With the goal of building a class contenting street stock engine, we knew we needed to find a good balance of budget minded decisions, and taking full advantage of what the aftermarket has to offer. We started with Chevy Performance 602 Crate Engine as the foundation, and found right away that we were heading in the right direction.
In our last article, we stuffed the stock small block with sealed bolts intact, into our second-gen Camaro Street Stock test car to find what’s the best this engine could put out with common upgrades and combinations such as 2- and 4-barrel carburetors, air cleaners, and carb-spacers. To take this engine to the next level, we worked with our friends at COMP Cams to come up with a valvetrain combination that was specific to our car, track, and most importantly rules.
To Seal or Not To Seal, Isn’t That The Question?
It’s no secret that sealed crate racing has caused a stir across the circle track world over the last 10 years. While some tracks have adopted rules that make running a spec engine like our 602 in stock form or a open built engine “equally” competitive, many tracks are still late to adopt this thinking. First thing is first, this article is not designed to show which is better – both have their good and bad side. Our local track didn’t have any rules that favored keeping the engine sealed, so we are simply using it as a starting point for our street stock build. At the end of the day, it’s a great ready-to-run power plant that is under $4,000 – perfect for the racer wanting to hit the track to get some experience and be competitive.
What makes or breaks a race motor is the quality of parts going into it. The rules in our class are similar to a lot of Street Stock or Hobby Stock classes across the country. The block and the bottom end had to be stock or stock replacement, and it didn’t appear there was much we could do with the heads or valvetrain either. COMP Cams had other ideas. We reached out to COMP’s Billy Godbold for information on what would not only fit with in the rules, but take full advantage of them.
2013 Perris Auto Speedway Street Stock Rules
HEADS: All heads must be factory castings Vortec Heads: Standard OE Production Vortec castings are permitted: GM L-31 (Casting #062 or #906 Only). All other Vortec and Vortec-style heads prohibited, including but not limited to Vortec Bow Tie, Edelbrock, EQ, GM Fast Burn, etc.
No aluminum heads allowed. No aftermarket heads allowed. No port matching, no pocket porting or blending. No porting or polishing of any kind. No angle plug heads. Stock type stamped steel 1.5 ratio rockers only. No rollers. Screw in studs & Guide plates OK. Maximum valve spring diameter 1.260. Steel retainers only. No titanium or aluminum valve train parts.
MAXIMUM VALVE HEAD DIAMETER:
1.94” intake 1.50” exhaust
CAMSHAFT: .485 max valve lift. No roller cams. No solid lift cams. No gear drives allowed. “Maximum allowable lift of any camshaft at the valve is 0.485. Camshaft lift measurement will be taken at the lifter and multiplied by the rocker arm ratio” (i.e.: 0.323″x1.5 = 0.485″)
What we used:
- COMP Cams Flat-Tappet Camshaft (PN; 12-000-5; Custom Ground)
- COMP Cams Valve Springs & Retainers (PN: 1750-16)
- COMP Cams Valves (PN: 941-16)
- COMP Cams Pushrods (PN: 7808-16)
- COMP Cams Lifters (PN: 84000-16)
- COMP Cams Guide Plates (PN: 4808-8)
- ARP Screw-In Studs (PN: 134-7101)
Who We Used:
L&R Engines in Santa Fe Springs, CA provided all the machine work needed for the heads. Derek and his team are top notch, and we’ve always enjoyed working with them no matter if it’s a 1,400 hp drag racing engine, or our 350 hp Street Stock engine.
Working with Vortec heads might seem like a walk in the park if your a die-hard Gen One small block engine builder, but there are a couple of aspects to watch out for when building a race motor. We’ve already covered almost all there is to know on the differences in Gen One and Vortec heads, but here is a short list of the main things we dealt with on our 602 Engine upgrade.
Self-Aligning Rocker-Arms – If you’re building a serious Saturday night contender, then ditching these might be your best bet. While we did a considerable amount of dyno testing with these still on the engine, and had our engine out in a race and had no problems, Godbold puts it best, “You can think of the guide plate versus self-aligning tip debate much like the belt vs. suspender debate. Both work very well, but some people certainly prefer one system over the other.” He went on to say in lift rule applications, he would lean on the side of guide plates for one simple reason. “The self-aligning systems only have a limited tip overhang before they interfere with either the lock or retainer,” he stated, “Therefore, if you loft the valve, there could be an instance where the rocker rides on the edge. With that much loft, something else is just as likely to become a failure point.”
Guide Plates – This is a must if you are ditching the self-aligning rocker arms. You are going to have to use a hardened pushrod, so the stock 602 pieces will have to go, even if this is the only upgrade you are doing and the length isn’t changing. Toss in some screw in studs while you are at it. It’s a good move to do anyways, and you’re already going to be changing the stud to work with the guide plates. We choose ARP’s PN:XXX for our build.
The Max Area Lift Rule lobes used on this camshaft are the best we have for making max power in a lift and RPM-limited flat tappet engine build – Billy Godbold
Retainer to Valve Guide Clearance – This is a big one to watch out for. If you’re familiar with the Gen One style heads, they can seemingly gobble up cam lift without any issues other then normal clearancing of pushrod holes. Vortec heads have a very shallow retainer to valve guide clearance (the distance the spring compresses until it contacts the valve guides). Our heads measured in a .480″. Godbold recommends a distance greater than what it takes to coil bind, just to be safe. L&R machined the heads to have plenty of clearance, and echoed Godbold’s recommendation.
COMP Cams Flat-Tappet Camshaft & Lifters
There is so much that goes into selecting the right camshaft for a race engine. While many tend to focus in on max lift and duration, there is just as much to be understood about the way the valve reaches max lift. COMP Cams has over 18,000 unique lift profiles that they have developed over the years. Because our engine is equipped with Vortec heads, COMP specifically ground a cam with the airflow available from our head and even asked questions about typical track size and fuel system used. “The Max Area Lift Rule lobes used on this camshaft are the best we have for making max power in a lift and RPM-limited flat tappet engine build,” Billy Godbold of COMP Cams explained about our specific lobe design.
It was pretty simple on our end. With no extra cost to custom grind exactly what COMP thought would work best for our engine, we got something that made not only for our application and rules, but intended use as well. COMP also specified the perfect lifter set to go with our custom ground bump stick.
COMP Cams Spec Sheet:
- SN # U7374-11
- Advanced duration 266 Intake – 273 Exhaust
- Duration at. 50: 240 Intake – 248 Exhaust
- Lobe Sep: 108 Degrees
- Lift: .483 Intake – .483 Exhaust
COMP Cams Valve Springs & Retainers
Anytime you are pulling the camshaft out of an engine, there are a couple of accommodating upgrades that should go along with it. Depending on the the amount of change in lift, swapping out the valve springs may be needed. It comes down to coil bind. If the springs you got can compress the max lift of the cam, and still have room to spare, you’re good. If coil bind is close (or before) max lift is reached, a change is necessary.
COMP Cams Rocker Arms, COMP Cams Valves, COMP Cams Pushrods, COMP Cams Guide Plates, ARP Screw-In Studs
Similar to replacing the lifters with a camshaft, double (or even triple) checking pushrod length is always a good move. We used COMP Cams’ push rod length checker to determine the exact length we needed. We also choose to ditch the stock style self-aligning rocker arms in favor of COMP Cams’ to handle transferring 1.5 times the lift of the camshaft to the valves – which we choose to upgrade as well. COMP again was able to recommend their valves for our heads.
With the self-aligning rocker arms gone, we needed a new way to keep things in the right place while our engine was reaching for the 6,200 rpm limit we were gunning for. The team at L&R Engines milled down our heads to accept a set of COMP Cams Guide Plates. We also choose to mill the heads for a larger valve spring retainer for valve guide clearance. With the max lift of our cam dangerously close to the limit, we took more than enough meat out of the top of the valve guide to give us the room we needed to open the valve as much as allowed by our class rules.
Swapping Out The Slippery Stuff With DRIVEN Racing Oil
Lubricants play a huge role in the performance of any engine. With an all new valvetrain we needed to make sure that we properly broke it in. So we decided to fill our engine up with 8 quarts of DRIVEN Racing Oil’s BR Break-In Oil. More than just a fancy label, Lake Speed Jr of DRIVEN tells us that this is the oil that Joe Gibbs racing using on all their NASCAR engines. It’s specially made for flat-tappet camshaft engines with all the right amounts of zinc and phosphorus, but we liked the most about it was the value we could get out of it. Many times the break in oil is a throw away fill – you break in the engine for 20 minutes, and then drain the oil and pour your new oil in.
However, DRIVEN specially formulated their BR oil to not only provide the protection needed for those critical moments of start up, but it can also be used for up to 2 hours of break-in and full power dyno runs (or one night of racing if you’re going right to the track). That’s perfect for the racer looking to get the most out of every investment made.
What was the results of all of this? We’ll be strapping down our second-gen test car to our DynoJet dyno in the next article to figure out what our gain on the cam swap was.