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Author Topic: 369 AFR 220 heads cam question  (Read 29835 times)
scienceguy
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« Reply #45 on: August 30, 2014, 04:20:29 pm »

How much increase in lash should I try? Right now I'm at .018 intake and .019 exhaust.

You might try around 0.024" - 0.026".  I'd set it cold.  Lash grows on an aluminum headed engine as it heats up.  A small block with aluminum heads grows about 0.006", so I'd set it to around 0.020" COLD, and give it a try.  

This is just a GUESS, as I haven't pushed things like this very far.  You may be able to go further...  I like to set the lash as tight as I can.  Tight makes a lot less noise, as there is a lot less pounding going on.  

Maybe someone will have some personal experience to share...

Good Luck!
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Outlaw Bill
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« Reply #46 on: August 30, 2014, 05:11:50 pm »

Loosening the lash will tell him what needs to be done. Most solid rollers are in the .022-.024 lash range anyway. Sometimes engine builders run the lash slightly tighter or looser if it picks up power and is still in the safe range.
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btls66coupe
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« Reply #47 on: August 30, 2014, 06:04:12 pm »

   I'll give it a try. Yeah with a .006 increase with heat I'm at .012 and .013 cold lash setting. I set them hot lash .018 and .019 then let them cool and checked lash.
 When I get back from drag week I'll order a different cam that'll work a little better.
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Joel5.0
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« Reply #48 on: August 30, 2014, 07:15:01 pm »

How much increase in lash should I try? Right now I'm at .018 intake and .019 exhaust.

You might try around 0.024" - 0.026".  I'd set it cold.  Lash grows on an aluminum headed engine as it heats up.  A small block with aluminum heads grows about 0.006", so I'd set it to around 0.020" COLD, and give it a try. 

This is just a GUESS, as I haven't pushed things like this very far.  You may be able to go further...  I like to set the lash as tight as I can.  Tight makes a lot less noise, as there is a lot less pounding going on. 

Maybe someone will have some personal experience to share...

Good Luck!


Suggestion....... do NOT guess. Set them to 0.024" hot.... the same way you did it initially. Keep variables out of the data you want to get in order to decide. My  My 2¢

Remember.... reliability of results depend on the repeatability of the procedures.... don't follow shortcuts.   Naughty
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289nate
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« Reply #49 on: August 30, 2014, 07:48:20 pm »

Do not set the lash cold.  That is something you do when you start a solid lifter engine for the first time.  Always set them hot.  Even to the point that I would get the engine back to operating temp if the first bank takes long enough that the engine cools down too much.

I have set my lash cold on a couple occasions to try and find the difference between hot and cold lash on my particular engine.  Every single time the lash has ended up varying too much on different cylinders for me to feel it was close enough.  This is not at all uncommon after talking to several other people.

Playing with the lash can tell you a lot about your cam and what your engine wants.  Just don't go opening the lash some absurd amount, find that it runs better, and think you've fixed the engine.

I've had rockers back off twice during passes at the track turning north of 7,500 rpm.  There was zero evidence of any issue when I removed my heads for some porting.  Threw the valves and springs back on and the head porter said they had a nice valve job when he looked them over.  Opening the valve lash a bit is not going to kill your valve train in one pass.
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289nate
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« Reply #50 on: August 30, 2014, 07:52:17 pm »

I also believe there is more to this than a cam.  I think you need to test more with what you have.  Shift point and tune on the carburetor are two that could pay off big.
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\'65 fastback pump gas 289, 4.56 gears, and faceplated T5.  11.123 at 122.4
CDW6212R
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« Reply #51 on: August 30, 2014, 08:10:10 pm »

I also believe there is more to this than a cam.  I think you need to test more with what you have.  Shift point and tune on the carburetor are two that could pay off big.

Ditto, decide if the cam really is too big, and then adjust the carburetor(not just the idle screws).
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btls66coupe
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« Reply #52 on: August 31, 2014, 12:28:34 am »

   Will do. I'll have a lot of time to practice in a week.  I'll work on tuning this think. I did these runs with the Quick Fuel 750 cfm carb. Now I'll put the 950cfm carb and see if that changes anything.
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btls66coupe
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« Reply #53 on: September 22, 2014, 12:38:40 am »

   I went back to the track today. I had some issues with the transmission not want to go into gear. So I took the transmission out and had it rebuilt. Without doing anything else other than the transmission. Best run so far was a 10.84 at 122 mph 1.49 60 ft. I can't wait to see what it'll do when I switch out the cam.
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