A87 head on anL16

[Jetboater Pop]

Good morning people. I have been using your forum for  a while now , its been a

great source of info for me. I have an unusual set up , no car but a 12ft jet boat powered by an L16 Datsun engine.Pretty rare these days Id say.

so ive joined in the hope you can answer a question for me. I replaced the standard head a few years back with an A87 head. The valves adjustments were running out , I had no adjustment left on some cylinders so I pulled the head. some of the valves are have recession so need to get new seats and a couple of new valves etc. Now what I have noticed on the exhaust side of the cylinders on the top of the block is a small half moon mark .Ive no idea what caused this. Its as if the valve has been just tapping ? the edge of the cylinder?.

So im trying to figure out what caused it. I had a thought that the A87 head (the valve size is bigger than the L16 ) and Im sure its an L 18 head on the L 16 block may move the valve postion out a tad so that it possibly hits the very top edge of the cylinder?? or am I totally wrong.

Can the L18 A87 head fit straight on to the L16 block with no issues or am I stuffed.

A big question for a first post but ant help would be appreciated.

Cheers, Pop.

[datzenmike]

There is no worry about valves hitting the edge of the cylinder walls. The wall on an L16 is only 1mm (0.040") closer that an L18 that also used the A87 head. That's about the thickness of your thumb nail.

The A87 head will drop the L16 compression to 7.72 from the stock 8.58. This is because the stock L16 head has a smaller combustion chamber. The A87 head sometimes comes is a closed chamber design with a smaller combustion chamber but it still drops it to 8.21. Any gain from lager valves and breathing is lost by the lower compression.

 

The reason the valves sank up into the head is because they came with bronze seats that were lubricated with tetra ethyl lead, an anti knock ingredient, but with the introduction of un-leaded gas the seats don't last as long now. Newer engines use hardened seats.

[flatcat19]

Still doesn't answer his question.

 

What head did you remove? A 210 head? Do the pistons in the L16 have a little dish to them? Or are they completely flat minus the exhaust valve grooves?

 

These marks were present when you removed head?

 

 

Your remarks are a little vague. Maybe hard to decipher with the run-on sentence.

 

Pics always help.

[datzenmike]

Read the quote I posted from his other post on the same thing. It begins...
 

There is no worry about valves hitting .......

 

 

 

 

All open chamber L heads have a small relief machined beside the exhaust and intake valves. The head gasket is also not perfectly round either. It's probably just a gasket imprint on the block.
 

[Jetboater Pop]

Cheers for the replies guys. Ive had the engine for 25 years..old fella...so when I got it i dont know what it came out of other than I was told its an L16. The original heads long gone. Cylinder width is L16 size so thats how i know its an L16. The newer head has larger valves than an L 16 also A87 on the side so I assume its an L18 . I got the L 18 head from an engine shop probably 15 odd years ago and its been on the engine till now. The marks were present on the edge of the block when the head was removed.

maybee it is a gasket imprint.Its been a long time since fitting  Pistons have a slight dish to the middle. Im taking the head to a machine shop to get the new seats fitted. should I get it shaved to help with a slight raise in compression?.as for posting up a photo i havent looked into that as Im not that flash on a computer :confused: , rather have a spanner in my hand.

Doing rings and bearings at the same time while the heads at the shop. Anything else i should look at ? .Many thanks again.

[Crashtd420]

I think the mark you are referring to is this...

 

 

I believe it is normal...

I think it is there because of the smaller bore diameter vs the head....

I though it was extra clearance for the valve....

[Crashtd420]

When I prepped my engine for reassemble the book ( how to modify your datsun engine) talked about descrouding the valves by grinding that area back, there and also in the head using the head gasket as a guide....

[datzenmike]

Yup, set the gasket in place and scribe around the gasket. You can safely remove some of the block around both valves but stay away from the top ring. This would lower the compression even more though.

 

 

Yes you can remove head material to raise the compression but this moves the cam sprocket closer to the crank and adds just a touch of slack to the timing chain. L16s usually come from the factory with the sprocket in the #1 position so you have #2 and #3 positions to work with to adjust the slack out.

 

Removing 1mm (0.040") would make the combustion chamber 5.4cc smaller and the compression would be 8.55 which is way better than in the 7s.

[banzai510(hainz)]

yep that's unshrouding the valves for the block. Usually for a 44 mm valves with a higher lift cam esp on a 83mm bore of the L16 as the later L18/20s are 85mm

 

I have ran all those heads on a L16. a 87 w53 and U67.

 

Buy a Duropro graphite head gasket  which I think they sell in Austraila and poss NZ

 

 

replace with harder valves seats and make sure the valave lash is even across so you can dial in the valve lash with out needing bigger or smaller lash pads

[Jetboater Pop]

I think the mark you are referring to is this...

 

 

I believe it is normal...

I think it is there because of the smaller bore diameter vs the head....

I though it was extra clearance for the valve....

 

Yep thats exactly it Crash.Thanks for putting up a pic..Am I right in thinking that the valve has tapped that little half moon mark (always wondered why I couldnt adjust out that tapping noise ). So am I right in thinking that I should remove a small bit of the area where the mark is ?(descrouding i ll have to google that ) :blush: . Im unsure if the head will need resurface as it may have been done previously. already on 2 notch . i ll have a chat to a mechanic mate who is going to help me.Im  after reliability as much as anything as I go up rivers miles from nowwhere and you cant paddle back so street race performance is not essential.A bit crisper ,responsive would be great. Many thanks again , cheers, Paul.

[Crashtd420]

No the valve isn't hitting that spot at all... the ticking is just flat tappet cams, they aren't the quietest setup..

I can only assume the motor is visable so you probably just hear it more vs a car with the engine under the hood...

 

There is a measurement for the height of the head, i forget the number... also if you look where the head is stamped if your missing the bottom of the number then it probably been milled....

 

As far as the cam being on number 2, it's better to check it with an indicator and a degree wheel... There s a couple ways to set the cam timing up using that..

[Crashtd420]

My recommendation is to get these books... you probably don't need the how to modify one but it's a good read... the how to rebuild book would very helpful since it's just about the motor...

 

[Crashtd420]

Here's a couple pages from the how to modify book about descrouding and valve reliefs....

 

 

 

 

 

[datzenmike]

Head gasket surface to valve cover gasket is 4.248" if uncut.

[Jetboater Pop]

Thanks once again Crash and Mike. That info is exactly what I was after, cheers very much :thumbup: .I will follow those instructions when I get the head back and give it a hone. Hopefully when its running I will put up some pics.

[captain720]

Or you could you know put up some oics even though it's not running ?

[datzenmike]

I wouldn't advise unshrouding on this. Using an open chamber head has already lowered the compression too much, grinding away material on the block and or the head will only lower it more. If doing this at least have the head milled

[Jetboater Pop]

Just thought I’d let you know how the “ overhaul “ ended up. After removing the head  I Dropped it off  to be reconditioned. It was an L18 head so had bigger exhaust valves. The old valves had recessed badly so there was no valve adjustment left on some. 4 new valves and seats all done , skimmed the head slightly. All came back nice and shiny and I reassembled it . With the help of my mechanic freind we pulled the pistons , rods etc. He was really impressed on the condition of the engine even after all these years. Then over the many weeks I stripped and cleaned, polished etc everything. We honed the bore ( stock size bore and rings)  and slightly removed an area for the larger exhaust valve on the edge of the bore as described in Crash’s  post. New seals , gaskets rings and bearings and carefully reassembled. Set  the timing etc , cam chain position etc, primed oil pump and filter and she was ready. Pulled plugs and cranked to get oil pressure up , plugs in and she started first pop.Bolted back up and fitted heat exchanger etc and other bits that jet boats have. Took it down to the local lagoon a few times to do the “run in “  process . What a difference. It goes like a cut cat , Clean instant start , way more power.Crisp is the word. Really pleased with the outcome so many thanks for your help. Got to say it’s been a great experience and considering we did this on an old kitchen table in the garage I’m impressed with the finished product. Cheers again , Paul. Ps if I can get a photo up I’ll do it soon as it looks as mint as it goes.

 

[Stoffregen Motorsports]

I love the smell of a new motor in the morning.