Ported Heads Question
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Road Warrior
Joined: Jul 2011
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From: Central TX
Ported Heads Question
I have a set of mild street port heads on my 95 TC wit HQ39g cams, bored 48mm TB and Lowcat 2-1 exhaust. Been thinking about getting better flowing heads to bump power. I have attached the typical flow sheet for the heads (each set is not flow tested) and description of work done. I am wondering if I got some heads done from reputable shop with larger 1.90 intake and maybe a little bigger exhaust and recontouring of ports, will it be a noticeable bump in power on the street? Was looking at Kirbys Stage 2 and Dan Vance raised port Stage 4 heads. Looking for increased torque, quick throttle response, and pull all the way to redline. If I was starting with a build right now, I would do the extra head work, but debating whether the power increase over what I have is worth the money. Also wondering about exhaust valve size with the HQ39 cam long exhaust duration - dont want to overexhaust and give away power. I know no one can say for sure without seeing my current heads, but would you expect a set of stage one heads to be able to be used if additional porting is done. Current heads already have higher lift springs for the 39 cams.
HDF Community Team
Joined: Jun 2006
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From: san antonio
I will defer to the head porters for a definitive answer if one is possible. However, unless your heads are flow tested, you don't have a baseline so you are flying blind. The numbers in your attachment are decent numbers for Stage I heads yretaining OEM valves and lapping valves in lieu of a multi-angle (SERDI) valve job. BTW, what does "full porting of intake and exhaust runners" mean?
My limited experience has taught me that once heads are ported or machined, most reputable porters won't touch them. Having said that, the only way you would know if flow can be improved would be for a porter to flow the heads on their bench first to determine if they could improve flow based on the way they port heads and then determine if it was possible to do the required work to your heads to make that improvement.
Consider selling those heads and starting from scratch with the porter of your choice. Additionally, again based on limited experience, HQ cams work best with HQ heads, so you might also consider replacing cams and bumping compression as well.JMHO.
My limited experience has taught me that once heads are ported or machined, most reputable porters won't touch them. Having said that, the only way you would know if flow can be improved would be for a porter to flow the heads on their bench first to determine if they could improve flow based on the way they port heads and then determine if it was possible to do the required work to your heads to make that improvement.
Consider selling those heads and starting from scratch with the porter of your choice. Additionally, again based on limited experience, HQ cams work best with HQ heads, so you might also consider replacing cams and bumping compression as well.JMHO.
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Yes.
We have improved upon many heads, many times, as our Superflow 600, and Superflow 120, has both shown us.
258 cfm is a bold claim with a 1.800" valve, at .600" lift, and why not optimize/equalize the combustion chambers via a milling machine and cc'ing, vs the use of sandpaper on the cylinder head gasket surface?
Scott
We have improved upon many heads, many times, as our Superflow 600, and Superflow 120, has both shown us.
258 cfm is a bold claim with a 1.800" valve, at .600" lift, and why not optimize/equalize the combustion chambers via a milling machine and cc'ing, vs the use of sandpaper on the cylinder head gasket surface?
Scott
Last edited by Hillsidecycle.com; Feb 28, 2019 at 03:02 AM.
Banned
Joined: Sep 2009
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From: deland,florida
having YOUR heads flow tested after porting is very important (is here anyway) every head done here comes with a flow chart. who`s sheet is that? it dosnt mention if guides are replaced on the stage II porting or what the seats are machined with (stones,neway,SERDI??)
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Road Warrior
Joined: Jul 2011
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From: Central TX
Thanks for replies. Bike has plenty of compression now - ccp is 205 f/r. I would rather not give name of porter - dont want any one flaming him. These heads gave a definite low-end improvement over the previous ported larger valve heads that came with my 95 BB. Just wondering what kind of power gains to expect from a mild street port to a Stage 2 head? When I ran a FatCat with louvered baffle, I had around 98hp/105tq. What the difference between a hot rod and touring head work?
Last edited by txphatboy; Feb 28, 2019 at 09:42 AM.
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A touring head, ie low-end torque, will focus manufacturing power in that area, and a hot-rod head/combination, will generally produce power that is left-side, dyno report biased.
Scott
Scott
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Can you explain what you mean by left-side? I assumed the right and left side of a dyno report was using the point where HP and torque cross (5250 rpms), and right-side would be high rpm. high HP for the hot rodders.
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Thread Starter
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Road Warrior
Joined: Jul 2011
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From: Central TX
Thanks for all the feedback. I spoke to the guyt who ported my current Stage 1 heads and he said I might gain 5+ hp/tq, but did not feel it would be felt much on the street. I am going to save the money. Found a used Fat Cat and going to install that and upload old map and have it fine tuned instead. If I can get back to the 98hp/105tq and nice broad torque curve I used to have with that pipe, I am going to ride it as is and try to stop finding ways to spend money! Need to stop looking at this forum.
Banned
Joined: Sep 2009
Posts: 3,569
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From: deland,florida
Thanks for all the feedback. I spoke to the guyt who ported my current Stage 1 heads and he said I might gain 5+ hp/tq, but did not feel it would be felt much on the street. I am going to save the money. Found a used Fat Cat and going to install that and upload old map and have it fine tuned instead. If I can get back to the 98hp/105tq and nice broad torque curve I used to have with that pipe, I am going to ride it as is and try to stop finding ways to spend money! Need to stop looking at this forum.