Stock Rebuild in 2022?

[jukematt]

I need to rebuild my engine after a shredded timing belt and my piston(s) slamming into my valves. The problem is, it seems that stock rods and pistons are extremely hard to come by these days. I don't really see any threads about stock replacement stuff, probably since the stock internals are so strong. I am not looking for big power so stock internals will be more than enough for me.

In the absence of stock, what are some recommendations for new rods and pistons that aren't intended for 700-1000 HP? I've heard forged internals are not great for a street car making short commutes to work or whatever so I don't want to go nuts with those since my power goals aren't anywhere near that high anyway.

Background for those who are curious:
My timing belt shredded almost five years ago but my living situation didn't allow me to work on my car anymore. I love the car so much I don't want to ever get rid of it. So I put her in storage and am now FINALLY able to get her out to work on. I figured it was likely a seized oil pump but it turns out my driver side engine mount came loose. The nut spun off and the two bolts were starting to back out. Well, that mount holds the timing belt tensioner pulley and idler pulley apparently causing the timing belt to misalign and shred. No teeth at the crank gear and strings of the belt were wrapped around it. The belt was actually still under tension but with no teeth on the lower end, the pistons and rods could still turn. I bought a Leak Down Test kit at Harbor Freight and felt air coming out from the O2 housing (I had already dropped the oil pan so no downpipe was attached). So I pulled the head and saw the damage. At least two valves were bent and a nice shiny impact point on one piston, with possible contact on other pistons.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[pauleyman]

If all you have is small dents in the pistons is it not a requirement that you replace then. You can clean them up and move along.

 

[jukematt]

If all you have is small dents in the pistons is it not a requirement that you replace then. You can clean them up and move along.

Really? A couple of different people who I shared what happened told me they would be worried about micro fractures and it wouldn't be safe to reuse them.

 

[AWD-Tony]

The indent on top of the piston is fine. I would pull the cams, put a light on the combustion side and look through exhaust and intake port to see if light shines through. If it does, you’ll have to pull the valves and inspect if it’s the valves or the seat.

You must be logged in to view this image or video.

You can also pour water in combustion chamber to see if it leaks through.

 

[jukematt]

The indent on top of the piston is fine. I would pull the cams, put a light on the combustion side and look through exhaust and intake port to see if light shines through. If it does, you’ll have to pull the valves and inspect if it’s the valves or the seat.

You must be logged in to view this image or video.

You can also pour water in combustion chamber to see if it leaks through.

Interesting. With the shiny impact on the piston, four separate people told me I could have a damaged rod or piston underneath, but none of them know these cars specifically so maybe these are stronger than most cars?

Cams are already off. I removed them before pulling the head actually. In my last picture the two valves on the left appear to be bent. The other two may be or just old seals. Or are you saying that the light will determine if the damage with the valves on the left is the valve or the seat? I was planning on getting new valve seals anyway (seal same as seat?) and I assume new valves and new guides.

 

[AWD-Tony]

Interesting. With the shiny impact on the piston, four separate people told me I could have a damaged rod or piston underneath, but none of them know these cars specifically so maybe these are stronger than most cars?

Cams are already off. I removed them before pulling the head actually. In my last picture the two valves on the left appear to be bent. The other two may be or just old seals. Or are you saying that the light will determine if the damage with the valves on the left is the valve or the seat? I was planning on getting new valve seals anyway (seal same as seat?) and I assume new valves and new guides.

The marks on the piston are very common with slight valve contact (mine had them also) and does not damage the bottom end. Light and water will show if they’re not sealing. Valve seals are seals that go on the end of valve guides to prevent oil from leaking down into the combustion chamber. Valve seats are machines into the head. Valves contact the seat to seal combustion chamber. It is what’s machined when machine shop performs a valve job.

I would remove all the carbon build up from the valve and chamber before checking for leaks. And don’t mix up the valves as they should be in the same hole it came out of.

Valve seat

You must be logged in to view this image or video.

Valve seals

You must be logged in to view this image or video.

 

[Kryndon]

Highly suggest you look for some used stock Evo 8 or 9 rods + pistons combo which should be obtainable for $100-150. Look for ones which still have most of skirt coating intact. Not only are they lighter, better cast, but the rods are stronger than the stock 7 bolt ones. This is only applicable if your block is a 7 bolt block judging by the picture. There is just no point in putting another pair of stock DSM 7 bolt internals. No extra modification needed, and your CR and clearances remain the same.

 

[jukematt]

The marks on the piston are very common with slight valve contact (mine had them also) and does not damage the bottom end. Light and water will show if they’re not sealing. Valve seals are seals that go on the end of valve guides to prevent oil from leaking down into the combustion chamber. Valve seats are machines into the head. Valves contact the seat to seal combustion chamber. It is what’s machined when machine shop performs a valve job.

I would remove all the carbon build up from the valve and chamber before checking for leaks. And don’t mix up the valves as they should be in the same hole it came out of.

Valve seat

You must be logged in to view this image or video.

Valve seals

You must be logged in to view this image or video.

Thanks for the explanation. I can see light when I look through to or from the intake manifold side. Here are a couple more pictures. I can see the valves are bent.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

 

[jukematt]

Highly suggest you look for some used stock Evo 8 or 9 rods + pistons combo which should be obtainable for $100-150. Look for ones which still have most of skirt coating intact. Not only are they lighter, better cast, but the rods are stronger than the stock 7 bolt ones. This is only applicable if your block is a 7 bolt block judging by the picture. There is just no point in putting another pair of stock DSM 7 bolt internals. No extra modification needed, and your CR and clearances remain the same.

Wow I didn't know. With the swapped orientation, MIVEC, etc. I didn't think these were stock replacements. Good to know! Maybe I'll get a set to hold onto. What is "CR"?

 

[AWD-Tony]

Thanks for the explanation. I can see light when I look through to or from the intake manifold side. Here are a couple more pictures. I can see the valves are bent.

You must be logged in to view this image or video.

You must be logged in to view this image or video.

Time for new valves. Possibly new guides as well. I’m currently having my head built. Valves, guides, valve job and it runs about $1k parts and labor ($400-$500 in parts)

 

[jukematt]

Time for new valves. Possibly new guides as well. I’m currently having my head built. Valves, guides, valve job and it runs about $1k parts and labor ($400-$500 in parts)

Yeah I would get new valves, seals, and guides. I figured it would cost roughly that much. Thanks for the help!

Out of curiosity, if in the future I ever do have to get new rods/pistons, if I can't find any Evo ones, are there aftermarket ones that are essentially stock replacement? I know obviously all these rod and piston manufacturers have a ton of options, but are they all forged for big HP goals?

I have a Big 16G now and an Evo III 16G on hand that I was going to have ported. My goals for the car are more in the range of 300 HP; not 700, 900, etc. My other issue is I'd like to get my hands on the Complete version of Ceddy Mods with the Speed Density, boost gauge as a knock gauge... (I posted another thread about it), but it seems I'm out of luck since the site is down and can no longer be purchased.

 

[1990TSIAWDTALON]

There is nothing wrong with deburring the small marks on the pistons and if ANY damage were done I would check the ring lands and make sure the rings are not stuck. I haven't seen any do that, and even I have slammed all 16 valves into my pistons. I took mine apart to check and they were fine. You can use a dremel tool and smooth out the sharp edges and the pistons can be reused. You may be able to find a used set of stock valves if you post a WTB ad for them.

 

[AWD-Tony]

The stock piston will handle 16g no problem. Just go with emclink V3 but you’ll have to find a 95-96 ecu. They sell for about $6-700. Grab one if they pop up because they go quick.

 

[Kryndon]

Wow I didn't know. With the swapped orientation, MIVEC, etc. I didn't think these were stock replacements. Good to know! Maybe I'll get a set to hold onto. What is "CR"?

The block is flipped and the head is different but the rotating assembly is a direct replacement. When you do this swap you have to orient the pistons so the dots are still facing the timing belt. Stock valves and cams otherwise you need to degree the motor and double check for clearance issues.

I believe there should be OEM-style aftermarket pistons for you engine which you could look for, part number for a stock turbo 7 bolt piston is MD307819.

 

[jukematt]

The block is flipped and the head is different but the rotating assembly is a direct replacement. When you do this swap you have to orient the pistons so the dots are still facing the timing belt. Stock valves and cams otherwise you need to degree the motor and double check for clearance issues.

I believe there should be OEM-style aftermarket pistons for you engine which you could look for, part number for a stock turbo 7 bolt piston is MD307819.

I would have the block crosshatched for new pistons, but Idk what you mean by "degree". I searched it and found a video about finding correct TDC. Is that what you mean? Also, are you talking about the arrows on the top of the piston pointing to the timing belt when you say dots facing the timing belt?

I just want to make sure I get these things right if I ever do this myself. I'm still learning when it comes to engine internals.

 

[1990TSIAWDTALON]

Degreeing in the camshafts.

 

[jukematt]

Degreeing in the camshafts.

I have stock cams. Still necessary? I've never heard the term. Is it for finding true TDC of the piston before installing the cams? That's what it seems from searching.

 

[DSMPT]

I have stock cams. Still necessary? I've never heard the term. Is it for finding true TDC of the piston before installing the cams? That's what it seems from searching.

No, not necessary to degree cams, anyways you can't degree cams if you don't have adjustable cam gears and a cam degree kit. What Kryndon wanted to say was checking piston to valve clearance if you would use the EVO 4-9 pistons. This is not necessary if you use DSM pistons.
The cheapest way would be like Paul said you reuse your rods (Reconditioning if necessary) and reuse the pistons by smoothening the valve contact marks (If the pistons don't have any damaged like Marty mentioned above) and replace only the rings with new,. Or just get a new OEM replacement piston kit.
As TK's9d2TSi mentioned, you would probably need more money for rebuilding the cylinder head with new valvetrain components. Maybe find a complete used cylinder head would be cheaper.

 

[CrackedDSM]

For what it’s worth, if you use Evo pistons they aren’t the bump in compression some might hope for. They come out to something like 8.3:1 or 8.2:1. You can still find NPR 2G pistons brand new if you search a little, and those will hold well after the stock rods let go. They’re also 8.5:1 and no worries about turning them the wrong direction or whatever.


Everything else has been covered pretty well. To be honest with the abundance of modern tech, I’d just throw in a set of AFFORDABLE(not cheap) H beam rods and forged pistons, and call it a day. The engine will hold whatever you want to throw at it within reason, and it isn’t really that much more expensive.


But, otherwise, grab a set of NPR/Nippon Racing pistons for the 95-99 turbo 4G63, get the rods checked out by a machine shop and have them put your pistons on the rods while you’re at it. Get some new bearings, slap it together, done deal.

 

[1990TSIAWDTALON]

We have a motor that @CrackedDSM is describing (only a 6 bolt version) on a stand, getting ready to go into the White 90 GSX in the arsenal. Stock rods (but coated), ARP bolts, NPR Pistons and rings. We expect it to run very good in stock form and will push it as it goes. (Stay tuned for all that jazz).

 

[Spleen8urLSX]

It might have been said and I missed it, but unless something else was occurring a full rebuild isn’t even necessary. Deburr the sharp edges on the tops of the pistons from the valves hitting, throw your rebuilt head or a known good head on it and go.

As far as if you wanted to do full on rebuild, stock replacement pistons are sold through company names like NPR, “Nippon Racing”, ITM, and others. These stock replacements are the same thing out of the same factory as the 4g63’s came with. As far as rods go for doing a full rebuild with stock rods you can have the machine shop check them and clean them, if they find a problem with them you pick up a used replacement or 2 and have them clean and check those then use them in the damaged rods place, good as new. If a machine shop says they can’t do that and insists you need to buy “new” rods no matter what, you politely tell them thanks for their time and grab your parts and take them elsewhere as if they can’t do that they have no business working on it.

 

[jukematt]

It's interesting to hear different opinions. There's a guy at my work who knows a lot about engines and a very knowledgeable shop guy. He said the one thing is he would NEVER reuse pistons if valves hit them for two reasons:
1. He has either seen evidence of microfractures or even reused some and had a piston blow up and throw the head off the block.
2. Each knick in the piston affects the compression, so the ratio difference between the different cylinders would increase.

To be on the safe side I would get replacements, though maybe with 1G style rods since I know they are stronger.

I was actually able to find a rebuilt engine for cheaper than I could rebuild myself so I'm just going to hold onto my existing one. For now I'll probably wrap it up nice to prevent rust and later when I have my own garage, stick it on an engine stand and rebuild it.

Thanks for all the different perspectives!

 

[pauleyman]

It's interesting to hear different opinions. There's a guy at my work who knows a lot about engines and a very knowledgeable shop guy. He said the one thing is he would NEVER reuse pistons if valves hit them for two reasons:
1. He has either seen evidence of microfractures or even reused some and had a piston blow up and throw the head off the block.
2. Each knick in the piston affects the compression, so the ratio difference between the different cylinders would increase.

To be on the safe side I would get replacements, though maybe with 1G style rods since I know they are stronger.

That's not quite how it works. There are 6 bolt engines (EARLY 1G) and 7 bolt 1g. All 7 bolts use the same rods for 1 and 2g. 7 and 6 bolt rods do not interchange so you can't just use the stronger 6 bolt rods in your 7 bolt block. You would need to build a 6 bolt motor.

I was actually able to find a rebuilt engine for cheaper than I could rebuild myself so I'm just going to hold onto my existing one. For now I'll probably wrap it up nice to prevent rust and later when I have my own garage, stick it on an engine stand and rebuild it.

Thanks for all the different perspectives!

 

[Spleen8urLSX]

It's interesting to hear different opinions. There's a guy at my work who knows a lot about engines and a very knowledgeable shop guy. He said the one thing is he would NEVER reuse pistons if valves hit them for two reasons:
1. He has either seen evidence of microfractures or even reused some and had a piston blow up and throw the head off the block.
2. Each knick in the piston affects the compression, so the ratio difference between the different cylinders would increase.

To be on the safe side I would get replacements, though maybe with 1G style rods since I know they are stronger.

I was actually able to find a rebuilt engine for cheaper than I could rebuild myself so I'm just going to hold onto my existing one. For now I'll probably wrap it up nice to prevent rust and later when I have my own garage, stick it on an engine stand and rebuild it.

Thanks for all the different perspectives!

And I don’t say this in a negative way, but how many 4g63’s has he built and made good power on? You’ll find probably hundreds of us here that have reused pistons that have hit valves, some of us have done this multiple times including myself. However, you can dig through 20+ years of posts on here and it’d be a long shot to find ONE post about someone who had pistons that hit valves fail after using them, let alone due to “micro fractures in the pistons”. Sure, I can see that being true in something like a 2.2 Ecotec that had weak internals right off the rip, hell I’ve seen one of those slightly bend a rod even from hitting the valves, but not a 4g63 or 4g64.

Next time your at work with that guy ask him how many 4g63’s (not small block Chevy’s) he’s personally seen “had a piston blow up and throw the head off the block” or has built himself. Again, I say this in no disrespect and you’re learning but, what he said there is literally one of the dumbest things I’ve ever heard in regards to reusing a piston that’s hit valves in one of these in the 17 years I’ve been messing with them, and that says a lot as I’ve had even some old school engine builders tell me some pretty laughable stuff in regards to what you should and shouldn’t do when rebuilding a 4g63 but that one takes the cake. In regards to your engine, I wouldn’t go to that guy for any more advice let alone let him work on anything as if he believes that’s even possible he’s not as knowledgeable as he claims, or not in the least bit smart at all for that matter.

As far as buying an already rebuilt engine that’s not at all a bad way to go. However, if you’re not very familiar with whoever assembled and/or have seen that engine run well for a couple thousand miles in a buddies car or something, or have paperwork where a reputable machine shop performed the assembly, still plan on tearing it down and inspecting EVERYTHING. All too often with our platform someone finds a rebuilt or built 4g63, only to put it in the car and find out after 50-100 miles that whoever assembled it had zero idea what they were doing or banged it together for a quick sale. Not to talk you out of it but if origins aren’t clear and known you may be in for just as much work if not more than rebuilding what you have.

 

[1990TSIAWDTALON]

When I do builds, they all have a spec sheet. I feel it's very important for any issues down the line. Most people don't remember to jot down all the measurements and clearances etc but if you do a build yourself, do yourself a favor and at least keep a notebook of all the things you check. You will learn more and be glad you can reference that info later on.
Marty