Cylinder Head Replacement

[billvl]

I recently picked up a 1994 Plymouth Acclaim 2.5L 4 cylinder from a friends father-in-law. The vehicle is in very good shape and for $300 it was hard to refuse. All that needed to be changed was a head gasket. When the car is started there's a thick white smoke coming from the exhaust with a sweet smell. So i brought the car to have it inspected to get it certified and found the brakes in the front and back also needed to be changed. So i bought about 400 in parts, liquids and consumables to get the job done. After I changed the head gasket and started the car, there is still a thick white smoke. This has me believe it is either a cracked block or cylinder head. I told this to the person I bought hte car from and he told me he has a parts car, a 1994 Plymouth Sundance 2.2L. So i figured I would check to see if hte cylinder heads were the same and swap them out in hopes that it is a crack cylinder head. After checking with All Data I find that the head gasket, timing belt, valves, valve cover etc etc are all the same part numbers but the cylinder head has a different part number.

The cylinder bore is also the same on both engines but the stroke is longer on my 2.5L engine. This makes me think that the difference between the two engines oculd possibly be the height of the block.

I was just wondering if it is possible that the heads are still inter-changable?

[MagicRat]

The 2.2 has less displacement than a 2.5, so the head's combustion chamber is smaller if the compression ratios are the same.... therefore, the design is different, even if it might interchange.

Theoretically, Putting the 2.2 head on a 2.5 block will give you a higher -than-normal compression ratio, requiring premium fuel to prevent a pre-ignition (ping). Theoretically, the combustion efficiency would increase, giving you slightly more power.

The valves may be slightly smaller too (I am not sure).

Keep in mind that using an old cylinder head is a bad idea. The 2.2 head may also be worn out too. I suggest getting a professionally- rebuilt 2.5 head, where you have an assurance that it is good and will last a long time. They really are not that expensive.

BTW I always send heads out to a machine shop to be checked-out for cracks, straightness and wear before reinstalling them. I rebuild anything that looks bad.... it saves aggravation in the long run.

[billvl]

I want to avoid putting more money into the car especially since I am not even %100 sure that the cylinder head is the problem, there could possibly be a crack in the block.

[MagicRat]

Originally Posted by billvl

I want to avoid putting more money into the car especially since I am not even %100 sure that the cylinder head is the problem, there could possibly be a crack in the block.

If the 2.2 liter engine runs well, why not swap the entire engine?
So long as you have access to an engine hoist, the engine swap really is no more work than swapping a head, and would save you the risk of future unexpected problems related to cracked blocks.

If I was in your shoes, this is what I would do, so long as the 2.2 engine ran well with no smoke and no funny noises.

BTW for the 2.2 head on a 2.5 block.... I calculate that the swap will increase your compression ratio by approx. 1.5 points. The 2.2 and the 2.5 engines have a compression ratio of about 9:1. After the head swap your engine will have a ratio of about 10.5:1. This is very high compression for a street-driven car and is at the upper limits of what premium pump gasoline can handle.

With this swap, you will have to use (expensive) premium gas all the time and you might even have to add an octane booster additive to the gas to keep the harmful knock and ping at bay.

[billvl]

With an entire engine swap I'm thinking I would need new engine mounts. Plus I dont have access to an engine hoist unless I rented one, but I am working out of my one car driveway so a major problem I have been dealing with is to find a place to put the parts car if I take it.

As far as having to run premium fuel for the life of the car I think its more economical to just do an engine swap like you said. i can actually pick up a 2.5L 90K motor from a salvage yard for $200 which is becoming very tempting.

Right now what I'm leaning towards trying to fix the "parts" car. The car had electrical problems and ended up shorting out and melting a part of the harness. The job may be tedious and a pain in the ass but at least it wont require a dirty driveway filled with expensive specialty tools, just time and patience. The car is actually in better mechanical shape. So once I look at the car and the extent of the damage I'll know better what I'm dealing with.

I really appreciate all the quick feedback btw, this is defintely helping.

[MagicRat]

That sounds reasonable. Let us know how things go.