Why the differance
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Cruiser
Joined: Jan 2007
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From: Corpus Christi, Tx.
Why the differance
Looking at the service manual for 03 touring models page 3-1. The torque is 86 ft-lbs @ 3500 rpm. The combustion chamber is 85cc's. My question is, why is it that at stock my dyno read max tq 72.8ft-lbs? Shouldn't it have read 86? Where did I lose the tq? Also,The SE Performance heads have a combustion chamber of 72cc's and the htcc heads have a combustion chamber of 84cc's. What is the differance for the size? If the htcc heads have 84cc's and a stock head has 85cc's, wouldn't the stock heads be better? I have been doing alot of reading here to determine what parts I need to do a 95"bb. I have added the 510g cams and get 88ft-lb tq. With the cams I have, I need to stay below 9.7-1 cr. Stock compression is 9-1. If I install the SE high comp forged piston #22868-00 with stock heads my cr will be at 9.6-1. If I add the SE performance heads #16953-99b the cr jumps to 10.5-1. Like I said earlier about the SE Performance heads have a 72cc combustion chamber. Will enlarging the chamber drop the cr? Oh, also does "porting" mean enlarging the chamber?
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Joined: Jul 2006
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RE: Why the differance
OE manuals and specs are at the crank measured on an engine dyno, not the rear wheel. SE catalog is at the rear wheel. Dynojet dynos give rear wheel HP and ESTIMATED crank torque NOT rear wheel torque.
Also, read this http://www.carcraft.com/techarticles...ression_ratio/
Also, read this http://www.carcraft.com/techarticles...ression_ratio/
Tourer
Joined: Aug 2006
Posts: 484
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From: Indianapolis
RE: Why the differance
you really need to be careful when selecting your components. There are lots of tried & true combinations. Your best bet is to talk to some of the guys that build motors. Steve @ GMR Performance and Wes Brown at Cycle Rama are awsome and will get you straightened out. The guys at Head Quarters, R&R Cycles, Atwood, and Big Boyzare all very good as well. To answer your questions about porting heads. The stock heads are more than adequate to make big power they just need massaging.Harley is notorious for having very loose tolerances so the cc of the combusion chambers can be as much as 3-5cc different from head to head. So part of the porting process is to cc the chambers. When they do this they make them both the same.
They also clean up the runners to allow more air in and out. There are various stages of head porting to meet your specific needs and budget. Also consider having your stock jugs bored to 95" this will save you a ton over buying new ones and the bored stock jugs are considered better because they have been seasoned or heat cycled and will hold their shape better. Talk to any of the guys I mentioned and they will answer all of your questions
They also clean up the runners to allow more air in and out. There are various stages of head porting to meet your specific needs and budget. Also consider having your stock jugs bored to 95" this will save you a ton over buying new ones and the bored stock jugs are considered better because they have been seasoned or heat cycled and will hold their shape better. Talk to any of the guys I mentioned and they will answer all of your questions
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Cruiser
Joined: Jan 2007
Posts: 210
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From: Corpus Christi, Tx.
RE: Why the differance
OSE, that was alot of reading. Can you explain it in english now? lol Really, it was informnative but kinda confusing. I think I understand that Porting doesn't make the chamber bigger or else the compression goes up. Or is that the milling?.Either way I do Kinda Understand thje compression alittle better. How can I find out the size of a 95" piston to figure out the cr? I wrote down the formula and was going to try it but was unsure of the piston size. I didn't know if I should use 95" or 1550cc's. Also, shouldn't it be up tp the machinist to know deck height or chamber volume to determine what my cr will be after machining?
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XfasteddieX
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Sep 18, 2006 12:35 AM
