The key to making horsepower...
The key to making horsepower is a combination of good port flow and a matching camshaft. Our choice was based on performance per dollar, so we chose a set of World Products iron S/R Torquer 305 heads.
We then matched that with...
We then matched that with a Crane CompuCam hydraulic-roller camshaft.
While the World S/R Torquer...
While the World S/R Torquer 305 heads are a good choice, we decided to help them out with a pocket-porting job performed by Slovers Porting Service. Slovers improved the low- and mid-lift flow and is probably the best $120 weve spent.
The S/R Torquer 305 heads...
The S/R Torquer 305 heads come with a 58cc chamber and quality Manley 1.94/1.50-inch stainless steel valves. Tim put a 30-degree back-cut on the intake valves to improve low-lift flow. He also lapped the valves to ensure a solid valve seal. The intake-seat width is 0.060 inch with the exhaust at 0.100 inch.
The S/R Torquer heads come...
The S/R Torquer heads come with screw-in studs but no guideplates. This works for us since we will reuse the production 1.5:1 guided rocker arms, making guideplates unnecessary.
On the camshaft side of things,...
On the camshaft side of things, we opted for a CompuCam Crane hydraulic roller. We plan to reuse the stock roller lifters and stamped rocker arms, but Crane offers replacement lifters and rocker arms in both standard and rail type.
Starting in 1987, Chevy began...
Starting in 1987, Chevy began using a rail-style rocker arm that centers the rocker arm over the valve tip using these rails stamped into the rocker arm. Rail-style rocker arms do not require guideplates.
Along with the hydraulic-roller...
Along with the hydraulic-roller camshaft, Chevy changed the nose of cam requiring a specific late-model timing gear and chain set. We used an inexpensive GM cam-drive set that sells for under $40.
This is Crane Cams stock...
This is Crane Cams stock replacement hydraulic roller lifter. The good news about roller tappets is that you can reuse lifters on a new cam. You cant do that with flat-tappet lifters.
In our last exciting episode, we left our hero 305 Camaro dangling from the 15-second dragstrip cliff, waiting to be rescued with an influx of high-performance parts. So far, our little Camaro has responded to every component we've bolted on. While it's still only a 15.80/86-mph car, at least it improves every time we bolt on a few more parts. Now it's time to get serious.
Power comes from airflow, and we're dealing with a weak 305 with restrictive heads and a tiny cam. We've enhanced the inlet and exhaust sides to uncork as much power as the stock motor can provide. So the next obvious step is to add better cylinder heads and a performance camshaft. Another important factor is emissions legality. The iron Vortec casting would be an excellent choice, but the Vortec heads do not include an exhaust-heat crossover passage. Since most small-blocks tap into that passage for exhaust-gas recirculation (EGR), this factor eliminates the Vortec as a legal choice.
Of course, our squeeze-it-'til-it-screams budget also constrained us from choosing a thumper aluminum head like the new 180cc Air Flow Research head. We considered a pair of alloy factory TPI heads since they are plentiful, relatively cheap, and lighter than iron. Unfortunately, these heads barely flow more than the stock iron 305 castings so the performance gain would be minimal. Further headhunting finally led us to a set of World Products S/R Torquer heads.
World Products has been casting iron heads for well over a decade, creating stock replacement (S/R) iron heads for the small-block Chevy. The S/R Torquer is a similar casting with better intake and exhaust ports and larger valves. Originally configured for 350ci engines, World also offers an S/R Torquer 305 with a smaller 58cc chamber and 1.94/1.50-inch valves compared to the stock 305ci 1.84-/1.50-inch valve complement.
Stock small-block Chevy iron heads generally fall in the 155-160cc intake port volume range with the aluminum TPI heads measuring around 163 cc. The S/R Torquer pumps the intake port volume up to 170 cc, which is relatively large for a 305ci engine. Add to this the stainless Manley valves, a 0.100-inch larger intake valve, and a good 3-angle valve job and you have the makings of a great combination.
We decided that while the S/R Torquer heads are an excellent investment, we'd spend a little more money and really make these heads romp. While we could have cheated and performed the head porting ourselves and saved the cash, we assumed that not everyone can execute a good pocket-port effort. So we took the heads to Slover's Porting Service in North Hollywood and paid them the going rate of $120 for a basic pocket-porting job. Tim then lapped the valves and used his own valve grinding machine to perform a slight 30-degree back-cut to the intake valve in an effort to increase low-lift flow.
The next important consideration is the camshaft. While a great-flowing set of heads will pump the power even with a stock cam, adding a little more lift and duration to the mix allows us to take advantage of the better flow by spinning the engine a little higher in the rpm range. The stock LG4 motor tends to run out of steam at about 4,500 to 4,800 rpm. By increasing airflow, and with another 14 degrees of intake duration from the camshaft, our plan is to raise the peak horsepower rpm up closer to 5,000 to 5,500 rpm.
We felt the key to making power with the 305 was not to go overboard with the cam timing. We consulted CHP's technical guru, Kevin McClelland, and he felt that any cam with more than 200 degrees of intake duration would tend to kill low-end torque-something we don't have in abundance with a 305ci engine. We decided on a Crane CompuCam grind with a relatively short duration and reasonable lift figures (see Cam Specs chart). For now, we'll stick with the stock 1.5:1 rocker arms, but we'll try a set of 1.6:1 rockers to see if that improves the power. Either way, we'll let you know the results.
Even with this short-duration cam, we've still managed to increase the duration by 14 degrees and lift by 0.050 inch. This may not sound like much, but this offers a significant increase in lift without sacrificing much in terms of low-end torque, which is important since this is still primarily a daily driver.
ConclusionBecause of the extra time required to pocket port the heads and do the parts swapping, we weren't able to complete the install before deadline. Part of the time was also spent in the body shop, since Tim had his pal Bob Moore perform a complete exterior makeover on the Camaro as well. We'll cover that at a later date, but that's Tim's Camaro on the cover lookin' good in its '69 Hugger Orange PPG paint. Now if we can only make this Camaro run as strong as it looks, we'll be stylin'.