97 Saturn SL1 with cracked SOHC head- can I do a DOHC engine conversion? - Fuelly Forums

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Old 05-25-2008, 08:09 PM   #1
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97 Saturn SL1 with cracked SOHC head- can I do a DOHC engine conversion?

My in-laws just bought a 97 SL1 with 1.9 SOHC engine and auto trans. It runs great but has coolant in the oil and oil in the coolant. What I have read on the internet is that these SOHC heads are notorious for cracking.

I found a complete 1.9 DOHC engine at a pull a part yard for just $140 and I have heard that the DOHC heads aren't prone to cracking. Can I put the 1.9 DOHC engine in the SOHC car or would I have ECM/wiring and trans bolt up issues?
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Old 05-26-2008, 12:12 PM   #2
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I had a coworker contemplating the same thing years ago . If they do fit you are going to need to track down an ecu and maybe half the wiring harness to take advantage of the changed flow characteristics or it will run like poop. also the combustion chamber might be another size so you chance losing compression ratio...good if you want to turbocharge, bad for mileage trials. I have a 1.8 mazda sohc that accepts a mazda dohc miata head...sounds great but it drops the compression ratio on an already sub 10.1 engine

yes people race saturns, there is a forum that caters to those guys. I would hit their faq's up.

Let me add that most of the time an engine swap is cheaper and less time than just a head swap if you take into consideration downtimes, like taking the engine apart and machining pieces, new gaskets etc. I'd yank the whole sohc motor and replace if there is a guarantee the dohc was fine and running when removed
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Old 05-28-2008, 06:43 AM   #3
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CHeck out
http://saturnspeed.com/smf/index.php

http://www.saturnfans.com/forums/index.php

or

http://www.sixthsphere.com/phpBB3/
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Old 05-28-2008, 07:12 AM   #4
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Aren't the SOHC engines more fuel efficient than the DOHC in the SL Saturns?
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Old 05-28-2008, 09:18 AM   #5
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DOHC engines are crap..... lol

or at least, they too are prone to cracked heads, ring failure leading to lots of blow-by (I can tell you all about that, at 1 quart of oil added every 300 miles currently, and getting worse) and the power you get from a DOHC is essentially the same as the SOHC. I think the DOHC cars have 20 more hp, but in this turd-mobile it doesn't make a difference at all due to the automatic trans gearing.

Stay SOHC, you'll be getting at leat 8mpg MORE than DOHC, and if you want to swap anything, swap a manual trans get make that 15mpg more than a DOHC auto.
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Old 05-28-2008, 09:41 AM   #6
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Hmm, thanks for the info. I guess its better to stay with the SOHC since it gets better mpg and the DOHC is also prone to cracking.

I'll have to look and see if a redesigned SOHC head casting that was less prone to cracking was ever made.
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Old 05-28-2008, 10:25 AM   #7
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I seem to remember DiamondLarry went to DOHC... think he had his head done specially for him by mpgmike... dunno if it went on that one but one of mpgmikes tricks with DOHC is to bias the ports so one flows stronger than the other or they flow different in different ranges... such that swirl is enhanced.
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