 |
924Board.org
Discussion Forum of 924.org
|
| View previous topic :: View next topic |
| Author |
Message |
CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
|
 Posted: Tue May 01, 2012 3:01 pm Post subject: Engine rebuild questions |
 |
|
The cylinders look fantastic on my engine. The euro pistons I have are the same size as the normal pistons. The engine appears to have been rebuild not that long ago and looks fantastic.
- Can I go with standard size rings? Do I simply need to measure the inner spacing of the cylinders and see what the measurement is to make this decision? I assume I need to take it to a shop and verify the shape of each cylinder to be proper. This engine has hone marks indicating that it's been rebuilt not long ago and it looks cherry inside from what i can tell so far.
- What are good brands of piston rings to use? What brands should I stay away from?
- Can I re-use the rod bolts? I understand the OEMs are stretchables, but can't they be reused once or twice? If it's a "risky move" then where can I get some reasonably priced rod bolts?
- Valve work. The valves look good, but it's obvious that there may be leaking as there is oil visibly leaking in small amounts down past the valves which is causing a lot of buildup in the cylinders as well as the valves. Where can I get the parts to replace this and do the valves as well? Will my machinist have this stuff on hand? Can they source it? Make something? Not sure how that works.
- Water pump... figured i'd order one off of pelican, I see they have the pump and gasket for less than $50. Brands to go for or stay away from?
- Head gasket - the head was obviously resurfaced last rebuild. It looks good to me. If it checks to be true at a machine shop, can I just clear off the material that's on it and go with a new gasket? Or do I still need to have it resurfaced? I have a head gasket kit already.
- My bearings LOOK good, no scoring. Can these be reused if they check true at a shop?
- Do the pucks need to be resurfaced? Or can they be machined and reused?
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS |
|
| Back to top |
|
 |
ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
|
| Posted: Thu May 03, 2012 3:44 am Post subject: Re: Engine rebuild questions |
|
|
| CorsePerVita wrote: | | - Can I go with standard size rings? Do I simply need to measure the inner spacing of the cylinders and see what the measurement is to make this decision? I assume I need to take it to a shop and verify the shape of each cylinder to be proper. This engine has hone marks indicating that it's been rebuilt not long ago and it looks cherry inside from what i can tell so far. |
The only way to know for sure is to check the wear limit based on the info in the Tech Specs manual. PM me with your email address and I can send you some info. If the cylinders are within the wear limit, then you should be able to use standard rings.
| CorsePerVita wrote: | | - What are good brands of piston rings to use? What brands should I stay away from? |
At last check, I can get Goetz ring packs for the NA for ~$120. TRW are even cheaper, but are not considered OEM replacement.
| CorsePerVita wrote: | | - Can I re-use the rod bolts? I understand the OEMs are stretchables, but can't they be reused once or twice? If it's a "risky move" then where can I get some reasonably priced rod bolts? |
You can reuse the bolts, and many people have without issue, but that doesn't mean you should. I personally have received 3 or 4 reports of failed rod bolts just within the past six months on street driven cars. You have two choices: ARP replacement bolts (*very* limited supply) or aftermarket rods. Neither option is cheap, so you ultimately need to decide if it's worth the risk to rebuild and then have a bolt failure. It's probably a bit less of a concern on an NA motor than a 931 motor, but if you're running Euro pistons, you will be at the higher CR...
| CorsePerVita wrote: | | - Valve work. The valves look good, but it's obvious that there may be leaking as there is oil visibly leaking in small amounts down past the valves which is causing a lot of buildup in the cylinders as well as the valves. Where can I get the parts to replace this and do the valves as well? Will my machinist have this stuff on hand? Can they source it? Make something? Not sure how that works. |
Unlikely that your local machinist will have the parts on hand, and may not even have the correct bits to remove the guides. This has been a challenge even here in Detroit with lots of machine shops to pick from. Best bet would be to go to a VW specialist. The oil leakage is probably from failed stem seals which are included in the head gasket kit, but it could also be from valve guides that are beyond the wear limit. Again, the tech spec booklet contains instructions on how to check this. Very strongly suggest that you have the guides and valves measured so you know what you're dealing with. If you need replacement valves and guides, I can get all of those for you from SI (stainless valves and brass guides). If you have the guides replaced, again, I strongly recommend that you have the guide bores checked for wear limit, as you do NOT want to have a guide come loose in the bore!!!
| CorsePerVita wrote: | | - Water pump... figured i'd order one off of pelican, I see they have the pump and gasket for less than $50. Brands to go for or stay away from? |
Important to know if you're getting new or rebuilt. That price sounds like a rebuild. The new units I resell are Geba brand (OEM supplier) and are somewhere around $60 including the gasket.
| CorsePerVita wrote: | | - Head gasket - the head was obviously resurfaced last rebuild. It looks good to me. If it checks to be true at a machine shop, can I just clear off the material that's on it and go with a new gasket? Or do I still need to have it resurfaced? I have a head gasket kit already. |
Your machine shop should be able to check it for flatness. The wear limit is 139.55mm (again the tech spec booklet shows where to measure this). You want to avoid going below this, so if the head needs to be surfaced, you want to remove as little as possible. It's less of an issue on an NA head than a 931 head, but you can still run into issues with the valve seats (may need to be remachined and sunk further into the head, which will in turn affect valve tip height), the spark plug hole, and the timing belt tension function.
| CorsePerVita wrote: | | - My bearings LOOK good, no scoring. Can these be reused if they check true at a shop? |
Yes...but STD bearings are relatively cheap, so if it were me, I'd just replace them. $132 for maines, and $62 for rods.
| CorsePerVita wrote: | | - Do the pucks need to be resurfaced? Or can they be machined and reused? |
I'm assuming you're referring to the lifters. DO NOT do anything to the lifters. They have a concave surface that is supposed to cause the lifter to spin in the bore so that it doesn't wear in one spot. If you have lifters that have pits on them, that is usually from improper oiling or insufficient ZDDP content. If they have longitudinal grooves in them, that means they have stopped spinning in the bores, and will eventually cause the cam lobe to start flattening. Check them all carefully. If you have damaged lifters, they can be replaced individually, but you may wish to replace them as a matched set (I have one or two sets available).
_________________
erstwhile owner of just about every 924 variant ever made |
|
| Back to top |
|
|
emoore924
Joined: 13 Apr 2004
Posts: 2822
|
| Posted: Thu May 03, 2012 10:06 am Post subject: |
|
|
| ...and no you can't reuse the head gasket. |
|
| Back to top |
|
|
CorsePerVita
Joined: 25 Jul 2008
Posts: 1992
Location: Redmond, Oregon
|
| Posted: Thu May 03, 2012 4:20 pm Post subject: Re: Engine rebuild questions |
|
|
| ideola wrote: | | At last check, I can get Goetz ring packs for the NA for ~$120. TRW are even cheaper, but are not considered OEM replacement. |
Is Goetz a reputable brand? Good quality? I am more concerned with quality on rings. If I'm going to race the car I don't want to put cheap stuff in it if I can stray from it.
| ideola wrote: | | You can reuse the bolts, and many people have without issue, but that doesn't mean you should. I personally have received 3 or 4 reports of failed rod bolts just within the past six months on street driven cars. You have two choices: ARP replacement bolts (*very* limited supply) or aftermarket rods. Neither option is cheap, so you ultimately need to decide if it's worth the risk to rebuild and then have a bolt failure. It's probably a bit less of a concern on an NA motor than a 931 motor, but if you're running Euro pistons, you will be at the higher CR... |
I'm fine with the cost if they are reusable over and over again and a reusable part. Last I spoke to you these were not immediately available, has this changed? If so I will happily put in an order. I am going with euro pistons.
| ideola wrote: | | Unlikely that your local machinist will have the parts on hand, and may not even have the correct bits to remove the guides. This has been a challenge even here in Detroit with lots of machine shops to pick from. Best bet would be to go to a VW specialist. The oil leakage is probably from failed stem seals which are included in the head gasket kit, but it could also be from valve guides that are beyond the wear limit. Again, the tech spec booklet contains instructions on how to check this. Very strongly suggest that you have the guides and valves measured so you know what you're dealing with. If you need replacement valves and guides, I can get all of those for you from SI (stainless valves and brass guides). If you have the guides replaced, again, I strongly recommend that you have the guide bores checked for wear limit, as you do NOT want to have a guide come loose in the bore!!! |
We have a few VW places that do work, I'll check with them and see what I can do.
| ideola wrote: | | Important to know if you're getting new or rebuilt. That price sounds like a rebuild. The new units I resell are Geba brand (OEM supplier) and are somewhere around $60 including the gasket. |
This was from pelicanparts.com listed as brand new. They had rebuilds for less. The brand they sell is Graf - again, I am not sure of the quality of said pump. Are there differences between the two products?
| ideola wrote: | | Yes...but STD bearings are relatively cheap, so if it were me, I'd just replace them. $132 for maines, and $62 for rods. |
That's a good price, you sell these?
| ideola wrote: | | I'm assuming you're referring to the lifters. DO NOT do anything to the lifters. They have a concave surface that is supposed to cause the lifter to spin in the bore so that it doesn't wear in one spot. If you have lifters that have pits on them, that is usually from improper oiling or insufficient ZDDP content. If they have longitudinal grooves in them, that means they have stopped spinning in the bores, and will eventually cause the cam lobe to start flattening. Check them all carefully. If you have damaged lifters, they can be replaced individually, but you may wish to replace them as a matched set (I have one or two sets available). |
I have a set from another car available as well as a spare, only some of mine are damaged.
| emoore924 wrote: | | ...and no you can't reuse the head gasket. |
lol yes, i'm aware of that, that would be a horrible idea. I realize some of these questions above may sound "silly" for those of you have gone through an engine, but this is my first time. So I'd rather ask questions and find out that assume I know it all and totally screw something up.
_________________
- 1977 Porsche 924 2.0 N/A (Trackday Project)
- 1979 Porsche 924 2.0 N/A (The other daily)
- 1980 Porsche 931 (Daily)
- 1987 Lamborghini Jalpa
- 1999 Ducati 900SS
Last edited by CorsePerVita on Thu May 03, 2012 5:26 pm; edited 1 time in total |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
