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Join Date: Feb 2008
Posts: 1,438
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Blue or black smoke on decel? Have you checked your plugs for oil? Compression/leakdown check?
If smoke started appearing immediately upon swap out from CIS to PMOs then it sounds like the problem is the carbs. Smoke at start up is common as oil will get past the rings while sitting and need to burn off. Also, with carbs there will be a bit of black smoke as the residual fuel in the idle circuit fuel galleries will drain into the cylinders and need to burn off, same if you pump the accelerators to prime the engine, raw fuel gets burned off. Under deceleration the throttle plates are closed and the only fuel delivery orifice left open is the one for the idle mixture screw so a great deal of smoke from this seems unplausible, unless the air corrector for one or more of the progression circuits was blocked and allowed fuel to siphon out the progression circuit holes. A simple check for this is to run the rungine, check fuel levels in the sight glasses and shut the engine off. Let the engine rest 10 minutes and check sight glasses again. If fuel levels have changed then you have a blocked air corrector. The air correctors (progression and main circuits) lean the fuel mixture more at the upper end of the operational range, this is a fine tuning item if the emulsion tubes (main jets and circuit) are selected pretty well; same for progression circuit and the idle jet selection. Jetting sounds OK, perhaps F3s would be a better emulsion tube but is probably hair splitting but this comment is based upon what Weber emulsion tubes would be suggested for your engine. Cheers, Paul Abbott Performance Oriented
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Paul Abbott Weber service specialist www.PerformanceOriented.com |
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10-01-2010, 12:52 PM
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Join Date: Apr 2007
Location: South Cackalacky
Posts: 879
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Do you have MSD ignition box, didn't see if you mentioned? If you don't, someone correct me if I'm wrong but isn't a plug gap of 60 kind of wide? I would think with too wide a plug gap and not enough juice behind the spark maybe you would be getting some unburnt fuel and perhaps smoke as you mentioned?
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10-01-2010, 02:25 PM
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AutoBahned
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do a compression test
when you take the plugs out, check to see if they are dirty, if so clean also regap to 040 |
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10-01-2010, 03:30 PM
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Banned
Join Date: May 2005
Location: Earth
Posts: 31,744
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Quote:
That's interesting about the fuel levels. Just the other day I was looking at my carbs after I had gone somewhere and noticed the rear float bowl on the right bank (between 4 and 5) had risen pretty far above the dot. I didn't look at the other side. I started the car and it went back to the dot. I thought that was weird but didn't think much about it. I figured it was normal. I think it was when RWebb suggested lowering the fuel pressure was when I noticed the higher bowl level. I looked at my gauge and it will only go down to about 4. I guess I was wrong thinking it was 3.5. That shouldn't matter. So you think it is a blocked air corrector? That would be cool if we (just kidding. I mean you) figured this thing out. Where is the air corrector anyways on the PMOs. It doesn't say anything about location in my PMO stuff. Are they the big screws under the plates on top? For some reason that is where I think they are. |
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10-01-2010, 05:57 PM
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Banned
Join Date: May 2005
Location: Earth
Posts: 31,744
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Quote:
MSD says 60 on the plug gap. |
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10-01-2010, 06:00 PM
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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a local NW pope says .040
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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10-01-2010, 06:06 PM
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Join Date: Jul 2000
Location: So. Calif.
Posts: 19,910
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Quote:
Perform a compression test (and subsequent leakdown test) so you know what area(s) to address. What do the spark plugs look like? Sherwood |
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10-02-2010, 11:12 AM
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Banned
Join Date: May 2005
Location: Earth
Posts: 31,744
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Humm, it seems o.k. now.
Yesterday I pulled the big brass screws out from under the top plate. I thought those were the air correctors and all the screws on the sides were the different jets. Boy was I surprised. It seems almost everything is on that one tube. I saw all kinds of familiar #s. F11, 135, etc. Anyways I cleaned each one individually and the only thing I saw that might of been a concern was a piece of what looked like nylon thread stuck on one of them. While I was at it i pulled all the screws from the sides of the carbs and cleaned inside them with a paperclip and wiped each needle jet clean. I even pulled the wrong one in my cleaning frenzy and drained one of the float bowls all over my engine. Ooops. Then I went through the rebalancing and tuning. I'm getting to be pretty quick at it now. I started it up and #3 is back at a respectable level and the overall idle is better. I'm not sure if it was those jets or the balancing but I may of been 1/2 turn wrong on one side of the idle stop screws too. I didn't get out the LM2, I just set each screw at 3 turns out and called it good. It is smoking a lot less already and soon I will see if I can get the mixture down when I check the AFR. I think I am going to put the cranckcase vapor recovery system back on. I did notice a little smoke or vapors coming out of the filter I have hooked up to the breather neck. It stunk. I'm not sure exactly what I did right but it seems better now. I may of had one of the idle stop screws out of adjustment and through the linkage one of the carb banks was not closing all the way. That could of prevented me from getting complete closure on deceleration on one side. Or it was the cleaning. I don't know, but I am happy with it. For now. Thanks for all the advice and one day I'll check the compression. If my compression is as bad as I think it is, is there anything I can do about it besides new rings? I don't want to get new rings because I am going to do new cylinders, pistons and cams at a later date. |
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10-03-2010, 03:25 PM
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