As always, thanks for answering my many, many questions as I sort out my newly acquired truck. I’m making progress, but the truck still has some issues. It is a 1974 F100 XLT shortbed with 3 speed manual trans. It originally had a 302, but now has a 1971 351 Windsor and a 2100 2bbl.

I posted an earlier thread about carburetor issues. The problem I’m having now is that sometimes the truck idles well, but other times it races, or won’t idle at all. My understanding is that these symptoms sound like a vacuum leak, but I can’t find a leak. So now I’m wondering if this might have something to do with the EGR spacer plate. (I’ve tried two different carburetors with about the same results.)

As shown in the pictures, the EGR spacer has been closed off on the rear end with a plate. Also, see the black remnants of exhaust gas that is circulating through the spacer (if this is relevant). I don’t know if the spacer is from the original 302, or if it is part of the 351 (again, if this is relevant). Could this spacer be causing the problem? Should I somehow close off the exhaust gas that is going into the spacer? Any suggestions regarding how I should arrange the spacer? Or do I need to keep looking for a vacuum leak? Should I remove the spacer? If I remove the spacer, the carb studs will be too long?

Note that I plugged the PCV port on the EGR spacer … I’ve connected the PCV directly to a port on the intake manifold which seems to make the truck run a little better.

Thanks for any suggestions/guidance.

 

Yes the EGR can and will play a roll in rough idling. Mine was idling rough surging up and down and after we fixed everything but the EGR it still was. Then we took off the EGR to peek inside it. It was filled with carbon, almost closing it off completely. After it was cleaned and put back on the truck idles like a dream now

 

Easy enough to take the EGR out of the equation:

• Get a gasket with just two round holes
• Get shorter studs or get a spacer

Install the carb without the EGR plate

Since the choke stove and EGR are both blocked off, might as well jettison the EGR

that you have a standard transmission makes it easier, as there is no modulator vacuum nor kickdown rod to deal with

 

Okay PapaBearYuma, what you are saying is along the lines of what I was thinking. If I end up having clearance issues without the EGR plate ... I'll check tomorrow, but I think the carb might sit too low without some kind of spacer ... where can I get a a plain spacer? Thanks.

 

Any speed shop, summit or jegs. Maybe even local auto parts store like O'Reilly

 

No EGR valves until 1973, so the 351W has to be from a 1973/74 Ford/Merc passenger car if it has a 2100 series 2V .. 2150 series 2V introduced in 1975.

The original EGR/carb spacer plates were aluminum, heat caused them to melt internally. They were also notorious for getting clogged up with carbon.

Circa 1976: Ford replaced the POS aluminum plates with cast iron plates.

351W: 1969/89 Ford/Merc Passenger Cars; 1975/97 Econoline, 1980/89 Lincoln; 1981/96 F150/350 & Bronco; 1997 F250 H/D & F350.

 

Ha, the problem was pretty obvious in hindsight ... the plate that was bolted to the spacer was not sealed at all, causing a substantial vacuum leak. I cleaned everything up, and reinstalled the plate with gasket sealer, and now all is well.

Regarding the gasket on the intake manifold that covers the exhaust gas port ... I used a 2 hole paper carburetor gasket to close-off/cover that port (i.e. placed between intake manifold and aluminum spacer). Any opinions on whether I need some sort of metal gasket ... will the paper gasket burn through eventually, or am I worried about nothing?

Regarding the year of the engine, with help from the forum, I determined that the casting date is from 1971, but I don't know what year the spacer plate is from ... my PO got the engine out of a 1980 truck, so it has been around the block, but seems to be pretty solid. The spacer plate is aluminum, so based on NumberDummys info, it must be 1973-1975?

Thanks.

 

If you find the paper gasket does "burn" out I am sure they make a thicker gasket you could use.
OR
Find a 2 hole spacer plate to fit were the EGR plate is (what I would do) and not worry about it again.
Dave ----

 

Thanks. Silly question, but is the two hole carb bolt pattern pretty standard? I did a quick look in Summit, and some spacers indicated they fit Holley 2bbl, but nothing specifically mentioned Autolite 2100. Is it the same as Holley?

 

If it fits the Holley v2 2300 carb it will work on your motor, both have the same bolt pattern.


If you want a little upgrade, swap on a Holley v2 500 cfm 2300 carb. It takes all the same "tune up" parts it's bigger v4 brothers do.
I did this swap on a 304 yes an AMC 304 that had a MC 2100 I could not get to run right. Best thing I did to that motor.
Dave ----