Chevy Small Block Part 9 - Comp Cams

Chevy Small Block Part 9 Intake Manifold

Edelbrock told us they've worked very hard to ensure equal runner sizes in all its Performer RPM Air Gap manifolds. We certainly believe them, because bolting this manifold on netted us the single largest horsepower and torque gains from any test yet.

Edelbrock told us they've worked very hard to ensure equal runner sizes in all its Perform

Test 7: A COMP Cams XE256H cam (256/268 adv duration, 212/218 duration @ .050, .447/.454 valve lift, 110 lobe separation) was swapped in, 2 degrees advanced, and we were rewarded with lots of grunt (compare Tests 6 & 7).
Max 413 tq, 357 hp
Avg 396 tq, 293 hp

Test 8: This was our very first weird test. We witnessed that the 3/8-inch screw-in studs in the heads were flexing as we lashed the valves, 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. Power and torque fell off at most rpm, so the stud girdle was later removed.
Max 413 tq, 356 hp
Avg 395 tq, 292 hp

GM's Vortec iron cylinder heads are cheap and powerful. Pictured here are all the parts you'll have to buy to run the Vortecs, because they won't work with the regular parts you may have lying around.

GM's Vortec iron cylinder heads are cheap and powerful. Pictured here are all the parts yo

	1 3/4		Full roller		COMP		Stud
	Headers		1.5 rockers		XE256H		girdle
	Test 5		Test 6		Test 7		Test 8
RPM	TQ	HP	TQ	HP	TQ	HP	TQ	HP
2600	377	187	380	188	387	191	384	190
2800	381	203	382	204	394	210	386	206
3000	390	222	391	223	401	229	398	227
3200	396	241	401	244	411	250	408	249
3400	400	260	403	261	413	267	410	265
3600	403	276	405	277	413	283	411	281
3800	407	294	406	294	413	298	413	299
4000	405	308	407	310	412	314	410	312
4200	401	321	402	322	406	325	407	325
4400	395	331	367	332	402	337	402	337
4600	387	339	388	340	394	345	394	345
4800	380	347	380	347	385	352	385	352
5000	368	350	368	350	375	357	373	355
5200	354	350	353	349	358	354	358	355
5400	N/A	N/A	339	349	348	357	345	355
5600	N/A	N/A	N/A	N/A	334	356	331	353
Max	407	351	407	351	413	357	413	356
Avg	388	287	389	288	396	293	395	292

Note how DM's powerband slowly increases as we keep trying different parts.

Tests 9-12: Bigger carb, "Air Gap" manifold, new carb spacer, bigger XE262H cam (December 2002).

Test 8 ended the day with a maximum 356 hp and 413 lb-ft of torque, and average figures were 292 hp and 395 lb-ft. This month we tried a new Speed Demon carb and an Edelbrock Performer RPM "Air Gap" manifold with a Wilson 1 1/4-inch open spacer. We also installed the next-size-larger COMP Cams Xtreme Energy camshaft. The final reward was a new max 386 hp and 438 lb-ft of torque, and the new averages were 316 hp/416 tq. Now we've got this stock iron-headed 355-cid Mouse making almost 390 hp and 440 lb-ft of torque! So far this looks like the best power formula with the stock heads, particularly since the motor didn't respond that well to the bigger cam. That means that we just about maxed out the stock cylinder head's flow potential and would either have to go in and start porting or install a new set of performance cylinder heads for more power.

Test 9: Installed Speed Demon 750 carb with 82/88 jets.
Max 418 tq, 356 hp
Avg 398 tq, 294 hp