L20b motor rebuild - Piston and Parts required?

[second chance]

So I did a bit more digging, I found a shadbolt 721 stamp on the cam. What application would suit this cam?

 

 

721 Profile: (purported to be a copy of Racer-Brown #391-R, pg. 54 of the later Steve Smith book.)

 

306 degrees duration (45-81-81-45)

 

Overlap: 90 degrees! (yeowch!, that's racy!)

 

Lift: 0.582” at the valve

 

Cam oiling spray bar MUST be used, along with max effort valve springs, and maybe even lightweight spring retainters

[datzenmike]

That's full on racing cam I'd just forget about it or sell it. Stock is 248⁰ and 0.413" lift. Stock overlap is about 30 degrees. 90 must be a miss print.

[second chance]

11 hours ago, datzenmike said:

That's full on racing cam I'd just forget about it or sell it. Stock is 248⁰ and 0.413" lift. Stock overlap is about 30 degrees. 90 must be a miss print.

Thanks, any idea where the best place would be to sell the cam? Looks like I won't be needing it.

[Stoffregen Motorsports]

Off the shelf cams have a couple downsides to them. First of all, most off the shelf cams have profiles dating back decades. Second is, they are pretty generic.

 

Why is a modern profile more appealing? Because things have changed in the Datsun L series world. Much has been learned and the cams now days can be bigger while offering more driveability, better idle and less wear on valvetrain components.

 

Why is a generic cam less appealing? Because it's a one size fits all cam. If you want a cam tailored to your engine and driving style, these generic cams are not always the best choice.

 

My suggestion - pick up the phone (yes, phone) and call someone who builds Datsun engines and get a cam from them. The go-to guys I know are Rebello and Ermish, but there are other Datsun engine builder out there.

[second chance]

6 minutes ago, Stoffregen Motorsports said:

Off the shelf cams have a couple downsides to them. First of all, most off the shelf cams have profiles dating back decades. Second is, they are pretty generic.

 

Why is a modern profile more appealing? Because things have changed in the Datsun L series world. Much has been learned and the cams now days can be bigger while offering more driveability, better idle and less wear on valvetrain components.

 

Why is a generic cam less appealing? Because it's a one size fits all cam. If you want a cam tailored to your engine and driving style, these generic cams are not always the best choice.

 

My suggestion - pick up the phone (yes, phone) and call someone who builds Datsun engines and get a cam from them. The go-to guys I know are Rebello and Ermish, but there are other Datsun engine builder out there.

Thanks but I'm not specifically looking for a different cam.... I literally inherited this cam yesterday and was wondering what it was or the application it was ground for. 

I have no problem calling shops to get what I need but I don't like wasting anyone's time. I figured the forum was a good start, guys have been great on here answering questions as time permits. 

I know know what I have now, next step is going to be finding someone that can use it.

[datzenmike]

Start here, maybe someone  will suggest someone. may not even be a member just someone perusing the forum.

 

https://ratsun.net/classifieds/category/6-datsun-parts/

[Rat-a-tat-Dat]

Bystander question, curious to know if these L20B engines are prone to head gasket failures?

I'm on my second since procuring this vehicle.

[Draker]

9 hours ago, Rat-a-tat-Dat said:

Bystander question, curious to know if these L20B engines are prone to head gasket failures?

I'm on my second since procuring this vehicle.

no, they’re not. Probably a warped head or engine deck, or cooling is not sufficient.

[datzenmike]

Agree. It's not a significant problem on L series engines and seems to be mostly on Z24 blocks but is preventable. If the L series has been over heated it can cause the head to 'warp'. I had a head given to me, and no wonder. When I checked it, it had a high spot 0.015" or pucker right between cylinder 2 and 3. To check you need a very good straight edge laid diagonally across the length in an X and try to slide a feeler gauge anywhere under it. Nissan allow up to 0.004" of warp or about two thicknesses of newspaper. This can be sealed by the head gasket but less is best. Mine was almost 4 times the allowable limit.

 

Head and block surfaces should be spotlessly clean for best results. Do NOT use any sealers or gasket coatings this isn't the '50s and gaskets today are very good. Make sure the head bolts are clean and undamaged, they are totally re-usable. Clean the threads out in the block also.

 

R  A  D

7.......8

3......4

1.......2

5......6

9.....10

 

This is the tightening pattern, more or less tighten from the middle outward. Do this in 3 stages. First to 20 ft lbs, then 40 ft. lbs. and finally 60 ft. lbs. Use a good torque wrench. The head gasket does not require it to be re-torqued later after a few runs but if you feel the need loosen one bolt and immediately tighten to 60 ft. lbs. Only when this bolt is tight do you move to the next bolt. Using this method you can do in any order you like.

 

With the rockers out I pulled the head back and forth on a large sheet of glass covered with 80 grit sand paper. Finished with 150 grit.

 

 

 

 

 

 

 

Took about 45 min. Or if you have time a machine shop can mill it flat.

[Rat-a-tat-Dat]

I don't want to high jack this thread and go on about my issues so should I start a new thread or just add my questions to my existing project?

[second chance]

19 minutes ago, Rat-a-tat-Dat said:

I don't want to high jack this thread and go on about my issues so should I start a new thread or just add my questions to my existing project?

If you want input from the wider community you might want to start your own thread. 

[Rat-a-tat-Dat]

Great! thanks.

For those reading this, I have continued my conversation on my Datto Project.

Cheers