Finishing Madd Maxx’s Engine Rebuild. The Long Block

[Bobby Kimbrough]

Our Street Stock project car, which we lovingly call Madd Maxx because it has a face that only a mother could love, was in desperate need of a bullet proof power plant. We had a first time dirt track driver behind the wheel.. our own Super Tom, which resulted in complete and utter destruction of the existing engine. Rendered unusable after a practice session where our eager, but very green Rookie driver, exploded the engine two turns after taking the green flag turning the motor into a useless pile of metal. A boat anchor at best.



We Take A Test Drive With Our New Engine:



This unexpected turn of events forced us into building a fresh engine for Maxx. After several calls to our friends at Pro Power, Comp Cams, Torres Performance and Machining, and Ferrea Valves. Armed with a great combination of parts and a well thought out plan of attack, we assembled the short block and took the heads out to Rancho Performance Machining to be assembled. Now it was time to put all the pieces together and install the freshly rebuilt muscle back into the chassis. For a quick reminder of what we did for the short block build, check out Part 1.


Hole punched into the cylinder wall when the engine was blown up by our rookie driver.


Connecting Rod from the blown motor.

Getting Started



Our first step in completing the long block was installing the lightweight Pro Power Balancer. We selected the 6.75” damper that has less mass than many on the market, yet still handles any harmonic vibration caused by the rotating components. Rated for safe rev limits up to 10,000 RPMs, the Damper is made of 1045 steel and machined to match the OEM equipment dimensions. Installation of the Damper was identical to the procedures of installing a stock damper. With the damper in place, it is wise to check the timing marks on the damper to the timing tab with the #1 piston at TDC before the heads are installed.

Cylinder Heads

After our over eager Rookie threw a couple of rods through the engine block, we pulled the Double Hump cylinder heads off of our destroyed engine and sent it to the machine shop for a thorough inspection. We were expecting the worst but was pleasantly surprised by the damage report. Three valves were bent, but all of the valve guides were still in great shape. These cylinder heads had been previously rebuilt when we first got the car, and all of the valve guides had been replaced with bronze inserts and top of the line valves from Ferrea Racing Components. After replacing the bent valves, our heads were ready to bolt back on.


Installing the cylinder heads.

A Little Info On Stock Small Block Cylinder Heads.

Small block cylinder heads have been manufactured since 1955 and there have been a number of modifications in different series over the years. For most street stock classes requiring stock heads with stock valve train, there are a couple different casting numbered heads to look for. In the street stock classes in the local area, for 2009 rules specified no Vortec, no Bowtie, and no large valves. That kept us limited to the late 60's and early 70's style heads to develop any real power. Most racers prefer the 64cc combustion chamber because they tend to be good horsepower heads and have accessory mounting holes. The 76cc combustion chamber heads are from the mid to late 70's and were designed as "smog compliant" heads.

List of acceptable stock heads by casting number:
3890462 "Camel Hump" were available in 1966-1967 and were 64cc combustion chamber with no accessory holes.
3917291 "Camel Hump" were available in 1967-1968 and were 64cc combustion chamber with no accessory holes.
3917292 "Camel Hump" were available in 1968 and were 64cc combustion chamber.
3927186 "Camel Hump" were available in 1969-1970 and were 64cc combustion chamber with accessory holes.
3927187 "Camel Hump" were available in 1969-1970 and were 64cc combustion chamber with accessory holes.
3932454 Available from 1969-1979 in Chevy Trucks. These are not commonly used in higher horsepower engines.
3947041 Referred to as 041's, these heads were available in 1969-1970. A good horsepower head. Both large and small valve versions from the factory.
3947041X These heads were available in 1969-1970. A good horsepower head.
3973370 Over the counter heads. Available in 1969-1970. 64cc combustion chamber.
3973414 LT1 "Camel Hump" available in 1970 on 370 hp 350 engines. 64cc combustion chamber.
3991492 LT1 Over the counter "Camel Hump" available in 1970. 64cc combustion chamber.

Installing the Cylinder Heads

The cylinder head installation is always simple enough not to cause any problems if you have the correct parts and torque the head bolts correctly. We used the off the shelf Fel-Pro head gaskets. These composite gaskets are very compliant with any nicks or dings in the mounting surfaces, and are less sensitive to warpage. Simply place the gasket into position and ensure that the dowels on the engine block are fully inserted into the holes in the gasket.


Applying silicone sealant around the bottom of the head bolts.

Lifting the reconditioned cylinder head into place on the engine block, the alignment dowels on the block must be positioned so that the dowels are inserted into the alignment holes on the heads. Because the head bolts go all the way into the water jacket of the block, we coat the bottom 1/2 inch of threads with silicone sealant. This prevents water from working up the threads and into areas where it shouldn't be. As an added bonus, the sealant acts as a lubricant for the bolt when torquing. Every bolt on the engine should have some kind of lubrication used during installation.


Cylinder head bolt torque sequence.

Torquing the Head Bolts

With the cylinder heads in place, we gently screwed in all the head bolts finger tight. Factory torque specs for head bolts are 60-70 ft/lbs, so we were shooting for 70 ft/lbs for our final torque. We were using a "click type" torque wrench which is a ball detent and spring type clutch mechanism, with the internal spring being preloaded with an adjustable screw and calibrated in torque units like foot pounds. With a preloaded spring type torque wrench, it is common practice not to use the top or bottom 10% of the torque wrench's scale. We decided to use a 0 to 250 foot pound torque wrench to perform the torquing. Starting from the center bolts and working outward in a circular pattern, we starting torquing the head bolts in steps. Our first step was to take the head bolts to 30 foot pounds then re-torque the bolts at 45 foot pounds. Our final stage was to torque all the bolts to our final torque at 70 foot pounds of torque.


Installing the valve train begins with coating the lifters with Royal Purple assembly lube.

Installing the Valve Train
When the engine was disassembled, the rocker arm assemblies and push rods were inspected and labeled. Having taken the time to label and place each set into parts bags greatly enhanced the re-assembly process. Testing the push rods was the key item in the inspection process because of the mechanical damage that happened when our driver broke two connecting rods. The simplest means of testing a pushrod for straightness is to roll each push rod across a flat plate of glass. Bent pushrods will wobble whereas a straight pushrod will roll true.

Our valve train combination when we had the heads built originally consisted of Springs, Retainers, locks, valve seals, shims, stamped steel rockers and hydraulic lifters from COMP Cams. We targeted the valve spring installed height at 1.680" to get the seat pressure about 120 psi. We felt this would give us the best combination with the COMP Cams camshaft that we were running. The COMP Cams camshaft we selected is designed for circle track cars with lift rules. Our local track implemented a standard .485 lift rule, and this camshaft was a perfect fit for those rules.


Installing the pushrods and coating the rocker end with assembly lube.

Our Valve Train Combination:

• Camshaft: COMP Cams
• Hydraulic Lifters: COMP Cams Part #84000-16
• Valve Springs: COMP Cams Part #26981-16
• Steel Retainer: COMP Cams Part #787-16
• 7 Degree Retainer Locks: COMP Cams Part #648-16
• Valve Seals: COMP Cams Part #501-16
• Valve Seat Locator Shims: COMP Cams Part #4693-16
• Stamped Steel Rocker Arms: COMP Cams Part #1212-16

We laid the valve train out on our parts table making sure that we had all the components and orientated them to their correct cylinder placement on the engine. We placed the previously numbered push rods into their original places with the smear of moly lube on each end of the push rod. With every pushrod in place, we put moly lube in the push rod cup end of the rocker arm and on the valve stem end or the rocker arm.

There's no need to go crazy with the moly lube, just a smear on the contact surface will help protect the machined surfaces. Each rocker arm was then placed on it's respective stud and the spherical bearing was coated with moly lube and installed on the rocker arm stud. It is important to keep the spherical ball with the rocker arm as a pair if you intend to reuse them. You cannot use a spherical ball from another position with a rocker arm from a different position. They wear together and must be kept as pairs. If you are using new ball seats and rocker arms, you just need to dab moly lube on the contact surfaces and they will "wear in" during the break in period.


Installing the COMP stamped steel rocker arms.

Setting Valve Clearance with Hydraulic Lifters

Starting with rotating the engine to top dead center of the number 1 cylinder firing, we started adjusting the rocker clearance. With #1 at TDC you can adjust both the intake and exhaust valve clearance. We like to perform this with the intake manifold off so that we can see the lifters and rotate the pushrods between the fingers. Using a box end wrench, tighten the adjusting nut until all the excessive play is taken out of the assembly. Keep tightening the adjusting nut until the pushrod just barely rotates between your fingers. At this point, the adjusting nut is tighten another 1/2 turn which puts the pushrod tip about 0.025" into the spring loaded action of the lifter.

When we finish adjusting the rocker arm clearance, we like to rotate the engine back to top dead center on cylinder #1. Doing this makes installing the distributor an easier task and get the initial timing setting close enough to start and run.

Installing the Intake

The Intake manifold we chose to use is one of two aftermarket intakes allowed in the class. We had the choice of a stock intake or the Torker or Performer manifolds from Edelbrock. A quick check through the pit area and the choice was a no brainer. The Performer manifold was the intake of choice for most everyone in the division. Edelbrock has an impeccable reputation in dirt track racing for their intake manifolds so this was a very comfortable and confident decision.

Engine gasket kits come with intake manifold valley seals, and more often than not, they come with a set of pre '68 blocks and '68 and later engine block seals. Most dirt track engine builders discard these seals and use a thick bead of silicone sealant on the engine block valley lip where the intake manifold sits. We opted for the silicone sealant as our intake gasket.

The intake manifold gaskets in small block chevy engine building kits are year specific. From 1955-1972, all Chevy 350 blocks in cars and trucks used the open port heat riser gasket. In 1973, all cars and light trucks used a restricted left side and open right side intake gasket except the heavy duty 3/4 ton trucks used open port heat risers on both sides. In 1974, GM cars and trucks with 2 bbl carbs used restricted left, open right gaskets. The 4 bbl carb 350's used restricted on both sides with the exception of the heavy duty 350's that used open on both sides. Beyond 1974, the gasket kits become more engine specific. For our purposes, we chose to use intake gaskets that had open heat risers on both sides.

Installing the intake gaskets is a fairly simple process. We chose to apply a thin bead of sealant around the square water ports in the gasket to prevent any possibility of leaks. Once we had one side prepped with silicone around the water ports, the gasket was placed in position and the other side of the gasket was prepped with silicone around the water ports. With both intake gaskets in place, and our thick beads of silicone at each end of the lifter valley lip, we carefully place the intake manifold into position and hand tightened the intake bolts. Intake manifold bolts are all 1 1/4" bolts. We made sure that our bolts were the correct length because we have seen mechanics try to use longer bolts which can cause a bind in the pushrods and eventually bend the pushrod. Torquing the intake bolts is extremely important as well. Working from the center out, much like torquing the cylinder heads, tighten each bolt to 20 ft/lbs.



Installing the Carb and Wilson Adapter

It's hard to beat the Wilson Manifolds Spacers in carbureted applications. So we called up the guys at Wilson Manifolds and ordered their 1 inch, 2 bbl to 4150 tapered adapter. Installing the spacer was as easy as tightening four bolts. Our SMI 4412 carburetor bolted on top of the spacer and we had plenty of clearance for throttle springs, fuel lines and throttle cable. The SMI & Wilson adapter combo is a comfortable high performance upgrade for the street stock class rules.



Finishing Up

Our long block was pretty well done by this point. We still needed to get the distributor set into the block after we mounted the engine in the car, filled the engine with oil and primed the oil pump. The water pump and KRC front pulley drive kit would be mounted after the engine was installed, and we would finish up by adding MSD plug wires and a set of normal heat range spark plugs. Confident that we had finished building an engine capable of withstanding "rookie driver" abuse, we put the tools away and waited for the chance to install this durable mill into our dirt warrior.


Our finished engine, installed in Maxx and ready to run.

Harmonic Balancer 101:

Balancers are tricky. This should help. Because of the mixing and matching of parts over the years on small block Chevys, so here’s the 411 on harmonic balancers, timing covers and timing marks:

All Generation I small block 350s that have two piece rear main seals were internally balanced. Small block 400s were a different story with external balanced flywheels or flexplates. All of the one piece rear main seal 350s from 1986 to the late 90’s were externally balanced. Therefore, most of the SBC 350’s used in the street stock or bomber classes are the internally balanced crankshafts with a vibration damper on the crank snout. The key thing to remember when selecting harmonic dampers is that GM tuned the stock dampers to work in an RPM range suitable to street driving. Higher RPM driving requires a damper tuned for that application.

Small Block Chevy vibration dampers came in several different diameter sizes with different timing mark positions. Our solution was to buy an aftermarket vibration damper manufactured for our engine spec and RPM range, however, if you are planning on using a stock damper here is the basic rule of thumb; Until 1969 the TDC or 0 degree position on the crankshaft damper was 2 degrees before the crankshaft keyway. In 1969, GM moved the TDC or 0 Degree mark to 10 degrees before the crankshaft keyway.

Other information on stock dampers:

6.75” damper (GM #6272221) was used on 1969 and later 350s. Timing Mark Position is 10 degrees before crankshaft keyway. Use timing tab 12341904 or 12342000 (GM Part number).

6.25” damper (GM #12341632) is a GM/Fluidamper and is for use on internally balanced engines. The Timing Mark Position is 2 degrees before the crankshaft keyway.

7” damper (GM #24502534) is the NASCAR approved damper. It’s a rebuildable elastomeric style damper tuned for higher RPMs and utilizes the common 2 degree before crankshaft keyway timing mark.

8” dampers came stock on several engine models. The GM # 6272224 damper was common on 1970-1974 Z-28s, LT1 engines, L82 engines and some 350 crate engines. Timing Mark Position is 10 degrees before crankshaft keyway and timing tab 12341915 or 12342011 should be used. There was also a 8” damper (GM #364709) that was designed for off road use manufactured with high temperature elastomeric rubber and tuned for high RPM operation. These are identifiable by the “MALL” marking which is an abbreviation for malleable iron.

Sources:

COMP Cams
COMP Cams
3406 Democrat Road
Memphis, TN 38118
Tech Support: 1-800-999-0853

WILSON MANIFOLDS INC.
4700 N.E. 11 Ave.
Ft. Lauderdale, FL 33334
954-771-6216

SMI
17671 Metzler Lane unit A-7
Huntington Beach, CA 92647
Phone: 714-843-9169
Fax: 714-843-9165

Edelbrock
2700 California Street,
Torrance, CA 90503
Phone: 310-781-2222