anyone understand what my mechanic is talking about?

[Downfall]

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i brought my car to a shop to have my carbs balanced and adjusted properly on my 71 240Z. he said he could also modify the carbs to give a little more power. he couldn't really explain to me that well he said. his english isn't that good but he said something about a 90 degree bend somewhere in the carbs that he would grind to make the flow more smooth and not so harsh a turn. anyone know what he could be talking about? oh and he mentioned something like "venturi"? any help would be appreciated.

thanks.

[Stryder]

Maybe he was talking about boring out your carbs?

[sawilliams]

its sounds like he was talking about a port and polish job on your intake manifold. the port part is to gring away, shape and debur ( within the restrictions of its shape) the inside of the manifold. the polish part is to make it extremely smooth , so the gas/air mixture meets as little resistance as possible. rudimentary explanation to going FAST----------make the car breath as quick and efficient as possible. quick in---explosion, power-----quick out. porting and polishing is a very effective way to acheive better breathing.

[tttz]

So how much does a port and polish job cost, if you have a mechanic do it?

thanks,

ty

[sawilliams]

its been along time, but it is very labor intensive. hundreds for a good job. steve

[Gav240z]

I've heard that deburing and polishing too far causes the fuel mixture to stay binded in blobs as oppose to become a spray when entering the combustion chamber and can make the explosion uneven and cause the car to loose power ???

I've never done this or had this problem just something I was discussing with someone who said he worked with engines alot.

Could be like my crossflow head theory for those that read my post there and I could be talking complete bollocks.

Awaiting correction Gav,

[sawilliams]

from what i understand--atomization takes place until time of explosion. an even port job is more critical then the debth or width( simply talking about atomization) uneven porting can cause uneven atomization and grouping of mixed fuels. some lean and some rich. and an uneven burn------like i mentioned before----its expensive to be done right. dynos and all that stuff. but a basic cleanup----mainly a conservative polish job----tends to help out alot. by the way, im new to this site and i am very impressed by the people and the site. steve

[240ZX]

Downfall,

From your side of the fence, it sounds as though there is too many unknowns to this equation. If the guy is not a porting & polishing expert with loads of experience on Datsun L series engines......don't let him touch the manifold!!! Now if its just a matter of cleaning up the flashing left from the casting process, then maybe you'd be OK. But screwing around with port design is an art in it self!

But that's just one man's opion!!!

[sawilliams]

food for though-----it is not an exact science, unless your going to use state of the art computerized mapping of the ports. an "expert" cannot look at a curve in a manofold and say ya you know heres the physics of the fuel atomization that will take place right here. alot of people may disagree with this -----but there is a lot more room for error on the positive side than negative. just be careful and dont go nuts. steve

[sawilliams]

i might ad.-------if you really get a top notch port and polish-------------you really should take advantage of it and match jets and settings and all sorts of stuff.--------------bottom line. a nice clean is sufficient for a peppy daily driver. steve p.s. who let the dogs out ?:classic: