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I think I killed my '88 944 NA. Best way forward?

Old 09-01-2016, 05:13 PM
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CrookedRacer
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Default I think I killed my '88 944 NA. Best way forward?

Hi everyone,

I just had a fantastic weekend at Watkins Glen with NASA-Northeast!

I wrote up my weekend in my build thread over at Grassroots Motorsports.

https://grassrootsmotorsports.com/fo.../105890/page6/

But to repeat the important bit here for you 944 mavens:

...on my last 35 minute session, I was one of maybe five cars on track, ticking off fast laps. A couple laps after pulling my fastest time of the weekend, I noticed the car had less power.


I pulled it in about ten minutes early and it was making a fairly loud ticking noise that you couldn't notice when the car was revving.
Here's a video of my fastest lap and at the end you can hear the noisy engine. Something's really wrong.




........................


I think that at the very least, I have a bent exhaust valve. I certainly could have floated it while over-revving during a downshift at some point. But reviewing my footage, I couldn't find that moment or even determine when my loss of power began.


Please take a listen to the engine at the end of my video... and my question for you is this: to get the car running again for one more race weekend at VIR in October, wouldn't it be easiest to purchase a complete used long block and swap out this engine? Then I can take time this winter to do a really good job of rebuilding this one.



The other option is to buy a used head and put that on, assuming that's the issue. I've never been that deep into an engine before, and I feel like I'd be more comfortable and confident swapping the whole thing out.



I look forward to your opinions and expertise!


Thanks!



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Old 09-01-2016, 05:21 PM
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odonnell
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I have a head if you want it, $80 shipped. 8 good valves but the head itself need minor welding. The guides and seals are very recent. You could throw the valves into your head, or just have a machine shop rectify this one (I'd swap the valves if it were me).
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Old 09-01-2016, 05:39 PM
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Thanks, Michael.

The reason my head might not work is that one of the valve guides and seats was a bit questionable back when I replaced all the valve springs with the head still on the car.

https://rennlist.com/forums/924-931-...l#post13089686

One of the valves was able to wiggle in its guide, and when I would pull it up to its seal, it didn't make a positive tap... it sort of ka-chunked into its seal, as though it didn't hit the seal at the same time all around.

So if I go with a new head only, I'll probably want to be using the new head, not the one I have.
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Old 09-01-2016, 05:40 PM
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Can't see video at work but I have seen a few broken 944 valve springs in recent years from over-rev conditions...maybe enough to keep the valve a hair open so you lose compression/power from that cylinder.

You can replace the spring without pulling the head...so hopefully that's all there is.

If you did have to swap heads, and you had a spare good head ready to go, you could do the whole job in a weekend taking your time.
If you had an experienced helper a 944 head job is about a 6 hour job.
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Old 09-01-2016, 05:43 PM
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Unfortunately, that sounds like rod knock to me... and the falling oil pressure confirms it. I'm afraid you need an engine. (I'll give you $1500 for the car as-is!) Seriously, you're better off getting a used engine.

On your lap video, notice how you lift off the throttle when you hit the first curb of the bus stop? Had you not hit that, you could have stayed on full throttle and had a faster lap time.
Because of the small view through the window and the bad exposure, it's hard to see what your line is.
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Old 09-01-2016, 05:56 PM
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Thanks, Van! It is pretty loud, isn't it?

I have a used one lined up and hopefully I'll be able to pick it up this weekend. It's also an '88 with the high-compression pistons.

I figured whether the problem was in the head or in the short block, I'd be best off buying the whole thing.

If anyone else cares to opine on what it sounds like, it's pretty easy to hear the noise in the audio after I pit-in.

I really appreciate everyone's input. It's what makes this place so special!
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Old 09-01-2016, 06:01 PM
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Originally Posted by Van View Post

On your lap video, notice how you lift off the throttle when you hit the first curb of the bus stop? Had you not hit that, you could have stayed on full throttle and had a faster lap time.
My car has two seats. You should ride along with me.

I didn't usually hit that curb so hard, but yeah, I hit it pretty good that time. I didn't even realize I was lifting as a result. That's the stuff I'd love to have coached out of me.
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Old 09-01-2016, 06:12 PM
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How was your oil fill level? If too low you can easily spin a bearing - that's why the 911 has the oil pump in the oil tank. Doesn't sound like a bad valve to me. That's a 1988 SE, isn't it?
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Old 09-01-2016, 06:24 PM
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I checked the oil fill level before every session - and I had added oil that afternoon at one point. The oil fill level was just above the top line, close where the flat ends and the dipstick becomes a cylinder again.

I even checked the oil after I parked it (to see if it was shimmery or whatever) and it was at the top line at least.

But I'm betting oil starvation can be an issue at Watkins Glen, particularly around the long righthander Outer Loop/Turn 5 and Turn 10 lefthander which is also fairly lengthy when you do it right.
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Old 09-01-2016, 06:45 PM
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I can't watch the video at work so I can't offer too much feedback but if Van noticed that the oil pressure dropped then yeah - I can't think of any kind of valve problem in the top end thats going to cause your oil pressure to drop. Probably a bearing.

As we also run an 87 944 NA as a race car I'm interested in following what you do with it, how easy it is to source a replacement, and how you end up rebuilding anything if you do.

Do you run the turbo oil cooler?
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Old 09-01-2016, 07:26 PM
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Originally Posted by Holytin View Post
That's a 1988 SE, isn't it?
http://porsche944celebrationedition.weebly.com/

Yeah, it's a celebration edition with the Special Edition medallion stuck to the dash instead of inside the glove box. It was stuck on the dash by a prior owner.

But it has the grey plaid door cards (or it did).

Originally Posted by ddombrowski View Post
Do you run the turbo oil cooler?
No, I don't believe it has any special exterior oil cooler.

Originally Posted by ddombrowski View Post
I'm interested in following what you do with it
I keep up a build thread on Grassroots Motorsports (see my first post above) but if I have any seriously technical issues, I haven't found better than this place for specific questions. So I'll recap what I end up doing at the very least on this thread here, and start other issue-specific threads here as I go along.
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Old 09-01-2016, 07:31 PM
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Hey where you the guy I had lunch with on Monday? Nice to meet you.

Sorry to hear about your engine. Any different news now that you got it home?
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Old 09-01-2016, 07:43 PM
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Originally Posted by StoogeMoe View Post
Hey where you the guy I had lunch with on Monday? Nice to meet you.

Sorry to hear about your engine. Any different news now that you got it home?
I think so. If I told you the story about when our mutual friend Carter, one of my racing instructors, bumped me from behind on the front straight at Dominion Raceway. I should have asked where you were paddocked because I never could find you.

The biggest news has been Van's thought on what it sounds like. I'll do some peering into the engine tonight if I get around to it.
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Old 09-01-2016, 07:48 PM
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Sorry about your luck. Are you out in the suburbs or in DC proper?
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Old 09-01-2016, 07:54 PM
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Originally Posted by jhowell371 View Post
Sorry about your luck. Are you out in the suburbs or in DC proper?
Silver Spring, just outside the beltway.
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