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Post Info TOPIC: Valve Lash.


- MotorHead -

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Valve Lash.
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Mine is set loose at .024" because we don't know CAM specs.  With tighter lash, will the RPM climb faster after 5k?  Right now it winds fast basically 3k-52k then starts to struggle.  My heads are a 6500 red line.

Thanks in advance. 



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- Mike -
Olalla, Wa


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Not sure the heads really have a "red line". I'd be checking the valve spring pressures if you think there's an issue.

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- MotorHead -

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1094's without the spring upgrade description notes 6500 max rpm. My apologies for being unclear

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- MotorHead -

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Is it normal to climb slower at the top?

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- Durand -

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Tightening the lash will effectively make the cam larger in both duration and lift.
Wither or not it will RPM faster with a tighter lash, depends on a lot of other factors besides just the lash change.

The 1094's I'm assuming are the 195cc AFR's.
The PAC springs on those heads are 140lbs seat pressure and good to .600 lift.
I doubt those are the issue in the 5000-5500 rpm area.

Have you looked into or played with the timing curve?

Knowing what cam would help a lot.
A little more about the rest of the engine would also.

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- MotorHead -

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LaVelle wrote:

Tightening the lash will effectively make the cam larger in both duration and lift.
Wither or not it will RPM faster with a tighter lash, depends on a lot of other factors besides just the lash change.

The 1094's I'm assuming are the 195cc AFR's.
The PAC springs on those heads are 140lbs seat pressure and good to .600 lift.
I doubt those are the issue in the 5000-5500 rpm area.

Have you looked into or played with the timing curve?

Knowing what cam would help a lot.
A little more about the rest of the engine would also.


I've never over revved on these heads. I feel like the secondaries come on early and that I should try a single plane manifold. It's very distinct when the 2nd chamber comes into play. The timing is idle: 21 Rpm: 36. I have new springs for the hei and need to do that still.

4150 830cFm, dual plane Weiand street dominator, AFR 195, 65cc heads, 11.1 domed pistons(maybe .120" dome) .550+ solid cam from Berg performance shelf cams for old circle track cars.  4speed.  12 bolt 373's.  

cold be an insufficient manifold. I think it's good to 6k...



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- Durand -

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I agree manifold wise.
It would most likely like a single plane better.

I don't think that's your problem though.
I'm leaning towards, it wants more total timing, or lack of fuel supply.


Give it a couple more degree's and see what happens, give it what it likes.
Every engines is different, I've had some that wanted 40+ total.
Just don't go to far, and stay out of detonation.

What size fuel line and pump are you running?

 

 



-- Edited by LaVelle on Tuesday 18th of July 2017 03:50:21 AM

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- Martin -
Everett, WA


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I run .018 int, .020 exh cold set.

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- Martin -
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Brandon1984 wrote:

Is it normal to climb slower at the top?


yes 



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- MotorHead -

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LaVelle wrote:

I agree manifold wise.
It would most likely like a single plane better.

I don't think that's your problem though.
I'm leaning towards, it wants more total timing, or lack of fuel supply.


Give it a couple more degree's and see what happens, give it what it likes.
Every engines is different, I've had some that wanted 40+ total.
Just don't go to far, and stay out of detonation.

What size fuel line and pump are you running?

 

 



-- Edited by LaVelle on Tuesday 18th of July 2017 03:50:21 AM


 Fuel line is braided with probably 3/8 inside diameter.  Stock mechanical fuel pump and I don't know the volume or anything.



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- MotorHead -

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Tazman wrote:

I run .018 int, .020 exh cold set.


 I think I'll try something like that.



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