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EFV-8 Club Forum / General Ford Discussion / soot at carburetor base

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Posted By Discussion Topic: soot at carburetor base -- page: 1 2     Stroker 11-13-2010 @ 1:30 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 40 Coupe- Right you are, I should have done my homework,(or at least studied Gary Mallast's wonderful resource a little closer). This means then, that the aluminum manifold I have for my 38 may actually be a 37, as it appears identical, san's the hole. I know it's not a 48-6520 (35-36), given the height of the generator mount. Thank You for clearing that up for me. Since dad changed engines in 1940, I never saw the original. Since the hole does create some issues with a CG carb, does that mean that only 97-equipped 38's used the aluminum manifold, or did they make the manifold with/and without the hole depending on carb choice? I'm planning on running a CG carb on my "hole-less" aluminum manifold; but not if that would be inappropriate, as Ford38V8 might be watching. 40 Coupe 11-13-2010 @ 12:30 PM reply profile send p.m. Senior Posts: 1679 Joined: Oct 2009 Stoker: I believe the manifold he pictured is also shown in the 38-9 restoration book on p. 4-39. Note the photo is for 38 but 78-6250 was an option on 50% of the cars for Ford in 39. Again I am not sure of the Merc. Stroker 11-13-2010 @ 10:56 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 40 Coupe, was this a one-year, 39 only deal? My aluminum 38 manifold does not have that hole, and in fact after over 55 years of "messing" with early Fords, I've never seen a manifold like that. 40 Coupe 11-13-2010 @ 4:58 AM reply profile send p.m. Senior Posts: 1679 Joined: Oct 2009 I am not a 39 Merc expert. Make sure you have the correct intake manifold which to my eye and your photo appears to be OK for a Ford. It appears to be the only aluminum intake offered for 39 Ford the other intake is a cast iron. the different intakes have different configurations for carb bases. Ford used two different carbs in 39 both the small logo 97 with the additional 67 marking and the Chandler Groves. The 97 has a "D" shaped base and the Groves a 91-99 style triangular shaped base. The triangular shaped base has the holes for the PV vacuum directly over the small hole in your intake manifold. The "D" shaped base of the 97 does not have a hole for the PV vacuum on the carb base face. This carb will block the small hole in the intake which is exactly what you want! You either have to change the intake manifold to the cast iron and run a C-G or use the aluminum intake and the 97. You can not use the carb you are using on the manifold you have without additional modifications supereal 11-12-2010 @ 10:38 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 The heat passage in the intake manifold is fed by two holes in the block on either side of the manifold. There should be no exhaust connection to the fuel side of the manifold. You can safely block off the passage between the block and the intake manifold. As Alan said, we used to use pennies for that purpose because we thought it increased the exhaust sound from our dual tailpipes. All that said, if the walls of the intake manifold have been breached, and that cooked the power valve, your rough running was likely a combination of the leak and the destruction of the valve. Replacement of the intake manifold is probably the only reliable "fix". The hole you see in the carb mounting flange is open to provide vacuum to the power valve, and no exhaust should be present there. This message was edited by supereal on 11-12-10 @ 10:45 AM fordmerc 11-12-2010 @ 7:39 AM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 I checked again, but my carburetor seems unlike the one ford38v8 describes. I have a hole in the base which connects to the heat riser hole in the manifold, through the carb base, into the chamber formed by the base and body where the economizer valve is scr*w*d into the base. The economizer valve opens into the float bowl. This carburetor(Ford Model 21-29) is essentially the same as a Model 8BA which came from a 51 Merc. All gaskets (3 spares)have a hole to match the carb base. This engine, including manifold, carburetor, all wiring and distributor are newly rebuilt, and have yet to run properly. The rebuilders are considered competent. The car has never backfired since engine installation. My understanding is now that the heat riser hole should be connected to the exhaust system, and yet there is no flow of exhaust gases through that hole, just temperature equilibration ?? ?? Before I pull the intake manifold and then decide I'm out of my league, can I block off the connection between the manifold and economizer valve without harm? (I don't understand what that valve accomplishes Thanks to all for comments and suggestions This message was edited by fordmerc on 11-12-10 @ 7:43 AM ford38v8 11-11-2010 @ 8:48 PM reply profile send p.m. Senior Posts: 2765 Joined: Oct 2009 Fordmerc, The hole in the manifold is the heat riser. It runs down to both banks, where it connects to the middle exhaust ports. This crossover port through the intake manifold serves a dual purpose. It equalizes exhaust pressure between banks, as the center cylinders fire alternately, and it serves to preheat the fuel entering the manifold to provide a more complete combustion from the fuel vapor. The heat riser meets a dead end at the cast iron carburetor base, and is not channelled to your economizer valve. Some guys have installed an extra wooden spacer at this point to reduce the heat at the carburetor. Some also have removed the intake manifold to install copper pennies in both ports on the block itself, thereby eliminating the heat riser altogether. With the volatility of modern fuel, the heat riser causes more problems than it ever solved anyway, so the penny modification is not a bad idea to do in any locale that enjoys a mild winter. A side effect, though, may not be welcome to some V8ers: The separation of the two exhaust banks makes for a louder exhaust note, particularly if dual exhaust pipes are installed. Your burnt economizer valve looks to me as though you have had considerable backfiring through the carburetor. As the economizer measures vacuum at the throat, it is vulnerable to any backfire, and does not have the fuel wash to keep it clean from these events as the throat has. Even one backfire can and does easily destroy an economizer valve. A trashed economizer valve does not explain the rough running of your engine, but can explain soot black plugs and poor performance. The rough running caused your backfires and burnt economizer, so once you get your distributor timed correctly, you should be on track to get your engine purring like it should. If your distributor is set up correctly, another explanation may be plug wires that are crossed or shorted to one another, or a carbon track on an inner distributor cap, either of which could fire one or more plugs out of time. Alan Stroker 11-11-2010 @ 3:11 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Some of us, (especially myself), use this forum as a learning experience. My background does not include vintage Mercurys, and I have never seen an intake manifold with the extra port leading to the power valve. The only Merc. manifold I ever had was the later 49-53 4-bolt style, that was designed for the rear intake Holly. So.....I'm really puzzled as to what was the purpose of that extra port. I can't imagine that it was intended to connect to the heat riser passage in the manifold, so I'm assuming that you have a "burn-through". Stroker 11-11-2010 @ 2:19 PM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 I'll go with Supereal's theory that you have a hidden burn-through inside the manifold letting the heat riser exhaust gases enter the intake tract. fordmerc 11-11-2010 @ 2:01 PM reply profile send p.m. New Member Posts: 180 Joined: Oct 2009 another image: this of the power valve / economizer by-pass valve This message was edited by fordmerc on 11-11-10 @ 2:03 PM

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