Small Block Chevy Performance Parts

Chevy Small Block Performance Parts Dyno

The New Bumpstick Certainly Adds Some Grunt!
Our second dyno test session for Danger Mouse (DM) could really just be considered an extension of the baseline testing we did last month. We found some great low-end power increases, especially after swapping in a slightly larger COMP Cams XE256H cam. We really didn't pump up peak power figures that much, but our new combination would definitely have responded well on the street with all the extra low-end grunt we made.

Chevy Small Block Performance Parts Waterpump

Last month we had to borrow a water pump from Westech for testing. This time DM gets its own Meziere electric beauty that itcan keep.

Last month we had to borrow a water pump from Westech for testing. This time DM gets its o

Power Recap
Last month during DM's first time on the dyno, we were rewarded with a maximum 349 hp and 405 lb-ft of torque, and the average power and torque figures were 278 and 390, respectively (see: Test 4). That was outstanding for a mild 355-cid motor running stock iron heads and a tiny cam. So this month we thought we'd install a new cam and some bigger headers, along with a few extra parts to see what they'd do. The reward this month was a maximum 357 hp and 413 lb-ft of torque (+8 and +8) and 293/396 (+5 and +6) averages.

Test 5: 1 3/4-Inch Headers
The first new test item was a set of larger, 1 3/4-inch headers. Why, you ask? 'Cause that's what people do. They think if 1 5/8 headers are good, then 1 3/4 may be better. And in fact, they were, barely. Compare tests 4 and 5 and you'll see that average torque was down 2 lb-ft, but average horsepower increased by 9. That's a fair trade to us, so we left them on.

Chevy Small Block Performance Parts Torque Chart

Test 6: Full-Roller Rockers
After the header test, we wanted to see if replacing the roller-tip rocker arms we used last month with a set of full-roller, 1.5:1-ratio aluminum rocker arms would help. We've tried this same type of test many times before with mixed results. If an engine responded favorably to the full-roller rockers, it probably had stiffer valvesprings than DM, and that created more friction and heat. DM's springs aren't that stiff, so it didn't really benefit from the new rockers. Average and max power really didn't change at all (compare tests 5 and 6). However, we did get 5 more lb-ft of torque at 3,200 rpm, so like the headers, we left them in place.

Test 7: Xe256h Cam
Now things really started to get fun. The first cam we used in DM worked exceptionally well. We never would have guessed that a cam so small could make such big power. However, this time we swapped in a slightly bigger cam, installing it 2 degrees advanced to maximize low-end power, and were rewarded with lots of grunt. DM was now making over 400 lb-ft of torque at 3,000 rpm! That's cool. Both max and average power also increased, so the new cam was deemed a success (compare Tests 6 and 7). Low-end grunt improved so much (+17 lb-ft at 2,800 rpm) compared to the first cam in Test 4 that this new cam would really be a tire-fryer in a hot street car. And since the cam was only about 6 degrees longer at 0.050 with around 0.020-inch more lift, it still idled well and would be very docile on the street.

Chevy Small Block Performance Parts Dyno Chart

Test 8: Stud Girdle
This was our very first weird test of the series. Most people would never think of installing a stud girdle on such a mild engine, but we're not most people. In last month's tests we witnessed the 3/8-inch screw-in studs in the heads flexing as we lashed the valves. The flexing was visible to the naked eye, so we hypothesized that it might kill some lift and duration. In an attempt to prove our hypothesis correct, we installed a COMP Cams stud girdle, which ties all the rocker arm studs together adding tremendous rigidity. It didn't help. Power and torque actually fell off at most rpm. We can't explain why, but the results speak for themselves. The stud girdle will come off next month.

Speaking of next month, we feel it's time to try a new set of heads to see what they're worth. We won't tell which heads we'll bolt on first, but let's say that DM won't be going on a diet any time soon.