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post #1 of 34 (permalink) Old 05-08-2013, 08:39 PM Thread Starter
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Cylinder head question

Looking for some advise. Getting ready to rebuild the top-end of my dads motor. 88-inch twin cam, going to 95-inch. Already has Headquarters HQ-0034 cams, SE air cleaner, rhinehart true duals. Plan is to keep cost low and reuse everything listed.
I picked up a set of 2008 heads also for the rebuild. My question is what to do with the heads, for maximum torque output. I was thinking bigger valves and light porting. But my dad thinks he will get better lowend performance with light porting and leaving the stock valves in the heads. Can someone share their knowledge with me, as to go bigger valves or leave stock? Goal is for more torque. Thanks in advance for input
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post #2 of 34 (permalink) Old 05-08-2013, 08:55 PM
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I'd probably go with a street port w/ a 1.9 intake and stock exhaust if torque is the goal. Most head porters offer an affordable street package that focuses on making torque early.


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post #3 of 34 (permalink) Old 05-08-2013, 09:00 PM
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The HQ-34 is a low end torque cam, (a very good one by the way) so if it were mine I would do what most shops refer to as a street port with stock valves and good multi-angle valve job. Set the comp. at 9.7 to 1.


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post #4 of 34 (permalink) Old 05-09-2013, 01:36 AM
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By upgrading to the newer heads the HQ cam you currently have will be way less than optimal due in part to the better intake to exhaust ratio of the late model heads.
You will no longer need 14 degrees more exhaust duration to make up for the crappy intake port on the early heads and the late model heads are configured to accept more lift.

You can leave the stock valves in the heads and have a competent shop do a clean up and valve job,done right well worth the effort especially if the heads are off the bike.

Installing just a new intake valve without removing the guides will not increase airflow enough to warrant doing the job,either do the minimal clean up porting or go full on and have them fully ported,new guides/valves the works.
post #5 of 34 (permalink) Old 05-09-2013, 08:02 AM
prodrag1320
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we dont remove the guides on our street port heads (we do replace them on stage II or III headwork),with opening up the bowl for 1.900 intakes and conturing,they flow 155+ @ 10",
post #6 of 34 (permalink) Old 05-09-2013, 09:52 AM
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If airflow numbers don't translate into power production,what would be the point of the extra work ?
post #7 of 34 (permalink) Old 05-09-2013, 11:34 AM
prodrag1320
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??? how you figuring air flow dosnt translate into more power???more air flow = more power
post #8 of 34 (permalink) Old 05-09-2013, 11:11 PM
Torqueinc
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Re read my post,take it from there

If a [email protected] 10" head makes no more power than a 140 or mid 140's @ 10"

happens frequently.
post #9 of 34 (permalink) Old 05-10-2013, 07:41 AM
prodrag1320
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still not following ya pal,if your saying stock heads flow mid 140`s your wrong (more like 125-130)plus a motor flowing 155 WILL make alot more power than heads flowing 140ish,after over 25 years of having my dyno (sold it when i moved to floida)ive seen power increases from 5 cfm increases

Last edited by prodrag1320; 05-10-2013 at 10:51 AM.
post #10 of 34 (permalink) Old 05-11-2013, 02:18 AM
Torqueinc
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Nobody is saying stock heads flow [email protected]"

Let me make this VERY simple

2 bikes same engine same cams....one with 140 cfm heads and one with 155 cfm heads....if they both make the same power OR the bike with 140 cfm heads makes more power...what is the point of the 155 cfm heads ?
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