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| The Weekend Rebuild; and XFi cam swap | |
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| Topic Started: Jan 26 2009, 08:12 PM (4,630 Views) | |
| dimetrodon | Jan 28 2009, 01:15 AM Post #16 |
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I brought a set of rod bearings but the wear pattern on the originals was so uniform that it seemed risky replace them. One might think that every bearing surface in a car engine would gradually wear away and go out-of-spec at the same time as the valves and piston rings. But I don't think that is a safe presumption. As long as an oil film separates two pieces of metal, they may essentially never wear. |
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| Will | Jan 28 2009, 09:36 AM Post #17 |
Victory is mine!!!!
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Man, sounds like a real good trip you will not soon forget. It's not too often that you run into Native Americans you did not know were even there. |
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| PushnFords | Jan 28 2009, 04:49 PM Post #18 |
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Wow, what a trip? Did you hone the cylinders? If so, what grit? |
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| dimetrodon | Jan 28 2009, 05:21 PM Post #19 |
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Yes. John brought a hone from work. It was silicon carbide abrasive - pretty course grained from the looks of it. In retrospect, I think both John and I had misgivings about using it. But the bores were as smooth as glass and it didn't seem good to leave them that way. It is said that honing is necessary for both trapping of lubricant (in the long term) and for the seating of the rings (in the short term). Nevertheless, it is possible that using that hone might not have been the best idea. The only thing I would want to do differently next time is to buy a hone with brand new, fine grained stones made of aluminum oxide abrasive instead of silicon carbide. SiC is so hard that if a grain gets embedded in the cylinder wall, it might stay there for a long time wearing away at the rings. I know from experience that Alox is much softer than SiC so even if a grain does get embedded in the sleeve, it will not last long. Another possibility is to not use a hone at all. It might suffice to merely use fine grained emery paper wrapped around a very large sponge, rotated and spun by hand. This might be good enough to remove the varnish and carbon at the top of the stroke and to remove the shine from the cylinder wall. |
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| pacapo | Jan 28 2009, 08:04 PM Post #20 |
Member
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That's exactly what another GeoMetroForum member and I did here: http://teamswift.net/viewtopic.php?f=14&t=39927 I had a nice hone with fresh stones, but we decided to go the wet and dry sandpaper route. The rings seem to have seated and no oil consumption as of this writing. |
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| Johnny Mullet | Jan 28 2009, 08:33 PM Post #21 |
"Mullet of Ox"
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I was skeptical about honing the cylinders with the one I had available. I ordered a ball hone, but it came in today and not when I needed it. I did run a fine up and down on the cylinders which did not leave a perfect crosshatch, but definitely a workable surface for the rings to seat. Actually, the bottom end of this car was in exceptional condition and the head rebuild would have probably been enough to repair it, but going the extra mile sure didn't hurt especially with new parts available and the car had high miles. The connecting rod bearings were in like-new condition and re-used for this job. I was very confident in the entire job and it actually went well with the exception of the surprise wrist pins and forgetting my valve stem seal remover. Simple hand tools were used, but having the air compressor and the roloc discs and air blow gun for the head bolt holes were a bonus. |
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| PushnFords | Jan 29 2009, 08:12 PM Post #22 |
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At one time I'd found a chart showing what type of grit and what size of grit to use with each type of cylinder material and ring material but I can't find it anymore. I'd bet the engine is better off with a hone than without. I found this on the Goodson website: "use the 120 grit for a cast ring and 320 for a moly ring. Always use the next larger dia hone for a slight pre load on the abrasive, and use cylinder honing oil for the best finish."
Edited by PushnFords, Apr 20 2009, 05:41 PM.
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| Ryan | Jan 30 2009, 01:36 PM Post #23 |
Ryan
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I brake for penguins. |
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| dimetrodon | Jan 30 2009, 06:31 PM Post #24 |
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"I brake for penguins." The 92 Metro doesn't get one of those stickers until I figure out why there is little or no vacuum boost to the brakes. 
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| Johnny Mullet | Jan 30 2009, 07:35 PM Post #25 |
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"Mullet of Ox"
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Clogged vacuum line to the booster. It's a common problem. |
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| raygo | Jan 31 2009, 02:49 AM Post #26 |
Subordinate of my own Mind
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That is so awesome, Great job guys. I am about to do the exact same weekend rebuild as you did next weekend. |
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| dimetrodon | Jan 31 2009, 10:24 AM Post #27 |
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Good luck with your rebuild Raygo. Let us know how it goes. Hey, maybe we can get a "wave" thing going. Metro rebuild o' the week.... Or do a rebuild-o-palooza sometime. |
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| dimetrodon | Feb 1 2009, 10:37 PM Post #28 |
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After-action update on the 1990 weekend rebuild: I measured the compression yesterday with an inexpensive compression gauge I just received from Harbor Freight: 160psi, 155psi, and 158psi. Given that the stock compression is supposed to be 9.5:1 (about 140 psi), and I have never machined any material from the head, I think those are good and consistent numbers. One "fly-on-the-cheeseburger" is that I have an oil link when starting the car. It flows several drops per second until it is warmed up, then after a drive it seems to stop dripping completely. The dripping is apparent at two locations. The bottom of the timing cover, and up higher at the head gasket next to the timing cover. Questions for the experts: 1.) For lack of time, we did not replace the oil pump. But I am wondering if I should send it back to Parts Dino or keep it and install it later. This has me wondering how one can actually measure the oil pressure. I've checked the Chilton's and cannot find any clue. 2.) Does anyone know which brand of head gaskets actually have the correct size and location for the oil feed hole to the above left of the #1 cylinder? The set we installed during the rebuild was APEX brand from Parts Dino. If I go into the engine again, I'd rather not have to modify the gasket. 3.) The engine revs pretty high on start up - which aggravates the oil leak. The idle adjustment is set to be just right AFTER the car has fully warmed up. If I lower it far enough to reduce the idle speed while it is cold, it will die out at stop lights when it is warm. How do I get it to idle at the right speed under both warm and cold engine conditions? 4.) Is there any way to fix the oil leak besides taking the engine apart again and installing a new head gasket? This engine has leaked oil from these locations for as long as I have owned the car. I hoped it would go away with the rebuild. With the benefit of 20/20 hindsight, this may have been indicating a pre-existing warped head. 5.) As mentioned in the rebuild story, we installed an Xfi cam and an 8 degree advanced timing sprocket. If I hook up a timing light after these mods, approximately how many degrees advanced would one expect to see the timing marker? The car runs great, but I am seeing the mark at about 21 degrees BTDC. Standard timing should be 6 deg BTDC, and if I add 8 degrees for the advanced sprocket, that would be 14 degrees. So why does the car run so well at 21 degrees BTDC? |
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| Johnny Mullet | Feb 1 2009, 10:59 PM Post #29 |
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"Mullet of Ox"
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1) I would hang onto that part if any just in case you need it down the road. 2) The Felpro kit I purchased did not need modified as your Apex gasket did. 3) The car is supposed to idle high on cold startup and drop to normal when warm. There may need to be some fine tuning done with idle and air/fuel mixture to get it just right. 4) I doubt the head is warped. There are a few places it could be leaking like the dipstick tube, front main seal (looked good at rebuild), or hopefully elsewhere. How bad is the leak? Mine has a front seal leak I been dealing with since I bought the car. 5) Before testing the timing, the engine must be warm and the vacuum advance lines on the distributor must be ran together. |
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| metroschultz | Feb 2 2009, 11:49 AM Post #30 |
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NHRA N E 1
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Did you change the cam seal? I believe you would have given you changed the cam. The front cam bearing, which holds the seal, needs to have rtv or Permatex on the mating surface after removal. This prevents oil from wicking to the outside through the mating surfaces. I would recommend pulling back the T. belt cover enough to get a good look. And have someone start the engine, cold, while you look for the leak. Then you know what to fix. !!Keep you fingers clear of the cam and belt!! S |
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