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Old 09-29-2008, 04:31 PM
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combo questions

hey a couple of real quick questions
1. is 10" OF vacuum enough for a trans modulator i have a resivour cansiter for the power brakes should i hook it up to there
2. i am replacing my roller rockers with new ones the spec on the lash is .26 hot where should i set cold for a baseline
3. and finally any good resources for tuning a holley 850 with 4 corner idle

thanks

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Old 09-29-2008, 07:06 PM
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i am sorry i meant .026
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Old 09-30-2008, 04:24 AM
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really?
no one is interested in this post?
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Old 09-30-2008, 02:57 PM
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what are modulators normal specs? 10#'s sounds low. what is at the brake booster?

is your timming curve correctly set up,and running?

4 corner idle isnt needed really. unless the 4 ports are individually separated in the plenum. try the company that designed the carb for literary matterial.

1.5 turns out primary side
.75-1 turn out secondary.. try that.

Last edited by spinn; 09-30-2008 at 03:02 PM.
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Old 09-30-2008, 03:24 PM
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"2. i am replacing my roller rockers with new ones the spec on the lash is .26 hot where should i set cold for a baseline"

More info please. Iron block with iron heads or aluminum block with iron heads or iron block with aluminum heads?

And by the way, the correct figure is written as 0.026"
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Old 09-30-2008, 03:35 PM
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Quote:
Originally Posted by bradykat
hey a couple of real quick questions
1. is 10" OF vacuum enough for a trans modulator i have a resivour cansiter for the power brakes should i hook it up to there
2. i am replacing my roller rockers with new ones the spec on the lash is .26 hot where should i set cold for a baseline
3. and finally any good resources for tuning a holley 850 with 4 corner idle

thanks
Knowing something about the car, engine, and tranny would be helpful.

For any stock type automatic from the OEM, at 10 inches of vacuum it would assume you were in the throttle and it would be adjusting line pressure and shift points upward. Knowing what this thing is will help us aim at whose and which modulator, in terms of vacuum applied, you should be looking for.

As for lash, starting with the hot setting is good enough to get going on. I expect you meant .026 not .26? To the point where the lash isn't so tight as to hold valves open when they should be seated, this isn't that touchy. For years guys have used lash, other than recommended, as a way to tune. Tighter lash adds duration and overlap, and starts opening sooner while delaying closing, wider lash reduces these features.

4 corner idle adjustment is intended to get away from having to drill air bypass holes in the throttle blades to get the throttle plates on a hot cammed engine to be positioned below the idle to main metering transfer slot while getting enough air in the motor to idle properly. You just have to fiddle the throttle position and fuel screws to get the necessary idle speed with a mixture ratio that keeps the throttle blades just short of exposing the transfer slots to manifold vacuum. If they are exposed below the throttle blades at idle, you'll have a hard time getting a clean idle, it'll tend to be overly rich. You'll also get a lean bog as the throttles tip in before main metering can catch up. This can be hidden with more accelerating pump, but that's rather like wearing gloves 'cause your pen leaks ink.

Bogie
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Old 09-30-2008, 04:31 PM
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sorry i did mean .026
the car is a 73 monte carlo
the engine is a .30 over 454 11.75 pistons 685lift solid lifter 781 heads large valves port work
trans is th400hd
anyway i was thinking that i didn't need the vacuum modulator as i could shift it manually
as far as the rockers the spec on the cam card is .026 hot so i was looking for a cold reference point to set them to
i didn't know if there was a close idea of how it would change hot
and as far as the carb i think i have it tuned
thanks
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