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Z24 rebuild kit


frankendat

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My search capabilities are failing me, because I am confident this has been asked before. Is there a Z24 kit that is better quality or preferred? I could not find any Z24 kits on rockauto, on ebay and amazon, there seem to be 3 flavors: DNJ,  DNJ Master, and Evergreen. The DNJ Master is the same as the DNJ with the addition of a water pump, oil pump, and timing kit. The best option, thus far, would appear to be purchase of a DNJ kit, a separate  timing kit, a separate oil pump (from a KA) and a separate water pump.

 

My rationale is, according to the rebuild manuals, it is recommended to replace the water pump, oil pump, and timing kit, when rebuilding engine internals. Sound advice on ratsun is replacing the Z24 oil pump with a KA pump, so purchase of a DNJ Master kit that includes an oil pump is not necessary. I have not found any information on a water pump or timing kit upgrade option. My timing chain and gears, are worn, but within spec, however it has been strongly suggested that a new timing kit,when rebuilding and engine, is money well spent.

 

Are there options that I am missing? Is my reasoning sound? In case  it changes your answer. I have removed the engine, stripped it to the block. The pistons and bearing will be replaced.

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Engine kits almost always use inferior components. Right, that sounds like a huge generalization, but in the case of the Datsun/Nissan kits, they almost always use aluminum engine bearings (as opposed to tri-metal bearings), the rings are usually cast iron (sprayed chrome would be better, chromoly is best), and the gaskets included int he kits are thin cardboard (not the compressed fiber gaskets like OEM).

 

Sourcing the individual parts is more time consuming, but well worth the effort.

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Some companies make rings and that's all they do so they do it right same with bearings. A kit with everything is probably a mish mash of generic parts selected by cheaper price. It used to be Hastings rings and Clevite bearings with Felpro? gaskets. I can't vouch for their quality today.

 

Cast iron rings are good for quick break-in on less that perfect (but good enough) cylinders given a quick hone job. If boring to oversize and new oversize pistons the cylinders are perfectly round and without taper and you can use the latest chrome moly rings.

 

Total timing chain renewal is a very good idea as they are very difficult to get at later. Water pump I wouldn't bother changing till it needs to be changed and it bolts to the outside of the engine and easy to get at. KA oil pump is also good idea. 

 

If the head is getting new valve seats be sure you ask for the newer hardened ones.

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On 6/21/2020 at 11:43 AM, Stoffregen Motorsports said:

Engine kits almost always use inferior components. Right, that sounds like a huge generalization, but in the case of the Datsun/Nissan kits, they almost always use aluminum engine bearings (as opposed to tri-metal bearings), the rings are usually cast iron (sprayed chrome would be better, chromoly is best), and the gaskets included int he kits are thin cardboard (not the compressed fiber gaskets like OEM).

 

Sourcing the individual parts is more time consuming, but well worth the effort.

 

On 6/21/2020 at 12:43 PM, datzenmike said:

Some companies make rings and that's all they do so they do it right same with bearings. A kit with everything is probably a mish mash of generic parts selected by cheaper price. It used to be Hastings rings and Clevite bearings with Felpro? gaskets. I can't vouch for their quality today.

 

Cast iron rings are good for quick break-in on less that perfect (but good enough) cylinders given a quick hone job. If boring to oversize and new oversize pistons the cylinders are perfectly round and without taper and you can use the latest chrome moly rings.

 

Total timing chain renewal is a very good idea as they are very difficult to get at later. Water pump I wouldn't bother changing till it needs to be changed and it bolts to the outside of the engine and easy to get at. KA oil pump is also good idea. 

 

If the head is getting new valve seats be sure you ask for the newer hardened ones.

 

Thank you gentlemen for guidance. I made some inquires, on the rebuild kits that I was considering and you were correct; the bearings are aluminum and the rings cast iron. To measure the cylinder bore and the bearing journals, I have a digital caliper. I would like to provide the pistons, rods, bearings and crankshaft to the business  that is boring the block, for a precise fit and for reassembly of those components. My Z24 was ala carte and without history. My preference is to bore the least amount possible. Similarly,I would like the bearings to be the least undersize. When research engine replacement parts, the standard overbore is 0.20 (50mm) oversize and for bearings 0.10 (25mm) undersize. Is there a method of using my digital caliper to confirm the block and bearing races are not worn to the point of requiring more than 0.20 overbore and/or 0.10 undersize bearings?

 

 

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It cost the same to over bore to the max, same with replacement pistons and rings. Go big.

 

If machining the block don't bother with cheap cast rings. Get the much harder and long lasting moly ones.

 

You don't need undersized bearings unless there is a problem with the crankshaft and it needs to be ground down. Almost never happens as the bearing shells are soft and do all the wearing down, and are cheap and easy to replace. Crankshaft damage is usually a spun rod bearing. The machinist doesn't need the crank other than to check the journal diameters or if he's the one putting it together.

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It's not likely that in your lifetime you will ever need to bore the engine again, so I would go the max bore size, which is usually .040", inches, or 1.0MM metric.

 

Cranks on Nissans are very stout and often times only need a polish. I would tell the machine shop to polish only if possible and use standard size bearings.

 

One word of caution- on the pistons, since there were a few variations of that engine, be sure the pistons you are ordering have the same dish/dome/flat top, whatever. If you want to increase the compression, look into one of these variations as a possibility. And be sure to do the engine math to calculate the compression ratio too. Around 10:1 CR is great for a Nissan street engine.

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5 minutes ago, datzenmike said:

It cost the same to over bore to the max, same with replacement pistons and rings. Go big.

 

If machining the block don't bother with cheap cast rings. Get the much harder and long lasting moly ones.

 

You don't need undersized bearings unless there is a problem with the crankshaft and it needs to be ground down. Almost never happens as the bearing shells are soft and to the wearing down, but are cheap and easy to replace. Crankshaft damage is usually a spin rod bearing. The machinist doesn't need the crank other than to check the journal diameters or if he's the one putting it together.

 

Thank you for the prompt response,  regarding the pistons, I have found forged pistons to be cost prohibitive, but would like better than the made in china pistons. For a middle ground, hypereutectic pistons. Keith Black offers performance alloy cast pistons. Hasting rings are still considered quality. It seems Keith Black pistons with Hastings chrome rings would be the ticket for a builder on a budget. Are there other options to consider before  spending my hard earned?

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2 minutes ago, Stoffregen Motorsports said:

It's not likely that in your lifetime you will ever need to bore the engine again, so I would go the max bore size, which is usually .040", inches, or 1.0MM metric.

 

Cranks on Nissans are very stout and often times only need a polish. I would tell the machine shop to polish only if possible and use standard size bearings.

 

One word of caution- on the pistons, since there were a few variations of that engine, be sure the pistons you are ordering have the same dish/dome/flat top, whatever. If you want to increase the compression, look into one of these variations as a possibility. And be sure to do the engine math to calculate the compression ratio too. Around 10:1 CR is great for a Nissan street engine.

Thank you, I appreciate your and Datzen Mike's  expertise and will bore to 1mm.

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Forged pistons are over kill unless running nitrous or turbo. Unlike hyper eutectic pistons the forged pistons swell more with heat so are loose in the bore cold and expand to closer tollerance and noisy on cold start up. This is the advantage of hyper eutectic as they are 12 -20% silicon and don't expand much when heated so they will run quieter in a tighter bore when cold. If you go forged make sure the machinist has them to measure so he bores the proper clearance.

 

A stock Z24 piston has a 15cc dish and a compression of 8.25. If you substitute 1mm oversize KA24E pistons  that have a 2.8cc dish your compression would be 9.68

 

 

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In an attempt to create a quality rebuild kit at a reasonable price, I searched for 1mm over hyper eutectic pistons and tri metal main bearings/rod bearings. Below are the options that presented best value, in terms of cost/quality. In the words of former New York mayor Ed Koch, "How am I doing?"

 

https://www.summitracing.com/parts/hsn-2c4452040

 

https://www.summitracing.com/parts/uem-9115-1-0mm

 

https://www.summitracing.com/parts/cle-ms2042p

 

https://www.ebay.com/itm/Rod-Bearing-Set-fits-Datsun-Nissan-L16-L18-L20-Z20-Z22-Z24-Standard-/172357684900

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10 hours ago, frankendat said:

In an attempt to create a quality rebuild kit at a reasonable price, I searched for 1mm over hyper eutectic pistons and tri metal main bearings/rod bearings. Below are the options that presented best value, in terms of cost/quality. In the words of former New York mayor Ed Koch, "How am I doing?"

 

https://www.summitracing.com/parts/hsn-2c4452040

 

https://www.summitracing.com/parts/uem-9115-1-0mm

 

https://www.summitracing.com/parts/cle-ms2042p

 

https://www.ebay.com/itm/Rod-Bearing-Set-fits-Datsun-Nissan-L16-L18-L20-Z20-Z22-Z24-Standard-/172357684900

 

Everything looks good so far, as long as the pistons match what you have.

 

I like the idea of using the KA oversize pistons for two reasons - as Mike mentioned, you can raise the CR by over a point, and second, they use a better, more modern ring pack (steel top ring and a more compact grouping).

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2 hours ago, Stoffregen Motorsports said:

Everything looks good so far, as long as the pistons match what you have.

 

I like the idea of using the KA oversize pistons for two reasons - as Mike mentioned, you can raise the CR by over a point, and second, they use a better, more modern ring pack (steel top ring and a more compact grouping).

Thank you for weighing in SM

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