1973 Rebuild

[Matthew Abate]

Zed Head,

Needed rods regardless so went with 240 to get the better rod angle (max of 17.277 degrees) to reduce ware and get that microscopic increase in downforce during combustion.

Madkaw,

The pistons will be 87mm diameter with a pin height of 35.35 and a 6.008 to 6.314 dome, which should yield a CR of 9.75 to 9.8 with a 1mm head gasket. This is where I'm splurging.

[Patcon]

1 hour ago, madkaw said:

How are dealing with the 3mm

Are you talking about rod interference at the block or something else?

[Zed Head]

6 minutes ago, Matthew Abate said:

Zed Head,

Needed rods regardless so went with 240 to get the better rod angle (max of 17.277 degrees) to reduce ware and get that microscopic increase in downforce during combustion.
 

Alrighty.  Seems like L28 rods with L28 flat tops would get you where you're going.  I thought that you had a complete ZX (F54) short block.  A simple piston swap and you're there.

I think that it's pretty well recognized that the big power increases are in head work.  Porting.  The stock L series heads just don't flow much air, and they don't flow it well.  Some people go completely stock on the bottom end and put all of their money in to the head, the cam, and the intake and exhaust systems, flywheel and clutch, etc.  

I'll stop now.  There are several engine builders on the forum, one just posted about his six spare engines.  I'm just trying to stretch your dollars. 

[madkaw]

Yes I was referring to piston height , but sounds like you have it covered . So these will be custom Pistons or did you find some that worked from another engine to get that pin height? 

[Matthew Abate]

11 hours ago, Zed Head said:

Alrighty. Seems like L28 rods with L28 flat tops would get you where you're going. I thought that you had a complete ZX (F54) short block. A simple piston swap and you're there.

I think that it's pretty well recognized that the big power increases are in head work.  Porting.  The stock L series heads just don't flow much air, and they don't flow it well. Some people go completely stock on the bottom end and put all of their money in to the head, the cam, and the intake and exhaust systems, flywheel and clutch, etc.

I'll stop now. There are several engine builders on the forum, one just posted about his six spare engines. I'm just trying to stretch your dollars.

Yeah, I am planning to do a lot to the head, which is why I hired Lary. He did my dad's last two engines and they perform very nicely, plus he has enough L-series experience to make me feel confident having him work on it.

And, yeah, we have a complete L28ET in addition to what we are making for my 240, but that one is my dad's for some project he's planning. Not sure what.

Also, I get the impression you felt like you were overdoing it with the comments, which is not the case. I appreciate the advice!

This is foreign territory for me, which is why I have professional engine builders putting it together rather than trying to do it myself. But even then, we are looking at what you guys have done and had success with for guidance. I'm not taking anything at face value, but I'm not dismissing anyone's comments either. I've seen a lot of really great ideas on this forum and well as Hybridz, Zcar.com, and others. I've also seen a lot of backyard hack stuff. Just gotta look deeply on every tip and investigate the long run impact, such as the diesel crank or shaving the head or offset grinding the crank. They are all great for particular applications, but they aren't precisely right for the direction I chose to go. I'm glad that I went deep on my research for all of those things before I chose NOT to do them because now I am certain of WHY.

 

1 hour ago, madkaw said:

Yes I was referring to piston height , but sounds like you have it covered . So these will be custom Pistons or did you find some that worked from another engine to get that pin height? 

I found two solutions, both expensive:

• Have a custom piston manufacturer make them to your specifications. I am going with Wiseco because I have had a better experience with them on the phone, read that they have good customer service, and have gotten the impression that their product is reliable and the quality matches the price (if anyone strongly disagrees please speak up). I am going with this solution because it matches the precision build strategy that we opted for.
• Get a set of Z22S pistons and mill of 1.5mmoff with a CNC machine to get rid of the dish. Essentially doing the same as above but starting with a piston that is already halfway there rather than a cylindrical chunk of solid forged steel. This is fine, but You would probably want new ones, and then you are voiding any kind of warranty they came with by modifying them. I think in the end this is actually more expensive, unless you do this to a set of used pistons and I'm not certain it really gives adequate CR despite having read about this on a few threads.

 

---

 

Something I forgot to mention above is that the new pistons will also be relieved for valve float, which makes the dome even taller (although we're only talking an additional ~6CCs total, so while it's bigger than the dome on the Datsun competition / European non-turbo 290ZX pistons it's not a huge bulge.

Edited July 25, 2016 by Matthew Abate

[madkaw]

I am going with Rebello plan just for all these reasons. Better rod angle and Pistons  choices. He seems to cover both by offset grinding which gives a journal size for eagle rods. Too much sciencing for me , so I will leave to the experts. I am happy to put all the pieces together which will save me some monies:)

Your CR seems a little conservative especially if you go bigger cam- which I would assume you will. I'd bump it up a whole point if that's the case- 

[Matthew Abate]

Your CR seems a little conservative especially if you go bigger cam- which I would assume you will. I'd bump it up a whole point if that's the case

Okay this right here is something I really don't have a firm direction on. I had been keeping it low due to numerous comments about pump gas being a problem at high compression. I definitely don't want 10:1 because that seems to be a guarantee of problems when using regular pump gas, but I want to sort of push it to the highest it can be on regular even though I'll probably run supreme.

So you're saying take it to 9.85? There's plenty of room to add more CCs to the dome.

[siteunseen]

I was thinking a high lift/duration cam would negate the pinging from pump gas?  I hope so or I've bought the makings of a grenade.

[Zed Head]

Diseazd started where you started.  You might browse through his old posts.  He started thinking long-stroke but ended up short-stroke instead.  But many of the same questions along the way.

http://www.classiczcars.com/forums/topic/26395-want-to-build-a-high-performance-l28-advice-needed/

http://www.classiczcars.com/forums/topic/39741-new-engine/?page=1

 

[Matthew Abate]

Good stuff. Thanks!


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[madkaw]

Regular pump gas?

So you willing to run premium grade?

 

[LeonV]

Get a big cam and run the triples, you will not regret it. Call and talk to your cam grinder to figure out what profile fits your needs.

Regarding compression, I ended up at nearly 11:1 on CA pump 91 and didn't realize my CR was so high until I re-ran the calcs. I haven't noticed any pinging but I'll admit I haven't had a chance to do a whole lot of tuning yet...