Rustys Race Motor

[DatDoug]

My Datsun buddy has been racing his 69 Dime & his motor is getting tired so hes building a L16 M2 block with Flattop pistons & putting a A87 peanut head with bigger valves & cam.

 

What I want to know is what do you do so the valves dont hit the pistons?

[Skib]

My Datsun buddy has been racing his 69 Dime & his motor is getting tired so hes building a L16 M2 block with Flattop pistons & putting a A87 peanut head with bigger valves & cam.

 

What I want to know is what do you do so the valves dont hit the pistons?

 

 

depending on how big the valves are, how shaved the head is/HG thickness, and the cam size you may or may not have to do anything.

 

 

 

but assuming it hits every way possible youll need to notch the cylinders to clear the vavles and cut releases in the pistons

 

 

[DISLEXICDIME]

let me go look at my old l16 and i will let you know. if he is using z car valves tell him to cut reliefs in the block just to be safe it saved my ass on my last engine

[DatDoug]

 

I just realized that it should not be a problem. When the piston is all the way up then the valves are closed :blink:

 

This should be a lil screamer :hyper: Hes going to be running dual mikunis. Now he just needs to update his brakes & suspension.

[DISLEXICDIME]

it will be a screamer what happened to the head that came on that block.that is a crate engine see the way the crank case breather is. that is a later model l16. if he still has the head pull out the valve springs and compare how stiff they are so a us engine.

[banzai510(hainz)]

if the cam is really tall the valve could het the side of the bore. But I cant remember if it was the intake valves or using the 38mm exhaust valves.

Dont matter ,when you turn the crank over a few times and it dont lock up then I assume your fine.in the nissan book its called unshrouding the valve(the old how to race your 510/610/240z book)

[DatDoug]

it will be a screamer what happened to the head that came on that block.that is a crate engine see the way the crank case breather is. that is a later model l16. if he still has the head pull out the valve springs and compare how stiff they are so a us engine.

 

Yhis block came with a truck I bot last year & did not av a head on it. If I remember correctly :unsure: the head that was in the bed is a W53 peanut.

[DISLEXICDIME]

Yhis block came with a truck I bot last year & did not av a head on it. If I remember correctly :unsure: the head that was in the bed is a W53 peanut.

 

darn

[defdes]

Those M2 blocks are nice, they can handle being bored out to 95mm for an L16/18 cheater motor.

[datzenmike]

 

This is the first L16 I have seen with the block vent NOT coming straight out the side like the

 

L20B:

 

L16/18 note there is no boss at top of block and no provision for dip stick holes on this side.

 

Also I have an M2 block. It's an L20B from a '78 truck:

 

 

The top edge of the block has a raised boss just like the Z and KA series, also two positions for dip stick tubes, never seen that on an L series. That block looks closer to a Z22:

 

 

 

Weirdest L16 I ever saw.

 

 

 

Those M2 blocks are nice, they can handle being bored out to 95mm for an L16/18 cheater motor.

 

 

Holey fuck! 95mm! the bores would touch!

 

.

[HRH]

All you have to do to keep the valves from hitting the pistons on a tight motor like that is REALLY stiff valve springs. Probably in the 160 pound range, but double check me. That's if you want to rev to 9 grand. (Really)

[Master-O-Turbonics]

Those M2 blocks are nice, they can handle being bored out to 95mm for an L16/18 cheater motor.

 

 

That is not physically possible for any L series.

Bore spacing is 94mm-94mm-96mm-94mm-94mm on an L6, and 94mm-96mm-94mm on the L4 motors.

Largest bore I have heard of on any L series was 92mm, on a wet sleeved 3.5 liter stroker L6(bigger crank than the diesel)

[defdes]

Ummmm.... typo. 85mm , the L18 comment didn't give that away?

[datzenmike]

Thought you had a secret JDM block source or something. Understood. :P

[DISLEXICDIME]

i still have one of these blocks in my garage it was a perky little engine pulled nice from 3000 all the way to 7500 . the head was shaved half way through the nissan letters on the side. lol it had 17/8th inch exhaust with 38mm su's and very stiff valve springs. The reason i pulled it was because the clutch died and the valve stem seals where leaking.

[datzenmike]

 

I just realized that it should not be a problem. When the piston is all the way up then the valves are closed :blink:

 

This should be a lil screamer :hyper: Hes going to be running dual mikunis. Now he just needs to update his brakes & suspension.

 

DatDoug you sure that ain't a Z22 block? Got a picture of the front or the other side???

 

 

 

I just realized that it should not be a problem. When the piston is all the way up then the valves are closed :blink:

 

On compression they are but on exhaust they are both slightly open

[RoadRace]

both valves are closed because that's the compression stroke, its the exhaust side you have to worry about with P to V. the duration and degree of opening for exhaust valve is the primary reason for notching the piston. as the piston moves up the exhaust valve opens to get rid of the spent gases that the piston is pushing out, if the valve hangs open too long, the piston will hit it on the way up.

 

if there is any doubt, use check springs in place of the normal valve springs when you are degreeing the cam in. you can quickly push the valve down manually and verify the actual clearance. Set up a dial indicator and make sure you have at least .090" P to V on the exhaust, .070" on the intake.

 

I made cutters to notch my pistons out of 2 old valves and i brazed old lathe cutting tools on the valve face and then sharpened them. i just use an old bare 210 head and mark the valve stem on the spring side with a sharpie for depth and use a drill on the valve stem.

[DatDoug]

Well the valves did hit the pistons :( We used 2 dif. heaDS & bent valves on both of them. What is the best solution for this problem? He is going to build the head with a 488/275 cam & that is going to send the valves out even further. Should he just get stock pisstons or notch the flattop Z ones?? Is ther enuff meat? Use a .020 shim? Anyone use this settup?

[Dime Dave]

Datsunmike,

Look at the serial # pad on the breather (int/exh) side of the block. The L series is on the spark plug side. Could this be a non-USDM Z16 or Z18 block?

[Dime Dave]

DatDoug,

I built a 3mm overbore L16 with cast flat top 86mm 280Z pistons and had the pistons notched. The casting thickness of the dome will determine what depth the notches can be cut. If you can measure the thickness of the piston head, your machine shop should be able to tell you how much depth they can safely cut the notches to.

[banzai510(hainz)]

what size are the valves?

 

I have 475/275 and a 460/270 lift cams and no proplems But 42mm/35 and the other 42mm/30mm on the other Both L16s.

 

I assume you spun the motor around a few times to see it it hit the block or pistons.

 

I dont think those cam durations are long enough to hit a piston if its timmed correctly flattops or not. Its when you get in HUGE durations overlap cams and Dome Top Pistons

 

 

Notice when you dial up to TDC you should see your rocker arm closing or fully close before the crank gets up to Zero on the pulley.

 

Unless you have photos of the pistons being damaged with the bent valves.

 

 

My green 521 Had the L16(.040over) U67head 460/270 L16 with Flattops and NO valve reliefs. Had no proplem. No this head is on the L18 .

[DatDoug]

Let me clear this up. The heads which we used had STOCK cams. He is going to build a head with a bigger cam. But the heads that hit had STOCK cams. We did hand crank the motor first & it did not seem to hit. The head had been shaved to maximum.

[banzai510(hainz)]

The head had been shaved to maximum.

 

 

 

What does this mean? Maximum? I seen some heads where bottom of the letters where cut off.( I avoid these heads) I assume thats alot material cut off.. I personlly try to NOT shave a head at all only enought to get a straight edge. to get longer use out of them and limit the number of cam tower shims used.

 

Only suggestion I have is get a straight near stock cut head(so there is not a stack of cam tower shims). and use the stock valves. 42mm/35mm

35mm exhast is close to L16s

 

Maybe put cam setting to 2 or 3

 

If head is cutmilled alot like you say I think you know to get cam tower shims to make up the difference that the head was milled. if not it cuases the cam to RETARD the closeing later while piston is comming up. But I think you know this already so I can only assume it OverSize valve related. As Im sure you and Datsunfisch have put together motor very similar and he has not had a bent valves. L16s you have to watch out for. But if you open the motor you know where it hits.

let us know Im intriged on what the proplem is

[datsunfish]

I have been perplexed on this one too. I thought that ported A87 had a regrind cam in it..? I would think that there would be something obvious during setup to know ahead of time if there was contact. The L16 in my truck has stock dish pistons but a very deep cut in the a87 head with no shims and the chain is sloppy as shit but never tapped a valve.

Did they shave the block?. It really shouldnt hit,doesnt the z motor those pistons come from use the same larger intake valves??

[SHADY280]

i had the exact l16 in my truck with the breather exactly like that. trucks gone now so i cant take pix. really strong motor tho. i thought the m2 marking was a bit strange. it also had 2 dipsticks on the pass side. the rear one was functional and the front was shortened as a plug