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Old 10-03-2007, 08:07 PM   #11
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To have a shop do it, you'd have to TELL them HOW to port them. Intake ports? Exhaust ports? Opening the bowls? How much? How deep? What size?

You have to fully disassemble the valvetrain. Heads must be stripped. After porting, it'* best to lap each valve.

This is definitely NOT a meet job. Porting your own cylinder heads is a major undertaking. Bottom line is that if you've never done porting before, don't attempt it. This isn't anything even remotely close to port-matching a LIM to the head ports. Totally different animal.
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Old 10-04-2007, 02:42 AM   #12
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I have heard that someone in my area owns a shop that will round out slightly my LIM and match it to my intake. How does rounding do in the 3800 engines? I've seen on this forum how rounding out D-shaped exhaust pieces is strange for the engine, so I'm not into doing anything that'll regress my engine.
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Old 10-04-2007, 07:49 AM   #13
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Not sure that I understand about rounding the intake runners. Do you have any more information?

One thing I'd ask is .. why are they rounding a rectangular port?
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Old 10-04-2007, 10:03 AM   #14
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The exhaust port in the heads is D shaped for a reason. Try googling D shaped exhaust ports.

Do not round them. Look up my head porting topics to see why/how.
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Old 10-04-2007, 11:26 AM   #15
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Agreed, do not round the port.... The " D " shape does a lot more than you know..

Also how can you say the compression is not stock if you have never tested the compression?

Even on an 8.5 : 1 engine you can get good compression.. I'd say your compression is stock... Looks like no one has ever had anything off the engine to be able to pull the heads..

Just be careful with what you do... 1 mistake could hurt the performance

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Old 10-04-2007, 02:39 PM   #16
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Quote:
Originally Posted by jr's3800
Agreed, do not round the port.... The " D " shape does a lot more than you know..

Also how can you say the compression is not stock if you have never tested the compression?

Even on an 8.5 : 1 engine you can get good compression.. I'd say your compression is stock... Looks like no one has ever had anything off the engine to be able to pull the heads..

Just be careful with what you do... 1 mistake could hurt the performance
The engine was twice rebuilt without porting, polishing, or replacing parts (except for gaskets, couplers, etc.). I recently had someone take off the supercharger and clean the walls slightly. Same guy rebuilt the engine twice. I'm just guessing on the compression going down, and I agree it wouldn't be noticed.

Boosty, I'm talking of someone telling me I can round off the rectangular holes in the LIM.
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Old 10-04-2007, 02:49 PM   #17
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If during the previous rebuilds the block or heads were decked, your compression will be higher; if not, there is no reason for it to be anything but stock.
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Old 10-04-2007, 02:55 PM   #18
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So, I'll primarily do a compression test, then. However, I'd still love some tips on porting so that I do nothing like the aforementioned D-O ports and the like. Is it ok to round off the LIM, or should it just be ported in its OE shape?
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Old 10-04-2007, 03:10 PM   #19
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You want the ports to match to the heads when put together.
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Old 10-04-2007, 03:16 PM   #20
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What you can do is kiss the edges of the intake ports to smooth them out... All you are really doing is to smooth the edge out so you have no sharp edges... Also like it was mentioned match the ports of the lower intake to the heads..

Even doing this on an NA makes a nice difference..

And the compression will stay the same unless the heads have been shaved to remove any unevenness, in that case you may have as much as .5 in compression added to stock.. But we haven't seen many instances where this was required on a 3300 or 3800.. But it is possible..

If you have 9.0 to 1 compression you should see compression in the 180-190psi range iirc.. I think if you are 8.5 to 1 in good shape 170psi should be easily attainable... But keep in mind this doesn't always ring totally true.. And its hard to know if the heads were shaved, and how much was shaved off if they were shaved..

But a good compression test would let you know how the piston rings and valves/ valve seats are

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