reverse_fault_frank Posted August 24, 2020 Share Posted August 24, 2020 I'm planning on desmogging my 460 and I've never done this before so I wanted to consult the experts before I start doing irreparable damage. My plan as of now is to remove the whole EGR system and replace the stock intake manifold with a Weiand Stealth intake (https://www.summitracing.com/parts/wnd-8012). I also am planning on replacing the valve cover gaskets at the same time. What modifications will I need to make beyond the intake manifold? Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 24, 2020 Share Posted August 24, 2020 When you eliminate the inert gas from the fuel mix you need to change the curve in the distributor for the ignition timing. The fuel/air/inert gas mix burns more slowly than w/o the inert gas, so they add a lot of advance. In other words, they had to light the fire much earlier to get everything burning at the right time as opposed to w/o the exhaust gas in the mix. Fortunately most of that advance was done via the vacuum advance since it was mainly at high vacuum situations when the EGR valve is to open. And most, if not all, of the vacuum advance units are adjustable. You stick a very small Allen wrench, 1/8" I think, in where the hose connects and turn the wrench counterclockwise to reduce the advance. You'll want to do that after you get it together and drive it. Take someone along with good hearing and listen for pinging at light throttle. If you have some take a turn or two of the wrench and go again. Do that until you have no pinging. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 24, 2020 Share Posted August 24, 2020 When you eliminate the inert gas from the fuel mix you need to change the curve in the distributor for the ignition timing. The fuel/air/inert gas mix burns more slowly than w/o the inert gas, so they add a lot of advance. In other words, they had to light the fire much earlier to get everything burning at the right time as opposed to w/o the exhaust gas in the mix. Fortunately most of that advance was done via the vacuum advance since it was mainly at high vacuum situations when the EGR valve is to open. And most, if not all, of the vacuum advance units are adjustable. You stick a very small Allen wrench, 1/8" I think, in where the hose connects and turn the wrench counterclockwise to reduce the advance. You'll want to do that after you get it together and drive it. Take someone along with good hearing and listen for pinging at light throttle. If you have some take a turn or two of the wrench and go again. Do that until you have no pinging. I'm pretty sure it is 3/32"... But I installed a Crane adjustable advance and lighter spring (1 of 2) ...so the stock one may be 1/8 The other part of desmogging is removing the thermactor system. I just went through all that on the forum, and Myrl883 added that he plugged the back of the heads with .666" Welsh plugs form in the cab through strategically placed 1.25" holes. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 25, 2020 Share Posted August 25, 2020 I'm pretty sure it is 3/32"... But I installed a Crane adjustable advance and lighter spring (1 of 2) ...so the stock one may be 1/8 The other part of desmogging is removing the thermactor system. I just went through all that on the forum, and Myrl883 added that he plugged the back of the heads with .666" Welsh plugs form in the cab through strategically placed 1.25" holes. Put a straight up timing set in it, cheapest is a 1988-97 EFI one, it is a double row roller chain, no more plastic gears to break and jam the oil pump. To really get the most out of it, the air ports in the inside of 6 of the exhaust ports need to go. The two at the exhaust crossover are dummies and also need to be cut out. Your stock exhaust system is pretty good, if you take the flame arrestor screens out of the tail pipe (this is from an exhaust shop I have trusted for years) he said he could sell me a little bit better muffler for $250 (in 1994) or, I could knock the screens out and get the same thing. One item, another member on here put a different carb on and has a very difficult hot start, it acts flooded. The original bowl vent system on these vent to the canisters through 3/8" hoses and steel tubes when the engine is off. He no longer has that and all the fuel vapors end up inside his air cleaner and until he moves enough air it is too rich to start and run. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted August 25, 2020 Share Posted August 25, 2020 Put a straight up timing set in it, cheapest is a 1988-97 EFI one, it is a double row roller chain, no more plastic gears to break and jam the oil pump. To really get the most out of it, the air ports in the inside of 6 of the exhaust ports need to go. The two at the exhaust crossover are dummies and also need to be cut out. Your stock exhaust system is pretty good, if you take the flame arrestor screens out of the tail pipe (this is from an exhaust shop I have trusted for years) he said he could sell me a little bit better muffler for $250 (in 1994) or, I could knock the screens out and get the same thing. One item, another member on here put a different carb on and has a very difficult hot start, it acts flooded. The original bowl vent system on these vent to the canisters through 3/8" hoses and steel tubes when the engine is off. He no longer has that and all the fuel vapors end up inside his air cleaner and until he moves enough air it is too rich to start and run. Advancing the cam 4* to straight up is a simple mod to pre smog timing. You will find noticeable power there. I found the Cloyes street true double roller set was under $50 from Amazon. (Cheaper than my LAP wanted for the '88-'97 replacement set) Link to comment Share on other sites More sharing options...
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