Valve Adjustment!!! Correct Specs!

[dmcerm]

Hi all it's me again...

From the old forum... I had bookmarked a great thread many of you were helping me with regarding my pending valve adjustment (this project was sidetracked when my new clutch install did not go as planned and has plagued my DeLorean ever since... but I digress) one of you, some of you gave me some really great tips to see that it got done correctly and one of you even lead me away... far, far away from the original DMC shop manual's number and you actually scanned a page from another motor manual that had the actual, accurate numbers... if you're out there and remember that conversation... could you scan that/those pages again in a reply?
After I get my A/C recharged (seem to have to do that once a summer... and despite dye testing, they just can't seem to find the leak...) my first priority is this valve adjustment... it will happen... I have my valve cover gaskets already and am just waiting until after my first big show of the season to put her under the knife...
Any help with this post would be appreciated and again, thanks for all your help and advice.

Mark
16891

[DeloreanJoshQ]

Hi all it's me again...

From the old forum... I had bookmarked a great thread many of you were helping me with regarding my pending valve adjustment (this project was sidetracked when my new clutch install did not go as planned and has plagued my DeLorean ever since... but I digress) one of you, some of you gave me some really great tips to see that it got done correctly and one of you even lead me away... far, far away from the original DMC shop manual's number and you actually scanned a page from another motor manual that had the actual, accurate numbers... if you're out there and remember that conversation... could you scan that/those pages again in a reply?
After I get my A/C recharged (seem to have to do that once a summer... and despite dye testing, they just can't seem to find the leak...) my first priority is this valve adjustment... it will happen... I have my valve cover gaskets already and am just waiting until after my first big show of the season to put her under the knife...
Any help with this post would be appreciated and again, thanks for all your help and advice.

Mark
16891

+1....I set my per the manual .06" intake, .10" exhaust and the engine valve clack is louder than other Deloreans....Danny Botkin at DMC CA said they do both valves at .07"....
I am going back in Thurs and rechecking...hopefully someone will chime in confirming or with another figure before then.....

[dmc6960]

Manual says .004" for the intake, .010" for the exhaust. The reason for having a gap is to account for expansion of the valve as it heats up. The listed clearances are calculated rate based off of normal engine operating temp. You'll find little to no gap in a hot engine. You dont want it too little of a gap when cold, otherwise the valves wont fully seat when hot. You also don't want too much gap, so that the tappets are still lifting off and hitting down on the valves when the engine is hot. I would not deviate far from these numbers, they are what was recommended to me for my performance engine build as well.

[DeloreanJoshQ]

Manual says .004" for the intake, .010" for the exhaust. The reason for having a gap is to account for expansion of the valve as it heats up. The listed clearances are calculated rate based off of normal engine operating temp. You'll find little to no gap in a hot engine. You dont want it too little of a gap when cold, otherwise the valves wont fully seat when hot. You also don't want too much gap, so that the tappets are still lifting off and hitting down on the valves when the engine is hot. I would not deviate far from these numbers, they are what was recommended to me for my performance engine build as well.

Jim, how quiet is your valve clack? Do you have any recent video of the engine idle to share?

[dmcerm]

Ok cool.

Well that is sort of my issue... when I last posted about this issue, I was told in no uncertain terms to NOT use the numbers in the original shop manual because they were wrong or not optimal... so that is why I'm asking here, hoping that adjustment guru from the old forum will get on and re-post that scanned pages from the other motor manual he uses, that he said were correct.
I will do some more digging around nad thanks a lot for your numbers... I will certianly use them as a reference point when I take this issue to my mechanic.

Yeah, I'm trying to get over some of the valve chatter and since originally they valves were supposed to be adjusted every 10,000miles, I at least wanted to get it done once.

Keep thos comments coming!
Love DMCTalk!

Mark
16891

[dmc6960]

Jim, how quiet is your valve clack? Do you have any recent video of the engine idle to share?

Can hardly hear it. I'll try to make another video tonight when I get the Megasquirt computer reinstalled and go for a test drive.

[content22207]

773
There's something to be said for hydraulic lifters....

Bill Robertson
#5939

[dmcerm]

Bill,

So are those numbers on that PDF the ones that I should be using when I tell my mechanic where to set them?
Thanks for the scan, not sure if you're the one who scanned valve info for me last summer but thanks for your input!

Mark
16891

[content22207]

Those are Volvo's studied opinions.

Bill Robertson
#5939

[dmc6960]

Looking carefully at that picture you'll see the same specs for our engines as the DMC manual, .004" intake, .010" exhaust.

[content22207]

It's the same engine (Volvo owned the tooling).

Bill Robertson
#5939

[dmcerm]

Ok, well I was just out the garage to find my manual and I also found the print outs from last year's discussion on this same subject... now just the PDfs that were sent to me from the other manual... but yes... the numbers, as was just stated in an earlier post, are the same in both the Volvo manual and the DMC one... so I guess the problem that wasn't is now solved... I will be sure to have them do it to specs in the DMC manual and use the Volvo guide for the in-depth procedure, if they'd need it for any reason.

Thanks again people and I'll keep you posted on the projects progress... after June 18th, I hope to have it scheduled...

Thanks and keep posting any helpful hints that any of you may know about...

Mark
16891

[jmettee]

The reason for having a gap is to account for expansion of the valve as it heats up. The listed clearances are calculated rate based off of normal engine operating temp. You'll find little to no gap in a hot engine. You dont want it too little of a gap when cold, otherwise the valves wont fully seat when hot.

That's what I always thought, but the warm engine clearance values are larger than the cold engine vlaues... :confused:

[82DMC12]

That's what I always thought, but the warm engine clearance values are larger than the cold engine vlaues... :confused:

Not sure how many people would be trying to adjust valves when the engine is hot anyway!

Andy

[content22207]

Valves and camshaft are made of steel -- it's not them that expands, it's the head itself (aluminum expands at a much lower temp than steel, and it expands more).

Bill Robertson
#5939

[DCUK Martin]

aluminum expands at a much lower temp than steel, and it expands more

Sort of correct but misunderstanding the coefficient of thermal expansion. Given the same circumstances, aluminium will expand more than steel for a given temperature increase. It's not true that it "expands at a much lower temp". The camshafts, and the rocker arms (I believe) are made of cast iron.

It's a lot more complicated than that because it's not free to expand in every direction, so for example the tension in the head bolts increase rather than the heads getting taller.

[content22207]

Speaking as someone who has liquified aluminum while trying to heat it up to bend it, I 100% assure you that aluminum behaves very differently to heat than steel does. If you don't believe me, take an acetylene torch to a 1/4" piece of aluminum and a 1/4" piece of steel and see what happens....

Speaking also as someone who just replaced the water pump on a cast iron bus engine after his church boiled the coolant (with absolutely no warpage to the heads, thank you very much) I 100% assure you that ferrous metal expands much less at 212+ degrees than aluminum does.

Bill Robertson
#5939

[Bitsyncmaster]

http://www.p1m.com/expansion.htm

Here is a table of expansion and melting points.

[David T]

It is a whole lot more complicated than just measuring expansion rates of different metals. As pointed out things can't expand equally and in some cases the tolerances do not behave cumulatively. These clearances were found by trial-and-error starting at a calculated point. Deviating from factory specs, as always, is at your own risk. Remember these clearances are set for the correct operating temperature so if your cooling system is making the car run hotter or cooler the factory specs will not be optimum. There is very little if anything to be gained by deviating form the factory specs. When you do check the valve clearances you will find you may only have to actually adjust 1 or possibly 2 valves anyway. Don't forget to reset the Lambda counter and replace the O2 sensor at the same time.
David Teitelbaum

[DCUK Martin]

Bill, you said "aluminium expands at a much lower temp than steel". That statement is meaningless. It has a higher coefficient of expansion than steel. But even that statement is conditional. A cylinder head is restrained by its head bolts and can't therefore freely expand..

[content22207]

Ain't no bolts holding the camshaft cradles.... (Hence the larger valve lash specs for a warm engine).

Bill Robertson
#5939

[Bitsyncmaster]

Ain't no bolts holding the camshaft cradles.... (Hence the larger valve lash specs for a warm engine).

Bill Robertson
#5939

I bet push rod engines had to really make a large gap. I guess that's why every used hydraulic lifters.

[DCUK Martin]

The camshaft "cradles" are clamped by the head bolts and these

http://www.delorean.com/store/p-6180-rocker-inr-support.aspx

To properly examine the relative expansions and internal stresses and strains within the heads and valvetrain, you'd need a computer, a pretty sophisticated model and FEA. Or, much more simply pull some valid experimental data. I'm not getting into a dumb argument about all-cast-iron engines being somehow "better". It's irrelevant to this topic and my point was a simple one.

[content22207]

I bet push rod engines had to really make a large gap. I guess that's why every used hydraulic lifters.

You don't want any gap with push rods.

To adjust old pedestal mount rocker arms (solid lifters) you rotate the engine to unload various push rods, then spin them between your fingers as you tighten the rocker arm down. You want just a hair of resistance.

Hydraulic lifters totally alleviate the need to do even that -- simply bolt the rocker arms down and start the engine.

Bill Robertson
#5939

[content22207]

... I'm not getting into a dumb argument...

Something's expanding somewhere (more than something else), otherwise warm engine valve lash would not be larger than cold engine lash.

Either that, or Volvo doesn't know what it is talking about.

Bill Robertson
#5939

[DCUK Martin]

Something's expanding somewhere (more than something else), otherwise warm engine valve lash would not be larger than cold engine lash.

Yup. Never disagreed with that.

[DeloreanJoshQ]

Michael (DMC1983) and I adjusted the valves and triple-checked each one on my car today at Dave B's shop. They are quieter, but the clack is still present. I will just live with it. 4 were ok and didn't get touched, the rest varied from slight to loose enough warranting re-adjustment.
I didn't notice any performance improvement. However, it was over 90 degrees out and the A/C was on.
Thanks for the specs and thanks Michael for the help!

Josh Q

[content22207]

Did you check the condition of your camshaft lobes? (See the ZDDP thread).

Bill Robertson
#5939

[DeloreanJoshQ]

Did you check the condition of your camshaft lobes? (See the ZDDP thread).

Bill Robertson
#5939

They appeared ok; used Brad Penn break-in oil with ZDDP and after 500 miles put pennzoil 20W-50 in...