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Fed
GenII
 
11/18/2005
12:16:48
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 Subject: Port & Polish 3.9 heads.. worth it?
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have any of you done this?
Is it worth the $4 - 5 hundred?
'93 Dakota CC 3.9 auto
(4.10, LSD, magnaflow exhaust, K&N intake, lowered)
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.boB
Dodge Dakota
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11/18/2005
13:32:12
|  RE: Port & Polish 3.9 heads.. worth it?
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No. Not unless you have some other serious mods to make use of it. Like a blower or 12:1 pistons.
OTOH, there's a lot of value in a general clean up and port match for almost any engine. That's something you can do at home with less than $20 in supplies and a drill motor.
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Kevin
Dodge Dakota
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11/18/2005
13:43:39
| RE: Port & Polish 3.9 heads.. worth it?
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boB can you explain further on this port match? I have heard the term before, but I am not really familiar with it.
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blk47dak
Dodge Dakota
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11/18/2005
16:24:47
| RE: Port & Polish 3.9 heads.. worth it?
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Talk to Dan at www.thefastman.com. He can hook you up with a set of 3.9 heads with bigger valves and port/polish. That would be worth the money.
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.boB
Dodge Dakota
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11/18/2005
17:06:44
| RE: Port & Polish 3.9 heads.. worth it?
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It's really pretty simple. You don't need to be a rocket scientist to do this.
Port match: All you want to do is make sure there's a fairly smooth transition from the intake manifold to the head. If the hedge of the head port sticks out 1/4" into the manifold port, you'll get a lot of turbulance and that causes a significan imbalance in the port flow.
Be sure to check the exhaust ports and manifold/headers for the same thing.
Many people use the intake gasket and match both ports to that. I prefer to make a cardboard template that blends both sets of ports in to one template, and then cut from there. Use a carbide cutting bit, and make a soft transition about an inch or so in to the port.
Porting: Just look in to the ports and make sure there's no big hunks of casting flash haning out in to the port to obstruct air flow. Don't go wild and reshape or polish the ports. Just clean them up a little, and only if needed.
Polishing: The head chambers are often pretty rough and bumpy. These rough spots can create hotspots, which lead to detonation. With the VALVES IN PLACE to protect the seats, use a sanding roll to gently clean up those areas. You're not looking for a mirror smooth polish, just a light clean up. You can almost ignore that tiny area between the valves.
The most important thing to remember is that you're just cleaning things up a little. You're not trying to reshape anything.
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intensedak39
*GenIII*
11/18/2005
17:29:42
| RE: Port & Polish 3.9 heads.. worth it?
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great info .boB
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Kevin
Dodge Dakota
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11/19/2005
00:05:22
| RE: Port & Polish 3.9 heads.. worth it?
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Thanks for the clarification. I don't really have time to take my heads off right now, but in the future if I get extra time, or if I am forced to take them off for a different repair, I will definetlly try this.
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.boB
Dodge Dakota
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11/19/2005
01:13:23
| RE: Port & Polish 3.9 heads.. worth it?
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That's a good plan. On a stock engine, I don't think it's worth doing unless you already have the heads off for some reason.
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formerdakownr
Dodge Dakota
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11/19/2005
13:29:06
| RE: Port & Polish 3.9 heads.. worth it?
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..or find a set at the slavage yard to mess around with, that way if the results are negative you can put the old set back on.
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toolfan
GenIII
11/19/2005
13:59:36
| RE: Port & Polish 3.9 heads.. worth it?
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one of my friends did this to his Ranger. i have thought about port the heads myself but you never know if its a good idea. .boB's idea sounds like a good one that would be worth trying if the heads and manifold are off of the engine and sitting in your garage. what if you just grounded out the exhaust valves would you gain if you had the headers to support it.
and some mods to slow it down!
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.boB
Dodge Dakota
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11/20/2005
12:28:44
| RE: Port & Polish 3.9 heads.. worth it?
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Port matching on the exhaust side isn't worht a whole lot of power to begin with. You only do it because you're doing the job anyway, so you might as well do it all. I would waste time or effort trying to port match the exhaust only with the heads on the truck. No gain, lots of risk.
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toolfan
GenIII
11/20/2005
13:22:56
| RE: Port & Polish 3.9 heads.. worth it?
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thanks .boB
and some mods to slow it down!
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N56629
Dodge Dakota
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11/20/2005
14:46:44
| RE: Port & Polish 3.9 heads.. worth it?
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<i>"Port match: All you want to do is make sure there's a fairly smooth transition from the intake manifold to the head. If the edge of the head port sticks out 1/4" into the manifold port, you'll get a lot of turbulance and that causes a significan imbalance in the port flow."</I>
I agree with you Bob, so why do people insist on gasket matching just the intake manifold? Doesn't that just increase the mismatch and resulting turbulance?
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.boB
Dodge Dakota
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11/20/2005
17:23:02
| RE: Port & Polish 3.9 heads.. worth it?
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It does if you do it wrong. To gasket match, you lay the gasket across the intake manifold ports and scribe the lines. Then you lay the same gasket on the head ports and scribe lines there. Then you use the cutter on both the head and manifold ports to get them to match the gasket lines.
I use cardboard to trace out the head ports and make a template. Then I put that template across the intake ports. Sometimes I have to make template a little bigger in one area to match the intake port. Once the template is done, I use it to scribe matching marks on the head and intake surfaces. When I'm done, all the ports match exactly with no step down or step up. The other problem is that the gasket is often bigger than the ports. If you hog out the ports to match the gasket, you'll create an hourglass shape. That does strange things to the air flow.
Additionally, I check the gasket fit to make sure it doesn't protrude into the air flow path. Sometimes it needs to be trimmed just a little. If it sits back from edge a little (and it usually does), that's OK. You just don't want it sticking out.
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N56629
Dodge Dakota
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11/20/2005
20:07:37
| RE: Port & Polish 3.9 heads.. worth it?
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That's the problem, Bob, they are hoging out the intake manifold to match the gasket and doing nothing with the head. There are plenty of proponents claiming significant gains.
As for getting an hour glass shape, I'm not sure whether that would be good or bad. It may vary by engine design but I don't think I would want to experiment unless I had some spare parts and a lot of time on my hands.
Tell me, on the magnum engines, how do you get the intake manifold and head ports in perfect or near perfect alignment? Some engines have dowels but not these.
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.boB
Dodge Dakota
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11/21/2005
13:57:05
| RE: Port & Polish 3.9 heads.. worth it?
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It's not easy, but it can be done. Just like on a Ford, there's no locating dowels; you could make same without too much difficulty. You just have to eyeball the bolt holes.
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RRDakota
Dodge Dakota
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1/20/2014
07:11:12
| RE: Port & Polish 3.9 heads.. worth it?
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Hogging out the intake manifold ports. & doing nothing to
the head intake ports is azz backwards...a large port flowing
into a direct shoulder & smaller port is a HUGE mistake....It
would be much better to have a smaller intake manifold port
flow into a larger head intake port without the shoulder
interference....Some turbulence is Ok on the intake runners
for instance the rough casting, and polishing is only for all
out high RPMs....A Shoulder Is NOT beneficial and hinders
airflow bigtime....porting the exhausts is more beneficial for
flow out....Unshrouding the valves is the best mod along with
a 3 angle valve job.....the valves are the biggest resistance in
air flow, so make that area flow better.....
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Jim
Dodge Dakota
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1/20/2014
20:23:17
| RE: Port & Polish 3.9 heads.. worth it?
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I had a valve job done for my 3.9l recently. I took the heads to a friend
who has a machine shop
and does alot of head work for Dodge and Chevy
owners. The guy who does his head work checked my
for valve seat cracks and found them to be in good
shape. He shaved the heads .030 inches and mild
porting and cleaned up the combustion chambers
and port matched the intake. After getting every
thing back together I picked up about 25 hp at the
wheels. I had the truck dynoed about 2 months ago. I then made 5 runs with the latest G-TECH and
averaged them and came within 5 hp of the dyno runs. After the valve and intake work the truck
runs were made with the G-TECH it showed the increase. The truck runs alot stronger than
before with great acceleration all the way to
4000 rpm. Gas mileage has increased by 2 mpg
under normal acceleration.
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