Looking into Port / Polishing my intake manifold to go with the ported head, did a few searches and came up with a few bits of info. Just wondering if there were any specific how-to's, any info anyone can provide, pointers or guides?

Im in no rush to do it, and got a couple of spare ones lying around. Always good to learn something new and do something yourself.

 

ttt

 

have sum1 with experience do it... and its just porting.. not polishing..



but if u mean portmatching? well just trace the ported head's port on a carton and overlay it on the IM's flange and scribe a line etc etc etc

 

if its going on a built motor id do it, send it out if you dont have the tools to do it, im sure you will make some sort of gain,

 

i just finished porting & polishing a b16 manifold for a customer. it looks easy but its time consuming.

 

dont polish the runners.
the air flow carrys more momentum over a slightly rough/pitted surface as the air that gets trapped in the small pockets of roughness form a cushion for the air towards the center, allowing it to flow much much faster. mirror smooth surfaces jsut disrupt msot of that. alot of high end itb stacks i have seen also keep a pitted surface after the trumpets/stacks.


dont polish the intake ports smooth either, it messes with fuel atomization.

if you dont know what your doing, then leave well alone!

 

Deff. dont do it unless you can hook it up & make sure every runner is flowing about the same cfm n all that good stuff.

 

How can it mess up fuel atomization, as the injectors are at the head face?

 

What a rough/pitted surface finish does is effectively "shrink" the runner size in the manifold due to the larger boundary layer. DonF is correct also, its kind of hard for to mess with atomization in the manifold seeing as how there is never fuel in the manifold.

 

Porting a manifold is easy. Porting a manifold to get all four runners to flow the same its another story.

I can do it if you are interested, I have a flow bench. I flow all four runners before and after the porting.

Depending on the manifold you want it to flow a decent ammount so it does not restrict your head. But you don't want it to flow too much where it will loose velocity and have a negative effect.

 

HuH? You can actually flow a Honda plenum manifold, with throttle body, on a head and get it to flow to much? Doesn't the restriction behind the valve and on the short side increase velocity? Have you ever actually gained flow with a manifold ant TB?

 

i agree wth donF... i always read and hear people about - oh dont polish it oh it wont atomize... etc i guess their injectors are on the throttle body LOL

 

Im talking about the manifold its self. Too big its not always good.

I flow the intake manifolds with out the head before and after the porting.

Then if I have the customers head, ill put it on the head and see if its big enough not to restrict flow to the head. Then if the manifold + head flows less than the head its self, then the manifold need to be bigger.

 

in 20 years of flowing heads and manifolds, i have never seen more flow with a manifold and TB. Atleast i hope you are using a radiused inlet for the head. I know of no-one who claims more flow with manifold and TB, but we all can learn something. Any numbers, or are they just for your trick racers?

 

Ive heard that a few times, when doing various searches and everyone seems to think your talking about the intake ports when you specify the manifold.

Whats the difference between a B16 and a B18C IM? B18C ones are ported?

 

hold on *****, where did i say it effected the atomization in the manifold?

 

I never said that the head will flow more with the manifold and tb on it.

I said that the manifold need to be big enough not to restrict the flow to the head, but not too big where it does not match the rest of your set up.

If you have 20 yrs of flowing heads and manifolds then you know that there is a certain cfm that the manifold need to flow more than the head in order for the manifold not to be a restriction.

I do use a radius inlet for the head when I flow the heads by them selfs.

 

All very true. However, ive found that most IM's dont need all of the runners to flow exactly the same. The only real way to know what you need each runner to flow is to put it on a bench with the head and IM/tb thats going on the setup, then do alot of calculating. Ive had manifolds that have a difference of up to 9-10cfm between runners in order to get a balanced flow through the valves. This was on an stock srt4 IM, most aftermarket IM's for Hondas wont have that much of a difference in cfm because they allow for a better balance of flow through each runner. My terminology probably sucks because i only do this for run. Im sure most of you guys know much more than me, this is just what ive found from my own testing.

 

I was thinking on doing the same thing to my p73 IM, but I want it done by a professional. I've read about some shops that do this kind of work but I'm not sure on who to send it to... Any input is greatly received!!! Oh, and the head will have a port work done soon, but from what I've been told the shop doesn't port IM

A friend of mine suggested me to use a victor x IM but I am a conservative guy and like the look of a stock IM. I have hope that a ported p73 IM will perform better than an aftermarket if the job on it is well done. The engine will not rev past 9,500 so I’m not looking for power beyond that!!!

 

Maybe you could be interested by my post


https://honda-tech.com/forums/all-motor-naturally-aspirated-44/my-home-made-intake-polishing-%2Apic%2A-2464682/

 

I thought you wanted everything as smooth as possible up until the point of the injectors then you wanted a little rougher surface for atomization.

smooth = less restriction of airflow = more air in less amount of time

Or maybe I am just stupid.

Portmatching is still best bang for buck if doing nothing else to a manifold. unless and until you get to the point of race-only. Honda spent alot of money for research for a reason.

Port-matching is just that. makes true holes from bigger tb's and ported heads so there are no edges to restrict.

 

I was told that u want to polish the plenum but not the runners. Something to do with fuel atomization. If u have the TB opening bored to say 72mm in plans for a larger tb, but use a stock 62mm tb in the meantime, will there be any adverse effects from having the opening so much larger than the tb?