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470- What and why?

Engines > Street-Strip 470

What is a 470?

Simply put, a 470 BBB is the cubic inches we ended up with, when machining the crank and bores to fit the most advantages parts available. It was just dumb luck that we ended up with a cool-sounding round number.

4.350 bore, 3.95 Stroke are the specs.

Two Challenges present themselves when building a Buick 455 for Performance. A brief discussion of these issues will help you understand why we build a 470 Buick.

Piston compression height - Often referred to as "compression distance" or CD, is simply the dimension from the center of the wrist pin, to the piston crown or top. And nearly all Buick 455 pistons on the market now have what I consider the "wrong" CD.

Genesis of the issue:

Buick 455 pistons in the aftermarket today all are more or less "Blueprint spec"  pistons. When the Buick engineers designed the engine, the created a set of specifications for the engine, one of which was compression distance on the piston. Virtually all Aftermarket pistons on the market now are based on that spec.

The problem with that is the fact that the stock piston was designed to be .030 to .040 below the deck surface of the block. This allowed for production variance in sizing, on everything from the crank, rods , pistons ... to the block itself. Pistons sticking out of the bores would be the death on the assembly line, so that could not happen. Hence the very conservative CD of the stock piston.

Nearly all aftermarket pistons available for the 455 Buick, have a compression distance of 1.975 to 1.985.

Where we end up:

If we do the math, we see that to reach 10.570, which is the deck height of the 455 Buick, we need a piston that has a compression distance of 2.02. If we were working with an NOS block, we would want a piston with a CD of 2.02. In normal rebuild situations, we have found that it takes a .020 cut to perfectly square and clean up the deck of the block, so with stock crank and rods, we would want a piston with a 2" CD in a rebuild situation, to produce a zero deck clearance.

What what happens when you use "inexpensive" pistons

To use previously available forged pistons, and achieve the preferred zero deck clearance, it is common to have to machine .040-.055 off the decks. I did this many times. And when you cut the decks this much, even with new heads, the intake does not fit anymore. As the decks go down toward the crank centerline at 45*, the "V" gets narrower. So now we are cutting the intake, or intake side of the heads to make it all fit  together. More than a few guys just slotted the bolt holes to physically get the intake on. Not ideal for sure, and doing it the "right way" with all the milling, is just wasted time and money. All because we don't have the correct piston available. Most machinists I have worked with charge a double charge for decking more than .030.

Why you should care about this

Your new Performance engine is the most efficient, the least prone to detonation, and the most powerful when the pistons are level with the surface of the cylinder block. This is know as "zero deck clearance", and is universally accepted in the performance aftermarket to be the most desirable situation. Why would you settle for less? We can accommodate special requirements for both CD and dish volume if the situation  required it, for a small extra fee. We also can build zero deck pistons for stock rod/crank 400/430/455 Buicks, in any bore size required, without the full custom price.

Knowledge is Power

Even if you don't buy Pistons from TSP, and build a 470, you should understand the issue. Call your machinist and ask him how much he will charge you to cut .055 off the decks of your block. Most often, you will find that you could spend that money on the right pistons, and have better parts, instead of using it to support your machine shop. Your machinist won't mind, the last thing he wants to do is cut .055 off a block.

Stock Buick Rods - the other issue

For stock use, the Buick 455 connecting rod is plenty rugged, and the reason not to use them, even for moderate performance use, has little to do with durability. The problem with stock rods is that they are hard to work with-- here's why:

• Factory bolts don't dowel the cap in place- When Buick built the rods, the cap could slide around laterally on the rod body. During production, they simply clamped the cap to the rod with the bolts, and then bored the big end dimension. No one cared about the actual position of the cap, in relation to the body, as long as they stayed together as a mate, the rod would align itself on the crank, and everyone was happy.

• Enter ARP Rod bolts- the standard for an upgrade to the factory bolt, they bolts now do "dowel" the cap in position. The problem comes, when one of these mis-position rods from the factory were put together with ARP bolts. The cap could be .020 offset from the rod body- not good, and nearly impossible to repair.. all you can do is get another rod. Back when I used a lot of stock rods, it was normal to take 12 cores to get a good set of 8. Even then, if you could get a set of rods who's length was within .005" of each other, you were doing good.

• And finally, after you get past that hurdle- you have the balancing issue. Most rods have a weight pad  on both the small end and the big end, so those weights can be equalized easily. No such luck in Buick land, we are stuck with one balance weight just up from the big end. Buick rods take at least twice as long to balance a set as just about any other rod out there. More time = more money.

It was not at all uncommon to have $300+ in a set of nice, prepped stock rods. And they are more susceptible to failure in a high performance engine that a good HD aftermarket rod.

The 470 combo

This combo is not new, we certainly did not "come up with it" at TSP. In fact, there were several builders who had built 470ci engines. The deal is pretty simple- resize the crank to fit a widely available aftermarket rod, and have custom pistons made to make the whole thing work out, dimensionally. Eliminate the goofy 1" pin size of the Buick, for the much more common .990 pin.

The problem was in the past, the custom pistons cost around 1K, so no cost savings were realized.

What had to happen is that 40 pistons had to be purchased from Diamond racing pistons, and with that buy-in, they would create a shelf stock part number for the piston, and sell it at the shelf piston price. This brings it back down to the cost of other good quality aftermarket pistons. With 5 engines on the docket already in May of '09 it was a no brainer to make this happen.

Here are the specifics:

The stock Buick 400/430/455 crank pin  has to be offset ground .050, which reduces it to 2.200, and increases the stroke from 3.9 to 3.95. It is also widened to 2". This allows the aftermarket BBC rod, and the BBC rod bearing to be used. Now we have a multitude of rods available. I chose the 6.800 inch length, as the longer rod reduces stress on the cylinder walls. Rod costs range from mid $400's to just over 1K, depending on the manufacturer you select to provided them. Rod bearing choices are excellent, and cost considerably less than what is offered for the Buick. Billet steel, Forged Steel H and I beam, Aluminum and I would imagine even Titanium rods are available. Finally, you can pay attention to the BBC section of your catalog for something!

The custom piston we created is from Diamond Racing Pistons in Michigan, and is an exclusive part created for us and sold only buy us.  We do sell these pistons outright, it is not required to by an engine from us to get this piston.

The piston is exactly right to fit into a block that is decked .020. It goes in with no modifications to the rods, and the bore size is the desirable 4.350. It's 1.775 CD, a 6.800 long rod, and the .050 stroked crank, combine to produce the desirable "0" deck clearnace, without the need to re-fit the intake manifold due to excessive milling. If the heads have not been excissively milled, everthing fits together perfectly, thus reducing or eliminating several costly milling operations. I don't know about you, but if i have to spend X dollars to get my BBB right, I would rather spend the money on better parts, than on machine shop labor.

Our pistons feature:

  • 1/16 compression- 3/16 oil ring

  • Designed to zero deck your shortblock with just a .020 clean up cut on the block (10.550 deck height)

  • 25cc spherical dish- 10.6-1 compression with 68cc heads, ideal for alum head street combos.

  • extra deep .300 x 15* symmetrical valve reliefs

  • .030 offset pins for quiet operation cold, with the .0045 piston to wall clearance recommended.

  • 2618 material- the superior piston material for all applications- more expensive than 4032 pistons.

  • Standard duty Pins and Spirial locks included

  • Pin fitted and ready to go

  • H-11 tool steel Pins available for all applications.

  • Change any spec to customize your pistons, for just $8 per change/per piston. Up to 2 changes allowed- we can supply a quality custom piston for any 455 based combo, for less than the custom piston price.

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