Well, this all started off as a simple carb rebuild, but when I took the carb abd EGR castinf off the manifold I found more issues. The EGR casting has holes burned right through the walls of it, and some of the passages onthe underside are burnt out as well. I can't imagine either of these things are great for performance or general operation. So, I've searched the forums and found some info but am still unclear on exactly how to space my carb from the manifold. Its a Motorcraft 2150 2V on 1979 351M.

Here's my planat this point. The EGR casting is about an inch thick. I can get the OEM phenolic spacer that Bubba mentions in another post, but it is only 5/8" thick according to that post. So I'll lose 3/8" of space under the carb. Is that going to be a big impact? I would like to spaceit at an inch like the original casting is but am having trouble finding parts.

Bubba shows his stack as the OEM EGR casting (1"), a "gasket" from a carb rebuild kit (1/4"), and then the OEM phenolic space (5/8"). That's a total of 1 7/8". Is this a better scenario than losing height? Any advice is appreciated. In the mean time I may hit a junkyard and see what I can find.

 

Eric,
Forget the EGR plate. It is a piece of trash. The phenolic spacer is the way to go. I had identical problems on my 78 F150 351M. If you want the height put two spacers on. The 1/4" base gasket helps seal the carb off properly. The higher the carb the better the top end. You will notice a decrease in throttle response as the height of the carb increases. The phenolic spacer also helps insulate the carb from the manifold to avoid vapor lock.
Good Luck,
KingFisher
PS You will probably have to change your intake studs to match the new height. I use a coarse thread 5/16' stud and cut to length.
PSS Don't over torque carb bolts, It warps the carb body.

 

The EGR plates are famous for doing that. Especially the aluminum ones. I do not favor these earlier EGR systems. More modern ones with computer controls work pretty good.The spacer or it's thickness should not make a lot of difference on a mostly stocker. You should retune your idle mix and possibly adjust your timing.

I'd wager you've been having trouble with you idle quality and surging.

 

Don't forget to plug that egr crossover port under the carb. Your parts store has small freeze plugs to block it off.

 

Thanks for the input everybody. I stopped at my local Ford Dealer and ordered the 5/8" spacer today after work. I also hit the junk yard and scabbed one off an old Lincoln. I think it was a Town Car or something. The important thing is that it had the 2V phenolic spacer with the correct bolt pattern and was only $2. So now I'll have the new one and a spare that add up to about 1 1/4" total height if I were to stack them up. So from my original set up with the EGR casting, I'd be a bit taller than before. My engine is completely stock except headers so it sounds like I may feel a slight difference at higher RPM's from what you guys are telling me. Then again I guess I may not too. We'll see what happens. Here's another question for you guys, do I have to put a gasket between every part that I stack or just between the intake manifold and the bottom spacer? My tentative stack would be manifold, phenolic, phenolic, "paper" spacer/gasket from carb rebuild kit, carb. Where should I gasket?

Thanks for the advice on checking my mix and the crossover channel as well. Are you talking about the extra hole in the manifold as the crossover? I'll have to look at it a bit closer to see how to plug it. I think in a previous post somebody mentioned that as long as the phenolic and the gasket cover the hole it would be okay for quite a while. What do you guys think?

Also, yes, I was having a bit of idle quality problems and I posted an "Off Idle Stumble" thread as well. Maybe I can kill two birds with one stone. Or two spacer as the case may be! I'll try to check back in once I get the carb back on and everything re-adjusted. Thanks guys!

 

If you want to get rid of the egr completely, You have to plug the hole under the carb spacer in the intake. Otherwise the hot ex gases will be trying to burn your new bottom carb gasket & your spacer plate.

 

Use a gasket between each componet. I prefer the slightly thicker ones than plain paper.

 

As mark a. recommends, you should block off the EGR port on the manifold's carb flange to keep the hot exhaust gas from burning or melting the gasket and phenolic spacer. IMO, the OEM EGR spacer with an inactive EGR valve is the best way to accomplish this (that's what I use). If you look around a junk yard, you should be able to find an EGR spacer in decent shape.

And as beartracks recommends, you should use at least a paper gasket between each component in the stack.

The plenum volume is relatively small in the OEM manifold, and the addition of 0.5-1.0" to the stack under the carb will significantly improve the engine's upper-mid range and top-end power (i.e., anything over 3.5K rpm on a stock engine).

In my experience, with the relatively small plenum volume, even after adding almost an inch of "spacer" below the carb, throttle response is affected much more by carb tuning than it is by the change in plenum volume. Obviously, changing spacers under the carb changes the characteristics of the induction system, so you will need to re-tune the carb for optimum performance.

Also, if you disable the EGR by blocking it off somehow, you will have to re-tune the carb to compensate. In general, you need to at least enrich the main metering system with bigger jets to prevent over-lean mixture problems (excessive combustion temps, pinging, and possibly overheating). You might also have to tweak the ignition advance curve.

 

Sounds like I'm on the right track so far. I live in SE Michigan and haven't had much luck with junkyards around here. I know it seems odd that Detroit wouldn't have piles of old trucks lying around. Maybe I just haven't found the right yard yet. I may consider looking for an old OEM EGR spacer for a future project. Will any late 70's Ford/Lincoln spacer work as long as the footprint matches?

For now I'm going to go with the phenolic spacers. I'll just need to measure everything and decide how high to stack stuff up. Is the reverse situation true, that if I lower the stack height I will have BETTER low RPM response and WORSE high RPM performance? Or doesn't it work that way?

What should I use to block the crossover passage in the intake manifold? Mark A. mentions freeze plugs and I have to admit that I'm not sure what I would be looking for. Do you have any particular part numbers or sizes that you can recommend? If I had access to all the proper tools I think I would just machine a steel plate that matches the footprint of the spacers and gasket that in place. I could cut a hole out of the gasket in the area of the crossover to avoid buring the gasket but would be sealed everywhere else. Does that sound reasonable? At any rate, I don't have the tools, so more suggestions on blocking that hole will be greatly appreciated.

Fortunately, my carb is set a little rich as it is so I hope to not have too much adjustment to make when I put everything back together. If so, I guess I can back the timing off a bit and maybe richen up the mix even further. Hopefully I'll have the truck back on the road tomorrow night or Saturday at the latest and I'll let you know how it works out. Thanks again everybody.

 

Well, here's a little update on my carb rebuild/EGR replacement project:

I had a hard time finding the right size freeze plug to press into my intake manifold to plug the EGR crossover passage. The more I thought about it the more nervous I got about a plug wearing out over time and ending up down in my engine somehow. So I started the hunt for a metal spacer plate again. No luck there at any of my local stores. So I decided, screw it...

I figured that the phenolic plates are made to sit directly on the manifold and should be fairly resistant to heat. So I went for it and put the junker plate on the manifold and then stacked the new one on top of that. So my total height below the carb is about 1-1/4". The carb bolted back on fine except for the manifold line that hooks up to the choke. I'll have to work on that some more. Anyway, I was all fired up to see how the truck would run with the rebuilt carb and the spacer plates so I jumped in, turned the key, and...nothing. My battery was dead! (Apparently I have another project on my hands tracking down the electrical draw that killed my battery.) So I pulled the battery out of my other car and the truck fired right up.

It still starts a little differently than it did before I touched the carb in the first place but it runs fine once it gets warmed up a bit. I think I just need to adjust the timing a little and I should be okay for a while. I still have some off idle stumble until the truck gets warmed up so I didn't solve that one either.

In the meantime, my buddy's neighbor said he could get me a metal spacer machined at the company he works for. When that's done I'll replace the spacer stack that I have right now and continue fine tuning the timing and fuel mixture until I'm satisfied with how it's running. So at the very least it was a good learning experience and the truck still runs to boot! I'm sure I'll be back for lot's more advise as I keep taking on these little projects. Thanks again for the help, and please add any final thoughts you have for me to this link.

 

If you decide you need to find an EGR spacer, just look for any '73-up Ford/Lincoln/Mercury vehicle that was available with a 351M and/or 400 engine. All 400s after MY1972 were equipped with EGR, and all 351Ms were equipped with EGR.

Check out this page for info on which vehicles to look for:

http://home.earthlink.net/~bubbaf250...history10.html

I don't think the EGR spacer from any other engine type would work, but I don't know for sure.

 

Thanks Bubba. I'll take a look at your link to get a list of possible donors. Then all I need to find is a good junk yard.

I hate to drag out this link but I was wondering if you could give some more pointers on what to check to aleviate this off-idle stumble I have. I posted it in a seperate link but I can't remember if you responded or not. Basically the truck seems to stumble off the line, in some cases even popping like it wants to stall. My engine is a stock 351M with the 2150 carb, #57 jets, timing at about 10 BTDC base (don't know what the advance is doing), and the 1-1/4" spacer pack under the carb. The carb was just rebuilt. The EGR has been removed.

I know I need to check for vacuum leaks. What's the best method for that? Should I just replace all hoses as a start? What other items should I check that could cause my problem? Distributor, coil, plugs, wires, etc? It's not a huge problem I just really want to get it running as well as I possibly can. In the meantime I'll have to review your website again to get my head on straight and see if I can think of anything else. Thanks for all your advice.

 

You might need a little more initial timing. Make sure your acc. pump in the carb starts squirting as soon as you move the linkage.

 

It occured to be in the middle of the night that even a fabricated metal spacer in leiu of a plug is not a good idea. You still need a gasket which may eventually burn out horizonally. The exhaust passage is much hotter than the rest of the manifold.

 

I was thinking about that too Beartracks. But here's my logic on why I think it would be okay. The OEM EGR spacer is gasketed between it's bottom surface and the intake manifold. That gasket has pockets that only surround the exhaust crossover port (which is wide open) just like I'm proposing to run it. So, if the OEM gasket scenario doesn't burn out horizontally, I think my proposed fabricated spacer and gasket would be just as well off as OEM.

The only difference is that with OEM, the exhaust has a place to go (through the EGR system). With a solid spacer the exhaust will just bounce against the bottom surface. So it may get a little hotter than OEM, but how much?

I'll need to make sure I cut the proper pockets in the gasket so there is no material directly over the exhaust port and make sure that there is still a good amount of gasket to do the sealing around the outer perimiter of the spacer. But otherwise it seems like the same basic set up as OEM. What do you think of my logic?

If you still think I should plug the hole can you put my mind at ease and tell me what type of plug to use and whether or not you think it will ever break down from the heat and fall into the engine. For now I have to run it like I have it or just leave it sitting in the driveway so....

Anyway, thanks again for your input. I know you guys have a lot of experience out there so I appreciate it.