How tight is it safe to lash street Hemi valves

[AR67GTX]

I can’t be quite 100% sure this has the original hemi street cam in it but I’m pretty confident it is. I ran the valves today and the intakes were lashed .019” to.025”, most around .022/.023. Exhaust were from .023“ to .026”, most around .027”. I set them marginally tighter than the FSM at .026” intake and .030” exhaust - cold.

But for future info, just how much tighter would it be considered safe to lash the valves on stock cam in a weekend cruiser without risking anything?

thanks

 

[Cranky]

Stock or aftermarket and hydraulic or solids?

 

[AR67GTX]

As far as I can tell, all stock mechanical (solid lifter) 66 - 69 cam/valve train.

 

[pnora]

Myself I would run them at the factory specs. .028 Intake and .032 Exhaust. This is a cold setting and I often wonder what the actual temperature is.

 

[451Mopar]

If they are too tight, the engine will start loosing power when it gets hot because the valves are not seating.

 

[RemCharger]

Myself I would run them at the factory specs. .028 Intake and .032 Exhaust. This is a cold setting and I often wonder what the actual temperature is.

I always thought the standard was about 70 degrees.

 

[pnora]

I always thought the standard was about 70 degrees.

That's what I would think. I was wondering if a guy was setting them and its 90 or a 100 outside how much would that change things.

 

[Geoff 2]

First thing you need to do is to check what, if any, difference there is hot or cold:
- turn the crank to ANY position. Note the position so that you can return to it.
- in that position, find a loose rocker & check/record the lash.
- run engine to get to operating temp & have tools ready to remove v/cover, measure lash, rotate crank.
- once hot, rotate crank & measure hot lash on valve checked earlier.


You can go down to 0.010" hot lash if you wanted to, it will cause no harm. But because of the large lash, this cam will have long ramps & would probably idle very rough once you tighten lash.
From the above test, you will know the hot/cold difference & that will allow you to adjust the lash, cold.

 

[AR67GTX]

Thanks but this is strictly a driver, I’m not going to deal with checking hot valve lash as it’s too big a pain with pulling wires, plugs, tubes and those big valve covers hot. I went .002 less to maybe attenuate some of the warm up clatter but I plan to stay close to FSM specs.

Just based on how the PO had apparently closed them down tighter before I was curious if there was any go-by on how tight you could go or experience with cold vs hot lash change.

My garage was around 80 degrees.

 

[gtxrt]

Thanks but this is strictly a driver, I’m not going to deal with checking hot valve lash as it’s too big a pain with pulling wires, plugs, tubes and those big valve covers hot. I went .002 less to maybe attenuate some of the warm up clatter but I plan to stay close to FSM specs.

Just based on how the PO had apparently closed them down tighter before I was curious if there was any go-by on how tight you could go or experience with cold vs hot lash change.

My garage was around 80 degrees.

on average the lash grows .004 on iron block and heads when hot. to loose is just as bad as to tight as the lifter will pound the camshaft.

 

[gtxrt]

if i recall a non tight lash cam you can go up to +4 more or -8 tighter

 

[eric383]

Myself I would run them at the factory specs. .028 Intake and .032 Exhaust. This is a cold setting and I often wonder what the actual temperature is.

I used these settings last year on my 67 GTX and no problem.

 

[Geoff 2]

AR67,
Post #8. I am NOT suggesting you lash the valves hot. This is a one time only to check the difference between hot & cold lash [ if any ]. Once you know this figure, you can check the lash cold very time.

 

[AR67GTX]

Thanks for the suggestion but I don’t think I need to go there. For one thing, whats the spec for hot? The only spec I’ve seen is for a cold setting. If you don’t have a Chrysler recommendation for hot its of no help in backing into a cold setting. I’ve done this on my aluminum head BB Chevy but I had recommended hot settings and pull 6 bolts and I have a valve cover off In literally minutes. But with it having aluminum heads there was a purpose.

On a Hemi I’m messing with trying to get the plug wires off the plugs without pulling them apart, getting the plugs out, pulling the barrels loose, removing 10 bolts, trying to maneuver the VC out around all the crap without beating everything up. By the time I get to the valves i‘ll be down to a Luke-warm setting at best and then if they are say .035 E and .032 I, what’s the significance? I don’t think I need this to bop down to the monthly cruise night.

 

[pnora]

Thanks for the suggestion but I don’t think I need to go there. For one thing, whats the spec for hot? The only spec I’ve seen is for a cold setting. If you don’t have a Chrysler recommendation for hot its of no help in backing into a cold setting. I’ve done this on my aluminum head BB Chevy but I had recommended hot settings and pull 6 bolts and I have a valve cover off In literally minutes. But with it having aluminum heads there was a purpose.

On a Hemi I’m messing with trying to get the plug wires off the plugs without pulling them apart, getting the plugs out, pulling the barrels loose, removing 10 bolts, trying to maneuver the VC out around all the crap without beating everything up. By the time I get to the valves i‘ll be down to a Luke-warm setting at best and then if they are say .035 E and .032 I, what’s the significance? I don’t think I need this to bop down to the monthly cruise night.

I would not overthink this. You are right on the valve covers. By the time you get them off the motor has cooled plus the pain to pull them. They always say set them cold. Then run it and measure them to find your actual hot lash setting. If you were racing and this was a norm you would know what a hot setting would be for your combo. For what its worth I believe Ma Mopar had that figured out for us with the .028 and .032 cold lash.

 

[451Mopar]

On my big block aluminum headed engines the lash usually gets larger as they heat up. I usually adjust 0.014"/0.016" cold on those engines, sometimes even tighter.
I don't have a hemi or other iron headed engine with solid lifters, so not sure how much lash change there is at the engine gets hot?

 

[OLD-DOG]

Thanks for the suggestion but I don’t think I need to go there. For one thing, whats the spec for hot? The only spec I’ve seen is for a cold setting. If you don’t have a Chrysler recommendation for hot its of no help in backing into a cold setting. I’ve done this on my aluminum head BB Chevy but I had recommended hot settings and pull 6 bolts and I have a valve cover off In literally minutes. But with it having aluminum heads there was a purpose.

On a Hemi I’m messing with trying to get the plug wires off the plugs without pulling them apart, getting the plugs out, pulling the barrels loose, removing 10 bolts, trying to maneuver the VC out around all the crap without beating everything up. By the time I get to the valves i‘ll be down to a Luke-warm setting at best and then if they are say .035 E and .032 I, what’s the significance? I don’t think I need this to bop down to the monthly cruise night.

The correct valve lash for a stock 426 Hemi is .028 intake and .032 exhaust cold as in 70 degrees and hot it is .030 intake and exhaust. I always set mine cold and used two feeler gauges for each, .028 as a go gauge and .029 as a no-go gauge for the intake, same with the exhaust .032 as a go gauge and .033 as a no-go gauge. It is permissible to be one or two thousand loose, but never tight. And yeah, everyone who rode with me told me my lifters weren't supposed to be that loud and I told them that the manual said nothing about using a decibel meter.

 

[64BEL]

I figure if she's singing like a Singer (sewing machine) all is well.

 

[gtxrt]

to loose is is as bad or worse than to tight.

 

[threewood]

On my big block aluminum headed engines the lash usually gets larger as they heat up. I usually adjust 0.014"/0.016" cold on those engines, sometimes even tighter.
I don't have a hemi or other iron headed engine with solid lifters, so not sure how much lash change there is at the engine gets hot?

I'm currently running .008" and .010" with AL heads, solid lifter. Cold lash.