Valve lash compensation

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boilermaker

boilermaker

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Running a 318 with a 528 solid cam ( iron heads) . I ran 273 rocker arms last season with great results.
I went to Crane gold 1:6 rockers this year. Both 273 and Crane’s were set to .026”& .028” cold.
Valve noise is now noticeable much more than the “273’s”.
Is there a compensation in lash going from cast arms to aluminum?
Thanks
John
 
I cant think of any set formula from iron to AL, the only way is to measure when hot. Most of the AL lash is from AL heads that expand more than iron. AL has an expansion rate of ~2X that of iron but rockers are pretty small in volume.
 
No. The rocker doesn't know or car what it's made out of.

Secondly, I have never seen lash get tight when an engine heats up. So the idea of setting the lash loose cold with cast iron heads and block is wrong. I set my CI stuff .002-.004 tight cold. And then check them hot to see how much they close up.

Third, there is no way if lash that cam at .026 cold. Not for all the tea in China. If it were me, I'd start at .018 cold and then check it warm. I wouldn't go any looser than .020 hot and maybe, and it's a damn skinny maybe .022 hot on the exhaust. There is no reason to run the lash that loose. That lobe has a long slow lash ramp. Pick it up further up the lobe.
 
yellow rose said:
No. The rocker doesn't know or car what it's made out of.

Secondly, I have never seen lash get tight when an engine heats up. So the idea of setting the lash loose cold with cast iron heads and block is wrong. I set my CI stuff .002-.004 tight cold. And then check them hot to see how much they close up.

Third, there is no way if lash that cam at .026 cold. Not for all the tea in China. If it were me, I'd start at .018 cold and then check it warm. I wouldn't go any looser than .020 hot and maybe, and it's a damn skinny maybe .022 hot on the exhaust. There is no reason to run the lash that loose. That lobe has a long slow lash ramp. Pick it up further up the lobe.
Click to expand...

Thanks for the info. I got the cam without a card and ( I confirmed it’s the old 528 Mopar ) from what I read about this cam it’s a loose lash . Had it set to .022 & .024” and it ran great.
I’ll tighten it up a bit.
I’m just a bit paranoid about the solid valve train noise. The cam makes great power all the way to 6500 rpm.
John
 
Running that same cam in "Georges" Cuda, and set clearance at .018 / .020. You're wayyy too loose on your setting!
 
Max1196 said:
Running that same cam in "Georges" Cuda, and set clearance at .018 / .020. You're wayyy too loose on your setting!
Click to expand...
I’m going to tighten them up.
You run a vacuum gauge ?
If so what kind of vacuum at idle in gear you have?
I also found more issue with noise this morning. The Cranes have way too much side movement.

Going to order some shim rings today.
 
It idles at 800 but were using the vac can on the distributor to bring up the initial timing. It has a FBO restrictor plate in the distributor, without the vac it's 12 initial, with vac it's 30 initial. total is 34. No vac to distributor at 800 it's unstable at about 10 for vac, things improve with the vac hooked up to add advance. Static compression is 10.93 to 1
 
Max1196 said:
It idles at 800 but were using the vac can on the distributor to bring up the initial timing. It has a FBO restrictor plate in the distributor, without the vac it's 12 initial, with vac it's 30 initial. total is 34. No vac to distributor at 800 it's unstable at about 10 for vac, things improve with the vac hooked up to add advance. Static compression is 10.93 to 1
Click to expand...
Thanks for the info. I tightened up the lash to .024"& .024". Mopar distributor set to 28* initial at 750 rpm ( in gear) all in 34* at 2000 rpm. The 302 heads don't like much more. Vacuum at idle (1000 rpm) is 10-11" and 6" in gear. I cured my Valve train noise. The new rocker arms had way too much gap. Got them set up to .025-.030" clearance.
 
And a lot of the noise increase may just be in the rocker material. All cast, ductile, and malleable irons are pretty good at absorbing noise (high damping capacity).
 
The change in ratio can make it louder. Remember the speed that the lash is being taken up is faster with a 1.6 rocker. The greatest benefit to running a 1.6 rocker is usually not the increase in gross valve lift. Its the shorter time it takes to get the valve open to a useable lift amount. It could have also throw off the geometry.
 
your geometry may be FUBAR- you may need to raise your shafts - your rockers are angled up by the amount of the radius of the roller
and how did you figure your new pushrod length

edit the following poster jimjim posts a good link read it a couple of times there are four parts
 
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jimjimjimmy said:
check your geometry and take a picture of your sweep pattern and show us .

AND READ THIS . B3 Racing Engines LLC - Mopar Rocker Arm Geometry Tech
Click to expand...
My geometry is very good ( I think?).
My Dart ran 13.45 at 100 mph on the first outing. Like to shoot for 12.99. Thanks to all who chimed in on this . You guys make my experience in Mopar land that much better.
 
I'll let others chime in but look usable to me
chevy rockers are longer than mopar so being off to one side is to be expected
nice pic
can you shoot from the end up , half lift, full lift- you take nice pics
at half lift a machinist rule sitting on the retainer should run through the retainer about the same height as the stem is above the retainer AND T the live from the center of the shaft should go through the pin in the nose of the rocker
the two lines should be parallel
etc
 
boilermaker said:
View attachment 1715206292 View attachment 1715206291
My geometry is very good ( I think?).
My Dart ran 13.45 at 100 mph on the first outing. Like to shoot for 12.99. Thanks to all who chimed in on this . You guys make my experience in Mopar land that much better.
Click to expand...


I'd send the pictures to Mike at B3 and let him look at them. IMO, you can correct it a bit but you aren't far off. I'd rather have the pattern narrow and off center than make it centered and wide. Wide is bad.
 
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yellow rose said:
I'd send the pictures to Mike at B3 and let him look at them. IMO, you can correct it a bit but you aren't far off. I'd rather have the pattern narrow and off center than make it centered and wide. Wide is bad.
Click to expand...
I will send these to Mike .
Thanks for the feedback.

John
 
yellow rose calls it and I agree
one other advantage of chevy rockers is that the pushrod cup is also further away from the shaft lessening pushrod interference- especially with over 1.5 rockers
If this was a race motor I'd have fewer threads- longer pushrod- but it's not
looks better than any other roller rocker setup I have ever seen without shaft spacers
congrats
drive it for awhile
report your compression
cheers
 
yellow rose said:
No. The rocker doesn't know or car what it's made out of.

Secondly, I have never seen lash get tight when an engine heats up. So the idea of setting the lash loose cold with cast iron heads and block is wrong. I set my CI stuff .002-.004 tight cold. And then check them hot to see how much they close up.

Third, there is no way if lash that cam at .026 cold. Not for all the tea in China. If it were me, I'd start at .018 cold and then check it warm. I wouldn't go any looser than .020 hot and maybe, and it's a damn skinny maybe .022 hot on the exhaust. There is no reason to run the lash that loose. That lobe has a long slow lash ramp. Pick it up further up the lobe.
Click to expand...
.028 for instance..." for valve seat cooling time "
Well **** I got hard seats and/or stainless valves now... guess I'll tighten up.
That's what I thought of it after reading years ago it considering all that I done at that time.
 
boilermaker said:
View attachment 1715206292 View attachment 1715206291
My geometry is very good ( I think?).
My Dart ran 13.45 at 100 mph on the first outing. Like to shoot for 12.99. Thanks to all who chimed in on this . You guys make my experience in Mopar land that much better.
Click to expand...

When I see that I think of valve lift acceleration but definitely not the duration you'd expect... more like a mystery grind...haha Plain and simple when the geometries off your not translating the lobe correctly. I need to send Mike the measurements from my own and get a kit myself... but you're probably close to lift ...haha .020 close. It would be a laugh to have everybody measure lift at the retainer to see how much lift they are losing.
 
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MOPAROFFICIAL said:
When I see that I think of valve lift acceleration but definitely not the duration you'd expect... more like a mystery grind...haha Plain and simple when the geometries off your not translating the lobe correctly. I need to send Mike the measurements from my own and get a kit myself... but you're probably close to lift ...haha .020 close. It would be a laugh to have everybody measure lift at the retainer to see how much lift they are losing.
Click to expand...
Here is t trivia question. What am I doing in this picture? First person to answer wins a new Kcar
 
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