Head Work VS Big Bore
HDF Community Team
Joined: Jun 2006
Posts: 12,774
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From: san antonio
If the bike was a pre-06 model, I think it's a coin toss as the early heads truly were a bottleneck. However, with the improved flow of the later heads, more displacement and cams would be my choice if doing heads and big bore at the same time was not possible.
Do the big bore and install a good fuel management system like the TTS Mastertune or the PowerVision; you will get a nice power boost that may be sufficient. If/when the "new" wears off and you want another 10HP/TQ or so and funds are available, have the heads ported but, as has been suggested, be prepared to replace the cam set but you may be able to keep the same cam set, just need to work that out with the head porter.
Do the big bore and install a good fuel management system like the TTS Mastertune or the PowerVision; you will get a nice power boost that may be sufficient. If/when the "new" wears off and you want another 10HP/TQ or so and funds are available, have the heads ported but, as has been suggested, be prepared to replace the cam set but you may be able to keep the same cam set, just need to work that out with the head porter.
Last edited by djl; Oct 22, 2014 at 01:55 PM.
Seasoned HDF Member
Joined: Mar 2010
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From: Poolville
small blocks
I am a proponent of small blocks, I just love the idea of blowing away larger cubic inch bikes with my 83"er. Like I've said in the past" any one can get good power with more cubic inches but to be able to get great power with less is an art"...up the compression and do the heads an cam all at once. Save the big bore for when the motor gets tired and you really need it.
Club Member
Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
I am a proponent of small blocks, I just love the idea of blowing away larger cubic inch bikes with my 83"er. Like I've said in the past" any one can get good power with more cubic inches but to be able to get great power with less is an art"...up the compression and do the heads an cam all at once. Save the big bore for when the motor gets tired and you really need it.
Extreme HDF Member
Joined: Nov 2007
Posts: 14,670
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From: East of the Sun, West of the Moon
The main benefit of using a big bore kit, especially a bolt-in one, is not the extra few cubic inches gained so much, but the increased CR that usually comes with the new pistons. As an example an 883 Sportster converted to 1250 (several kits are available), but with stock heads can give almost double the HP, for a 42% increase in capacity.
Seasoned HDF Member
Joined: Mar 2010
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From: Poolville
prefrences
I am just stating my preference, boring a motor to a maximum size limit to me will put that cylinder at the end of its life expectancy sooner so the next time you need rings or a Fresh up
You'll have to replace the jugs at an added expence that's all. I like the longevity thing..
You'll have to replace the jugs at an added expence that's all. I like the longevity thing..
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Joined: Dec 2007
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What 98hotrodfatboy is refering to is the 83"er he is having us complete here, with a combination we've used since the mid-1990's.
Makes folks suspect that the engine is MUCH larger than the actual size.
It is making great power now w/o the 2/1 pipe that is now en route, and w/o any carb adjustments/tuning yet, only a couple of timimg tweaks for now, just to record the 2/2 power.
Scott
Makes folks suspect that the engine is MUCH larger than the actual size.
It is making great power now w/o the 2/1 pipe that is now en route, and w/o any carb adjustments/tuning yet, only a couple of timimg tweaks for now, just to record the 2/2 power.
Scott
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