animal1000rr Posted July 5, 2016 Report Share Posted July 5, 2016 I guess this question is geared more toward builders but all input is welcome. Is there a great difference in the porting and setup of a dirt drag as opposed to an asphalt engine? just cylinder and case setup, I know final drive setup is totally different. Quote Link to comment Share on other sites More sharing options...
special06shee Posted July 5, 2016 Report Share Posted July 5, 2016 My understanding is, Power is power, how you get it to the ground is another story.. The only think i can think of is fuel, id say for asphalt, pumps are used being the longer distances ran. Quote Link to comment Share on other sites More sharing options...
JTmachining Posted July 5, 2016 Report Share Posted July 5, 2016 300ft vs 1/8 mile there's a diff Quote Link to comment Share on other sites More sharing options...
RagunCajun Posted July 5, 2016 Report Share Posted July 5, 2016 360 feet i bet 2 Quote Link to comment Share on other sites More sharing options...
animal1000rr Posted July 5, 2016 Author Report Share Posted July 5, 2016 1/8 mile is the distance, so from the input so far there is a slight difference but the major difference is the setup after the combustion? Quote Link to comment Share on other sites More sharing options...
animal1000rr Posted July 5, 2016 Author Report Share Posted July 5, 2016 and thanks for the input guys! Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted July 5, 2016 Report Share Posted July 5, 2016 I've assembled and tuned a couple of asphalt bikes for local guys. The main things that I found made a difference were gearing, clutch, less timing, slightly less compression, and tire width. There are two schools of thought. Some guys like to set it on kill and charge hard right from the hole so the bike is hanging it's lungs out at the finish. Other guys like to get to leave ok, and then really charge on the big end. IMO, I've seen faster accelerating bikes MPH less but still be faster, and that's how I like to do it. It's worked for me on two bikes I set up for drag guys, as well as my Oval racing set ups. Quote Link to comment Share on other sites More sharing options...
SlowerThanYou Posted July 6, 2016 Report Share Posted July 6, 2016 I guess this question is geared more toward builders but all input is welcome. Is there a great difference in the porting and setup of a dirt drag as opposed to an asphalt engine? just cylinder and case setup, I know final drive setup is totally different. I started with a purpose built 1/4 mile asphalt quad. No one had a clue, builder's or BHQ member's. Most still don't when it comes to asphalt. Heck maybe I don't either, but have some good numbers to back it up. Anyway, I got called out/challenged to put it on sand for hill drags. While it wasn't the fastest quad, it beat most up the hill on the big holiday weekends. Then somehow, a few BHQ member's got their feathers ruffled; including myself. I was challenge that I couldn't make a 3 second run within my 1st 3 passes on 300' sand/dirt. My 1st pass ever on 300' was a 4.01 & I weighed 230 lbs. 2nd pass, after a few minor adjustments & my lighter Son (180 lbs.) it went 3.92. I had one pass left with me on it to get into the 3s & got it with a 3.99! The bike got faster the more runs we made on 300'. This was all done with the same chassis, motor set-up & transmission we started with for 1/4 mile asphalt. The key items in precedence besides paddle tires; #1, Gearing, #2 the shorter the distance; the more aggressive you can get with the tune-up. The final & most important key is using your brain for your combo. I find it funny how BHQ member's regurgitate info, but have no hands on experience/clues actually doing it. I still don't have a clue, but at least I've done it! 1 Quote Link to comment Share on other sites More sharing options...
animal1000rr Posted July 6, 2016 Author Report Share Posted July 6, 2016 That gives me more insight on my question. Thanks to all that answered and those that read and just put in some thought! Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted July 9, 2016 Report Share Posted July 9, 2016 I set up both a lil diffrent with portwork n domes. Like STY I'm coming from an asphault background but build quite a few dirt motors. This is just my opinion. If you can get the motor to make peak hp later later in the rpm curve and pull more rpm then your opponent you will run better et's than most and have a good asphault setup. Can you take this setup to dirt yes . My advice would be build something inbetween the dirt-aspault parameters but don't plan on killing both categories.theres also big things like primary drive ratios/clutch tune/timing curves/effective swinger length Quote Link to comment Share on other sites More sharing options...
SlowerThanYou Posted July 10, 2016 Report Share Posted July 10, 2016 If you can get the motor to make peak hp later later in the rpm curve and pull more rpm then your opponent you will run better et's than most This is a key statement & we use it on most of our race platforms! Learned that trick from a well known old school car engine builder. I've posted the article on BHQ before, it's a great read & can repost if needed. Quote Link to comment Share on other sites More sharing options...
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