{"id":6701,"date":"2014-07-08T14:21:05","date_gmt":"2014-07-08T21:21:05","guid":{"rendered":"http:\/\/www.racingjunk.com\/news\/?p=6701"},"modified":"2016-12-02T12:28:33","modified_gmt":"2016-12-02T20:28:33","slug":"drag-race-101-paper-tigers-dyno-testing-our-ls-bracket-motor-combination","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/drag-race-101-paper-tigers-dyno-testing-our-ls-bracket-motor-combination\/","title":{"rendered":"Paper Tigers: Dyno Testing Our LS Bracket Motor Combination"},"content":{"rendered":"
\"Photo:<\/a>
Photo: Dart\/Moore Good Ink<\/figcaption><\/figure>\n

Years ago, I worked for the old Bracket Racing<\/b> USA<\/b> magazine. One of the most popular features the late Dale Wilson (Editor of the magazine) and I hatched involved the construction of \u201cpaper\u201d racecars.\u00a0 We called them \u201cPaper Tigers\u201d and we used computer simulation to test the cars and engines. It turned out to be an excellent series and plenty of readers actually built combinations similar to what we built on paper. Dale is gone now, but when The Burnout<\/em> editors called, it occurred to me that I could dust off that old simulation software (Engine Pro) to see how well our paper LS motor worked. Now there are more sophisticated software programs available today, but I always found that Engine Pro was quite reliable. And if anything it was often on the conservative side. \u00a0But enough \u00a0back-story.\u00a0 Here\u2019s how the computer sims went on our hypothetical LS motor.<\/p>\n

The first test of our 427 (actually, the displacement works out to 428, but what\u2019s a cubic inch between friends?) produced a series of results we more or less expected. The custom LS motor cranked out a very respectable 641 horsepower at 7,000 RPM.\u00a0 The torque peak of 476 foot-pounds occurred at 5,700 RPM.\u00a0 Engine Pro recommended a shift point of approximately 7,700 RPM.\u00a0 And that\u2019s entirely possible with today\u2019s high RPM hydraulic rollers (although everything needs to be right and most likely light).\u00a0 Typically, though, a shift point 5% above peak horsepower will be a good starting point.<\/p>\n

In terms of mechanics, our LS combination has a bore to stroke ratio of 1.03:1.\u00a0 The rod ratio is 1.53:1 and it has a maximum piston speed of 7715 feet per minute at peak power.\u00a0 You\u2019ll need a pretty good size header for the combination too:\u00a0 Something in the order of 2.00-2.125-inches in diameter with a primary length of approximately 32-inches.<\/p>\n

Bottom line here?\u00a0 This is one stout yet relatively mild combination \u2013 one that will go rounds without much fuss.<\/p>\n

But then, what\u2019s a \u201cdyno test\u201d without testing stuff?\u00a0 It crossed our mind too, so the first thing we did was to swap the 850 Holley for a larger 950.\u00a0 With no other changes, our 427 barked to the tune of 686 horsepower at 7,150 RPM.\u00a0 Torque went up too \u2013 all the way up to 509 foot-pounds of torque at 5,800 RPM.\u00a0 That folks, is a serious improvement.\u00a0 Here, the mechanics didn\u2019t change (aside from a small increase in piston speed to 7880 feet per second).\u00a0 The software did recommend a bit larger header (and rightfully so, considering the amount of air going through this engine).\u00a0 We stoked. Now what?<\/p>\n

While we were on a roll, we decided to plug in a Crane solid roller camshaft \u2013 one with a split duration of 262-degrees intake and 268-degrees exhaust (@ 0.050-inch tappet lift) and a lift of 0.670-inches.\u00a0 We went back to the baseline 850 Holley carb too.\u00a0 The power production was extremely impressive:\u00a0 736 horsepower at 7,300 RPM.\u00a0 Peak torque was 547 foot-pounds at 6,100 RPM.\u00a0 Here, the maximum piston speed was measured at 8045 feet per minute at peak power.\u00a0 The header primary can probably be shortened by an inch or so with this setup.\u00a0 And the shift point can go up too \u2013 we\u2019d start at 5% over peak power and test all the way to 10% over peak power (8,000 RPM) to see which is quicker and faster in the car.<\/p>\n

The next test was pretty simple:\u00a0 Swap back to the 950 Holley carburetor.\u00a0 And as you might have expected, we once again saw an improvement.\u00a0 It was simple swap, but the power increase was more than we expected:\u00a0 Our hypothetical 427 LS cranked out a mind-numbing 787 horsepower at 7,450 RPM!\u00a0 Maximum torque worked out to 583 foot-pounds at 6,200 RPM. Piston speed is up due to the increase in RPM (8211 feet per minute), but it\u2019s tolerable.\u00a0 This combination works out to 1.84 horsepower per cubic inch. Considering the off-the-shelf parts we picked in the build, it\u2019s pretty impressive.\u00a0\u00a0 If the car is equipped with an automatic, you\u2019ll have to pick the converter carefully, and to be honest, it will likely work best with a three-speed.<\/p>\n

At this point we figured it was pretty much done and we\u2019d stick a fork in it.\u00a0 But then we thought about the combination for a bit. What if we increased the compression to real racecar levels (honestly, an 11:1 LS can probably run pretty well on pump gas)?\u00a0 If the CR went to 13:1+, we figured it might make a difference. And it did:\u00a0 By bumping the compression ratio to 13.2:1 (keeping the mechanical roller cam and the 950 carburetor), the LS hammered out 809 HP at 7,550 RPM.\u00a0 The maximum torque measured 611 foot-pounds at 6,200 RPM.\u00a0 As you can see, increasing the compression ratio does wonders for torque production \u2013 this is common on most engines.\u00a0 Basically, we gained 32 horsepower and 28 foot-pounds of torque with the change.\u00a0 Keep in mind this is race fuel only combination. But it’s a stout one.<\/p>\n

In the end we think one major thing stood out with the LS engine: Its one very capable power plant and probably an outstanding choice for a bracket car.\u00a0 Yes, the parts are more expensive than they are for a conventional small block or a big block.\u00a0 But an 800 horsepower 427 is hard to argue with!<\/p>\n

\"We<\/a>
We used an old race engine simulation program for our tests. It\u2019s called Engine Pro. Yes, there are more sophisticated Sims out there today, but over the years, we\u2019ve found the software provides reliable results.<\/figcaption><\/figure>\n

 <\/p>\n

\"We<\/a>
We ran five Sims, beginning with a baseline, working our way up to a whopping 800+ horsepower combination. What it does show is how responsive Chevy\u2019s LS architecture is to modifications. It\u2019s definitely a serious bracket race platform.<\/figcaption><\/figure>\n

 <\/p>\n

——————————————————————————————————————————————————————–<\/p>\n

So You Want to Be A Drag Racer: Buying, Building, Wrenching and Racing<\/strong><\/em><\/p>\n

The allure of the drag strip is easy to understand \u2013 a place where \u00a0it takes less than 10 seconds to make a stand, prove your skill, speed, and nerve.\u00a0 But the road to the races can be intimidating.\u00a0 The Burnout wants to make that road a lot smoother for aspiring racers, whether it\u2019s through building a new car, modding a used one, or taking that ride all the way up to the burnout box and beyond.\u00a0 This series is a work in progress, an ever expanding comprehensive guide to all the things that take drag racing from concept to reality.<\/em><\/p>\n

Want to chat about this on social media? Use #RJDragRace on Facebook or Twitter<\/p>\n","protected":false},"excerpt":{"rendered":"

To come full circle as we build our LS engine, we run the engine through a computer simulated dyno to test its effectiveness on the strip.<\/p>\n<\/div>","protected":false},"author":20,"featured_media":6706,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[3448,3465,5008,11,3698,9],"tags":[965,1026,989,962,1027,961,1047,1048,69,1028,1046,991,966,321],"class_list":["post-6701","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-drag-race-101","category-drag-racing","category-engine","category-how-tos","category-tech","category-tech-tips","tag-rjdragrace","tag-bottom-end","tag-build-it","tag-build-it-or-buy-it","tag-cylinder-block","tag-drag-race-101","tag-dyno-testing","tag-engine-pro","tag-ls-engine","tag-ls-next-block","tag-paper-tigers","tag-small-block","tag-tech-tuesday","tag-wayne-scraba"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.racingjunk.com\/news\/wp-content\/uploads\/2014\/07\/Dyno-1Feature.jpg","jetpack_shortlink":"https:\/\/wp.me\/p42YSK-1K5","jetpack_sharing_enabled":true,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/6701","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/comments?post=6701"}],"version-history":[{"count":7,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/6701\/revisions"}],"predecessor-version":[{"id":33370,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/6701\/revisions\/33370"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media\/6706"}],"wp:attachment":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media?parent=6701"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/categories?post=6701"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/tags?post=6701"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}