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Old 09-21-2006, 08:29 AM   #1
firedog424
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Smog/Emission removal

(1975 Midget) As I remove my engine and components, What's the good or bad (performance wise) about removing (and not replacing) my emission/smog equipment.

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Old 11-25-2006, 07:24 PM   #2
frinkmakesyouthink
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Re: Smog/Emission removal

Good things - less restriction in the exhaust meaning slightly improved performance

bad things - it will fail it's MOT because cars after 1974 have to have emissions equipment. Luckily my Midget is '69 so I can have straight pipes if I want
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Old 02-04-2007, 01:52 AM   #3
the Colorado Kings
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Re: Smog/Emission removal

There are a few more considerations wrt removing the smog equipment, though passing an emissions test is the most important. If you're going through the effort of a rebuild (which I assumed because you're pulling the engine) and you aren't worried about emissions, now is the time to remove the smog stuff, but there are some issues that you should consider. I have completely rebuilt my 1980 Midget with the following:
  • bored .30" over with flat top 9.1:1 compression pistons;
  • mild porting of intakes and smoothing/matching of all intake/exhaust ports;
  • three-angle valve job and replacement of worn exhaust valve guides;
  • mild camshaft and hardened lifters from ARP;
  • new main and conrod bearings;
  • dual Weber 40 DCOE carbs;
  • Try-Y header;
If your Midget is a California or later FED car, the compression ratio is 7.5:1, the intake and exhaust are brutally restrictive, and the air pump robs a lot of power. Besides doing the above mods, there are a few other ways to gain a couple horsepower and better mileage. I also:
  • installed an electric fan (removed old clutch fan);
  • put on a remote oil filter (using Fram PH8A 1/2 quart filter which increased oil capacity, is a fraction of the cost of a UK filter, is much easier to access, and no oil spews down the block);
  • installed a Hayes 16 row oil cooler;
  • installed electric fuel pump (removed old diaphragm pump);
  • added custom 7/8" exhaust and turbo muffler;
  • lightened the flywheel by a few pounds
I think I may have missed a few things, but the whole engine was hot tanked, cleaned and painted with new bearings, seals and gaskets everywhere. It was as easy as rebuilding a lawnmower engine, took less than a couple weeks, and did not cost a great deal - less than $1K using local auto supply places, eBay, Moss, ARP and Redline Weber. If you're not in a hurry, there are great sales before and after Christmas. The expected improvement in power will be something like double, from stock 50HP to a reliable 100HP.

I am working on the body at the moment. I deleted the (what I consider) brutally heavy and ugly rubber bumpers, and am replacing them with a custom design of my own. They'll offer good protection, and will act as a lifting point for a '60s-style quicklift jacking system. I also removed and filled in the side marker lights, front turn signals and rear licence plate mounting holes. I replaced the front turn signals with modern LED units that mimic the round lights from the early '60s. I have lowered front and rear suspension, and installed stiffer springs and sway bar(s). Expect paint to happen some time in the spring. I hope to post some photos and results of this effort in the coming months.

I did this because it was relatively cheap doing things on my own and using local suppliers, and I hated the anemic performance of the '75 and later MGs. My wife got the car from her father, and after 8 years of living with its disappointing performance, we're really looking forward to seeing an improvement in the handling and power.

If all you're looking for is pulling off the air pump, I really don't think I would. I considered all the pros and cons, and decided it was an all or nothing deal in the end. Partial removal of smog stuff leads to more probs than it's worth IMHO, especially getting it tuned properly.

Good luck with your project.
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Old 11-27-2009, 04:49 PM   #4
MgMidget79
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Re: Smog/Emission removal

I am rebuilding the motor on my 79 Midget and i was just wondering how exactly you block off everything when you remove the emissions control. I will be running a weber DGV conversion. I know how to work on the motor itself but am unfamiliar with emmissions systems. I know i would have to remove the air pump and the EGR valve. Im sure i would just block that off the exhaust with the right size bolt. i Know i would remove all the vacuum tubes but what else would i need to block off in order to keep my engine running right. i will plan to go to pacesetter headers in the future so i would need to remove these things anyway because they come with no hook-ups. And anything that gives me more power is on my list.
My mods that ive made is RV cam, flat top pistons and rings, all new bearings (rods/crank/cam). machining cylinders, flywheel, lifters, etc. shaving and surfacing the head. reseating the valves and replacing exhaust valves. dual valve spring conversion. all new timing set, new clutch. Double barrel downdraft weber carb and intake manifold.electric fan conversion.
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Old 11-28-2009, 09:33 AM   #5
the Colorado Kings
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Re: Smog/Emission removal

I'll try to remember what it is I did, but you can cross reference it with a check in your Haynes manual. There are a couple of really good pictures of the smog equipment layout in the manual, and also on line via the Moss Motors website that can give you an idea of the items and complexity.

Once you pull the air pump, that should lead you to the main bits and pieces that it services. You may have to block off a couple spots in the catalytic converter and manifold.

Tweaking the Stromberg carb is the biggest factor, I think, because you're going to change the air/fuel mixture. If you're replacing it with the DGV Weber, then that problem is solved (there are a bunch of vacuum and EGR lines that could affect the jetting of the carb).

Also, the charcoal cannister and all the tubing that runs from it and the gas tank/engine to collect fuel vapor also has to disappear. It won't affect the running of the engine, but it gives you a lot more space and cleans up the appearance of the engine bay. Hope this helps a bit.

Good luck!
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