Line-ream mains on an A-series, any point?

[pdp8]

On straight-sixes and some V-8s, it's a common longevity-thing to trim the main-caps and ream them uniform and in a line.  Was the Japanese machining good enough and the A-series block short-enough that this is a waste, or is there some value in it?

 

 

[Tom1200]

So over the last 38 years we've rebuilt / built 5 engines (4 of them for racing) and I've never done anything more then install fresh bearings in the lower end.

 

The only failures I've had were heat related head gasket failures.

 

My so called race motors are mildy tuned and I only rev them to 8200 rpm it's still far more than a street motor will be stressed.

[Stoffregen Motorsports]

Line honing a Chevy V8 is common because machine shops gotta make money.

 

As Tom said, in all the years building Datsun race motors, we only ever line honed them if they were damaged and we didn't want to start with a new block.

[datzenmike]

The proof would be in plasti-gageing everything for peace of mind but I doubt very much it needs this much attention and expen$e.  If removing the main caps keep in order for when put back. The #2 and #4 might actually interchange.

[Tom1200]

Mike, I probably shouldn't admit this but I've never even plasti- gauged a single set of crank bearings in the A-series.

 

I use a digital caliper to measure the journals and cross check it the manual.......then call it a day.

 

These things are stout and pretty "Tom" proof.

[datzenmike]

It's quick and cheap and only used to show if there is any concern areas, then digital calipers would be needed to narrow it down more accurately. Datsuns were made pretty good back then.

[Stoffregen Motorsports]

14 hours ago, Tom1200 said:

Mike, I probably shouldn't admit this but I've never even plasti- gauged a single set of crank bearings in the A-series.

 

I use a digital caliper to measure the journals and cross check it the manual.......then call it a day.

 

These things are stout and pretty "Tom" proof.

Tom, you're probably using the same brand of bearing over and over again, which aids in consistency and repeatability.

 

Some of these modern brand name bearings, like the kind you get at Rockauto, are less than consistent in their thickness.

 

My first go-around with actual gauges consisted of a dial bore gauge I bought at Harbor Freight and a pair of micrometers I got used at a swap meet. They don't need to measure accurately because your taking a relative measurement. Relative to the two parts of the assembly. The block and the crank.

[Tom1200]

Yes I'm pretty sure my measurements are relative. 

 

I'm also using a cheap caliper so that probably makes the measurements even more suspect.

 

I also get the bearings from Rockauto I think Federal Mogul

 

Thankfully the A-series motors are Tom proof........that or God really does look after fools and little children

[pdp8]

Plasti-gauge won't tell me if the bores aren't in-line, but hearing nobody worries about it and knowing the block is short and fairly stiff, I guess I won't fret over it.

The manual does say the main caps should be installed and torqued before boring the cylinders, so that seems like a thing to do.  I'd really like to have a head or pretend-head on there to pre-distort the block, but unless someone knows someone with one, I might not take the time to make one for just a couple engines.

 

Interesting the point about measuring tools, in measuring the valve-stems I first tried calipers (guessing sticks) and wasn't happy with the results, next broke out a well-used Starret micrometer, didn't like those results, calibrated it against a gauge-block of a nearby dimension (.3), still wasn't happy, so made up a stack of gauge-blocks and used those to really and finally have numbers I couldn't doubt.  At issue is the fact there is .0006" between max and min, and that I'd expect the unworn part of the valve stem to be somewhere between the min and max values, but the genuine Nissan valves have stems that are at most .0002" over the min values in the service manual and some are actually below the minimum value in the manual at every part of the stem!  Interestingly, a third-party valve out of another head is well withing spec.  Just weird.

 

[Stoffregen Motorsports]

Rebello may have a torque plate for the A motor. I don't remember, it's been a long time since I worked for Dave. He can bore and hone the block though, so if you need it done right, have them do it.

 

Re- mics. When I was building engines for a living, I had trouble with the various machine shops we used. My measurements were always different from theirs. I'd send a crank out with specific instructions and get it back different. I finally went around to the machine shops we used and calibrated my mics against their mics and wrote the numbers down on the mic cases, so I could now have the work done using measurements I took myself bu then adjusted per the discrepancies I wrote down. Never had a problem after that.

[Tom1200]

The machine shops I used did indeed want the main caps on the block.

 

As for the valves they were either SI (they have narrowed stems that flow more) or out of my bag of valves that I collected over the years. Note it's literally a ziplock bag of old Nissan valves.

 

I'm sure most real engine builders would shriek in horror about the manner in which I slap motors together. The only operation that gets any extra attention is the valve job. I have my buddy who builds motorcyle racing games engines do that.

 

I know I'm giving up that last bit of horsepower but for my purposes it doesn't matter.

Edited July 20, 2023 by Tom1200

[pdp8]

22 hours ago, Stoffregen Motorsports said:

Rebello may have a torque plate for the A motor. I don't remember, it's been a long time since I worked for Dave. He can bore and hone the block though, so if you need it done right, have them do it.

Who is this now?  Contact info or a link would be a help.

Are you referring to www.rebelloracing.com ?

It's pretty amusing to have a motor where shipping it UPS for machine-work might not be cost-prohibitive.

Edited July 20, 2023 by pdp8

[Stoffregen Motorsports]

2 hours ago, pdp8 said:

Who is this now?  Contact info or a link would be a help.

Are you referring to www.rebelloracing.com ?

It's pretty amusing to have a motor where shipping it UPS for machine-work might not be cost-prohibitive.

Yes, Rebello Racing. Don't try to contact them by any means other than phone. No email, text or website contact. They won't reply to it.

 

You're in the bay area? So are they.

[Stoffregen Motorsports]

13 hours ago, Tom1200 said:

 or out of my bag of valves that I collected over the years. Note it's literally a ziplock bag of old Nissan valves.

 

I'm sure most real engine builders would shriek in horror about the manner in which I slap motors together.

I've built many an engine with the only new part being a head gasket. And they all ran great. The L16 race motors I would build for myself were all used parts, yes, even the rings.

[pdp8]

22 hours ago, Stoffregen Motorsports said:

I've built many an engine with the only new part being a head gasket. And they all ran great. The L16 race motors I would build for myself were all used parts, yes, even the rings.

I've used a ton of used parts in motors over the years, after all, the new parts are only new until you turn the key that first time!

A little something for all you guys recycling parts, this outfit claims to be able to make parts bigger:

https://www.motortrend.com/how-to/1511-save-some-money-by-coating-your-pistons-with-abradable-powder-coatings/

Since the motor I'm working on has three good bores and the fourth is about .004" big, I could have honed that fourth bore straight and had one or more pistons coated rather than all new pistons and boring the block.
 

[Stoffregen Motorsports]

That coating doesn't last long.

[pdp8]

On 7/21/2023 at 9:01 AM, Stoffregen Motorsports said:

That coating doesn't last long.

Good to know.  I did order some of the Cerakote for the piston tops, combustion chambers, runners in the head, not that I have trouble with an A-series overheating, but it will be interesting to see how the process works.

I did reach out to Rebello, they said they might still have a torque-plate for A-series but to call back Monday since they were closed Friday.  Fingers crossed!

[datzenmike]

I think ceramic coating of the piston top and combustion chamber a great idea. Efficiency is all about converting heat to mechanical work. All the heat removed by the cooling system goes to waste. Piston tops, combustion chambers and valves all rob heat away from the hot expanding gasses. If you get 3-4% increase in efficiency this is 'free' or reclaimed power normally lost. In addition the combustion chambers run cooler reducing pinging.