Leaving Well Enough Alone

MICHAEL HARRINGTON . May 23, 2022 . All Feature Vehicles

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Converting a 327 Small-Block Into a 350

Most vehicle owners are constrained to balance the budget between home life and the fun life. The decision to stick with the engine that came in the vehicle is one that many face while pursuing their own builds. In this case, the engine that came with the vehicle is a 1968 327-ci small-block. There’s little need to go into the virtues and history of Chevrolet’s legendary small-block engine. Suffice it to say that in 2011 GM claims to have produced 100 million of these engines (and that doesn’t include third party aftermarket blocks). With astronomical numbers like that, rebuilding one of the most commonly used engines on the planet is the perfect way to save some cabbage.

Many performance car owners lustily dream of big-powered mills pushing their vehicles down local highways and boulevards, those are good dreams to have. Stomping the loud pedal and snapping the vehicle in a straight line like a rocket on rails is an E-ticket ride, and the best seat in the house is behind the wheel. However, as most know, purchasing that E-ticket will siphon money from a budget faster than the IRS can drain Willy Nelson’s accounts.

Engine	Year	Bore	Stroke	Main Journal Diameter	Rod Journal Diameter	Main Bearings	Cylinder Volume	Rod Length
327 ci	1962-67	4.000	3.250	2.300	2.000	2-bolt	40.861	5.703
327 ci	1968-69	4.000	3.250	2.450	2.100	2-bolt	40.861	5.703
350 ci	1967-present	4.000	3.484	2.450	2.100	2 or 4 bolt main	43.803	5.703

With that nasty “B” word on the tip of the tongue and foremost in the minds of many vehicle owners, breaking the budget is simply not an option. For some this might appear to be a handicap, when in reality leaving well enough alone often serves as the best solution.

The 1968 Chevy small-block that came with the vehicle is one of the more desirable 327s that Chevrolet built. What made these engines better than the previous 327s were the larger diameters of the main journals. An earlier 327 would have had a main journal size of 2.300, whereas the new and improved larger journal size of the 1968 is 2.450. What this means is this particular 327 can easily be upgraded into a 350, which has become a standard in the aftermarket industry with tons of available parts. (Refer to the chart above for side-by-side number comparisons.) In 1968 GM claimed that the 327 produced that year was putting out 250 hp. Take into account parasitic loss of about 70 hp from the flywheel; through the transmission, driveshaft, rearend and finally the tires, and it’s a safe estimation that approximately 180 ponies were actually punching the pavement. An upgrade of 23 extra cubic inches will certainly help the old Chevy get up and go.

The worn-out 327 found a new lease on life at Larry’s Track-Pro in Montebello, California. Shop owner Jim Escamilla says that the upgrade from a 327 to a 350 is a simple enough task. But what if the 327 is an earlier model year with the smaller journals? Even if the 327 is a pre-’68 with smaller journals, Larry’s Track-Pro informs us that they can still work the smaller journal 327 engines into a better-performing 350. All that is required from the end user is the casting numbers and their shop will provide the necessary parts for the upgrade, an upgrade that they can complete at their shop, fully assembled from oil pan to intake manifold; or Larry’s Track-Pro will ship all of the essential parts for the do-it-yourself builder at home.

Components

1. The larger sized main journal diameters of the 1968 327 small-block, 2.450, are the exact size of the later 350 small-block. The difference between the two is the length of stroke on the crank, 3.250 for the 327 and 3.484 for the 350.

2. The connecting rod length from the 327 to the 350 is the same size, 5.703 for both engines.

3. Besides the crank stroke one of the main differences between a 327 and the 350 is cylinder volume. The 327s have a smaller cylinder volume of 40.861, while the 350’s cylinder volume is 43.803. The 327 has been bored and honed to match the volume of a 350 block.

Machining

4. Arriving at Larry’s Track Pro, the block had already been prepped. The block was jet cleaned and the cylinders were rebored and honed. While the deck was CBN milled, the line bore on the main journals was checked, a fresh coat of black was added and brass freeze plugs were installed.

5. Arriving at Larry’s Track Pro, the block had already been prepped. The block was jet cleaned and the cylinders were rebored and honed. While the deck was CBN milled, the line bore on the main journals was checked, a fresh coat of black was added and brass freeze plugs were installed.

Crankshaft

Camshaft

9. After the cam sprocket is installed (20 ft-lbs,) the double roller timing chain is next.’

10. With the bottom half of the engine secured, our technician thoroughly cleans every cylinder prior to piston installation.

Rods & Pistons

11. The connecting rods, wrist pins and bearings were also installed. The bearings are coated with assembly lube prior to installation.

12. New moly compression piston rings are gapped, installed and ready to go.

13. The new OEM-style cast flat-top pistons with valve reliefs are carefully installed.

14. Both the right and left bank pistons are installed, and the new stock-style chrome timing chain cover is bolted on next.

Oiling

15. A new Mellings high-volume oil pump, pickup screen and drive rod will pump the engine’s lifeblood for as long as the engine spins.

16. A stock 4-quart capacity oil pan is all that is required for this new 350.

Long Block

17. New flat tappet hydraulic lifters are lubed and ready to go.

18. If lifters are being reused, then each must be put back in its original place. Since new versions are being used here, and the block is newly machined, placement position doesn’t matter.

19. New gaskets from stem to stern are included in the rebuild kit.

20. The original 327 camel hump/fuelie heads were refurbished and put back on the block. The cylinder heads were jet cleaned and magnufluxed. The valve guides should be checked and replaced if necessary. New intake and exhaust valves, springs and hardened keepers finished off the job. The original camel hump heads had 160cc intake runners with 64cc combustion chambers, the intake valve is 1.94 inches and the exhaust is 1.50 inches. Since the heads were milled and surfaced, the combustion chamber may be a tick smaller at approx. 63-62cc.

21. The cylinder heads were torqued down first to 35 ft-lbs then 65 ft-lbs in a typical circular pattern.

22. OEM-style stamped steel rocker arms with a stock 1.5.1 ratio were used in this build.

23. New standard 7.8 length push rods were up next.

24. The valve lash is set on each intake and exhaust valve before the engine is shipped.

Accessories

25. The unassuming stock 327 single plane intake manifold was cleaned, repainted and put back into service.

26. Don’t bother using the inadequate rubber intake manifold gaskets. A better seal is made using a silicone sealant like Permatex.

27. A Professional Products 6 ¾ damper and pulley replaces the worn stock 6 ¾ damper.

28. A Professional Products 6 ¾ damper and pulley replaces the worn stock 6 ¾ damper.

29. At this point, the build at Larry’s Track Pro has reached its zenith, and in only a couple of hours. The 327 long-block is ready to be dressed and installed. The advantage of sticking with the tried-and-true 327 that millions of Chevy trucks came with is a definite plus in the money-saving category.

30. Our story hasn’t quite come to an end yet. After the build at Larry’s Track Performance, the engine and truck were brought over to Maloof Racing Engines where a few more tasks needed to be completed, like installing the engine in the truck.

31. The long-block was dressed to the nines at Maloof Racing, and owner Sammy Maloof recurved the distributor and tuned the small-block to get it purring like a kitten. The 327 is now topped with a Holley 670 carburetor and fuel pump, MSD ignition, wires and plugs, Tuff Stuff alternator, starter and water pump, Hedman headers and gaskets, K&N air and oil filter and Mooneyes valve covers and air filter cover.

32. The long-block was dressed to the nines at Maloof Racing, and owner Sammy Maloof recurved the distributor and tuned the small-block to get it purring like a kitten. The 327 is now topped with a Holley 670 carburetor and fuel pump, MSD ignition, wires and plugs, Tuff Stuff alternator, starter and water pump, Hedman headers and gaskets, K&N air and oil filter and Mooneyes valve covers and air filter cover.

33. The long-block was dressed to the nines at Maloof Racing, and owner Sammy Maloof recurved the distributor and tuned the small-block to get it purring like a kitten. The 327 is now topped with a Holley 670 carburetor and fuel pump, MSD ignition, wires and plugs, Tuff Stuff alternator, starter and water pump, Hedman headers and gaskets, K&N air and oil filter and Mooneyes valve covers and air filter cover.

Let’s recap: The 1968 327 was reported to come with 250 hp at the flywheel with an approximate parasitic loss of 70 hp from flywheel to the tires, with an actual 180 hp hitting the pavement.

Recently, a same year 327 was rebuilt into a higher performing 350, remade using only OEM-style parts to keep on budget. It’s now running 275 hp, 245 ft-lbs of torque with a pump-gas-friendly 9.25.1 compression. Take into account the 70-hp parasitic loss and 205 horses are pounding the pavement versus the original 180. That’s a gain of 25 hp just using OEM parts. There are some racers who willingly spend ten thousand dollars for an extra 25-hp gain, thankfully that isn’t essential in the case of this truck.