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Old 01-09-2007, 11:15 PM   #1
kbahus
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Default Head Gasket Thickness & Timinig problems

I may have discovered a serious flaw with my shortblock swap. I installed a jdm v8 shortblock with my ej20g complete setup. I used the new metal standard wrx head gaskets when building the engine. These gaskets were quite a bit thinner than the original composite head gaskets that were removed from the ej20g. They were so much different that I had to drill out the intake manifold bolt holes to get them to line up, I would guess about 1/16th of an inch off.

When installing the timing belt all of the marks seemed to line up ok, however I did experience a belt slip issue when torquing down the cam gears. I suspected I did not give the tensioner enough time for the hydraulic pressure to fully tighten the belt so I tried again and waited a while and no more belt slip. I do recall the belt was relatively easy to install though, easier than the previous one I replaced back when I did the swap. I also felt that the belt had good tension, but didn't seem as tight as I had remembered. After spinning the engine several times I concluded the belt should be ok and put it together.

I have ran the car about 200 miles now, it runs satisfactory but I am not pushing it with the power fc. I don't have any runability issues except for my idle. It is erratic and lumpy, however not super bad. It also seems to take an extra crank to start, which it never had before.

I am wondering if the head gasket thickness issues has shrunk my engine to the point that it is now causing timing issues. I am also curious about the compression ratio. Does anyone have any input?
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Old 01-09-2007, 11:27 PM   #2
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Thing that scares me is that you had problems fitting the intake manifold due to the shorter width of the engine.. That could explain the idle issue, vacuum leak perhaps? Or the timing is off enough to cause a rough idle, but no valve clash issues.

And maybe i'm thinking too much into it.. But is it possible that the fuel injector stream is getting affected by the manifold being slightly "off center".
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Old 01-09-2007, 11:42 PM   #3
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I thought about the alignment issue too, there would be about a 1/16th of a lip in the runners. which could be enough to disrupt the airflow. I am pretty sure the gaskets sealed up good. I only had to drill one side of the manifold, and drilled it 1/16 larger than the original size, but if you look at the original holes they are quite a bit larger than the bolt that goes through them as it was.

The crappy thing is never even though twice about all of this till tonight.
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Old 01-10-2007, 01:28 AM   #4
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I used an EJ20G manifold on a N/A EJ25 and had to open the holes on it to get the bolts to engage the threads nicely. I wonder if it's an EJ20G thing?

The lip shouldn't hurt idle performance much with the angle of the injectors. Do your timing marks still line up okay?
Sorry I can't help any more.

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Old 01-10-2007, 01:32 AM   #5
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WOW!!!!!!!!
You want to use EJ20G head gaskets. I did calculations for my friends engine, he put a USDM STi block on w/ EJ20G heads and Ej20G head gaskets and his compression ratio was like 9.4:1 becouse the pistons on the new motors come out of the block at TDC. Where as with EJ20G they stay in the block....
I hope you didnt damage anything.
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Old 01-10-2007, 11:29 AM   #6
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I don't know what to really do. I don't have any money or time left, I don't really have a choice but to run it as it is. Sucky

snowman, do you have a fritz on your wagon? I may have seen you in Utah last week.

Last edited by kbahus; 01-10-2007 at 11:34 AM.
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Old 01-10-2007, 11:38 AM   #7
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What belt did you use and what tensioners?
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Old 01-10-2007, 12:04 PM   #8
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Quote:
Originally Posted by kbahus View Post
I don't know what to really do. I don't have any money or time left, I don't really have a choice but to run it as it is. Sucky

snowman, do you have a fritz on your wagon? I may have seen you in Utah last week.

Unless he removed it, there was a Fritz on it when it was delivered to him.

Snowman,
Ej20G pistons stick out of the block even more than later pistons. That's part of the reason for the thicker gaskets. Noah once told me a story of a SLC guy who popped his USDM WRX motor and tried to use an Ej20G bottom end in the car. He used the new gaskets with the older block and it was enough to cause interference and mess up his valves.

Thankfully, Kevin's issues go the other way and really only effect timing, though I am a little concerned about the tension on the belt. While it doesn't cause interference now, it would if he slipped a tooth down the road...
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Old 01-10-2007, 12:37 PM   #9
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I am running a 98 dohc n/a timing belt, which appears to be the exact same as the new age usdm wrx belt as well as the original ej20g belt. I did upgrade to the new usdm style tensioner. The marks did line up.

I was getting some hesitation this morning when driving to work under boost. My knock counts are staying pretty low though which is good.
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Old 01-10-2007, 11:13 PM   #10
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Quote:
Originally Posted by kbahus View Post
I have ran the car about 200 miles now, it runs satisfactory but I am not pushing it with the power fc. I don't have any runability issues except for my idle. It is erratic and lumpy, however not super bad. It also seems to take an extra crank to start, which it never had before.

I am wondering if the head gasket thickness issues has shrunk my engine to the point that it is now causing timing issues. I am also curious about the compression ratio. Does anyone have any input?
Hmmm, this is interesting. I have the exact same setup with the exact same issues. Although my intake mainfold fit with no issues - other than the AVCS breather.

Cold starts are become increasingly more difficult and I have a very unpredictable lumpy idle.

At the time of install I could find was regular spark plugs (6s) that I gapped down to 0.025 (what my car seems to like). I have been pointing the problem to this and I just picked up some 7 series plugs that I am putting in tonight.

Not sure why you are tightening your cam pulley after you put the belt on...But my tensioner and belt (EJ205) fit no problems.

I originally thought it slipped a tooth - or I put it on off by one tooth. BUT, I checked it after about 500 miles and it was fine - but I took it off and did it again just for good measure (still had the lines on the belt).

Hopefully the plugs solve the issue - but now I am thinking there may be a bigger problem...
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Old 01-11-2007, 12:02 AM   #11
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Kbahus, you should have waved me down i would have loved to chat. And the green pickle looking things is a Fritz then huh? what the hell is it? i could never figgure out what it was, but i liked it so i left it on my car. When ppl ask me about it, i just say its a pickle w/ arms and legs becoue thats my best guess. lol
Matt I put in a EJ20G into a newer WRX using WRX heads, EJ20G headgaskets and it worked out amazing. However i can see where your coming from w/ the new gaskets on there. That would be a bad thing to do.

Kingsubi, let us know how your car reacts to the (7) heat range plugs. Becoue im thinking that is what might be causing the issue of my car running like crap.
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Old 01-11-2007, 01:09 AM   #12
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We were next to you in a blue bugeye wagon (navy blue) with a black roof box. If I would have known it was you I would have loved to chat! Oh well, I will be back out there for spring break hopefully and will track you down. Fritz is kind of like the mascot for awdpirates.net, the colorado subaru club.

I have always ran the 7b's with good luck. I am a firm believer in a one-step colder plug. I run them in this motor and my camaro that is on nitrous.

I made a post about this over at bbs.22b.com. Maybe some UK guys can chime in as I am sure were are not the only ones with shortblock swaps.
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Old 01-11-2007, 01:14 AM   #13
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Ok - so the new plugs are not in but pulling the old ones out have revealed some bad news me thinks.

They have a mark on the top and they are now gapped below 0.020... I think the piston may be tapping the plug and making the gap so small that it creates bad starts and a crappy idle



Checking the other side right now and putting the new ones in.

p.s. I also have always used the 7's...just could not find them when I did the swap
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Old 01-11-2007, 01:52 AM   #14
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Uh oh, thats about scary.

How long have you been running your car with the v8 shortblock?
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Old 01-11-2007, 02:17 AM   #15
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Only about 1500 miles. Well the 7Bs are in and it fired up right away!

I will check in tomorrow after work to report on any lumpy idle.

Here are a couple pics of the plugs to keep you from sleeping well...



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Old 01-11-2007, 03:44 AM   #16
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Unless you have some extreme pentroof (dome) style pistons, there's no way that turbopistons can knock the spark plugs - unless you're using the newer type long plugs (ILFR) in the old heads. This plug-problem is not related to any (belt) timing issues.

As for timing belts and tensioners:

When using the AA072 belt (old DOHC) then you must use either the very old rod-style tensioner or the newer style tensioner BUT WITHOUT the much smaller idler!!! In total you will be running 2 standard smooth idlers, one toothed idler and the tensioner.

When using the AA200/240 belt (new DOHC) then you must use the newer style tensioner WITH the smaller idler. In total you will be running 2 standard smooth idlers, one toothed idler, one small idler and the tensioner.

I have used head gasket thicknesses from 0.058 mm up to 1.37 mm with the same belt and idler setup on both Phase I and Phase II DOHC heads without any problems.

Can you post a picture of the belt/idler setup you have on the engine?
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Old 01-11-2007, 04:26 AM   #17
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I have the new belt with the old style tensioner and original pulleys (no small idler before the driver intake cam)

Well I hope you are right about the pistons and I had a hunch that the gasket could not make the difference b/w interfering and not.

The strange thing is the lumpy idle was getting worse, but the car still pulls strong - even at 7K RPM...
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Old 01-11-2007, 06:43 AM   #18
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The new belt is longer (it has an extra idler) and you should not use it on the old engines without that extra idler! It will skip teeth! You can use it on older engines but you need the new tensioner, the extra idler and the new bracket which mounts the tensioner and extra pulley!

Mixing this can be a cause for numerous timing, idling and misfire problems!
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Old 01-11-2007, 08:01 AM   #19
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i lined my 205 belt up with a K belt and they are the same length.

that extra idler is most likley there to compensate for the thinner headgaskets on newer engines.

plus, if you actually look at them side by side, it makes the belt path like 2mm longer (exageration, but really, its very little)
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Old 01-11-2007, 08:32 AM   #20
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When I get home from work I will count the teeth between crank and left intake came to make sure, I should have a few belts lying around.
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Old 01-11-2007, 12:03 PM   #21
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My motor is running the new style tensioner assembly. I did not add nor know about an additional idler pulley. Perhaps this is exactly what I need. I upgraded because my old 20g tensioner was leaking.

I used a 98 dohc timing belt. I also compared this to a 03 wrx belt and they appeared to be the same length, however I did not count teeth. I could see a 2mm difference creating this problem.

Thank you for the info guys!
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Old 01-11-2007, 12:48 PM   #22
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The belts are the same length. If they weren't the engine would interfere within seconds. Even an extra tooth at 1000 rpm and only 2xx teeth should make that clear.

When I installed it and hand cranked the engine over a couple dozen times the timing was still dead on
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Old 01-11-2007, 12:58 PM   #23
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Its gotta be an issue with the new style tensioner. I did some research and the original ej20g head gaskets are 1.37mm thick, the metal gaskets we are using are .6mm thick. Combined that is a 1.54mm difference in total engine width. If the extra pulley is designed to compensate for this tiny difference it will work, at least for me since I have the new style tensioner.
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Old 01-11-2007, 01:07 PM   #24
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Quote:
Originally Posted by kbahus View Post
Its gotta be an issue with the new style tensioner. I did some research and the original ej20g head gaskets are 1.37mm thick, the metal gaskets we are using are .6mm thick. Combined that is a 1.54mm difference in total engine width.
That is quite a bit - maybe the tensioner is just floating around too much

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If the extra pulley is designed to compensate for this tiny difference it will work, at least for me since I have the new style tensioner.
lol - nice, I am screwed...
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Old 01-11-2007, 01:59 PM   #25
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I went to the dealership today and picked up the small idler I am missing. The belt I am using is the AA072. I am going to attempt the install here in a few hours and will post results.

If this fixes it, I would anticipate you will need to upgrade to the new style tensioner assembly, bracket, and idler pulley. I just can't see the g-style tensioner is going to take up that much slack, especially if the both belts turn out to be the same length, which I believe is true.

Last edited by kbahus; 01-11-2007 at 02:08 PM.
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