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Old 11-04-2019, 12:26 PM   #1
Carmudgeon
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Default Engine Rebuild (Jumped Timing) - Advice Needed from DIY'ers

Greetings -

I typed out a long post, but it seemed to vaporize so forgive me if this is a double -

Purchased a new '05 WRX and it was one of the best cars I've ever owned. It became so much a part of the family that I had it rebuilt when it spun a bearing at 185k (about 25k and 2.5 yrs ago) - not logical, but we are emotional about cars around here.

Sadly, it appears it jumped timing. Shop that did the rebuild is out of business so I towed to a local for a diagnosis. They tried to re-time as a hail mary, but no compression on one cylinder. No apparent intermix, car will start, no CELs. Dang shame.

So here we are. When I rebuilt, we upgraded internals (racing rings, forged pistons, Killer B, etc). I do not need the car, but I want the car. However, I am not paying $5k - $10k for another total rebuild. So I was thinking maybe, just MAYBE I can tackle this myself.

I am an experienced shadetree, but have never done anything like this. What I have going for me:
  • Space - a separate garage that would be dedicated to this project.
  • Time, patience and income - I'm in no particular hurry, and yeah I'm an old guy so a lengthy project doesn't worry me - gets done when its done. I am also blessed to be able to throw some $ at needed parts.
  • Tools - pretty good assortment accumulated over a lifetime of wrenching. I also have access to an engine hoist and stand if needed.
  • Youtube

But there are limitations. I had the following questions/request some input on the following from those that have more rebuild experience than me:
  • What else is likely to be damaged from the typical jumped timing event? I am pretty sure I can remove heads and get through a valve job, but would there be damage to the head and pistons or block that would have to be addressed? I am pretty sure everything was re-bored to accept slightly larger pistons during the rebuild. This is likely make or break for me - I wouldn't even know what would be involved in machining a previously machined engine again.
  • What about the heads? Would I have to send out for cleaning, etc. prior to re-assembly? Any issues with the pistons or block?
  • Anything else in there that is probably toast? Parts don't necessarily scare me, its sending items out for rebuilding/machining that has me concerned. That said, it would be a shame if all the parts we put into it are now toast.
  • Has anyone addressed this with engine in? I don't see how this is possible TBH but figured I would ask.

Thanks in advance for any input/advice - if successful, this cars future would be as a toy, not a DD. Just trying to see if I can keep her goin'
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Old 11-04-2019, 02:18 PM   #2
trueno92
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im in to hear what the experts have to say about this.

i think u can jump 3 teeth without banging into things, so it is savable. i'l prob get the timing covers off, get some really good light on it, and see if all 4 cogs are in the same orientation looking timed correctly for this one.
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Old 11-04-2019, 03:31 PM   #3
Blktrax
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Step 1, slap a belt on it, and perform a leak down test. Will tell you how many damaged holes. Miracles do happen, you may escape undamaged.

Step 2a, Dead hole(s), pull the engine, pull heads.
(if only light impact marks on piston crowns, replace and re-lap only damaged valves and seals, check all valve clearances. Ship it.)

Step 2b, Heavy impact marks on pistons, highly likely piston is fractured or visibly cracked. Find a used or JDM long block, or sell it all as is.
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Old 11-04-2019, 05:31 PM   #4
sig
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One time, one of my idle pulleys exploded from lack of lubrication and my timing on the passenger intake cam pulley jumped 11 teeth without damaging the engine so miracles do happen. If there is damage its probably bent valves, in that case you could replace the head with a used one to save time or replace them yourself. I personally would buy a used head. I happen to have 3 heads for sale right now if your interested for an ej205, 2 passenger and 1 driver side all with good compression.
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Old 11-04-2019, 07:10 PM   #5
Carmudgeon
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Quote:
Originally Posted by Blktrax View Post
Step 1, slap a belt on it, and perform a leak down test. Will tell you how many damaged holes. Miracles do happen, you may escape undamaged.

Step 2a, Dead hole(s), pull the engine, pull heads.
(if only light impact marks on piston crowns, replace and re-lap only damaged valves and seals, check all valve clearances. Ship it.)

Step 2b, Heavy impact marks on pistons, highly likely piston is fractured or visibly cracked. Find a used or JDM long block, or sell it all as is.
Awesome, thanks. I think we are at 2a at least, as shop re-timed and no compression on one cylinder - not sure if he did leak down test, I need to speak to him anyway. My understanding is it jumped "several" teeth, not that much as even he thought we had a shot at a miracle. Not to be.

Assuming no piston damage, does it make sense to replace all the valves when in there or will it be pretty obvious which ones are bent by checking clearances? Does anything else need to be done to head before re-installing?

I take it if pistons are fractured/cracked that means damage to bore, correct?

Thanks again!
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Old 11-04-2019, 09:30 PM   #6
Blktrax
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Replace only the valves needed, and it will keep costs in check, otherwise you'll fall down the rabbit hole of "while I'm here".

Most machine shops do this test with Red ATF to see the dye trace.


If the valves hit hard enough, besides bore score, the issue is the person working on the engine, you start getting into piston size, ring gap, on top of engine condition.

Unless you're dealing with a known Surbau engine builder with lots of engines back on the road after repairs; you would be much further ahead, to just buy a used US or JDM long block and swap it in.
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Old 11-05-2019, 03:48 PM   #7
Carmudgeon
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Quote:
Originally Posted by Blktrax View Post
Replace only the valves needed, and it will keep costs in check, otherwise you'll fall down the rabbit hole of "while I'm here".

If the valves hit hard enough, besides bore score, the issue is the person working on the engine, you start getting into piston size, ring gap, on top of engine condition.

Unless you're dealing with a known Surbau engine builder with lots of engines back on the road after repairs; you would be much further ahead, to just buy a used US or JDM long block and swap it in.
Excellent, thank you so much - just what I'm looking for!
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Old 11-07-2019, 11:07 AM   #8
subaru_gc8
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i second the jdm ej205.. plus you will get avcs that a big plus
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