Minimum cylinder wall thickness

[Ja1lb8]

A bit of background, building a stroker l28 nissan, been done a million times but I want to use a talldeck block out of  a diesel with a petrol head. Also not uncommon

Going to offset grind the crank for max stroke.

 

I have my diesel block stripped down and brought a cheap ultra sonic tester in the hopes of measuring bore wall thickness.

After a bit of research and aware that the probe on these testers isnt any good on the inside of a cylinder bore because of the radius i found a guy who just sat the probe in the bore with some sandpaper and shaped the end of it so it couples properley to the bore diameter.

 

 

After doing this it pretty much makes the probe usless for flat surfaces , anyhow calibrated it on a known thickness as best I could using calipers and verniers to get a measurement down one of a water jacket and then measured in four places on all the cylinders.

 

Thinnest being about 3.7mm which i thought was pretty thin for  a diesel that hasnt been bored out before.

 So my queastion is what would be a guide for  minimum thickness of the cylinder walls. Well be naturally aspirated

 

[SOHC]

0.200" on the thrust side and 0.135" on the non-thrust sides on a Flathead v8

[sentra]

man i gave up trying to measure it and just cross sectioned a block with a saw to check properly, i worried that the roughness of the casting was accounting for too much of the reading when allready on the "limit"

there are some interesting posts i think on jolopy journal talking about some dude building (successful) v8 drag motors and after years of running the same combo he measured the walls and they were paper thin like 2mm and down to 1 at the bottom

[SOHC]

A lot of those vintage blocks the cores shifted when they were pored so it would be thick in places and thin in others, and the water jackets got rusted badly over time.

[RUNAMUCK]

once you start pushing the envelope on bore size, a torque plate becomes mandatory for honing. 

[Yowzer]

Wots a tork plate?

[Yowzer]

Oh I see. Thanks uncle googles

[SOHC]

Fill the blocks water jacket with plaster or grout and you will have a strong engine, another old trick.

[Yowzer]

And run on nitro

[RUNAMUCK]

And run on hydrazine

Fixed!

[BobbyBreeze]

.120" / 3mm is the 'normal' minimum bore wall thickness to aim for. You can go less but generally have deteriorating gains from increased blow-by. Grout filling the block, bottom end girdle and external bracing can all help if you want to push the limit. 

 

What size is the probe on your sonic tester? Should be able to find a tiny probe 2-3mm diameter that will have no issues doing cylinder walls. 

 

LD blocks with petrol heads is not common at all, it just isn't worth bothering with compared to running a petrol block. Most LD blocks are not able to be bored to take a stock L28 piston (86mm) as you have found. I assume you have a V07 block?

 

You are better off getting a L28 and slugging it out to 89mm for the classic '3.1 Stroker'. The shorter rod & bigger bore will make more power and torque than an 86mm bore long rod LD block.

[fletch]

It's a v57 block which apparently has thick walls. But has not.

The taller deck gives more room for more stroke from am offset ground crank.

Obviously only worth it if you can also go to 89mm or more bore

[RUNAMUCK]

I read one some skidder forum guys would start with A RD block for sustained high boost circuit racing applications. 

[M.H.]

It's a v57 block which apparently has thick walls. But has not.

The taller deck gives more room for more stroke from am offset ground crank.

Obviously only worth it if you can also go to 89mm or more bore

Taller deck also means better rod stroke ratio

[fletch]

Taller deck also means better rod stroke ratio

Yes, but only really matters on high rpm motors. This one won't see over 7000 so the only reason for doing it was the supposedly thicker bore that could go out to 89 or 90mm, and the taller deck to more easily fit a bigger stroke.

[fletch]

I read one some skidder forum guys would start with A RD block for sustained high boost circuit racing applications.

Yea it's the heavier casting rfb block. I think they use them some places as they are taller than the rb25/26 block.

Most people just run the rb30 block.

The LD is just an L28 block but 3/4 taller and bit smaller in the bore.

With a filthy deez head on it

[BobbyBreeze]

Yeah I have seen the dude in South Africa has a thick wall V57. He is the only one I have ever heard of finding one. I know some L builders have gone through 10s of LD blocks looking for decent thickness and not found any. 

 

You are better off with a short rod in a road motor anyway. I can't see any need for the taller block unless you are going over 90mm stroke. 

[RUNAMUCK]

Yes, but only really matters on high rpm motors. This one won't see over 7000 so the only reason for doing it was the supposedly thicker bore that could go out to 89 or 90mm, and the taller deck to more easily fit a bigger stroke.

I actually thought longer rods made more torque everywhere? Reduced rod angularity transmits energy from the piston more effectively. Or somesuch.

[fletch]

I actually thought longer rods made more torque everywhere? Reduced rod angularity transmits energy from the piston more effectively. Or somesuch.

One of the main reasons is slower acceleration of the piston at TDC and bdc.

For backyard cowboys like us it means you can use a cheaper piston and rod due to lower stresses.

I read somewhere that the screaming v10 f1 motors had to run a real long rod as at 20k rpm the piston would out accelerate the flame front at the point of ignition and lose torque!

[M.H.]

One of the main reasons is slower acceleration of the piston at TDC and bdc.

For backyard cowboys like us it means you can use a cheaper piston and rod due to lower stresses.

I read somewhere that the screaming v10 f1 motors had to run a real long rod as at 20k rpm the piston would out accelerate the flame front at the point of ignition and lose torque!

Longer stroke equals higher piston speed for a given rpm