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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: n20mstr]
#2768618
04/27/20 12:24 AM
04/27/20 12:24 AM
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Joined: Aug 2008
Posts: 4,066
Mo.
racerx
master
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master
Joined: Aug 2008
Posts: 4,066
Mo.
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It was different tho.  I have a ?.....what is softening the combustion chambers  ? imagine a shallow "bowl" cut into the chamber. it slows the flame front . NA type cylinder heads speed up combustion to make more power. Nitrous speeds up the combustion also, thats why you reduce the combustion speed by retard timing, reduce quench, etc. Its a balance of too much vs too little. Most mopar cyl heads have relatively small chambers and a lot of quench areas, (B1, 440-1) they are more geared toward NA Got cha...…..  never herd the term before(softening the chambers)guess that popular among the nitrous guys, learn something new everyday. 
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: 73DAD]
#2768661
04/27/20 08:13 AM
04/27/20 08:13 AM
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Joined: Aug 2003
Posts: 4,670
On the parachute mount
n20mstr
master
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master
Joined: Aug 2003
Posts: 4,670
On the parachute mount
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How much change in lash do you see between hot & cold on an all aluminum engine? I have seen as much as .015 , BUT you have to remember, what is your starting temp? It will grow .015 in April when its 50* out, but it may only grow .011 in July when its 90* . After a while you get a good idea of where you may start and where it ends up. Scary to think in the winter the lash may be .008 or less , always a little scary to start it at temps below 40 but who races in that weather? Block heater is your friend I guess at that extreme
....BAD A$$ STREET CAR.....
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: 73DAD]
#2768668
04/27/20 08:45 AM
04/27/20 08:45 AM
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Joined: Jan 2003
Posts: 11,996
Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 11,996
Benton, IL.
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On my old KB Hemi, I had to set the valves cold at about .005 and that was at 70* or more. Once warmed up, the lash was usually in the low .020s, depending. And I certainly didn't try to start the engine below 60* or so. In other words, I couldn't set the valves to the spec card hot, I had to set the valves at .005 at room temperature and live with whatever it ended up at hot because the engine would grow almost .020.
After having that experience, I went with iron on my current engine. Although I don't care for the extra weight on the nose, I just didn't want the issues that aluminum brings to my primarily street car.
And one last thing, I did drive my car a couple of times this winter on nice 50* days. I wouldn't have even tried that had the engine been aluminum.
Master, again and still
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: DaveRS23]
#2768689
04/27/20 10:38 AM
04/27/20 10:38 AM
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Joined: Dec 2013
Posts: 4,663
Wichita
GY3
OP
master
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OP
master
Joined: Dec 2013
Posts: 4,663
Wichita
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On my old KB Hemi, I had to set the valves cold at about .005 and that was at 70* or more. Once warmed up, the lash was usually in the low .020s, depending. And I certainly didn't try to start the engine below 60* or so. In other words, I couldn't set the valves to the spec card hot, I had to set the valves at .005 at room temperature and live with whatever it ended up at hot because the engine would grow almost .020.
After having that experience, I went with iron on my current engine. Although I don't care for the extra weight on the nose, I just didn't want the issues that aluminum brings to my primarily street car.
And one last thing, I did drive my car a couple of times this winter on nice 50* days. I wouldn't have even tried that had the engine been aluminum. That is quite the eye opener. Not sure I want to deal with something that finicky.
'63 Dodge 330
11.19 @ 121 mph
Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: RATTRAP]
#2768811
04/27/20 06:16 PM
04/27/20 06:16 PM
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Joined: Jan 2003
Posts: 2,296
NE Ohio
DoubleD
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,296
NE Ohio
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Aluminum block & Aluminum heads, Is the Coefficient Thermal Expansion not the same between the two, almost eliminating a change in lash as they both grow at the same rate? Stacking tolerance - meaning they both grow - so lash increases
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: Sammy]
#2768860
04/27/20 08:37 PM
04/27/20 08:37 PM
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Joined: Oct 2007
Posts: 4,205
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,205
New York
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Many Harley-Davidson owners should have looked into this 35 years ago with the new aluminum cylinders and heads (hydraulic cams).
As thousands found out the hard way: run it hard when cold, blow out the cylinder base gasket (where it sits on the crankcase).
Boffin Emeritus
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: RATTRAP]
#2768902
04/27/20 10:40 PM
04/27/20 10:40 PM
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Joined: Aug 2003
Posts: 43,097
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,097
Bend,OR USA
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Aluminum block & Aluminum heads, Is the Coefficient Thermal Expansion not the same between the two, almost eliminating a change in lash as they both grow at the same rate? Aluminum block and heads grows more than the STEEL pushrods, correct?  Hence the lash changing more when both parts, heads and block, being made from aluminum
Last edited by Cab_Burge; 04/27/20 10:41 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: Cab_Burge]
#2768910
04/27/20 11:13 PM
04/27/20 11:13 PM
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Joined: Apr 2016
Posts: 108
WNY
Moparrob68
member
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member
Joined: Apr 2016
Posts: 108
WNY
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My World aluminum block Edelbrock Victor Jr. aluminum head Hemi combination grows 0.019. I zero lash it cold to get 0.020 hot spec.
Last edited by Moparrob68; 04/27/20 11:14 PM.
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: RATTRAP]
#2768969
04/28/20 06:51 AM
04/28/20 06:51 AM
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Joined: Jan 2005
Posts: 2,540
Milwaukee WI
TRENDZ
master
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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The change is not at a constant temp.
The point is, the growth rate cold to hot is a balancing act. If you have .020” of expansion, and you wanted .015” lash hot, the engine would have the valves off the seats cold by .005”.
"use it 'till it breaks, replace as needed"
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: TRENDZ]
#2768995
04/28/20 08:51 AM
04/28/20 08:51 AM
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Joined: Aug 2003
Posts: 4,670
On the parachute mount
n20mstr
master
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master
Joined: Aug 2003
Posts: 4,670
On the parachute mount
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SIMPLE PROCEDURE, run the engine to operating temp, pull one valve cover off, lash two valves hot. Let it cool overnight. Set all the valves to that "cold" setting . DONE
When you have this type engine you go by cold settings and you note the temp when you set it cold. That's it
....BAD A$$ STREET CAR.....
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: n20mstr]
#2769010
04/28/20 09:25 AM
04/28/20 09:25 AM
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Joined: Jan 2003
Posts: 11,996
Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 11,996
Benton, IL.
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That system works for an iron engine, but won't necessarily work on an aluminum engine. What if the valves are held open when the aluminum engine is cold? And define 'cold'. On large all aluminum engines, the difference in lash between 60* and 75* could be measurable. I have always used the .005 minimum cold lash recommendation to insure that the engine will start when cold.
So, if the card wants .020 lash and my engine grows .015 to .020 depending on the engine's cold temp, if I use your method, the engine may not start because the valves are held open.
Master, again and still
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Re: Street/Strip aftermarket block. aluminum or cast iron?
[Re: DaveRS23]
#2769057
04/28/20 11:45 AM
04/28/20 11:45 AM
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Joined: Aug 2003
Posts: 4,670
On the parachute mount
n20mstr
master
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master
Joined: Aug 2003
Posts: 4,670
On the parachute mount
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That system works for an iron engine, but won't necessarily work on an aluminum engine. What if the valves are held open when the aluminum engine is cold? And define 'cold'. On large all aluminum engines, the difference in lash between 60* and 75* could be measurable. I have always used the .005 minimum cold lash recommendation to insure that the engine will start when cold.
So, if the card wants .020 lash and my engine grows .015 to .020 depending on the engine's cold temp, if I use your method, the engine may not start because the valves are held open. YES exactly, that's why in a previous page I typed, Its not great starting these all alum engines in less than 50* AND yes I have been running an all alum engine for 15 years now
....BAD A$$ STREET CAR.....
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