What cam is this? (1 Viewer)

[JohnJL]

Under the hood of my Nissan is a pair of synchronized coils, eight spark plugs, four cylinders measuring at 2.4L, which was competition for the 22R. Two spark plugs in each cylinder netted greater combustion efficiency than one, also, it creates peak pressure sooner in the piston stroke, by having the combustion of one flame-front increase the compression in the environment of the second flame-front. It used unprecedented amounts of reused combustion gas, up to 24% (on some models) by volume. It got better ratings for fuel economy, HP, and torque, than its predecessor motor without the dual spark.

There is only a short pipe for EGR cooling, The system is still clean when I disassembled it, but the EGR valve is subject to rust, internally. The valve is still available, new, OEM.

A little hijack here: I don't know this for certain, but the 4wd version of the Nissan pickup was likely the first marketed in the USA to deviate from a solid-front-axle set-up. It '86 Toyota, and everyone else, followed.

I have some with twin plugs too....

 

[1911]

Well its a Delta KC cam....no visible indication the timing gear rotated, the insulation seems uniform almost all around except in one spot.

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This is a little weird though...#1 exhaust and # 3 exhaust lobes are "pinched" at the lobe apex...

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Flat tappets are hard on cams; even harder if there is not plenty of zinc and phosphorous in the oil. But that makes me wonder if those two pushrods are not straight, or those valve rockers are a bit loose on the shaft?

 

[JohnJL]

Flat tappets are hard on cams; even harder if there is not plenty of zinc and phosphorous in the oil. But that makes me wonder if those two pushrods are not straight, or those valve rockers are a bit loose on the shaft?

Thanks for the reply and comment. I do use liquimoly additive to a diesel motor oil. The cam has like 10 kms and some idling on it, with an oil change after the first 30 mins break-in. The wear on those lobes seems uniform - like barely broken in - and the valves opened to the same measurements so I dont think there is any problem with those. I will go roll the pushrods again, I didnt see any damage to any. It just seems like when the cam was made it has narrower peaks on those 2 lobes. I am attaching those pics with some questions for Delta now.

 

[FJ40Jim]

The "pinched" lobes look like the lobes that were weld repaired and reground.
The important thing is that the lift & timing is correct.

 

[Dizzy]

I once read that the duration that the valve is in contact with the seat has some influence on the heat dissipation. Is that more or less the case? How do these cams compare with exhaust valve longevity?

How much does valve clearance change performance? I set mine .003" tight, as it eliminated a valve train click, and there is about a .003 step on the face of the rocker arm, so it was logical to me, as I'm not going to try to grind it down in my shade-tree-shop, and I can't get a feeler gauge to not cross the wear-step on the rocker arm. I've heard of hot rodders ditching their hydraulic lifters for solid one, and tightening up their clearances to where it will close but not much more, just to open up a bit more-helps at peak rpm.

 

[Mark Jennings]

I once read that the duration that the valve is in contact with the seat has some influence on the heat dissipation. Is that more or less the case? How do these cams compare with exhaust valve longevity?

How much does valve clearance change performance? I set mine .003" tight, as it eliminated a valve train click, and there is about a .003 step on the face of the rocker arm, so it was logical to me, as I'm not going to try to grind it down in my shade-tree-shop, and I can't get a feeler gauge to not cross the wear-step on the rocker arm. I've heard of hot rodders ditching their hydraulic lifters for solid one, and tightening up their clearances to where it will close but not much more, just to open up a bit more-helps at peak rpm.

These old I6 engines are water cooled...and as long as water is flowing through the head....and it’s not boiling over....exhaust valve seating duration shouldn’t be an issue....air cooled is a bit different (P-Car example above), old VW’s, Porsche’s, and Harley’s are sensitive to lugging where you have an open throttle at low RPM...lots of fuel/air, high combustion pressure and high temps...so high that the airflow across the fins can’t dissipate the heat fast enough....some of my early hot rodded VW’s...the hot setup was was sodium filled exhaust valves. I think for some Porsche’s, sodium valves are still available (JohnJL you need to check me on that, my P-Car is H2O cooled).

The valve/rocker clearance on flat tappet mechanical cams is set by the manufacturer for thermal growth of the engine, valves and pushrods. Even if you have an aftermarket cam....all other factors the same....the clearance shouldn’t stray that much different than stock.

.014 for exhaust because they are hotter and .008 for intake....they run cooler.

As far as your step in the valve....most likely cause is the adjuster ‘sliding’ across the the top of the valve stem and after years of service...wearing a step in the stem....they used to make lash caps....and on the VW/Porsche example....we used to get ‘swivel feet’ adjusters. Basically a ball bearing with one side ground flat pressed into the end of the adjuster.