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Re: 1969 Tri-Power

Posted: Feb 8th, 2016 11:19 pm
by rbryce1
I just went on line and many sites tend to say that polishing and porting will increase performance. I don't know if they know what they are talking about or Holman & Moody knew what they were talking about, but I did trust them as this was their primary business, not selling the kits to do the work with. Even the places selling the kits and providing the instructions are heavy on the warnings of difficult the job is and how easy it is to screw up. If you really realized the 20% power increase, I think the auto manufacturers would have been doing this for years now to increase performance and efficiency, but they don't. Maybe because it is too expensive, or maybe because it doesn't work on this level. I just don't know.

Not that wikipedia is an exhaustive source of information, but here's what it says:

"It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition suggests. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past, which develops a velocity profile (or gradient) across the duct. For surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this."



Again, I think porting and polishing is fine and almost necessary for a racing engine, but not for a street driven engine that spends 90% of it's running life below 2500 rpm and much of that at an idle. In my opinion, the increase in power is in theory and the gains you will most likely see in performance for the type of driving one normally does will never be seen, but the possible damage to the heads and the possible negative effects are not worth the risk.

In the end, you decide. let us know what you do and how it works. Interested to see.

Re: 1969 Tri-Power

Posted: Feb 9th, 2016 5:26 pm
by Love_69
Hmm...I tend to agree with all that you've written here, rbryce1...the many hours of work to see no real/tangible gain (except on the race track), would be pointless. I didn't intend on opening-up the ports to their maximum, as that would make a street driven car a pig to drive. I was more interested in the port matching aspect. So, after your input and from some Net research myself, I have decided not to do anything with the heads except recondition them.

Thank you for your input - much appreciated.

1969 Tri Power

Posted: Dec 4th, 2016 8:15 am
by rentdresknz
Does anyone know where you can find Tri Color desert TRUs, or any combat shirt with the velcro for patches? thanks.

Re: 1969 Tri Power

Posted: Dec 5th, 2016 1:24 am
by nwav8tor
rentdresknz wrote:Does anyone know where you can find Tri Color desert TRUs, or any combat shirt with the velcro for patches? thanks.
How do trolls like that even find this board??

Re: 1969 Tri-Power

Posted: Dec 5th, 2016 6:56 am
by rbryce1
I agree. Why would they even dream that someone on a Corvette site would respond to combat shirts? I think they hit their head too many times playing war games on their I-Pad.

Re: 1969 Tri-Power

Posted: Dec 5th, 2016 7:16 pm
by vito
Anyone willing to report this to the FBI? :D

Re: 1969 Tri-Power

Posted: Dec 6th, 2016 12:03 am
by ktruff46
Tweet it to Trump. He'll straighten him out! Lol

Re: 1969 Tri-Power

Posted: Dec 11th, 2016 12:58 pm
by MaineVette
:mad: These spammers are getting pretty clever. I have to approval every first post a new member makes - basically to make sure they aren't going to blow the forum up with spam. You'd be amazed at how many spammers join and attempt to post on this forum daily. Total waste of my time. :rolleyes:

Some of these spammers, such as this guy, actually go through the effort to make a first post about something relevant so I'll activate their account. He actually made about a half dozen seemingly relevant posts - although some were pretty suspect. I thought he was a spammer but was giving him the benefit of the doubt - I just thought he was clueless. :bang: Same guy who posted saying the rear bumper could take the place of the rear crossmember :skep: .

I definitely need to update my forum software - which would help significantly - but I just haven't had the chance. Anyway, happy to report this guy won't be a problem any longer - he's on a permanent vacation from the forum. :thumbs:

Re: 1969 Tri-Power

Posted: Dec 12th, 2016 8:18 pm
by ktruff46
:Hurray: :Hurray: :crazy:

Re: 1969 Tri-Power

Posted: Dec 13th, 2016 10:57 pm
by nwav8tor
Thanks for 86ing him.

Just what do those spammers hope to accomplish by joining forums such as this?

Are they just doing it to prove that they're A**holes?