Cylinder Head question

Frugal1966 · 11-14-2004, 03:57 AM

I have a 98 Saturn 4 cylinder that just started mixing the oil/coolant. I replaced the head gasket but problem still persists. Went to the salvage yard and found no SOHC head but they had plenty of DOHC heads there. One of the guys said the engine blocks are the same on both, so I take that to mean water and oil passages are the same on the motor. The question I have is "Is it possible to replace the SOHC head with a DOHC head and grab all the timing chain setup for it?" The reason I'm asking a SOHC head cost $778 and I can get the DOHC and timing stuff for $25 or the whole DOHC motor for $99. I would greatly appreciate any advice on this. It's a great little car and only has 45,000 miles on it, but I'm not looking at throwing awhole lot of money at to get it running again. Thanks!!!

mariner33 · 11-14-2004, 12:13 PM

I don't know if a switch can be done, but I would recommend that you first take the time to find out where the problem is. If you're sure it's not the head gasket, then it's either a cracked head or cracked block. It wouldn't make sense to go through the trouble of switching from the SOHC head to the DOHC if the problem is in the block. Pressure test the cooling system and locate the leak with a stethoscope. Then, when you know where it is, you can better plan your strategy. Although, $99 for a whole engine sounds like a sweet deal.

Joeybagodonuts · 11-14-2004, 03:33 PM

the blocks are exaclty the same, but the pistons are dished slightly, thus youll have slightly lower compression and not be quite as fast as a true twin, but wont be that noticeable...
you will need the timing chain, i recomend getting a new saturn kit (DO NOT USE AFTER MARKET TIMING KITS, ive ran into sevral bad ones from fly by night shops through the years, we had to replace bad tensioners that were brand new but shops had installed on cars and they were making the chain clatter)
everything else, cept the head gasket of course, GRAB IT, cause thats some cheap ass prices...

amazinghl · 11-14-2004, 04:29 PM

I'd get the whole engine for $99, so I don't have to deal with chaning the timing belts and what not.

Also, is your car manaul or auto?

If it is manual, you can just change the PCM, if it's auto, you'll need that tranny and the PCM.

jeep45238 · 11-14-2004, 05:23 PM

Hey, I've got a SOHC head for sale for pretty cheap. The head came off an engine with a busted head gasket so you may want to take it to a shop to have them check it for straightness.

http://cgi.ebay.com/ebaymotors/ws/eB...e=STRK:MESE:IT

I wouldn't worry too much though, the machine shop in the back of work only charges about $32 plus tax to mill a head.

Frugal1966 · 11-14-2004, 09:13 PM

Pressure tested the cooling system today, the pressure was going up steady I shut the engine off when it got to 18psi. According to the pressure tester there was no problems with the block. I may just go for the DOHC swap, I assume it's easier to do upgrades on. Guess I just need to find a place to work on it out of the weather now. I've noticed I never have any problems with my vehicles till winter gets here then they fall apart.

Anony00GT · 11-14-2004, 11:09 PM

I'm with mariner33 and amazingghl. If you replaced the head gasket and you've still got coolant and water mixing, something's cracked somewhere, block or head.

I'd take the whole DOHC engine for $99, just make sure to get the wiring harness and PCM from the same car, then just change out the engines. It'll solve your problem as well as give you a noticable gain in power.

Frugal1966 · 11-27-2004, 03:49 AM

Well I pulled the Head on the Saturn yesterday well the weather was nice. I was amazed it only took about 3 hours(I'm slow), but I found the crack in the head I was looking for. I had a question, do I need to change the PCM if I just swap to a DOHC head or is that just if I swap the whole motor? If I don't need to swap the PCM to switch to a DOHC head I'll be driving it by Monday. Also does anyone know if the intake manifolds are the same on DOHC and SOHC?

Joeybagodonuts · 11-27-2004, 01:26 PM

if they are both automatic pcms and you DO NOT change the tranny, YES you can run with the single pcm, or, the dohc pcm plugs in in 5 minutes, you do not need to swap the harness! yes, the intakes are the same, BUT the injectors are NOT, 3 bolts and the injectors slide right out, then pop in oh, never mind, if going twin head, use the twin cam injectors, so yes, guess youll be running by monday!

Frugal1966 · 11-27-2004, 05:50 PM

I assume it doesn't make any difference if they are both manual trannys.