Power head parts matching

[rcnations]

I need a head and connecting rod for an 87 Force 125. Can anyone tell me what years will work other than 87? Maybe you have what I need. I can be reached at 303-507-8501 Thanks.

 

[Frank Acampora]

Re: Power head parts matching

WOW! posting your phone number on the open forum? You must be desperate.

At any rate you have a choice of many different engines for the connecting rod. The same rod was used in Chrysler 20, 35, 45, 55, 70, and 75 through 140. Just avoid the rods from the Chrysler 55, 60, 65 big bore, twin carb engines (3.375). These were a completely different series of engines. These engines had a longer rod with a larger big end and more massive rollers.

I am not sure about Force, but I would not be surprised if they used the same rod in the 50. The same rod is used in all Force engines ,all years, from 85 through 125 and possibly 150 horsepower. So get the rod from what ever you can.

As far as the head, any four cylinder head will bolt up BUT If your 125 is a 3.3125 (3 5/16) bore then any head will fit. BUT if your 125 is a 3.375 (3 3/8) bore, you must use a head from the same diameter bore engine otherwise the piston crown will hit. I suspect your 125 is the large bore engine. So for the head, stay with later force engines--Let's say after 1987.

You don't even need to measure--just look at the piston crown. The smaller piston will have a flat part on the crown of the baffle only about 1/4 inch wide. On the larger piston, the flat part of the baffle crown will be twice as wide.

The same gasket is used on all heads. The only ill effect from using the larger head on the smaller bore will be a slightly lower compression ratio.

 

[rcnations]

Re: Power head parts matching

I do have an 87, with a 3.3125 bore....so will an 88 head work? I have noticed that some heads are rectangle and others follow the conture of the block (Hexogon). Mine is the older rectangle style. Does that have anything to do with it working or not, or does that say tell us what bore it is? I don't want to lower the compression that's for sure.

 

[Frank Acampora]

Re: Power head parts matching

If you have the 3.3125 bore, then any head, any year will work. I don't really remember if the 1988 125 was big bore or not. If it is close to you, you could measure it--I'm not quite sure and it is too late to go into the garage, but I think the combustion chambers were the same diameter as the cylinder bores. Lowering the compression by about 10 psi will not reduce the power too much and will provide a bit more resistance to detonation, so it is not necessarily a bad thing.

The rectangular head is an earlier head and it is exactly the same internally as all other heads. The factory just filled in the missing areas of each hex to make the head look more massive--you know--the perception of bigger engine, more power. Since the filled in areas are hollow, it is only a little heavier. But the water passages and to a degree the thermostats were the same. The later finned heads did mount the thermostat differently but if you have the therm. cover and the spring inside, then there is no difference. Matter of fact, I put a finned head on my Chrysler 140 to save a little weight and because it was the only good one I had available at the time.

 

[jim_b_20653]

Re: Power head parts matching

I have a rod and a head if you are still looking for them