OK I have a valve lash issue and don't know what to do. I've set my lash as usual set intake when exhaust starts to open and set exhaust when intake valve is wide open. My lash hot is supposed to be .014int .016exh My problem is with the aluminum block and heads I have found I needed to adjust them to around .004 and .006 to achieve my hot readings. I have found when doing a leak down test that at tdc I have have a preload condition. I'm sure that once the engine gets heat all this preload goes away? What would you guys do set them at zero lash at tdc and see what the hot lash grows to or just leave it like it is?

I have an aluminum block with B1 heads and set the valves exactly as you stated. My hot settings are supposed to be 22In 24Ex. and I set them at 10In 12ex, cold. Get them close, heat the motor up, and check the hot, then check them again when the motor cools. They do need to be pretty tight cold, so when warming the engine, I don't rev more than 2000 rpm. I'm not sure what you are talking about when you mention "preload". If your valves are binding agaist the pistons, you're too tight. I hope this helps.

Tom what I mean by preload condition is at tdc the valves are held .005 open. If I set them at zero lash cold at tdc to remove this I would have more lash than calls out on the cam card when the engine is warm. My other concern here about excessive lash is I'm running a set of all composite lifters and want my lash kept at the utmost minimum.

I give my aluminum Indy heads .008 extra cold. Iron block.
I think you are supposed to be doing exhaust when intake is almost closed on my cam the exhaust @ .050 is 23 ATDC and full lift on the intake is 102 ATDC and I think I measured .006 on the exhaust at 45 ATDC so not past enough to fully closed for me .

I would do some more checking as I found on my new cam I actually have to run the exhaust valve open a good bit, instead of just opening, to set the intake.

I was told also by a Big Time Mopar Man that Mopar engines need the exhaust valve about 1/2 open to set intake. When I set mine this way it runs a lot better.

Atoetly, I have found on my camshaft .012-.012 HOT. Its very hard to get both valves closed.When one shuts the other is opening at the same time.

I also have a aluminum block and heads. I was told to warm the engine up to 145 degrees to set valves.I like to get it up to 175 at least. What temp. does everyone else use.

Ya that a aluminum engine thingy.

I set mine to zero and they end up at 23ish with a 1.9 ratio. Different rocker ratios will give you different hot and cold numbers o a aluminum engine.

Allen, try .008 and .010 stone cold, leave the feeler gauge in one of the valves and rotate the motor over slowly to find where the valve is the looses on the lash and use that as your setting point Same thing on the other valve. These dang cam shafts that have inverted flanks and other magic lobes can drive a guy crazy

Alan
Your going to to have to run a looser lash adjustment, you don't want those valve hanging open. The cam you are running is a tight lash cam. My 500 in Engine Cam called for the same thing. I had to add .012-.014 extra to spec on camcard do to expansion & contraction of alum block & heads. This was recommended by cam manuf. and machinist. 1000s of passes no problems. set valve lash .006-008. cold, warm it up and see where you are at probably .020-.024 and go with that.

Thanks for the advice guys! I made a tool several years ago that allows me to adjust the valves with a dial indicator and if I like stuff a feeler gage in there also. Ron you are correct the exhaust valve on my cam wants to be open around half way and then I've got my sweet spot to adjust the intake valve. I never had this problem until I bought the alumium block and I've only got about 50 passes on it and most of those 1/8th mile. I told my wife the other day I should do a leak down test on it just to see how things look. It had 20% and it was pooring out the exhaust. Then I pulled the valve cover and found the valves where open, after I gave it some lash it went down to 5% where it belongs. Dave I think your right I will end up with more lash than what the cam card calls for at least .005 more anyway?

My last solid roller had an eccentric shaped base circle so I did what cab said (to find the loosest spot). I then plugged that info into the 8 position chart for valve adjustments and used that. So I had to take the cylinder numbers on the chart and slide them down a coulpe and re-did the chart in Word program on my computer and printed out a bunch of copies. That way I can just check off each valve as I go with a pencil.

Now I'm starting to think? I wonder if I have another cam ground with a wider lsa. current cam is on 110 lsa. Since at tdc we are not talking about the base circle of the cam a wider lsa might give me more lash at tdc but not sure.

Seems a tight lash ramp for an alu block/head combo , setting the lash .004" too loose could beat the valve train to peices , the lobes will tolerate a much tighter lash than going loose , get the ex vlve taking up all lash & lash intake , intake @ full lift & lash ex , the only way to be sure is to pull the valley plate/tray & check the lobes are on the base circle.

am i missing something here,i thought all cams start opening lifter before top dead center?

Is you're rocker ratio the same as the cam card states for lash settings? , .014" hot lash on a 1.5rr would equate to .016" when using a 1.7rr.

One of the guys I know will not run his engine cold,
he has alum block and heads, he uses a block heater
to warm it to 140* before he even thinks about firing
it... so if you were to warm the block it wouldnt
matter if your valve is partly open while cold

Other way around, no My bad,never mind

Everyone has a different opinion on this...

However...


FACT: adjacent rocker arms on the 'lobe' will cause shaft deflection.

I.E, if the intake valve is open and the exhaust is closed, the deflection will pull the exhaust arm away from the valve/lifter increasing lash.

Therefore: I always set my lash with BOTH valves closed at the same time.