Are ARP bolts needed in LZ2.3 big bore?

[datzenmike]

Negative. The largest stress on rod bolts is from high RPM. Approaching TDC the rod bolts must hold the rod and piston to the crank shaft and not let it fly off and hit the head. Tremendous deceleration generated at or near TDC causes the rod bolts to stretch and they will fail. On a 2.3 using a Z22 crankshaft this 'red line' can be figured out by the formula RPM X rod stroke in inches, divided by 6. This is the piston speed in feet per minute. If the answer is more than 4,000 lower the RPMs because you are approaching the failure point of the pistons, rings, rods and bolts. At 6,500RPM the piston/rings/rods are traveling at over 44 MPH and in the distance of 1.18" must decelerate to zero and back to 44MPH over 108 times a second.

 

The stroke of a Z22 is 92mm or 3.6248" so 6,500 X 3.6248 / 6 = 3,926 safe but getting close.  A Z22 crank should not be revved past 6,500 RPM..... YES you can go higher, and YES there will be lots of people who have and say they do this all the time but sustained 4000 ft/min piston speeds will fail. If you want to go higher reliably, you will need special strength fasteners and lighter aluminum or titanium rods to handle the stresses.

 

 

(wow the coffee is good today)

[510SSS]

Ya as usual Mike is right, the Z22 having the shorter rods and not revving as high as the Z20e, or even L16-L18 for that matter, you should be able to manage around town if you are just building a street motor for stoplight to stoplight, if you're doing SCCA though or decide to go for a cam that makes power high in the rev range, you might wanna think about utilzing ARP fasteners.

[Stoffregen Motorsports]

While there is a limit to what the stock fasteners can take, the stock rod bolts are usually ok in a street motor. 

 

The equation I use when deciding whether or not to use ARP rod bolts is a simple risk-vs-reward calculation. How much do I want to protect my investment?

 

But there's also another equation I use in every decision on every part of every job, need-vs-want. Do I need them? Mike's math says no, and I believe it.

 

Mike's math is good, and it's helpful, but if this were a $6500 investment, damn right I'd put ARP rod bolts in it.

[scooter]

Ive ran my 2.3 up to 7500 a few times, but I usually shift it 6500-7000. I wouldn't run it that high continuously. Even with the arp bolts rthats probably getting to the limit of stock rods. They seem to handle the 75 shot just fine.. So far. Don't know how far people have pushed the stock rods with power adders..

 

Mike's math is right on, and even with some nice rods it could still fail.

[scooter]

A good reason to bore to 89mm is so you can open the head up more on the chamber side of the valves to have less valve shrouding. Also no replacement for displacement.

[datzenmike]

Another advantage to boring to 89mm is so you can open the head up more on the cylinder side of the valves to have less valve shrouding. Also no replacement for displacement.

[Billychar]

I had a d21 with Z16 carb in. Got a Z22 and some cheap KA24DE pistons & rings. The coating was removed from the dished piston tops when cutting them down 1.4 mm for clearance . We floated the small end pins in the Z22 rods, & overbored the cylinders 0.078" ,decked the block and surfaced the head . I got an aluminium flange made for a Weber 36 dcnvh (12-100) synchronous carb. [ex.Maserati bi-turbo] and using a hole saw opened up the standard mount on the intake and had the new flange welded on top . A fellow fitted the flywheel into his lathe and followed my instructions removing cast from the edge behind the ring gear and from the two faces until we got down to sufficient lip to stop the ring gear at zero and weight to 12 Ib's . I was chomping at the bit to score a good cam for it also, but it ran for 18000 Km with no trouble apart from it had to be stalled when switching off once warm or it pre-ignites or compression ignites ,running on with terrifying sounds and events including  running backward in a forward gear one time . Performance increase was quite impressive but it wouldn't rev  over 4000 very smoothly. At low revs it pulled like a horny schoolboy although some discretion was required with throttle to prevent pinking down low. Coupled to the 4.88:1 diff ratio and being a truck it did everything I could expect of it. I have a KA24E cylinder head and was such temptation to bolt that on top but for the timing chain length and questions over the oil drains back to sump clashing with coolant passages. The bottom line is you can do the Z22 and oversize pistons from KA or Z24. Also the V6 range of Nissans has good options for pistons. (2 mm O/size) No trouble with cooling , gasket leaks or blowing. Otherwise however the L head or turbo the Z , because what you read about the restriction gets worse with cubic capacity and none of my Z's N.A. performed despite tinkering with the standard engine. I've had five with z engines, Gazelle S110 , Sylvia turbo , navara single cab flatdeck, and two crew cab wellside trucks . All went suitably but the Z22 hybrid was the pinnacle of the group as far as performance and economy goes. 

[Stoffregen Motorsports]

That was a mouthful.

[Billychar]

Yea!