Summit Racing Blueprint Engines Small-Block

By Jeff Smith   –   Images by the Author

The small-block Chevy has now come full circle. When the GM LS Gen III small-block debuted just before the start of the 21^st century, pundits immediately began foreshadowing the death of the Gen I small-block. But as Mark Twain once observed, “The rumors of my death are greatly exaggerated.” So it is with the small-block Chevy. It is way too popular to rust its way into obscurity.

The demand for this ubiquitous V-8 is so great that the clamor for usable engine blocks has now reached a critical point. Are they still out there? Of course. Does your brother-in-law have six, four-bolt main, standard bore, 350 blocks sitting in the corner of his shop pining for a new home? Probably not, unless he’s a hoarder. The point is that good one- and two-piece rear main seal standard bore 350 blocks are no longer lining junkyards in America.

In order to supply the continuing demand for this ubiquitous engine the folks at Blueprint Engines (BPE) invested in making their own block. Working with Summit Racing, these two companies collaborated to produce what is looking like the nicest small-block casting to come out of the aftermarket once GM decided it was no longer interested in carrying on the tradition.

The connection between BPE and Summit makes perfect sense. If you want to buy a new, complete small-block Chevy engine (not a rebuild), BPE will supply a fully assembled or even a partial engine assembly within a broad spectrum of sizes. But if you’d rather build your own engine with a really nice casting that will require mere honing to fit the pistons, then Summit’s Street, Performance, Competition (SPC) block is where you would start your search.

The blocks begin life in a high-tech casting facility in Germany where they know how to make things correctly. Then the raw castings, already powdercoated in black, are shipped to BPE’s ultra-modern facility in Kearney, Nebraska, where the complete machining process is performed on Makino CNC machines that produce a very fine machined surface.

This is where the magic happens because accuracy in setting all the critical machined positions is something that BPE takes very seriously with this new block.

We spoke with Chris Straub of Straub Technologies in Piney Flats, Tennessee, who is immersed in the business of building high-performance engines. His company purchased one of these new BPE/Summit blocks but before embarking on a typical build, they took the time to evaluate a few critical coordinates on this block.

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What they found was both enlightening and encouraging. As Chris says, “Out of all the aftermarket blocks we’ve have had on the machine, the Summit block was the closest to the GM print.” The machine he mentioned is a Rottler F69A that can not only measure but also completely CNC machine a block and heads with amazing accuracy. In this case, Straub used their Rottler to measure the accuracy of the BPE/Summit block relative to main bores, deck height dimensions, as well as lifter bore accuracy.

Straub found the decks to be within 0.002 inch on one side and 0.003 inch on the opposite bank of perfectly parallel to the crank centerline. He also found the main housing bores to be exactly in the middle of the GM spec. We were especially interested in the lifter bore positions since we’ve been the victim of a small-block one-piece rear main seal block that was so far out of spec as to almost criminal. That engine barely ran and defied tuning efforts for years.

The Summit SPC block that Straub tested was found to measure within 0.001 inch of perpendicular to the cam (on the vertical axis) and within 0.003 inch on the horizontal axis. The vertical axis test is the more critical of the two as it helps determine valve timing accuracy. This 0.001-inch spec remained true for all 16 lifter bores!

So, by now you should be thinking that this puts this BPE/Summit block leagues ahead of a high-mileage production block where you might have to invest $2,000 or more to get the same quality of component positioning. This is especially true when you consider that this bare block through Summit is priced significantly less than all the other similar aftermarket and factory iron castings.

But there’s still much more to talk about. Starting from the lower end and working up, these blocks are available through Summit in either the traditional two-piece or with the newer one-piece rear main seal, both as four-bolt main cap blocks. Bore sizes are available in either 4.00-inch 350ci engine size or in the 400 configuration with a 4.125-inch bore. Both bore sizes are delivered in a 0.005-inch undersize to allow for final torque plate honing.

The blocks are designed with additional crankcase clearances for a 3.75-inch stroke crank (depending upon connecting rod selection, of course) and can be machined for a longer stroke without worry of hitting water because the pan rail area is solid—a nice feature.

We’ve included a chart listing all the important block features, but a few are important enough to call out for special attention. The aforementioned four-bolt main caps are drilled with 7/16-inch inboard fasteners with outer splayed cap hardware at 3/8 inch. Summit’s Brian Nutter noted that the outer bolts are mainly there to improve lateral cap stability while still contributing to vertical holding power. The caps are also of a stronger, nodular iron material.

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The deck surface is much thicker at 0.600 inch and Straub tells us that the cylinders are all within 0.0015 inch of the 4.400 bore spacing spec, which is tight when compared to production blocks. Wall thickness was another important factor in the design and Summit says even at the maximum 4.185-inch bore diameter that the cylinder wall thickness will be a minimum of 0.220 inch. The SPC block is a Siamese design, which ties the adjacent walls of the cylinders together for added strength.

Moving into the lifter valley, you will notice that all the blocks are machined for the factory hydraulic roller lifter configuration that can use the OE spider and dog bones for the OE hydraulic roller lifters. The lifter bores are also taller than the older SBC lifter bores originally intended for flat-tappet lifters. When using a roller lifter make sure the tie bar is tall enough to clear the lifter bore housing. This requires the use of 0.300-inch taller roller lifters and it should be noted that this taller configuration means the heads must be off in order to service the lifters.

The cam bearings are also special for this block, and we’ve included the correct part number, which allows the use of either a flat-tappet or roller camshaft. One additional feature that all small-block Chevy roller cam fans will appreciate is the machined flat portion for an OE-style cam retainer plate. This eliminates the need for a custom cam button installation but will require the use of a stepped nose cam like those used in ’87 and later small-block applications like the Gen II LT1. The three main lifter gallery plugs are threaded and will require pipe plugs to seal the ends.

The deck height for the BPE/Summit block is lower at 9.00 inches compared to the production spec of 9.025 inches. This is because most aftermarket performance pistons today are designed around this shorter deck height.

While this new BPE/Summit block may not be the answer to a budget-limited small-block Chevy buildup, it certainly qualifies as the place to start for a serious small-block effort. For the serious builder, starting with a much stronger block and more accurate block can actually save money. This author recently invested over $2,800 in a stock small-block where every opportunity was taken to ensure accuracy. Summit’s current price is dramatically lower than this figure with a foundation that is inherently stronger and just as accurate. This is what technology and wise investments from big businesses can produce.

Sidebar – Rat on the Way

According to our sources at BPE and Summit Racing, this small-block will soon be joined by a BPE/Summit big-block cylinder block casting. The blocks will be cast in similar high-strength iron using the MKIV configuration and will be available in both short- and tall-deck versions. These new blocks will be cast in both 4.500- and 4.600-inch bore sizes with options for one- or two-piece rear main seals.

Block Specs: All specs in inches unless otherwise noted

Parts List

Sources

Blueprint Engines
(800) 483-4263
blueprintengines.com

Straub Technologies
(423) 391-7774
straubtechnologies.com

Summit Racing
(800) 230-3030
summitracing.com

Click on this issue’s cover to see the enhanced digital version of Summit Racing Blueprint Engines Small-Block.