamber and valve size on big block heads are basically the same. the 1967 430 heads (and a few of the 68's) are preferred by racers wanting to use relatively stock parts, as they dont have the AIR tubes that the later heads have, and they have a larger intake port cross-sectional area. they are generally refered to as 'big port' heads.<P>the 73 and up heads (maybe some earlier ones)<BR>have more smog stuff in them, but they have nice flame hardened valve seats, much better for street driving.<P>i personally would not try to run the higher compression. stick with a mild shave to get to 9:1. that should be fine.

[Guest]

All good advice from above. I would add that with the Hemi-killer cam's duration, 10.25:1 true compression can be used and run on 92 octane. I'm doing it right now. I suggest you use the sealed-power forged pistons, notching is required for the hemi-killer cam I'm pretty sure. Mine appreciates good gas, but doesn't detonate at 12 deg. initial and 32 deg total timing in by 2500 RPM.<BR>Unless you zero-deck the block, and mill a bunch off the heads you aren't going to have a true 10.25:1 from these pistons anyway. I suggest zero-decking the block, and you can decide where to go from there. This is all with '67-'70 heads. <P>Polish your combustion chambers and make sure there are no sharp edges anywhere. As for head improvemnts, have your machinist unshroud the valves out to the edge of the head gaskets, and back cut the valve with a 30 degree angle. Blend all of the 70 degree cuts into the bowls so there are no sharp edges, and narrow the guide up a little on the wide portion of the intake port. That will give you a good set of mild ported street heads.<P>I hope that carb is AT LEAT 750 CFM, or else you should switch to a '71-'72 Q-Jet. The mileage will be better too.<P>HTH,<P>Adam

[GSMAG]

There's a web page called "Big Block Buick" that belongs to the Buick web ring. It does a very good job of detailing what the changes were in the engines and when they took place.