391 Stroker Small-Block Engine - Tech

00,A&B
Although they can add power to the engine, windage screens like this one usually require modification/adaptation to work in street engines. Photo A shows the bolt hole that was opened up to clear the dipstick. Photo B shows where the tray was "clearanced" to fit around the dipstick tube. Note also that the main cap stud directly in line with the dipstick was replaced with a bolt for clearance.

It's all about breathing. Since we love small-blocks, but we also love big cubic inches, "stroker" small-blocks are tops in our book. Big cubic-inch small-blocks need lots of breathing room, and this month we're going to show you how to build the top end of an outstanding street stroker. Last month we told you about our feelings for the oft-built 383-c.i.d. small-block stroker. While the 383 is a fun and affordable motor to build, it's also very common and has consequently become somewhat of a bore to read about. For a new angle on strokers we hooked up with Sod Bogosian, owner of Hye Tech Performance (in La Puente, California) where he showed us how to stroke a small-block from a different point of view.

1. Last month, Roland Marquez from Hye Tech Performance assembled the rotating assembly of this 391 stroker small-block. The first parts bolted on this month were a Milodon High-Volume oil pump with a reinforced pickup and a pan baffle wedged under the pump to keep oil from climbing the back of the block under hard acceleration.
1. Last month, Roland Marquez from Hye Tech Performance assembled the rotating assembly o
2. Marquez checks the Fel-Pro one-piece oil pan gasket for clearance around the windage tray. The gasket fits well, but it must be laid in place prior to installing the windage screen so it will fit over the lower dipstick tube. Note the ratchet on the end of the crank that Marquez uses to rotate the crank 360 degrees to make sure that everything completely clears the windage screen.
2. Marquez checks the Fel-Pro one-piece oil pan gasket for clearance around the windage t
3. This Milodon oil pan is clearanced for longer stroke engines, and Marquez lowers the pan for a fit check, finding that there were no interference problems.
3. This Milodon oil pan is clearanced for longer stroke engines, and Marquez lowers the p

4. The Lunati hydraulic camshaft went in next. Then, Marquez installed the Lunati three-keyed, double-roller timing gear set straight up, torqued the cam gear bolts to 25 ft-lb, and locked them in place using a Manley locking plate.
4. The Lunati hydraulic camshaft went in next. Then, Marquez installed the Lunati three-k
5. Hye Tech chose Fel-Pro's PN 1010 head gaskets because they feature a copper compression ring instead of a stainless steel ring. The soft copper ring won't "brinnel" the aluminum cylinder heads and is plenty capable of sealing this street motor, even with a small shot of nitrous oxide.
5. Hye Tech chose Fel-Pro's PN 1010 head gaskets because they feature a copper compressio
6. Marquez says that you can't be too clean when assembling an engine, so he wiped the deck surfaces and JE piston tops with a clean, dry rag one final time before bolting the cylinder heads on.
6. Marquez says that you can't be too clean when assembling an engine, so he wiped the de

UNIQUE STROKER RECAP

Hye Tech Performance has taken the ordinary 383-stroker concept to the next level. By offset grinding the rod journals of a new C.A.T. Power Engine Parts 3.75-inch stroke, 4340-forged crankshaft to the smaller 2.00-inch diameter of the old 327 rod journal, Bogosian has created a reliable 3.832-inch stroke small-block crank. After boring a 350 block 0.030-inch over-size, Bogosian can assemble an affordable 391-c.i.d. street stroker using his custom crank. To further enhance power and strength of his long-arm "mouse," Bogosian installs C.A.T. 5.7-inch, 4340 H-beam connecting rods and 10.25:1 compression forged JE flat-top pistons. This bottom-end combination makes for a fast-accelerating and good-torque-generating small-block that'll last just about forever on 92-octane pump gas.

STROKER TOP END

Any stroker small-block worth its displacement has to breathe in order to make power. The longer stroke in these engines means that they can use a camshaft that's a little bigger than you'd normally see inside a 350 small-block. To give the 391-c.i.d. Mouse some breathing room Bogosian chose Holley's dyno-matched Street Avenger system, including a new Street Avenger 770-cfm vacuum secondary carburetor with Street Avenger aluminum cylinder heads and intake manifold. And since Lunati is also a Holley Performance Company, both companies have worked closely developing a dyno-matched hydraulic cam/lifter package for the Street Avenger system, and Bogosian ordered the complete set, along with Lunati 1.6:1 aluminum roller rockers and a double-roller timing chain from Jeg's High Performance.

By running a proven package, Bogosian knew that he could side step testing various components on his own time in order to achieve the best power levels. He also explained that this engine's owner was not looking for maximum peak horsepower, rather he wanted a strong small-block with a very wide and smooth power band for both cruising and bangin' gears. To that effect, Bogosian chose a camshaft that may seem a bit big for the average street small-block but will complement all that this stroker's almost 400 inches has to offer.

7. Besides their ability to make great power, lightweight aluminum cylinder heads sure are fun to work with. The Holley Street Avenger heads feature 68-cc combustion chambers and put this engine at 10.25:1 compression with the flat-top JE pistons.
7. Besides their ability to make great power, lightweight aluminum cylinder heads sure ar
8. The Street Avenger heads come with the intake ports matched to a Fel-Pro PN 1204 intake gasket. The gasket kit that Hye Tech is using included a slightly larger PN 1205 intake gasket, but there's really no drawback to running it instead. Holley left the intake runner walls rough-ported to ensure good a mixture.
8. The Street Avenger heads come with the intake ports matched to a Fel-Pro PN 1204 intak
9. The D-shaped exhaust ports on the Street Avenger heads come fully polished and ready to flow. Exhaust flow is important in any engine, and having a good relationship between the intake and exhaust ports (expressed as the intake/exhaust flow percentage) is critical to making the most power without using a huge camshaft. These heads have an outstanding 78-percent I/E ratio.
9. The D-shaped exhaust ports on the Street Avenger heads come fully polished and ready t

10. Marquez applied a liberal coating of GM Thread Sealer to the ARP head bolts and spread ARP's assembly lube under the washer and bolt head. The sealer keeps water from seeping up past the bolts since they lead straight into the water jackets, and the assembly lube will ensure accurate torque readings. ARP recommends these head bolts be torqued to 60 ft-lb when using its assembly lube on aluminum heads.
10. Marquez applied a liberal coating of GM Thread Sealer to the ARP head bolts and sprea
11. Here's a way to keep your hands and fingers clean when pre-lubing the lifters for a new cam. Marquez lines them upside-down on a bench and pours a liberal amount of MPZ Valco assembly lube on each lifter. He follows by squeezing some Valco lube into each lifter bore in the block, then twisting the lifters as they drop in.
11. Here's a way to keep your hands and fingers clean when pre-lubing the lifters for a n
12. Since this block was decked, and these are not stock heads, Marquez measured the pushrod length using a Lunati adjustable pushrod. Turns out that stock-length pushrods were the correct size in this case.
12. Since this block was decked, and these are not stock heads, Marquez measured the push

BREATHING ROOM

If your engine doesn't get enough air into its cylinders, then it won't be able to produce power that it can be proud of. Besides the camshaft, the cylinder heads affect breathing more than any other component. To get the best breathing possible without sacrificing streetable low-end power, Holley's Street Avenger cylinder heads feature an efficient 184-cc intake runner volume. With its high-tech 68-cc combustion chamber, and 2.02/1.60-inch stainless valves, the Avenger heads flow 223 cfm on the intake side and 173 cfm on the exhaust, both at 0.500-lift. That works out to an impressive 78-percent intake to exhaust flow ratio, and since we know that max cfm through the cylinder heads does not always equate to max power at the crank, we agreed with Bogosian that these cylinder heads should produce a strong and wide power band that will probably top out around 6,200 rpm on this engine. Capped off with Holley's dual-plane Street Avenger intake manifold and the vacuum secondary carb, this engine should pull some great bottom-end grunt!

LIGHT THE FIRE

A hot street engine can't do diddly without a hot spark, so Bogosian again choose the dyno-matched route and will install Holley's complete Annihilator ignition system, including a billet distributor, wires, a coil, and a digital spark box. Capable of supplying enough voltage to power a diesel/electric submarine, the Annihilator ignition should have no trouble lighting this big Mouse's fire! Also to be added before the dyno test session, will be a Holley mechanical fuel pump, Lunati pushrods, and a Weiand mechanical water pump with March Performance serpentine pulleys. Check back with us next month as we detail the dyno test session and find out if the stroker from a different point of view can muster the power to run with the big dogs.