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Old 04-21-2018, 01:16 PM   #1
Bearded1mx3
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Default Sohc to dohc

Alright all I'm here so it's cool now. Well I got my gf a 97 Saturn SL1 1.9 SOHC. It's a 5sp. Gots 219k runs like a champ interior pretty good considering age, mileage, and Vegas sun. Shifts are buttery smooth. So ima know out the easy stuff. Intake and exhaust...just catback. Longterm a DOHC Engine swap. Might only do a head swap. I know the engine would be easier but I live in an apt so I don't have a place to swap a motor right now. Next is to supercharge it screw turbos...lol see what I did there....anywho if I do manage to do an engine swap I want to rebuild it. What yes make models can I pull a donor from.

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Old 04-22-2018, 09:39 PM   #2
Saturn Night
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Default Re: Sohc to dohc

If you search the forums, there is a SOHC-to-DOHC swap guide that will explain what is needed.

Just know that the transmission makes a difference.

MT PCMs fit 1997 ONLY and depending on the year, the SOHC/DOHC PCMs make a difference.

If you ultimately plan on going to forced induction, you MUST install an aftermarket PCM(preferrably MegaSquirt) as the kits come with different pistons(lower compression), different injectors, and recalibrated MAP sensors to account for the positive manifold pressures that occur with forced induction aspiration.

...
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"He checks the gas, and fills the oil....."

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Old 04-24-2018, 01:03 AM   #3
Bearded1mx3
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Default Re: Sohc to dohc

So I could do the DOHC swap and use megasquirt. I believe I read on another post MS can take care of my TCM as well that true.

I know MS is a kinda DIY eco. What version should i buy and what 97 sl1 specific adapters or parts do i need please. I've never found those specifics b4.

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Old 04-24-2018, 07:52 AM   #4
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Default Re: Sohc to dohc

Adapters? LOL
MS Install guide: https://sixthsphere.com/showthread.p...iagram-How-tos

While MS can control the transmission it's a standalone unit, separate purchase from the engine controller. Most people find swapping to manual to be the better option...both in terms of cost and in terms of on-track performance.

Start researching on www.Sixthsphere.com ...pretty much if you can think it up someones posted a guide on how.

...
The proper way to fix a S-Series automatic is to replace it with a 5spd O:)

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Old 04-24-2018, 01:24 PM   #5
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Default Re: Sohc to dohc

I already have a manual. Do I still have a tcm to worry about. I'm not big on auto electronics. Hell yesterday I too a jolt from a coil pack at work.

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Old 04-25-2018, 11:52 AM   #6
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Default Re: Sohc to dohc

Quote:
Originally Posted by Bearded1mx3 View Post
I already have a manual. Do I still have a tcm to worry about. I'm not big on auto electronics. Hell yesterday I too a jolt from a coil pack at work.
Not on the Saturn S-Series and the 5-spd makes this conversion much easier. The PCM controls both the engine and transmission, which only applies to automatic transmissions.

The MS controller is only required, like I previously stated, for the forced induction.

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Old 04-26-2018, 05:18 PM   #7
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Default Re: Sohc to dohc

Ok so I've sourced a running DOHC from a 98. Does it matter if it came from an auto and I'm putting it on a manual. The engine is complete with all accessories. Other than the engine. What else will I need exactly. I've been reading and searching but I get vague and or confusing info I can't seem to put together in my head lol. No F/I for now just the dohc swap. Any input on things I need or should get from other years to put on this 98 engine would be greatly appreciated

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Old 04-26-2018, 08:12 PM   #8
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Default Re: Sohc to dohc

You will need to source a DOHC PCM, a set of 1997 DOHC fuel injectors due to the 1998 engine having a "returnless" fuel system. Wiring will be fine.

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Old 04-26-2018, 11:05 PM   #9
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Default Re: Sohc to dohc

Quote:
Originally Posted by Saturn Night View Post
You will need to source a DOHC PCM, a set of 1997 DOHC fuel injectors due to the 1998 engine having a "returnless" fuel system. Wiring will be fine.
Swap the DOHC injectors onto the SOHC rail, problem solved. You just need to keep the fuel return rail in the fuel return car and match the injectors to the engine.

I'm not convinced a '97 PCM is required, but mix & matching PCM's across the years does tend to lead to issue's when it can be the most annoying possible.
I believe CC & A/C are the only PCM programmed options that really matter, but it's worth the effort to match ABS as well. You'll need a 5spd PCM in any case to keep the SES light off and transmission codes gone.

Because you have a '97 you have 2 options for the alternator, 'low output' & 'high output' while the '98 only has 'low output' (difference of about 5amps peak). The '97's changed over around January of the model year (Jan '97), main swap difference is the harness plug changed in a big way. While checking which alternator to keep also check over the various other sensors for identical plugs (ignore the 'extra' EVO plug on the power steering pump on the DOHC car, doesn't do enough good to make up for the added weight).

Last edited by fetchitfido; 04-26-2018 at 11:10 PM..

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