Leon's Other 260Z

[Leon]

I've started this morning with measuring deck height. I'm at .021" (piston above deck). Looks like this is the same number you had, Matt. I'll be reading through your thread again.

 

EDIT: removed units from deck height measurement to avoid confusion.

Edited August 10, 2013 by Leon

[JCan]

It is actually bouncy during start or very light trottle/very low speed (springs on friction disk too soft?) but it is holding up fine in 5th gear at WOT on highways.

Quite frankly, I expect the clutch to be the next thing to fail on my setup (I better start saving $$$ !) I'll probably go for Fidanza flywheel + ACT clutch. I had good luck with such combo on my Evo in the past.

I hate to hijack this thread... but I see an issue that matt might have...

 

Matt.

 

I had the same issue you are having on my build also.    Are you sure the clutch is not partially engaged when your foot is off the clutch petal?  (Get under the car and see if there is at liest 0.100" play between the slave cylinder and the clutch arm.  You can do this by attempting to move the clutch arm with your fingers.)

 

If it is partially engaged, (like mine was).  Remove the slave cylinder and reduce the length of the pin that engages the clutch by measuring the distance the clutch is currently engaged.  I made this measurement by unscrewing the slave cylinder and measuring how far the clutch pushed it back.  I cut ~1/4 inch from the engagement pin at the slave cylinder side, then rounded the cut end such that it was similar to the original surface.

 

I hope this fixes your problem!

 

Jim

[madkaw]

Looks like a 1.25mm HG is in order to get you in a good spot.

Did you shave any off the block?

[JCan]

 A quote from Braap...

 

 

 

 

Edited August 13, 2013 by JCan

[Pharaohabq]

That's tight!  I wonder if Braap has a pict of that ghosted text...

[Leon]

Looks like a 1.25mm HG is in order to get you in a good spot.

Did you shave any off the block?

 

Yeah, the machinist said he took off .004" from the block deck. I calculated that I need the head gasket to compress to about 1.1mm. I have an OEM Nissan HG on hand which I hope should make everything a-ok. With that said, I'll be doing a similar check as Lazeum did by putting a dial indicator on the block and seeing the height difference of the head with and without a HG. This will allow me to calculate true compressed gasket thickness.

 

As a double-check, I've got silly putty on hand to check head-piston as well as valve-piston clearances.

 

 A quote from Braap...

 

BRAAP Quote.jpg

 

Thanks Jim, I've been reading through a ton of Braaps old posts! Speaking of which, I should've listened when he said to buy extra valve stem seals, because sure enough I cobbled some up...

[Leon]

Making some progress...

 

I banged in the core plugs, a much bigger pain-in-the-ass than I expected.

 

 

 

Busted out some turbo head bolts that I got for Christmas or a birthday present years ago and did some clearance checking. I used an indicator and a bracket attached to the head to get some relative measurements regarding gasket compression and piston-to-head clearance. The head was torqued down with a previously compressed Felpro gasket that Jim sent me. The indicator was then zeroed and all bolts loosened. The number on the indicator then represented how much the gasket was compressed.

 

The indicator showed .021". I measured the uncompressed gasket thickness as 1.5mm/.059", meaning compressed gasket thickness is .038" or .97mm. I also double-checked myself with the indicator by reinstalling the head but without the gasket. The indicator read .0385", so within .0005" of the calculated value.

 

I then triple-checked that using clay aka Silly Putty. Before the head was torqued down with the Felpro gasket, I placed the clay in one of the cylinders. The engine was rotated once with the clay inside. I measured the clay by slicing it in two with a fine blade and using the depth gauge of my caliper. The readings I got were .7-.8mm, or .027-.031", which should directly represent the actual piston-to-head clearance. That's way off from my other measurements and calcs, which I trust more. I'll probably use the clay for piston-to-valve checks but I'll rely on the indicator for piston-to-head numbers.

 

Using the .038" compressed gasket thickness, I get piston-to-head clearance of .017". Yes, that is pretty dang close but I'll be using a Nissan HG in the final iteration so I'm hoping for another .004-.008" from that. I will, however, use the indicator to measure compressed thickness upon final assembly to be sure.

 

 

 

In other news, I got a few parts the other day. My order of Nissan head dowels, wire-netting (PCV vent), and radiator hoses came in. Here's the wire netting compared to some old stuff I harvested from one of my other blocks. Obviously it's new and clean but I also like how the wire is soldered to the netting instead of just being wrapped around it. I've got some lash pads on order, should've bought those a while ago. Progress is being made and if I don't have the engine in the car this coming weekend then I've screwed something up. As far as I can think of, the only thing that isn't figured out is the fuel routing in the engine bay and the exact plans on the exhaust.

 

Edited August 20, 2013 by Leon

[Lazeum]

Hopefully, piston to head clearance will be ok with Nissan gasket but in my attempt to get proper clearance with Ishino (not quite sure of the brand, here...) unit, I ended up with compressed thickness equivalent to felpro unit.

 

Solutions were:

-either run the engine as is and risk engine failure

-or remove pistons and get them milled to get proper clearance, which took a couple of days to process. This is obviously the solution I've chosen.

[Leon]

Hopefully, piston to head clearance will be ok with Nissan gasket but in my attempt to get proper clearance with Ishino (not quite sure of the brand, here...) unit, I ended up with compressed thickness equivalent to felpro unit.

 

Solutions were:

-either run the engine as is and risk engine failure

-or remove pistons and get them milled to get proper clearance, which took a couple of days to process. This is obviously the solution I've chosen.

 

Here's my reasoning: if stock deck height is .021-.025" above the block as Braap said and I run a Nissan gasket, why would this be a dangerous scenario? I would of course like to err on the side of caution so I guess we'll see what the numbers are.

[JCan]

Leon.

 

Your build looks great!  and it looks like you are paying attention to all the little details.  I cant wait to see it run!

 

A couple comments - 

• (Regarding the clay measurement, it might read wrong due to the piston rocking inside the cylinder.  I agree you should use your dial indicator measurements.)
•  
• Regarding piston to head clearance, If during your final torque your new gasket compresses too far, ( I know you have great dial indicators to measure this) you have a choice to purchase a custom  copper head gasket with what ever thickness you chose the cost is $135 and you can chose piston diameter and gasket thickness (STANDARD MATERIAL THICKNESS .022, .032, .040, .043, .054, .063, .070,  .086, .093, and .125 inches.)   A Thickness of 0.054" would give you a fixed ~0.030" of squish. $135 at www.headgasket.com

Edited August 20, 2013 by JCan

[NewZed]

A thought on the use of Silly Putty - it's claim to fame is that it will flow and hold a shape given enough time but otherwise is rubbery and elastic on a short time frame.  Depending on how fast you turned the crankshaft for your test, you might have had some elastic recovery.  Your piston-head clearance might be even less than measured.

[Leon]

 

Leon.

 

Your build looks great!  and it looks like you are paying attention to all the little details.  I cant wait to see it run!

 

A couple comments - 

• (Regarding the clay measurement, it might read wrong due to the piston rocking inside the cylinder.  I agree you should use your dial indicator measurements.)
•  
• Regarding piston to head clearance, If during your final torque your new gasket compresses too far, ( I know you have great dial indicators to measure this) you have a choice to purchase a custom  copper head gasket with what ever thickness you chose the cost is $135 and you can chose piston diameter and gasket thickness (STANDARD MATERIAL THICKNESS .022, .032, .040, .043, .054, .063, .070,  .086, .093, and .125 inches.)   A Thickness of 0.054" would give you a fixed ~0.030" of squish. $135 at www.headgasket.com

 

 

I just hope it runs at all!

 

Good point on the piston rocking, although I'd hope that the piston doesn't rock enough to make .010" worth of difference!

 

Thanks for the tip on the copper gaskets. If I were proactive enough, I'd order one right now just in case. However, $125 for something that I might not use is a little hard to swallow. With that said, I'd probably opt for a .043" gasket as that would give me a very nice .022" piston-head clearance which is just about what I'm shooting for with the Nissan gasket. Are you guys using a copper gasket, Jim?

 

A thought on the use of Silly Putty - it's claim to fame is that it will flow and hold a shape given enough time but otherwise is rubbery and elastic on a short time frame.  Depending on how fast you turned the crankshaft for your test, you might have had some elastic recovery.  Your piston-head clearance might be even less than measured.

Yes, I considered the elasticity of the putty as well, hence my thoughts of trusting the numbers from the dial indicator. Those should be dead-on. The putty will not be used for piston-head clearance checks.

[JCan]

Leon.

 

I believe 0.022" gap is very tight!  I Think the minimum gap that I have read that is 0.024"  I know we are splitting hairs on this....  having said this, I started up my car and ran it, then removed the head and looked for piston to head wear and found one small place on cylinder 4 where a piece of debris lodged in between the head and piston indented the aluminum on both piston and head.  (I have pictures if you are interested), then engine eliminated the debris with the exhaust.  Point being, the engine ran at idle and revved up to 4krpm without incident using the felpro gasket I provided to you.!  If you really want a 0.022" piston to head clearance, I believe any of the stock gaskets will work.

 

I am using a copper gasket, it is thick though, 0.063" which yields a piston to head clearance of 0.040.

 

Your car will run, I'm worried about it's ability to idle with that super agressive cam you have!  I cant wait to see it at JCCS.  

[Leon]

Leon.

 

I believe 0.022" gap is very tight!  I Think the minimum gap that I have read that is 0.024"  I know we are splitting hairs on this....  having said this, I started up my car and ran it, then removed the head and looked for piston to head wear and found one small place on cylinder 4 where a piece of debris lodged in between the head and piston indented the aluminum on both piston and head.  (I have pictures if you are interested), then engine eliminated the debris with the exhaust.  Point being, the engine ran at idle and revved up to 4krpm without incident using the felpro gasket I provided to you.!  If you really want a 0.022" piston to head clearance, I believe any of the stock gaskets will work.

 

I am using a copper gasket, it is thick though, 0.063" which yields a piston to head clearance of 0.040.

 

Your car will run, I'm worried about it's ability to idle with that super agressive cam you have!  I cant wait to see it at JCCS.  

 

Jim, you're right that .022" is very tight. I should've said that I'm aiming for .022-.025", so .022" would be the minimum. I got the numbers from the guys that have built way more engines than I have: http://forums.hybridz.org/topic/58127-best-way-to-achieve-piston-to-head-clearance/

 

I'm anticipating being OK with the OEM gasket but I'll let you guys know how the numbers pan out. I definitely have confidence in getting the car to idle smoothly, THAT I do have experience in! I'm looking forward to JCCS, but first will be the wedding on the 31st and a trip to Hawaii afterwards...

[Gollum]

Personally, I'd go as low as .0220" as long as I knew the bearings were in good shape. If I was building something to rev to 8k+ I'd also be making sure the rod bolts are of good quality too. I know I haven't built a million L engines like Braap or 1 Fast Z, but I've done enough independent research and interviews on the topic to trust their claims.

 

If you have debris that's causing denting of the head/piston material at .0220, odds are you'll have debris do the same at .025. That's not a huge window to think about as "debris clearance". Now, if you're worried about the piston tapping because you're reusing an old bottom end that might be a tad loose, then I'd want to keep the gap a bit larger too.

 

Oh, and for reference here's some carbon build up from my '81 L28E. Stock bottom end, stock P79, both untouched for 250k miles as far as I can tell. The head gasket wasn't stock (felpro) but there's no signs of machine work. The carbon build up was certain thinner and even non-existent in the quench pad areas, but that said there's definitely some build up that decided to hang around in that area anyways.

 

 

So my question to people that think that even .025" is too tight of a piston to head clearance (trust me, there's people out there), if this engine ran JUST FINE in it's low performance configuration, and there was ZERO damage to the head surface from particles, and yet it can build up THAT much carbon... should you really have a problem with a CLEAN chamber running the .022-.025 referenced in that other thread?

[NewZed]

Here's a thread from the recent past on the piston-head clearance topic.  Some solid engine builders had some interesting comments.  Most recommended that you should only get close if you have the right engine components.

 

Clearance comes in at Post #10.

 

http://forums.hybridz.org/topic/106806-long-rod-short-piston-combo-l28-tech-questions/?do=findComment&comment=999867

[Leon]

I'm not going to dwell on P/H clearance too much, unless Braap or 1 fast z feel like retracting their claims. If it was safe from the factory, I assume it'll be safe with .004" taken off the block deck. Guess we'll find out, eh?

 

Got the .263" lash pads that were supposed to be correct for my cam, but of course they are not. I'll be scrambling to determine correct lash pad thickness tomorrow, as I need shorter ones. My guess is .240" should be just right, but I'll probably just bite the bullet and cut up some feeler gauges to be sure. I'll also be looking for a local shop with a surface grinder but will probably have to resort to turning them on a lathe...

[Gollum]

Here's a thread from the recent past on the piston-head clearance topic.  Some solid engine builders had some interesting comments.  Most recommended that you should only get close if you have the right engine components.

 

Clearance comes in at Post #10.

 

http://forums.hybridz.org/topic/106806-long-rod-short-piston-combo-l28-tech-questions/?do=findComment&comment=999867

 

PMC in that thread even goes directly what people quote from the how to modify book, which definitely shows that the "fat" gap in that book clearly doesn't event attempt to use quench.

 

And there's misleading information in that thread. Forged components won't "stretch" as much, meaning that high RPM performance will be closer tolerance to idle than non-forged... But the stock rods ARE forged. And how many people have all new forged cranks made? The only variable in this equation really is the piston... But guess what? Forged pistons GROW more than stock (with heat), hence why you run a much larger bore gap. If you run a larger bore gap doesn't it make sense to run more piston to head clearance? .030" sounds like it's in the ballpark to me...

 

And don't neglect grow factor. There's a bit of documentation out there showing that just pulling apart a LS1 and opening up the ring gap can increase the HP potential of the bottom end by as much as 50% possibly! Going for crazy force induced HP on the LS1 results in the rings growing too much and reaching their clearance limit. Open them up just a tad and voila, weakest link has just been fixed. There's a reason why there's such different specs out there for turbo/nitrous builds.

 

Point being, different builds will require different specs. For stock components I think it's safe to mill the block .004" and be just fine. Nissan didn't expect these to be throw away blocks, as nobody engineered things that way back then (except ferrari). If Leon was doing some radical build will completely out of stock specs and requirements, things might be different.

[NewZed]

I don't have an opinion, I just found it interesting that Leon's clearance was so much tighter than what the guys on the other thread were recommending.  Quench is a fun topic.  And even if Monroe (and Honsowetz) wasn't focused on quench, he's still focused on keeping parts from banging together.  The point about different builds and different specs. was the main point, at the end, in the other thread also.  It's all good discussion material.

 

I've read of another way to check clearance, using a piece of solder.  Stick it in the spark plug hole after everything is assembled and run the engine through a revolution.  The soft solder will compress and hold its shape.  Of course, the piston will be "rocked" to maximum clearance.  Maybe measure the rocking distance before assembly, the do the math after.  This could be one last measurement before real-world testing.

[Gollum]

No worries NewZed, I was just clarifying points, which it seems you are too. That's kind of the beauty of this place, there's no "best" which means all data is always up for interpretation to make up your own mind.