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post #1 of (permalink) Old 02-27-2008, 07:39 PM Thread Starter
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Port and Polish!

Hey all you AMC guys I've got a question. Ive got myself a 1974 CJ7 with a 304 and I've just bought a pair of reman. heads with a three angle valve job and new valves/springs etc. My question is would I be able to do a port and polish job on these myself with the help of my dremel tool? If thats not a good idea how much might it cost for these to be done professionally and what kind of horse gains could I expect? Thanks, I appreciate your input, J.Shank
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post #2 of (permalink) Old 02-28-2008, 05:51 AM
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Porting and polishing isn't something an amateur can do with any likelihood of success. It's really a black art that can only be learned with a flow bench and plenty of heads to practice on. Even masters can't always predict what will happen with a given change in port shape.

Also, it's probable that any power gains you might by chance get would be at the expense of low speed torque and throttle response - the two attributes a Jeep engine needs most.

Small ports with tight turns churn and swirl the mixture on its way to the cylinder. That delivers a more homogeneous mixture that burns better. If you open, straighten and smooth the passages you can get more mixture in at high speed, but at low speed the gasoline clumps into small droplets that don't burn completely.

And finally, a Dremel doesn't have enough suds to do port work. You need an air-powered die grinder and a very large assortment of burrs.

EVERYTHING's easy for the guy who doesn't have to do it.
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post #3 of (permalink) Old 02-28-2008, 09:43 AM
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Ditto on what Jim said.

Basically, if you want more power, raising the air pressure in the tires and waxing the body will do more for you than porting the heads.

In addition to the porting, you have to make the cam changes and other mods to take advantage of the port job....even then, porting is only going to have a real effect in the upper 10% of the RPM range....so if you plan to run your engine up around 7000 RPM all the time....not worth the effort.

You want more power? Put on an aftermarket fuel injection system....that will do more for you than anything else.

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post #4 of (permalink) Old 02-28-2008, 06:27 PM
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work on heads for power

like they say heads for the most part need to be left to a car shop the has the proper tools and equip. but depending on what you are after their are many bolt on items that will up hp... just remember that one change by itself wont do much... everything works with everything else... what i am trying to say is.... if you put more gas or air in a motor you have to be able to get more out also... when you change one thing it needs you to change something else they work together.... if you had a good three point job done to the heads not much more their you can do.... as long as any burrs or rough edges are removed....same thing on the intake make sure no factory casting to upset air flow and you should be good.... most of the jeep guys wont like headers... but again it is about what your after.... same thing with fuel injection.... i dont like it... cant do much with it.. make sure your spark is good... again if your adding more fuel better be able to burn it or it wont do you any good... all works togther.... right cam with right size carb with good hot spark and good way to get rid of it out of the motor means more power to the rear wheels.....hope this helps a little do a lot of thinking and compare everything before you buy anything..
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