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Help With Valve Clearance Specs

MJTru

By MJTru,
in Engines & Forced Induction

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MJTru Mentor

MJTru

Posted
Posted (edited)

Hi im having issues posting.

I would like to know the rb26dett valve clearance for the intake and exhaust valves please.

I think the exhaust is .015 +/- 1

But I hqve no idea what is the intake.

Edited by MJTru
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MJTru Mentor

MJTru

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Posted

Intake .45mm

Exhaust .38mm

Yes I just finish reading and found the best balance.

I found that I should run

.010 on the intake side

.013 on the exhaust side.

The stock specs are on the loose side but will work.

I just finished taking measurement

On the exhaust side all are about .014 in the exception 4 of them. Out of the four 3 of them are at .012 and one is at .010 now that one is to tight.

On the intake side 6 of them are at .014 and 4 of them are at .012 and 1 is at .016 and another at .010.

What do you guys think??

Well im thinking to get that one one the exhaust side thats .010 to .014 or around there.

The intake has more thats off. So if im going to get all these to .010 intake and .013 exhaust I will need to buy all new shims.

I will have to pull all shims one at a time measure them and add or subtract the difference.

Damn this is hard work. Wounder what a job like this would cost. Lol

portaz Mentor

portaz

Posted
Posted

Are they new cams? I had similar issue a few out of spec on both sides but after a quick run it seemed to settle itself I think the coating on the cams was the issue for me anyway and also many tuners run them tighter but exh is tighter I think because valves are sodium filled or something like that ?

MJTru Mentor

MJTru

Posted
  • Author
Posted (edited)

Intake .45mm

Exhaust .38mm

I understand all points. Can someone tell me what nissan consider the right specs are. From my past experience with engine building the exhaust should always be bigger do to thermal exspasion. You all will have to explain to me as why the exhaust should be the tighter side and why. Good luck with that mates.

These are different cams from stock but are hks 272 duration and 8.5 lift. Same as stock. But bigger duration. Not new but has been used for about 5000 miles.

Never the less if I was to do the math I would still try to place all intake valves at .010 and all exhaust at .013 or the most at .014 which most exhaust valve clearance are at rigth now on the exhaust side.

Edited by MJTru
MJTru Mentor

MJTru

Posted
  • Author
Posted

Lol. Im not sure if those are the spec from nissan but I remember seeing them as well. I was hoping for a screen shot from the manual.

Well im guess no one knows why the exhaust would be tighter than the intake. All im saying is that the exhaust valves sees way more heat and will expand way more than the intake side. Also 95% of the motor ive worked on the exhaust side the looser side. Or the bigger side.

Im left to wonder why the exhaust side would be tighter than the intake. If that is the case then all my specs needs to be changed. But I have room to work with. As the shims can be machined thinner. This will make the gaps bigger. The biggest one was .016.

MJTru Mentor

MJTru

Posted
  • Author
Posted (edited)

Thanks thats was a great explanation. Actually I was going to mention that last night but fell asleep.

I was looking around on this forum and found that same answer. Lol. But I also fund a a member than runs .012 on intake and .014 on the exhaust. He never mentioned have any issues with those settings. What I found interesting was the tips he mentioned can be used on the shims.

He mention that you can use a wet dry sand paper to get the shims in the right size if you arnt to far off, and that you can also clean up the edges so that it can fit in the retainers/buckets better.

What do you guys think about using this method to gain like .002 th. of an inch.

I got a new head I figure that all my vaules were going to be to big but it seems that they are to small. You mentioned moving around shims can also work. But that idea would only work keeping in mind of the shim size and if the difference is coming from the shim and not the fact that someone grind the back part of the valve. If thats the case then moving shims won't help.

Edited by MJTru
GTSBoy Grand Master

GTSBoy

Posted
Posted

Marcus,

You can manually sand down shims, but you really should do it very very carefully. You need to stick a sheet of suitable grade wet&dry onto a sheet of glass or a very flat steel plate and using copius amounts of water you need to linish the shim in a figure 8 motion, using very even pressure and rotating the shim 90 degrees every few turns of the figure 8.

I did this to a few Intel Celerons back in the 90s! I also did it to a few of the shims out of my ALFA engine I was building. Both jobs were a good way to use up a LOT of time.

In this day and age it is easier and not too expensive to just get a few new shims. You keep your old shims in a box and you may get to use them next time you're doing the same job.

The trick witih swapping them around is just that if you have a few clearances that are wrong, you may be able to get them closer by just moving shims between them. Luck of the draw whether you will get the opportunity to do it. But it is really really simple maths to work out what change in thickness you need and whether any of them will swap.

MJTru Mentor

MJTru

Posted
  • Author
Posted

Thanks GTSBoy. I do think its simple math to. Its just a pain.

Do you think if I was to run .012 on the intake and .014 on the exhaust it will be fine.

I only ask because if thats the case I can clean up the exhaust side quite easy.

The intake I can work out with new shims or extras I might have around.

Thanks mate

GTSBoy Grand Master

GTSBoy

Posted
Posted

Imperial sucks :)

You're telling me nothing new. I'm in our US office at the moment, helping the local guys do some tricky modelling work. I usually refuse to work in any units other than SI. In engineering work it is so good to be able to just divide and multiply by powers of 10 in order to get stuff done. Come to the US and suddenly I'm forced to work with the numbers that they are comfortable with and it is all mmBtu/lb and slugs and cfm and inches of water and other bullshit units that might as well be based on the length, mass and volume of a cordial bottle (a system of units that I invented for myself in year 12.......a long time ago, by the way) for all the logic and self consistency built into them.

I mean shit.....fluid ounces and mass ounces. Don't have anything to do with each other. 14 of them in a pound, 16 of them in something else. 12 inches in a shoe...no wait, my shoe is 1 inch longer than my foot, so that's 13 inches. Long tons and short tons. For Christ's sake! A short ton is 2000 pounds. That is a full 10% less than a real ton. A long ton isn't even equivalent to a metric ton because it's still about 2kg short of 1000kg. Heating engineers here use a unit called a "ton of cooling". This is the power required to freeze one ton of water in 24 hours. Or some such stupidity. No mention of the starting temperature of the water (assume it is zero at your peril). There are three different sets of "Standard" conditions. No-one ever knows what someone else means by "standard" cubic feet. All I can say is that US engineers have to have a real good understanding of the physics and mechanisms behind what they're calculating because they simply can't hide behind simple calculations where you can cancel off 3 or 6 zeros and still get the right answer!

MJTru Mentor

MJTru

Posted
  • Author
Posted

Lol. Yes it does. I actually like metric system but dont tell my friends that. Lol that was so funny.

Ok I give up ill just do the oem specs and hope for the best.

Intake at .45mm

Exhsust at .38mm

Intake at .017

Exhaust at .015

Thare all should be happy now.

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