Basically, I took on a customer's car-a 99 Eclipse RS-that was knocking. At the time, I could pull a 97 Neon DOHC that had a dash fire and I told the owner I could replace the block for him. The day the Eclipse was towed to my house, I went to the junkyard to pull the DOHC motor, to find it had been crushed earlier in the day. Now, there is not a DOHC motor for cheap anywhere in the KC Metro.
I happen to have a good 98 SOHC Neon motor in my garage and I am considering:
1-Swapping the pistons from the knocking Eclipse block to the SOHC Neon block and putting the Eclipse head on and dropping the motor in
2-Having the Eclipse crank machined, and just installing bigger rod bearings and putting it all back together (with the possibility of buying a new rod)
3-Putting the Eclipse head on the SOHC Neon block and hoping for the best since no one on DSMtalk has reported neither success nor failure
4-Coming out of pocket to drop in a good Eclipse/Talon motor ready-to-go.

My question is if YOU were to do this for another person, which route would YOU take? I am looking for maximum reliability with minimum cost, labor and skill.

I would take the neon SOHC. Have it checked by a machine shop and buy new pistons and rings....only $130. New bearings....assemble it and call it a day.

hmm put the DOHC head on the neon block if the neon engine is good. I don't know how the pistons will affect it though. I think the DOHC pistons are higher compression or something not sure though.

I'd get another Eclipse block if at all possible for simplicity sake. While I've worked on neon's, I've never tried swapping w/ an Eclipse. Then again labor & risk would cost me more than another Eclipse block would.

I suppose blood, sweat, & tears are still free...
...but supply is too limited.
- J

I was hoping to see a more clearcut answer...As far as buying new pistons, the DOHC pistons and rings that I have are fine, just have to consider swapping the rod with the spun bearing for another. And I know there are compression differences between the SOHC and DOHC pistons, but really, how much difference will that really make? (Would it be noticeable?) Has anyone here tried putting an Eclipse/Talon head on a SOHC Neon block yet? I already put a 95 Talon head on a DOHC Neon block and it ran perfectly...Any advice is welcome

Thought I might throw this out there for you.

http://www.dsmtuners.com/forums/showthread.php?t=225527&highlight=sohc+neon+block

Check out the post by TALON ESI-T. Terry is a highly respected member of this site. This may help you.

MB

The bottom ends of both are the same, the difference of all Neon's and Eclipses are the top ends. Heads flow the opposite direction which places the intake manifold and exhaust manifold on opposite sides of the engine between the two vehicles. As far as compression ratio's go there are no difference in pistons that effect compression. The difference there is caused by combustion chamber size being smaller on the SOHC head.
So my suggestion is use your Neon Block with the 2gnt head and accessories. So all you need to buy is the head gasket kit and head bolts. Oh yeah it would also be a great time to replace the water pump and oil pump.

-Kevin

Originally posted by shazow1969
The bottom ends of both are the same, the difference of all Neon's and Eclipses are the top ends. Heads flow the opposite direction which places the intake manifold and exhaust manifold on opposite sides of the engine between the two vehicles. As far as compression ratio's go there are no difference in pistons that effect compression. The difference there is caused by combustion chamber size being smaller on the SOHC head. So my suggestion is use your Neon Block with the 2gnt head and accessories. So all you need to buy is the head gasket kit and head bolts. Oh yeah it would also be a great time to replace the water pump and oil pump. -Kevin

I'm fairly sure that the pistons are different. That is why the SOHC guys use DOHC pistons to increase compression.

use the neon block. with the exception of the 95 neons, they are identical. Use the DOHC pistons with the DOHC head and call it a day.

buy the spare crank i have and put it in the eclipse motor :-D

Originally posted by shazow1969
As far as compression ratio's go there are no difference in pistons that effect compression. The difference there is caused by combustion chamber size being smaller on the SOHC head.

That is completely wrong. The pistons are completely different.

The SOHC neon pistons are more of a flat-top with an extremely mild dish cut in them. You could probably only tell by dragging your fingernail across them.

The DOHC Neon pistons, as well as the 2gnt's, are a dome piston with valve reliefs cut in them.

Now, the only thing that I really see is that by going straight to the neon block, you will loose a little compression. Since there are no valve reliefs, that may be an issue, too, but since we have plenty of room to upgrade to bigger cams and still not hit a piston, I don't think that's really an issue.

That's the cheap, easy way to do it, and the condition bottom end on the SOHC neon block is unknown unless you've already gone through it.

If you turn the crank & install new rod & main bearings, you know that part is in good condition and set for several thousands of miles.

I would check out the SOHC block to be sure everything is good to go. Obviously, to ensure long life and customer satisfaction, you should really consider new water and oil pumps along with new bearings and piston rings. However, if you just want to get this thing the hell out the door, so long as the SOHC block looks decent and spins nicely, you should have no trouble bolting the Eclipse head to it and sending it on it's merry way. You will, obviously, need to re-use the Eclipse sensors and wire harness to pull this off, but that's sorta common sense.


Good luck to you.

For the record, I used the SOHC block, everything went together smoothly and the car runs great. I don't feel any difference in how the car runs.
Thanks everyone for the info.