I do custom port work designed with your stroke and cam specs not just some dude with a grinder. all port work is not the same, total engine design is critical for gaining performance in the rpm range your trying to achieve. valve and seat size bowl erea port runner length and port cross sectional erea carb size exhaust runners and shape exhaust pipe diameter and length all taken into consideration when designing a proper port. all work is checked on a flowbench with before and after measurements sent to you with a worksheet when returned.
I don't know if that some dude with a grinder comment was directed at anyone in particular or not but everything you just said was explained via pm to this member ... Just hogging out a port can actually be counter productive !! It's all about the combination and power band goals you are trying to achieve ...
Trinik,
Can you explain when efforts might be counter productive? I'm new to the whole 'building' thing. I ported and polished my Hemi head (yup some dude with a grinder) and tried to minimize the material removed. Mostly just smoothing out any sharp edges and tapering everything else for what I perceive to be smooth flow. I followed common practice to leave the intake at 80grit, and polish the exhaust. I did not enlarge the runners.
Here are some pics of my head.
Plan for this motor is 5-6k rpm max, but high torque in lower rpms. (Black Mamba Jr, VM22, .875"ID Header 53" long, 26#, 10.5:1 CR)
In your opinion, did I help or hurt my motor?
Thanks!
Can you explain when efforts might be counter productive? I'm new to the whole 'building' thing. I ported and polished my Hemi head (yup some dude with a grinder) and tried to minimize the material removed. Mostly just smoothing out any sharp edges and tapering everything else for what I perceive to be smooth flow. I followed common practice to leave the intake at 80grit, and polish the exhaust. I did not enlarge the runners.
Here are some pics of my head.
Plan for this motor is 5-6k rpm max, but high torque in lower rpms. (Black Mamba Jr, VM22, .875"ID Header 53" long, 26#, 10.5:1 CR)
In your opinion, did I help or hurt my motor?
Thanks!
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Ole did a good thread on the hemi heads . Barry young and Brad Hill have both got very respectable flow numbers out of them . What I meant was some people go way overboard on how much and where from they remove material in the ports .. just making it bigger is not better and more times than not they are loosing port velocity . Leaving the intake port rough for atomization is a matter of opinion .. Sharp edges should be rounded off but the short side radius should be worked not ground away .. personally I like real Honda castings 14cc to be exact the valves are a little shrouded but can be opened up . Others like the 18cc heads for that reason ... Hemi heads have 27/25 valves stock which is nice and for a mild build cleaning up the ports will make an improvement ..
my comment was not directed at anyone. sorry for any confusion!! but trinik your right on with what you saying most people with a grinder take too much material out and usually in the wrong places. port velocity must be kept at the right speed for a given rpm range along with the right amount of cfm. we like to dye test and use velocity probes to test ports on the flow bench to see where the air is moving and at what speeds. big cfm without the right velocity can actually make less power!!
Rule number one to anybody getting "port" work done. If they guy doing the work doesn't have a flow bench then walk away.
A home mechanic can do a gasket match and polish (as long as the polish doesn't hog things out) but real port work requires more than a die grinder and tootsie rolls. It irks me to hear shade tree guys talk about all this port work they done but don't have a clue what a flow bench even is. As already stated its very easy to ruin power (and a head or set in the car world) just hogging out material.
A home mechanic can do a gasket match and polish (as long as the polish doesn't hog things out) but real port work requires more than a die grinder and tootsie rolls. It irks me to hear shade tree guys talk about all this port work they done but don't have a clue what a flow bench even is. As already stated its very easy to ruin power (and a head or set in the car world) just hogging out material.
Imma go ahead and respectfully disagree on this one.
Sure, one can screw things up by haphazardly gouging, but an experienced cutter can get within a couple percent with nothing more than a well-calibrated index finger and eye-crometer. Dry flow is just one part of a package. These stone-age industrial lumps rarely have enough material to hurt through area increase. Short side and bowl size/shape are horrid so decent gains are easy. We "fixed" a set of 427 SOHC Ford heads that had been hogged to death. Nearly 10lbs of epoxy between the ports and manifold, to get 40cfm more. The shop owner got mad that a porting apprentice was well in to the 2nd day on a set of aluminum BBOlds heads, and grabbed a raw one, assaulted one int/exh for literally 10 minutes, one carbide burr in the Milwaukee. He said "Touch up the seats and flow it". Was dead center in the target window. Had we not had a flowbench (or 4..), it still would have flowed well. We had some fancy swirl meters, wet-flow bench, one with enough push to test Top Fuel heads at 60PSI instead of vacuum. The good guys understand airflow dynamics, and more importantly, their role in overall engine output parameters.
Polishing is for trophies, not ports
Sure, one can screw things up by haphazardly gouging, but an experienced cutter can get within a couple percent with nothing more than a well-calibrated index finger and eye-crometer. Dry flow is just one part of a package. These stone-age industrial lumps rarely have enough material to hurt through area increase. Short side and bowl size/shape are horrid so decent gains are easy. We "fixed" a set of 427 SOHC Ford heads that had been hogged to death. Nearly 10lbs of epoxy between the ports and manifold, to get 40cfm more. The shop owner got mad that a porting apprentice was well in to the 2nd day on a set of aluminum BBOlds heads, and grabbed a raw one, assaulted one int/exh for literally 10 minutes, one carbide burr in the Milwaukee. He said "Touch up the seats and flow it". Was dead center in the target window. Had we not had a flowbench (or 4..), it still would have flowed well. We had some fancy swirl meters, wet-flow bench, one with enough push to test Top Fuel heads at 60PSI instead of vacuum. The good guys understand airflow dynamics, and more importantly, their role in overall engine output parameters.
Polishing is for trophies, not ports
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Disagree but if I walked into a shop charging to have port work done I would walk straight out if they didn't have a flow bench. There is a big difference in doing clean up and full porting. Clean up can be done with just a dremal. I've seen and fixed way too many "oh I know what I'm doing" jobs to rely on somebody by their word alone. I have a set of high dollar chevy heads under my bench that flow like somebody shaking bbs in a tin can done by pro on the side without using a flow bench. The shop he works for used to do all my head work when I was racing and at first I didn't believe the guy when he said who done them UNTIL I was informed on the details. We flowed them on my down and dirty homemade bench and I felt sorry for the guy even knowing it was a discount price he gave for the work.
If I got the time I try to mirror polish all my exhaust ports (and combustion chambers).
If I got the time I try to mirror polish all my exhaust ports (and combustion chambers).
I average building around three heads per week, and average four SA or 390 carbs. I get $80.00 to port..that includes flow testing (they are usually flowed a few times to get them exactly where I want them). I build them with all the info I can get from the customer. I want to know what it will be used for.. mini or kart..etc I want to know what rpm range it will be used in (peak and rpm drop).. Lift it will see at the valve. The more I know the better I can match it to the customers needs. I have sent heads all over the country, and have yet to have one that didn't outperform what they were currently using. I just sent a highly modified clone 14cc head (32 28 valves , even though they don't need the 28 exhaust valve.LOL, milled, chamber unshrouded..flowed a little over 100) to a guy in Arkansas who builds a lot of open engines.. and wins a lot of open races.. he just reported it made 1/2hp better than ever.. If I can help feel free to let me know (text 276-340-3278)