Serious question about engine builds

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Dec 22, 2007 | 02:38 PM

chornbe

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From: Chester County, PA

Serious question about engine builds

Let me ask a question regarding all these big-bore and performance builds going on.

In these typical (and by the sounds of them, not-so-typical) builds going on, how many people are changing the rev limiter settings and using cams and valve springs that increase the potential operating RPM, or are change gearing as part of the build?

I ask this because unless you increase the RPM operating range (or gearing), you're not really increasing the *theoretical* top speed, only the rate at which you can achieve said top speed.

Dec 22, 2007 | 02:43 PM

lil_gmac2

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From: Los Angeles, CA (live in Manteca, CA)

RE: Serious question about engine builds

All engine builds will get some type of Rev limiter, cam and gearingchange. I so command that most people do mention it anymore. It's like needing your keys to open your start your car.

Dec 22, 2007 | 02:45 PM

chornbe

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RE: Serious question about engine builds

Cool. Thanks. Rarely hear about people's new rev-range, etc.

Danke.

Dec 22, 2007 | 02:57 PM

acedantinne

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From: Easton, Pa.

RE: Serious question about engine builds

Read alot about engine rebuilts. Cams? Have not read any valve springshims added any where? Pretty much throw cam in and go. Most never read the instruction on proper valve spring rate.
This will set off a flurry of pissed off backyard mechanics! There is alot of need to know info to get the job done right! Longer duration (valve opening) more pressure needed to close valve. everything (changes has its limit). Set valvues.
If you do not know what your doing? seek out the professionals.
Next subject=ring end gap. just not meassured at top of cylinder.

Dec 22, 2007 | 03:14 PM

chornbe

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RE: Serious question about engine builds

Quote:

ORIGINAL: acedantinne

Read alot about engine rebuilts. Cams? Have not read any valve spring shims added any where? Pretty much throw cam in and go. Most never read the instruction on proper valve spring rate.
This will set off a flurry of pissed off backyard mechanics! There is alot of need to know info to get the job done right! Longer duration (valve opening) more pressure needed to close valve. everything (changes has its limit). Set valvues.
If you do not know what your doing? seek out the professionals.
Next subject=ring end gap. just not meassured at top of cylinder.

That's the thing... I'm not building my engine. It runs fine. But I see all these folks talking about upgrades and builds and it *seems* that only half the job is getting done (my first career was as a mechanic), unless it's just implied at the builders are doing head work, too. Some of the labor rates I'm hearing, I just don't see how that could be. Would be interesting to see some of these more intense builds torn down after some miles and check valve seats and cam lobes and such.

Dec 22, 2007 | 03:25 PM

SpikeCT

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RE: Serious question about engine builds

Yes... When HQ does the headwork the valves and springs are changed along with improved guides. I have my rpm limit at 6200 and now and then hit it to quickly....

Dec 22, 2007 | 03:39 PM

PhilM

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From: TX

RE: Serious question about engine builds

Quote:

ORIGINAL: SpikeCT

Yes... When HQ does the headwork the valves and springs are changed along with improved guides. I have my rpm limit at 6200 and now and then hit it to quickly....

Yea.... what he said! Just about anyone that does headwork will set the heads up for the build they are preparing the heads for. As far as "bolt-in" cams go.... well, that's why they are called "bolt-in". They are designed to worked well with stock components ~ including springs.

REV Limiter.... I also have my DTT set @ 6200. Most ignition upgrades suppport bumping the rev limt. As John said... it's surprising how quick you cam bang the limiter!

Some also change gearing. In 2002 (I think), the touring model harley's had a primary gear ratio change. It was 3.37:1 & changed to 3.15:1. It changed again in 07, but I do not know what it is now. Some folks like to swap the 3:15 bikes back to 3.37. It's not a bad mod on the stock'ish & milder builds. Personally, my feeling is that if you have a motor that will pull the gear, then the 3:15 is better ~ but that's just me.... & mine will pull it.