LUVTruck.com

received my new header in the mail yesterday and had a couple questions..As you owners know,the head has rectangular ports and the headers are round.Did any of you attempt to grind the ports kinda round to match,or grind the flange a little to more closely align the openings,or just bolt the sucker on there? I'm open to the first 2 because I'm cutting the whole thing apart anyway,to build a custom 4-2-1 header. When lining up the Pacesetter gasket with a new set of Felpro's,there is quite a bit of blockage,in a couple of the tubes,it's the thickness of the pipe for the height of the port. I don't have any issue with hogging those things out and re welding if required. I've studied the various forums in regard to header design and chose the 4-2-1 or tri-y design because I want the bottom and mid range power to overcome the gearing loss that will come with my planned taller tire project. The Pacesetter seems geared toward HP at the upper end of the rpm scale,not torque per se. Any input pro,con or indifferent is welcome..[and I have a clean,straight slate to work with,bumper to bumper,because my new tank is on the passenger side,so pipe size isn't an issue either]

Pacesetter in recent years changed the G180Z/G200Z header port from square to round(my old style has square ports), it is now essentially the same header as sold for the 2.6 4ZE1 engine. Very early models also had a 3" collector rather than the current 2.5". According to someone who bought one of the round port models and installed it the round header ports are large enough that they don't overhang the head port except slightly in each corner(this is also Pacesetter's claim). However most Pacesetter headers don't match the head ports all than well, I suspect these are the same. I would do some minor port matching, there is not enough material to completely blend the round to the square. You can't use the exhaust gaskets as a template either, they are way too big. This is what I did on a 4ZD1 head/header: make a separate template of the head ports and of the header ports. I used thin cardboard like a cereal box, aligned carefully using the mounting holes, then tapped around the perimeter of each port with a plastic hammer enough to imprint the port onto the cardboard, then carefully cut out each port opening with an Xacto knife. Then carefully aligning the head template on the header and the header template on the head mark any meta that protrudes into the template opening and grind out the marks, chamfering back fairly quickly(you can grind all the way to the tube side of the header flange, the tubes are welded to the flange away from the opening). This will smooth up the flow through the head to header transition, whether it is worth the effort I can't say. The exhaust gasket is large enough that it sits back away from the opening. The Gaskets Pacesetter provides are poor quality, I suggest replacing with something like the metal clad FelPro, however before tossing the fiber gasket test fit the header, on two occasions I have found the clutch arm contacts one tube, requiring dimpling the tube a bit. Doubling the fiber gasket with the FelPro gasket adds just a bit more clearance. At the collector the Pacesetter gaskets also fail quickly, I use Mr. Gasket #5980, usually two stacked & sealed together with hi-temp RTV. your collector is 2.5" so that's the max tailpipe size, I think the reducer supplied with the header is a 2", which is probably about the right size. Too large of an exhaust pipe will lose some low end torque, plus it will be very hard to muffle(not enough backpressure to combine the exhaust pulses can cause a "chuckle"). Err on the large side, you can always add a restrictor reducer on the tailpipe end if it's too big, if it's too small you replace the pipe. You can also install a Delta 260 camshaft for more low end & a Weber carb doesn't require sufficient rpm to build enough vacuum to open the secondaries, so more low end throttle response. IMO re-configuring the header design won't be worth the effort, I would at least try it first, then at least you'll have a base for comparison should you decide to go ahead.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

Well,thank you very much. This is exactly the info I was interested in. I already have a new Weber sitting in the engine bay. I wasn't going to fiddle with a cam until the engine needs a rebuild. [and I don't know when that will be,since I've owned the truck for 2 months and haven't ever driven it,just started it and fiddled around with it,since it's a retirement project.lol] If I can ask another question or 3,when I bought my 1st and only other Luv,brand new,in 1976,the speed limit was 55 and I never had trouble getting into trouble with the truck. This one is a 79 4X4. What's the top speed in it? My wife lives in another town and there is about 100 miles of 70mph on I-5 to get there. Can I expect to have to follow the semi's in the slow lane all the way? anyway,thanks again for the header advice..
Steve

A lot depends upon the terrain and what size tires you run. Your truck has 4.10 gears, stock tires were probably about 28" or less in diameter. With stock-size tires & no hills it will maintain 70 mph, albeit at 3,000+ rpms. You'll lose about 3-4% in power for each inch tire increase(which is definitely noticeable with a 80hp engine), add in hilly terrain and you're in the slow lane, especially with a stock vacuum carb.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.