swapping L series heads

[kelowg]

i have search alot on this, brain hurting. 

currently running motor with limited known specs of

z22e bored out .75mm believed to be from 83 200sx
Stroke: 86mm (L20b crank)
Headgasket bore: 88mm (that's a guess; I just figure it's gonna be 1mm over the stock bore)
Combustion chamber volume: 45cc (A87 open chambered head with  4.20inch total head height )
Piston dish volume: -9.32cc (stock Z22e pistons, but they are shaved down a bit, so this might be a little less)

dont know what rods where used tho
Deck clearance: .2mm over deck (shaved down from .4mm)
Shadbolt cam (510 lift, 280 duration)

 

i have a w58 closed chamber head that measures 4.22.33 inches

so, if i transfer cam and springs from the a87.  well the w58 have same valve to piston clearance? im thinkin it would, but i dont want to assume on something this important.

tired of pinging with timing anything over 2-3 degrees and some ping on hot days with 91 octane.

 

[flatcat19]

Why do you need cam and springs from an A87?  The W58 has the better cam if not the same. 

 

 

You'll have clearance. Why not just stick with the 87 head?

 

 

 

If compression is too high, open chamber head may serve you better. 

 

Lower your timing; use colder plugs. 

[datzenmike]

i have search alot on this, brain hurting. 

currently running motor with limited known specs of

z22e bored out .75mm believed to be from 83 200sx

Stroke: 86mm (L20b crank)

Headgasket bore: 88mm (that's a guess; I just figure it's gonna be 1mm over the stock bore)

Combustion chamber volume: 45cc (A87 open chambered head with  4.20inch total head height )

Piston dish volume: -9.32cc (stock Z22e pistons, but they are shaved down a bit, so this might be a little less)

dont know what rods where used tho

Deck clearance: .2mm over deck (shaved down from .4mm)

Shadbolt cam (510 lift, 280 duration)

 

i have a w58 closed chamber head that measures 4.22.33 inches

so, if i transfer cam and springs from the a87.  well the w58 have same valve to piston clearance? im thinkin it would, but i dont want to assume on something this important.

tired of pinging with timing anything over 2-3 degrees and some ping on hot days with 91 octane.

 

Sounds like a long rod 2.1 engine. L20B crank, Z22E pistons, Z20E longrods.

 

All L heads will have the same valve stem heights. Because they are tilted off vertical a larger diameter valve will reach down farther. If the head is milled they will be closer to the piston. A stock cam would be no problem but only way to be sure with a high lift cam is....

 

First place a small lump of clay on the piston top. Have the engine close to TDC on the exhaust stroke. Assemble the head to the block with a gasket. Rotate the cam through TDC by hand. Remove the clay and measure how thick the clay is under the valve indents.

[kelowg]

a87 has higher lift cam (Shadbolt cam  510 lift, 280 duration)but only change to valve clearance would b from differences of milled height,correct?

a87 milled a little more than the  w58, so if anything clearance would slightly more is my thinking.

[flatcat19]

Missed the custom cam part. 

[datzenmike]

a87 has higher lift cam (Shadbolt cam  510 lift, 280 duration)but only change to valve clearance would b from differences of milled height,correct?

a87 milled a little more than the  w58, so if anything clearance would slightly more is my thinking.

 

Only if the valves are the same diameter.

[scooter]

Kinda irrelavent here, but the 280zx valves i put ordered were 60 thou shorter than the 4 banger valves from what i remember. The quench from the close chamber isnt going to make pinging go away, due to compression going up.

 

Is the edges of your chambers deburred? Run 94? Put octane boost in the 94? Run water injection? Make sure your tune is good and not lean?

 

Put the coldest plugs you can get in it without having them foul. You can also file the electrode strap back quite a bit so theres let metal getting hot.

 

 

 

Another dumb one is have you made sure your tdc marks are actually at tdc? Sounds dumb but it wouldnt be the first time.

[kelowg]

Yea,ckd and tried all of that. some of things have help a bit. Been reading closed chamber head less prone to ping and knock is why im lookin into this. Also wondering what stock cc's is on the w58 head? Had this head on stock l20b which ran bout same as this lz 2.1. Doesnt seem right.

[scooter]

At the same cr ratio, yes, but your cr is going to go up too much for the quench to help you out. Does it do it all the time with light load? Or just wide open at lower revs ?

 

Somethings weird.

 

If u want it to run on cheap juice set up your router and cut a 50 thou dish into your pistons. Theres lots of work involved here but ive seen it it done a few times when people get too carried away with domes.

[kelowg]

Anybody know the uncut heights are for the a87 and w58 heads?

[datzenmike]

4.248" although some claim higher. All the ones I have measured with a caliper were this.
 
 

Been reading closed chamber head less prone to ping and knock is why im lookin into this. Also wondering what stock cc's is on the w58 head?

Closed chamber heads are 41cc


 

tired of pinging with timing anything over 2-3 degrees and some ping on hot days with 91 octane.

 
The engine you describe would have a compression of 9.48 with an open chamber head and 10.0 with a closed.

 

If you currently have an open chamber head and the compression is only 9.48 I wouldn't imagine the timing should be so low using 91 octane. Set the base timing with the vacuum advance disconnected. Make sure the idle is around 750.
 

At the same cr ratio, yes, but your cr is going to go up too much for the quench to help you out. Does it do it all the time with light load? Or just wide open at lower revs ?

Somethings weird.

If u want it to run on cheap juice set up your router and cut a 50 thou dish into your pistons. Theres lots of work involved here but ive seen it it done a few times when people get too carried away with domes.

10 is not too high if you run high octane gas. A quench head will be more resistant to pinging that an open chamber head with the same compression. Increasing the compression will cause the burn to be faster so less timing is needed.

 

Rather than milling a piston top I would unshroud the valves and make the combustion chamber larger.

[kelowg]

So datzmike, which head would u run? The a87 seems to have been shaved down alot(j in japan looks like an i)

I always run 91 octan and plan to continue reguardless.

[datzenmike]

CC the head and the true compression can be worked out. All you need is a CD case, some vasaline and a liquid medicine syringe for children.... http://community.ratsun.net/topic/358-how-to-cc-your-cylinder-head-for-free/

[scooter]

4.248" although some claim higher. All the ones I have measured with a caliper were this.

 

 

 

Closed chamber heads are 41cc

 

 

 

The engine you describe would have a compression of 9.48 with an open chamber head and 10.0 with a closed.

 

If you currently have an open chamber head and the compression is only 9.48 I wouldn't imagine the timing should be so low using 91 octane. Set the base timing with the vacuum advance disconnected. Make sure the idle is around 750.

 

 

10 is not too high if you run high octane gas. A quench head will be more resistant to pinging that an open chamber head with the same compression. Increasing the compression will cause the burn to be faster so less timing is needed.

 

Rather than milling a piston top I would unshroud the valves and make the combustion chamber larger.

I just dont think the quench is gonna do enough, thats all. I agree with you on unshrouding the valves. Much smarter plan.

[ggzilla]

Quench does a lot. Makes more power and more fuel economy both. Reduces detonation and engine dieseling too.

 

Quench doesnt occur with dished pistons.

[620Turbo4X4]

Quench does a lot. Makes more power and more fuel economy both. Reduces detonation and engine dieseling too.

Quench doesnt occur with dished pistons.

Exactly.

 

And the dished area in piston top that resides under the flat quenched portion of head does not get complete combustion. That's the reason nissan used the open heads. Too much HC emmissions (unburnt fuel) here in the US.

 

To get effective quench with closed heads you need flat tops.

 

So is it pinging under part throttle, full throttle, or both?

 

What plugs are in it?

[kelowg]

Full throttle, ngk's 2 ranges cooler than stock. Maybe ill just put the su's have on it. 

[kelowg]

did some math to calculate cc of each head. i know this isnt 100% accurate. a87 has had bout .043 shaved off, come up with 42.73cc

w58 has .0247 shaved off,come up with 39.90cc. so closed chamber close to same volume is the open one. not sure what to do, tear down and end up worse off or leave it alone.

[620Turbo4X4]

I don't see anything obvious with your setup that would cause pinging other than lean A/F ratio or excessive spark scatter.

 

Are you familiar with reading spark plugs. You can learn quite a bit from reading your plugs. Most know about the color of the insulator indicating lean and rich conditions, but you can also read the ground strap and threads for ignition timing and finding the correct heat range for your engine with used plugs.

 

http://www.4secondsflat.com/Spark_plug_reading.html

 

You should be seeing a color transition roughly in the middle of the ground strap. If all looks good there is one more possibility that can cause uncontrollable knocking that a friend of mine had back when we were in high school.

 

He had rebuilt his engine himself. Mostly stock other than RV cam, headder, and bigger carb. When he got it all back together it sounded like shit and knocked no matter what was done. Spent months fiddling with timing and timing curves, different carbs, jetting, blah, blah, blah... Nothing helped. The more throttle and RPM the louder it knocked. Stumped, we finally decided to pull one of the heads and look for anything obvious. Everything looked fine except for the notches that indicate front of piston were in the back. 180 out... Being young and dumb neither of us thought this could be a issue. Piston are round, pins are in the middle and shouldn't matter, right? Still stumped, we decided to go ahead and flip them around. Quick hone, new rings, and put back together and to both of our surprise, knocking is gone... Actually sound like a new engine. We both learned a lesson. Piston pins are offset to reduce piston slap and noise, installed backasswards the offset amplifies the rocking. Sometimes the simplest things can be the hardest to find....

 

If you run out of options, this might be something to look at. If you can get your hand on a bore scope pull a plug and take a quick look...

 

At least you could check that off the list. Sometimes it's a process of elimination.

[datzenmike]

did some math to calculate cc of each head. i know this isnt 100% accurate. a87 has had bout .043 shaved off, come up with 42.73cc

 

Correct if 0.43 is in mm.

 

 

w58 has .0247 shaved off,come up with 39.90cc. so closed chamber close to same volume is the open one. not sure what to do, tear down and end up worse off or leave it alone.

I'd be interested to see how you got the PI r² to work on a closed chamber that is not a circle.

Very very very roughly, the closed chamber has about 60% of the area of an open chamber head. This would work out to 1.4cc X 0.60 = 0.84cc or 40.16cc. Again 60% is my rough estimate so this is not a solid number. If you used some king of calculus magic let me know.

[kelowg]

no no, just play with numbers in cc that equalled 41 and 45 cc. like W 10.30cm x L 2cm x D 2cm=41.2 than figured out amount lost to milling on each.  this is what i was trying to get at earlier with open head shaved down so much more than the closed head. 

so i guess c/r would go up .5 to .75 of a point

[datzenmike]

Slow down this is interesting and I want to know how. The closed chamber head is not circular. It's a kidney bean shape. When slicing off a mm, how do you determine the area? Area X thickness of material removed would equal volume removed.

[kelowg]

its not actual measurement. i just imagined 2 boxes one 41cc another 45cc. shortened one diamenison by amount shaved off. but ur right it doesnt real well since chambers shapes so different.

[kelowg]

im no math wiz

[datzenmike]

Me either. Never was good at school and if I couldn't see a use for it I didn't want to know about it. If only they had suggested working out compressionn ratios and cylinder volumes!!