LUVTruck.com

So I got a 79 mikado a few weeks back. since then I have replaced spark plugs which made it run a million times better. They had all sorts of brown things growing on them. Replaced points, couldnt find condenser until yesterday, havent done that yet. Has a weber carb with a wood screw in one of the holes. Set the idle and adjusted mix for highest rpm then reset idle and adjusted etc etc etc. Set timing 10 degrees (didnt see the sticker until afterwards.) Dwell at 62 instead of 52, no biggie. Anyways the thing backfires out the carb when I get it lots of gas at low rpm with a load, IE last part of a shift. It has no power, loses speed in 3rd and 4th gear going up a slight hill. It also has a header and 2.5" exhaust. I plan to put the stock exhaust back on, I got it form the previous owner. Its a 1.8L 2wd 4 spd manual. I've put 2000 miles on it since I got it so I know theres only fresh gas in the tank. I've been getting 20-22 mpg commuting 70 miles a day mostly highway. I'd like to see upper 20s or 30mpg. Maybe the manual advance is getting stuck. Maybe not enough back pressure. Maybe needs valve adjustment. Burns oil and leaks oil. Needs a full quart every tank which is 3 days for me.

What do you guys think?

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1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

For what it's worth, here's what I think:
1. The engine has a Weber & headers so it's obviously de-smogged, so 10 degrees initial advance should be OK (I normally run 12) as long as it's not pinging under load. I think the points are too close & the dwell too large. I would open them a little- start about .019"- Luv points tend to arc easily & deposit a teat on one surface, which makes the gap narrower, which makes it act like the timing is advanced. This will probably help the backfiring, if not try retarding the timing in small steps. Make sure you disconnect & plug the distributor vacuum advance line first.
2. Adjust the valves ASAP, re-torque the head bolts & rocker arms first while you have access. If the valves are way out of adjustment you will notice a power increase. If you get a rpm increase when you remove the distributor vacuum line with the engine running then the distributor advance is working.
3. If the header is in good shape leave it in place, it will produce more power than the stock manifold. The 2.5" exhaust is too large, about 2" is max, try adding a restrictor tip, it should also help make it sound more normal.
4. LUV's never had a lot of power (80 hp) even when new, & if yours is burning a quart of oil per tank it is not in tip-top shape. Your truck came with 4.10 gears, so with a 26" diameter tire you are turning near 3,000 rpms @ 60mph. At those rpms you are most likely into the secondary on the Weber, so the mileage you are getting is about right. To get the higher mileage you want would require either 3.73 or 3.42 differential gears or a 5-speed tranny- but then your tired old engine would seem to have even less power.
Do what you can to get it running the best possible, but you are likely looking at some major engine work sometime in the future.

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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.