Stupid Main/Head stud/bolt Z24 question

[frankendat]

Before I make a terrible ignorant mistake, in a Nissan Z24 engine, are there 10 "MAIN" studs or bolts, AND 10 "HEAD" studs or bolts, AND are these studs or bolts THE SAME, (diameter, length, thread, etc.

 

[datzenmike]

Different. Different part numbers. Main cap bolts would be thicker than the head bolts. At this point the length doesn't matter.

 

The main bearing cap bolts are the same as the L16 bolts.

[frankendat]

Thank you DatzenMike

There are the same number of Main bolts and Head bolts, correct?

[frankendat]

I am 99.9999 sure there are 10 and I don't want to waste a question. There seems to be a consensus that a common upgrade is to use L28 bolts. Pasted below is from the datsun parts website:

 

These main bearing cap bolts are a higher bolt class (grade) than the regular L and NAPS-Z bolts, and can replace the OE bolts

The higher strength bolts can be torqued to a higher than stock torque value (60 lb/ft), but if you want to run the higher torque, you must align-bore the main bores at the higher torque

If you torque to the higher value without doing this, you will oval the bearing bores and lock up the crank

The Nissan Motorsports catalog reads as follows:

H/D MAIN CAP BOLT
These heavy duty bolts are constructed from a higher grade material,
which allows a 50% increase (to 60 lb/ft) in the torque setting
Heavy duty bolts are marked with a small "12"

 

What is meant by "align bore at higher torque"?

[datzenmike]

There are 5 main bearing so yes 10 bolts. 58-60 ft pounds is the torque rating for the Z24.  50% stronger is totally not needed or worth the bother.

 

Align bore means the caps are installed and torqued to 90 ft lbs (I assume this is the 50% more) the caps may deform slightly so a large 'drill' is run through the caps where the crankshaft would be normally. If distorted, this lines them up and trims them perfectly round for the bearings.

[frankendat]

On 5/24/2021 at 6:02 PM, datzenmike said:

There are 5 main bearing so yes 10 bolts. 58-60 ft pounds is the torque rating for the Z24.  50% stronger is totally not needed or worth the bother.

 

Align bore means the caps are installed and torqued to 90 ft lbs (I assume this is the 50% more) the caps may deform slightly so a large 'drill' is run through the caps where the crankshaft would be normally. If distorted, this lines them up and trims them perfectly round for the bearings.

 

First, I am thankful for your council and your opinion holds sway. Regarding the cap bolts, it is my understanding, 60 ft. lbs. of torque is the total after adding the additional torque. (original torque required for stock Z24 cap bolts - 40 ft. lbs, apply 50 percent increase for 280z bolts + 20 ft. lbs = 60 ft. lbs cap bolt torque.)

 

In other news, a fellow dropped his price on the fancy (most likely unnecessary) strong bolts and I jumped - ARP  Rod bolts, 280Z Main bolts, ARP Head Stud Kit for $200 (price includes tax+shipping.

[datzenmike]

If you increase the bolt torque you will likely 'squash' the main caps out of round. This is why I mentioned that the caps should all be torqued to the new amount and then have them all line bored perfectly round and in a straight line. I don't know how much this will affect them as stock bolts are good enough for me. Ask 

Stoffregen what he thinks about line boring for this.

[frankendat]

Thank you DatzenMike, I understand and will comply 🙂

[datzenmike]

You could install with Plastigauge and torque to 60 and check the squash.

[frankendat]

8 hours ago, datzenmike said:

You could install with Plastigauge and torque to 60 and check the squash.

I contacted Stoffregen and he recommended assembling to check clearances as well.

 

So, that will be the plan after the bolts arrive. Thank you for your continued guidance.

[Stoffregen Motorsports]

I'll just paste my reply to Keith below.

 

No, you don't need to line bore when you use stronger bolts with more torque capacity. He is right in theory, but in practice, there is virtually no change when upping the torque.

 

You should, however, check your bearing clearances to verify that you have enough. With modern oils, you can run tighter clearances anyway so even if the new bolts tightened up the clearances, they would probably be within range. Acceptable bearing clearances are between .0018" and .003". Ideally you'd be in the .002" range on the main bearings and around .0018" on the rod bearings.

 

There are a ton of other things you can do while you're "down the rabbit hole". You can hit every sharp corner with a dremel tool or carbide cutter on a die grinder, then sand it smooth with some emery cloth, you can also drill the #2 and #4 main bearing oil galleys (and the hole in those bearings too) for more oil flow to the rods. Chamfer the oiling holes where they come into the bearing saddles, and you could even give a slight chamfer to the oiling holes in the crank itself. Anything to help aid the oil in getting where it needs to go.

 

The bearing saddles and main caps should be hit with some fine sandpaper too, to make them nice and smooth and remove any burrs. Also. give a slight chamfer to the top of the cylinder bores to make it less likely of chipping a ring upon assembly (sanding roll on a die grinder). Assemble the rod and cap and torque them down and gently hit the sides on a belt sander or on sandpaper on a plate of glass to make the sides nice and smooth. I also tap the timing chain guide holes to 1/4-28 and use grade 8 bolts there. Complete block prep including all of these mods takes only about two hours, so I think it's time well spent.

 

If you want more specific details on these steps, you can google "engine block race prep" or look in the "How to hotrod your Datsun" book. I believe all that is covered in there.

[datzenmike]

2 hours ago, Stoffregen Motorsports said:

I'll just paste my reply to Keith below.

 

No, you don't need to line bore when you use stronger bolts with more torque capacity. He is right in theory, but in practice, there is virtually no change when upping the torque.

 

 

Good to know, I wasn't sure having never gone to this trouble.

 

Is there some reason a Z24 would need this?

[frankendat]

For me, it is attempt to gather any and all, budget friendly, low hanging, efficiency and performance fruit. It is my hope, that applying multiple unnecessary, procedures, (unnecessary in the sense that increased performance is minimal) the aggregate, will provide quantifiable increase engine efficiency or engine power.

 

I

[datzenmike]

Stronger head and main bolts won't really increase efficiency or performance. If you want increased efficiency, how about ceramic coating of the combustion chamber and piston tops?  Gas engines are at best about 30% efficient at converting heat from combustion into usable motion. Most goes into heating water and hot exhaust out the tail pipe... and noise. A ceramic coating acts like an insulation and contains the heat of combustion in the cylinder where it can expand the air and push on the piston tops. Efficiency is increased, not a lot but it is measurable. How about fully floating rods? The stock piston pins are pressed into the rods and only the piston is free to spin on the pin. The rod small ends can be bushed so the pin and rod are free to rotate independently of each other. Naturally the piston will need grooves cut in the pin bores for cir-clips to contain the pin from moving side to side and hitting the cylinder walls. This is a friction reducing modification that frees up power. Increasing the compression ratio is an easy way to increase efficiency. The smaller the combustion chamber is made in relation to the displacement, the less heat escapes through it into the water jacket or through the piston and absorbed by the oil. The Z24 has a relatively mild compression ratio of 8.2 so raising it (again, modestly) can extract more out of the fuel used in it. Each of these are only a tiny but measurable amount of efficiency but added together and with others, accumulate and make a difference. This is built in and permanent, it doesn't wear out and it doesn't go out of tune.

[frankendat]

The stronger bolts are a kind of belt and suspenders (or belt and braces, as foreigners might say) Increasing the compression ratio is a certainty and inspired the stronger bolts. I would have forgone the fancy bolts if I didn't get a good deal on them. As far as the coatings, I am all over it and coating the majority of parts in specialty coatings, some that reduce friction, some that release heat, some thermal barrier and even some I coated, because my garage is neither air tight, nor climate controlled, and coated parts do not rust.

I like the floating rod idea and will look into it further. A while back, there were forged connecting rods on aliexpress for the Z24 for $250,(total price including shipping for a set of 4) which was very tempting, but luckily disappeared, before I could gather the funds. Lowering rotational mass is usually to facilitate higher rpm, but I am not pursuing high rpm and thought at lower rpm, lighter, stronger connecting rods would decrease rotational mass and decrease engine load.

Thank you  

[datzenmike]

Mass absorbs energy to spin it up to speed so reducing it frees up power to do move the vehicle.