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obrut

L16 build, head advice

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Wow almost exactly a year later.  I'm back on my project.  Still building the L16 with flat tops and the open A87 head.  I will be running dcoe 40s on a cannon intake. 

I disassembled the head and port matched the cannon intake to the A87 head.  All I did was layout blue, installed intake, scribed a line around each port and then open the port to match the line.  I then used sanding drums to just smooth it a bit about 1/2" into the port.  I placed the intake/exhaust gasket on it and did the same to the exhaust ports.

I didnt touch anything else, is there anything else I can do?

I'm going to have the machine shop hot tank, replace valve seats and 3 angle vale job.  I also wanted to mill the head to increase the compression.  Any other simple things for performance?

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Be sure the seats are the newer hardened ones. Old seats were bronze and relied on the lead in the gas to lubricate them.

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Some of the biggest gains you will achieve on an L motor are inside the "bowl" of the ports. That's the area just under the valve. Blend the bowls with the valve seats and relieve the area just around the valve guide for a few HP. A good 3 angle valve job with about .050" valve contact is the best for performance. You can also "tulip" the valves by sanding them smooth and round off the harsh edges near the seat contact area.

 

Best performance is going to be from a good cam. You don't need to go big for performance either. My favorite cam for a mild street L16 is a "27C" which you can get from Rebello. It is so mild that it uses stock valve springs, yet the gains are enough to feel through the butt dyno. With Dual 40's, you may consider going bigger though.

 

And recurve the distributor, or have someone do it for you. Rebello or Advanced Distributors can help you with this. Jeff Schlemmer from Advanced Dist is here on Ratsun under "distributor guy". Rebello is best reached by phone (they do not respond to emails).

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On 3/14/2020 at 6:49 PM, banzai510(hainz) said:

Mill the head a min I’m I’m amount other wise you need head cam saver shims which I think are.015 in thickness

SilverSeal sells them look under Datsun

 

I bought head savers and wanted to mill the head to raise the compression, I would like to be right at 9:1 with the flat top pistons and A87 head.  I will always run 93 octane in this car, its not a daily driver and I'm not worried about gas mileage at all.

 

On 3/14/2020 at 8:30 PM, datzenmike said:

Be sure the seats are the newer hardened ones. Old seats were bronze and relied on the lead in the gas to lubricate them.

 

The intake seats are bronze and the exhaust are steal.  I was going to have the machine shop replace just the bronze seats and then get the 3 angle valve job.

 

On 3/15/2020 at 1:33 AM, Stoffregen Motorsports said:

Some of the biggest gains you will achieve on an L motor are inside the "bowl" of the ports. That's the area just under the valve. Blend the bowls with the valve seats and relieve the area just around the valve guide for a few HP. A good 3 angle valve job with about .050" valve contact is the best for performance. You can also "tulip" the valves by sanding them smooth and round off the harsh edges near the seat contact area.

 

Best performance is going to be from a good cam. You don't need to go big for performance either. My favorite cam for a mild street L16 is a "27C" which you can get from Rebello. It is so mild that it uses stock valve springs, yet the gains are enough to feel through the butt dyno. With Dual 40's, you may consider going bigger though.

 

And recurve the distributor, or have someone do it for you. Rebello or Advanced Distributors can help you with this. Jeff Schlemmer from Advanced Dist is here on Ratsun under "distributor guy". Rebello is best reached by phone (they do not respond to emails).

 

I think I understand what blending the bowl means.  When the seats are installed the material just under the seat should be even with the valve seat.  If that is correct, I checked my head and there doesn't seem like there is much to blend.  This head does have the 35mm exhaust valves instead of the 32mm if that makes a difference.

 

What does "relieve the area just around the valve guide" look like?

 

thanks for the help everyone.

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Aiming for some random compression isn't going to do much of anything. A half point increase, on  a good day, will maybe add 2-3% increase in power at max RPMs.

 

1/ IF you have an open chamber A-87 head. Should have 45.2cc combustion chambers.

2/ IF it hasn't already been milled down. From valve cover surface to head gasket surface, it should measure 4.248" or see 1/. 

3/ IF you have flattop 83mm L16 pistons and not an oversize or L18 flattops

 

If 1/ 2/ 3/ then milling 1/2 mm or 0.020" will decrease the combustion chamber by 2.7cc and bump the compression to 9.04

 

 

 

 You can also place an 85mm gasket over the block (you'll need one for the A87 anyway) and scratch around the outline. Then grind away the top edge of the block at it's closest to the valves to match the head above it. This is just extending the unshrouding around the valves into the block. Just don't extend down into the ring area of the pistons.

 

By itself any one of these mods won't do much but there's a tipping point where when added together the weight of several mods like 3 angle valve job, over size valves, gasket matching the head to the manifolds, unshrouding the valves, streamlining around the valve guides, blending the valve seats into the ports adds up to a difference. 

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a closed chamber head would be better.

machining the head for straightness is more important

as for changing the seats make sure they know what they are doing. I seen them come out otherwise just get them cut. But with a higher lift cam with stronger springs they will wear more.  maybe not really enough to worry about.

I got my L16 with steel guides and seats(l20 U67 head) and its just turned 200k on there and had not proplems with it. this has also 2 head shims stacked up as the head was bent top and bottom.

 

dual carbs and Cam makes the bgigest difference

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Mike, yes to all three.  And Yes I'm trying to do the little things that will add up, I will add relieving the block to unshroud the valves.  Most of this stuff I can do myself and I like to do anyway.

 

Hainz I was going to use the L20B cam that I have that was in this head.  I know budget a performance don't go together and that's why I didn't even look at cams.  How do you guys feel about buying and using used cams?

Edited by obrut

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my 2 cam one was a regrind and one was new.

others may know if you can run a used cam , But I assume if it comes with the rockers I assume its ok

But you spending all this money  and you don't put a big cam on there is a waist in my opinion.

The head makes the most power like match  port dual  carbs and a cam at least use up to 475 lift(so you can  still use stock springs or use one stock and one Performance)

putting the stock cam in there???

its cheaper to put a stock L20b and youll get more power

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Best would be an original Nissan L20B cam that was re-ground to increase the lift and a small duration increase. The problem is today's oil that has lower anti scuff zinc additives. If continuously used it will rear down the lobes. (and/or) the rockers) I have one and it's readily apparent. Just measure the narrowest and the widest part of the lobe and subtract. Multiply by 1.48 and this is the valve lift. I think you can go up near 0.480" lift before the stock springs stack. Above this and you'll need after market springs. I guess you could mill the head under the springs to get clearance but the higher lift might need stiffer anyway. If all lobe heights are the same or close enough probably ok. If you get one, be sure that it will spin in the head you are using before putting the rockers on.

 

Any new cam will require you to sand the rockers smooth. Wet sand paper and a sheet of glass. Polish with 800 grit?  

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6 hours ago, obrut said:

 

I bought head savers and wanted to mill the head to raise the compression, I would like to be right at 9:1 with the flat top pistons and A87 head.  I will always run 93 octane in this car, its not a daily driver and I'm not worried about gas mileage at all.

 

 

The intake seats are bronze and the exhaust are steal.  I was going to have the machine shop replace just the bronze seats and then get the 3 angle valve job.

 

 

I think I understand what blending the bowl means.  When the seats are installed the material just under the seat should be even with the valve seat.  If that is correct, I checked my head and there doesn't seem like there is much to blend.  This head does have the 35mm exhaust valves instead of the 32mm if that makes a difference.

 

What does "relieve the area just around the valve guide" look like?

 

thanks for the help everyone.

I don't have any pics, but basic and careful removal of the aluminum surrounding the valve guide, and blending it into a nice free-flowing shape around the valve guide. Think raindrop or teardrop shape.

 

Blending the bowls is taking off any sharp edges, not just making sure they are the same size as the seat.

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So after the valve seat is changed I can smooth the bottom of the seat to smooth it to the head? 

20200316_160326

Edited by obrut

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Yes. Just be careful not to get into the valve contact area.

 

You can also sand smooth the casting bumps in that area for some small gains.

 

For smoothing, use what is referred to as a cartridge roll https://www.google.com/search?q=head+porting+cartridge+roll&source=lnms&tbm=isch&sa=X&ved=2ahUKEwi3wPvUjqDoAhXlIjQIHfH1DMcQ_AUoAnoECAwQBA ...on the proper mandrel (you can buy whole porting kits that include the mandrel and assorted cartridge rolls).

 

Porting aluminum is best done at a lower RPM than on steel. For finish polishing, you can create a tear in the cartridge roll so that it flaps in a wide arc. Or you can spend extra money on a specific flap roll that fits in the die grinder. That's just extra money as far as I'm concerned.

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Yep I have those, I bought a eastwood kit some time ago.  I'll do most of it now and touch it up after getting the seats changed and valve job if I need to.

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I find gasket matching, porting, polishing extremely pleasurable to do. It's an attention to detail that the car maker wouldn't go to but that adds some small power benefits that NEVER go out of tune or need replacement. If you have never tried it you might find that you like working with your hands, after all, we humans are all tool makers and it's natural that we build things. It's beyond just assembling something it's making something.

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