Intake and Carb Swap
The 2-bbl carb and cast iron intake were begging to be replaced with a nice aftermarket 4-bbl aluminum intake and carb combo. I scored an Edelbrock Performer 302 intake (with EGR passage) and a Holley 1850 carb (600 CFM, vacuum secondaries, and a hot air choke hookup the same as the 2-bbl carb had) at a swap meet for a good price. I also got the EGR plate, a new valve, and gaskets for $11 extra. I picked up the rest of the supplies I needed (intake gaskets, new chrome intake bolts, new chrome water outlet, new thermostat, hoses, clamps, etc.) at the local parts store and started on the swap.
Right about now, most performance guys are asking "Why the heck did he get an EGR style intake when it's not required?" and/or thinking I'm some sort of uninformed eco-nut. Nuts, yes. But there is a reason for this. I like to run an EGR valve, but only with a very small amount of exhaust gas being recirculated into the intake. Why? It helps keep combustion chamber temps down at part throttle, and that helps keep part throttle detonation at bay. I can run cheaper gas and not have to worry as much. The EGR valve uses a ported vacuum source, so it's off at idle and at WOT (There is no vacuum at WOT unless your carb is way too small) so you can tune for a clean idle and good WOT performance without worrying about it. The key is to not recirculate any more exhaust gas than you need to - just a little bit will do the trick.
I ended up pulling the distributor because it made things easier and I could clean things up more with it out of the way. I was also planning a swap to a later DuraSpark II style setup, but I'm just putting the point distributor back in for now and worrying about that later. Once smart thing I did was take a picture of the distributor with the cap off just before I pulled it. That way I can see where the distributor housing was at and where the rotor is supposed to be pointing - when re-installing the distributor I just need to replicate this arrangement and the timing should be close enough to start the car with. No messing around with finding #1 TDC or anything like that - just install and go. And, the picture is going to last longer than your memory and you don't need to make ugly scribe or scratch marks on the distributor and/or intake.
Once I put everything back together again - I couldn't get the truck to run right and it was literally spitting water out of the radiator cap opening. I kept futzing with it and futzing with it to no avail. I talked to some of my Ford-loving buddies and they couldn't find anything overtly bogus with my descriptions of what I did, so I decided to take a chance and try the 351-style firing order on the chance Dad had used a 351-style cam in the engine when he rebuilt it. (He couldn't remember, so I was just trying it out to be sure.) While I was staring at the manuals, two things finally got noticed. First is that cylinder #1 is different than on a GM. I knew they numbered them differently, but I had not realized they started with a different cylinder! (GM starts at the front drivers side cylinder for #1 and alternates side-to-side on the block so that #2 is the front cylinder on the passengers side, #3 is the next one back from the front on the drivers side, and so on. Ford starts at the front passengers side cylinder and numbers the passengers side #1-#4 from front to back, then the drivers side is #5-#8 also from front to back.) Then I realized that some GM's (Chevy and Buick are the ones I have personal experience with) and Ford distributors rotate in different directions. (Chevy and Buick rotate clockwise, Ford rotates counter-clockwise.) And that's just for the V8 stuff - 6 cylinders are different, and I think Pontiac and Oldsmobile V8's use counterclockwise distributor rotation. My head hurts. (I need to make a tech page for this sometime soon with all the different engine makes represented...) I'm still working through this trying to get it to start and run right, but at least I have something that I know is wrong to work on and fix rather than having no clue what is wrong. It's progress, of sorts.
After getting the firing order right, the truck ran much better, but still not right. I grabbed my trusty can of carb cleaner and began spraying small bursts around each of the gaskets (intake to head, carb to EGR plate, EGR plate to intake, etc.) to see if it would change the idle quality. This is an old trick to find vacuum leaks - the carb cleaner + propellant burns more readily than just regular gas, so if there is a vacuum leak and you spray it, the idle will jump up a few hundred RPM and then fall back down as the fluid leaks in and burns better and the fluid temporarily helps to seal the vacuum leak. When I sprayed the carb base on the drivers side right under the linkage, I got a very sudden RPM spike with each burst of carb cleaner - there was a huge vacuum leak right there. I took the carb and spacer off, and as soon as I got a look at the intake surface and the EGR spacer to intake gasket I could see the problem. Look at the first 5 photos real close and see if you can spot it too. I'll wait while you scratch your head a bit.
There were two problems, neither good, and both stemmed from the same source. Look carefully at the bottom of the EGR plate and you'll see that it is "hollowed out" on the underside so that there is only a small strip of sealing surface around each hole and around the edges. Now look at the impressions and carbon on the gasket and two things are really clear. First is that there is a direct and large leak form the EGR passage into the passengers side intake - you can clearly see the pattern of carbon deposits on the intake that show you want did and did not line up. Second, on the drivers side, there is a small section right between the two holes where the gasket is not forced to seal against the intake - it's just flopping in the breeze inside the intake manifold - this was the source of the massive vacuum leak I found on the drivers side of the carb. I did some parts number hunting on the EGR plate and it seems it was really intended for a 429 or 460 motor which uses a different EGR passage than the 289/302/351 style motors do. I had read the 302-style EGR plate worked with the Edelbrock intake, and it never occurred to me that there could be a slightly different style plate that would subtly not work.
I figured if I could find a thin metal plate to go between the intake and EGR plate that followed the shape of the EGR plate edges that it would seal, but no such plate could be found. I could make one, but I was tired of futzing with the truck and wanted it to run again, so I just bought a 1" spacer for the carb and used that in place of the EGR plate. It left a small piece of the EGR hole in the intake exposed, so I used an extra-large carb to intake gasket to cover it. It's working for now.
Here's the final install done and completed. I re-used the same air cleaner because I had just bought a new filter for it. The old wing-nut was the wrong size, and the only one I did have that fit as an old GM one from another project. I thought it looked just fine on there, so I decided to keep it, if only to drive the Ford purists a bit nuts. :-)
I did have some fun tuning the combo - at first the float levels were all wrong, then I had the idle mixture set about 1/2 turn too lean causing the idle to "gallop" and eventually stall the motor. The lean idle also caused stuff to get way too hot, making working on the truck while it was running a finger-burning experience. I finally got stuff dialed in to a sane setting and it idles fine now. There is still some rough-running at just off-idle throttle positions, the throttle pedal linkage will only open the carb to about half-throttle, and the choke won't work quite right - but it's drivable again.
I still have to figure out the throttle linkage - I'm planning a swap to a cable-style throttle and pedal assembly from a 1969 Mustang.
I started a separate page for my EFI Swap plans.
Page last updated 01/02/2009 01:51:39 PM