93 head port & polish progress pics (56k a little slow) - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 09-21-2005, 09:33 PM   #11
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Port matching the LIM to the stock head ports will gain 20% flow.
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Old 09-21-2005, 09:47 PM   #12
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Quote:
Originally Posted by willwren
Methinks there are going to be a few pretty quick 93'* soon.
Bill whadda figure? Mine to...? I'm undecided, but im leanin toward some performance.

Looks like a good clean job you did there..look forward to the results.
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Old 09-21-2005, 09:48 PM   #13
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Hmmmm....

If you look at any GM performance head you'll see the exhaust ports are D shaped with the flat side down. At most I don't think I would have lowered the floor by more than 0.050", I think you're going to loose a lot of velocity on the short side radious.

Bigger is not always best, depending on how you use the car.

Hope the rest of the project goes well.

Cheers,
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Old 09-21-2005, 10:54 PM   #14
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What function does the flat area serve? Are these heads specific to the 3800 or performance heads in general?

I saw that both the upper and lower straight areas formed a sharp edge. When I rounded manifold mating surface, I also rounded the inner surfaces. The bottom can be seen clearly in one of the pics but the top is more subtle. I'm having a difficult time explaining it properly though so I hope I'm making sense.

The port is more * shaped than V shaped now. Am I doing more harm than good?
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Old 09-21-2005, 11:11 PM   #15
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Harm in the context of heads is a relative word.

Are these heads going to work? Yes they will. Will they flow more than stock? At maximum lift they likely will. But I think you're going to see a little less throttle response in the lower ranges.

As odd as it seems, having a step on the bottom of the exhaust poer where it exits the head is not bad. But more importantly, by lower the exhaust port floor, and by decreasing the short side radious of the port, you're making it hard for the flow to stay attached to the bottom of the port. This will increase the surface tension and break the laminar flow at lower velocities.

If you look on Intense'* web site, you'll see that not even the Stage III heads have the floor that low and the port is D shaped.

You haven't killed the heads or anything, but they could have been ported to allow better flow under conditions encountered on the street.

Cheers,
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Old 09-21-2005, 11:24 PM   #16
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Just for the heck of it, should I have the two heads flow tested to see what the difference is before going at the other one? Would a flow test indicate if a low end loss will be present? Where can I get this done and what can I expect to pay?

Maybe I'll PM Rogue to see if Intense can do a flow test but I would prefer a local shop.

Sorry for all of the questions. I guess this is the Brainstorming part of this forum.
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Old 09-22-2005, 12:52 AM   #17
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Yes, please continue this discussion. I'm suddenly concerned about the P&P job on some spare heads sitting in my dad'* shop..... enlighten us, Foghorn!
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Old 09-22-2005, 01:08 AM   #18
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how are you porting the heads...what tools are you using for all this...might be a project for me..

James
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Old 09-22-2005, 01:45 AM   #19
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Hold off on porting the LIM. New scan data tonight from the Zilla points to that as being a potential cause for raised cylinder pressures. If I can fix the KR with colder plugs, we're golden. I do have another couple things to try, but for the time being, it may be a problem.
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Old 09-22-2005, 02:55 AM   #20
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I am very interested in this for my car. I have a complete 93 L67 engine in my garage that I can pull parts from for this if you want to try a second set for me, or when you get this perfected. I will also see if I can get a set of heads and LIM off one in the junk yard to send back with bill. I know where there is a 92, but I think the heads are different (someone correct me before friday morning) I would love to have this done for my car. Got the manifolds in the basement ready to go.
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