Help find where recirculation lines go to on 1990 force 120

[bigfishjim]

Help! I have a 1993/4 force 120 but the cylinder cracked and I found a 1990 thick wall block to replace it,
problem is the 1990 block doesn't have the ports next to the carbs where the recirculation lines connect to.
The rest of the recirc. system looks the same. Where do the lines go to on the 1990 model??
Thanks for any help or pictures.

 

[Frank Acampora]

Re: Help find where recirculation lines go to on 1990 force 120



These photos are not really much good but they should show something. This is a 1990 125 and it should be the same. There are no recirculation lines on that year engine. The bypass side recirculation covers simply pass excess fuel and puddled oil between adjacent cylinders. I do have a couple of these plain covers around somewhere but They are in a "safe" place so I can't take photos of them alone.

If you want to use your original covers, run the hoses to the manifolds behind the carbs. Drill and tap for your existing fittings or if they are press-in, drill to size. OR, buy a couple of fittings from a local supplier.

Ahhh---define "thick wall block" please. If your block has a 3.3125 cylinder diameter, then it is a 125 block and uses a 2.875 crank. Your 120 hp 2.80 crank will change the port timing and will affect performance.

 

[bigfishjim]

Re: Help find where recirculation lines go to on 1990 force 120

View attachment 129298View attachment 129299View attachment 129300

These photos are not really much good but they should show something. This is a 1990 125 and it should be the same. There are no recirculation lines on that year engine. The bypass side recirculation covers simply pass excess fuel and puddled oil between adjacent cylinders. I do have a couple of these plain covers around somewhere but They are in a "safe" place so I can't take photos of them alone.

If you want to use your original covers, run the hoses to the manifolds behind the carbs. Drill and tap for your existing fittings or if they are press-in, drill to size. OR, buy a couple of fittings from a local supplier.

Ahhh---define "thick wall block" please. If your block has a 3.3125 cylinder diameter, then it is a 125 block and uses a 2.875 crank. Your 120 hp 2.80 crank will change the port timing and will affect performance.

Well, the block I got has ports in two of the side plates that connect by hoses to the elongated blocks that hold check valves in them that mount to the side of the block, and on the 94 continue on to intake manifold between carbs.
The 90 block with "thick walls" does have a smaller bore than the 94. But the guy that sold it to me (supposed engine mechanic/machinist) claims it is an early 90 year 120hp. When I ordered the pistons from a website they were listed as the correct smaller bore for the early part of 90. Is there any way to be sure of anything????

 

[Frank Acampora]

Re: Help find where recirculation lines go to on 1990 force 120

Some early 120s were the small bore as were all the Chrysler 120 engines. Since you have the engine apart, simply measure down from the deck to the top of the exhaust ports. If the measurement is the same, then it is a 120 block. The 125 has the exhaust ports raised to accomodate the extra stroke length.

Looking at wiseco piston catalog, 1990 was the only year Force made the small bore 120. Additionally, the 125 was only made from 1984 to (supposedly) 1989. So, if the block is indeed a 1990, then it is most likely a 120.

As far as recirculation, the oil is recirculated to eliminate low speed "puddling" and improve the idle. It is not critical where you route the excess fuel and oil.



These photos show how I modify my manifolds to recirculate oil. the fittings are always at manifold vacuum and thus always actively draw any excess oil from the bypasses. Additionally, this oil now passes through the entire engine, acting as additional lubrication.

Note that on the bottom manifold, you must drill and tap (1/8 NPT) the starter side because the flat boss is used by the throttle cam. Do not drill too far forward or you will hit the carb mounting stud.

Although this is on a Chrysler 105, (in the avatar) the blocks and manifolds are the same so it will work on any 4 cylinder Force.