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What do u guys run for cranking compression #2451932
02/15/18 12:19 AM
02/15/18 12:19 AM
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rook440 Offline OP
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Mines at 160 would like to see it up around 200...whats your opinions..thanks rook

Re: What do u guys run for cranking compression [Re: rook440] #2451934
02/15/18 12:27 AM
02/15/18 12:27 AM
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what's the motor set up???


Tom

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Re: What do u guys run for cranking compression [Re: rook440] #2451959
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It's a 60 over440 11.5 compression 67 heads fully ported big valves m1 intake cam is .645 lift intake .650 exhaust 280 at .50 intake 285 at.50 exhaust 106.5 Sep install at 103.5. .020 intake lash.016 exhaust

Re: What do u guys run for cranking compression [Re: rook440] #2451960
02/15/18 01:16 AM
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Was the engine blueprinted and the compression ratio calculated via measurement? That's a lot of overlap for hi cranking rpm pressures. Is there a particular reason you're looking for it?


Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
Re: What do u guys run for cranking compression [Re: rook440] #2451970
02/15/18 01:40 AM
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what about advancing the cam or even a smaller cam. For more performance is the ign/carb dialed in.


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Re: What do u guys run for cranking compression [Re: rook440] #2451973
02/15/18 01:51 AM
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rook440 Offline OP
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I have 160 psi with this cam right now..i calculated the compression by turning the plug straight up..filling with fluid from a graduated burrett and it came out about 11.5 to 1 I'm looking for 200 but no one agrees on this number some say 150 is ok some say 200 is the best..im just wondering if I should change the cam or give it a shot..

Re: What do u guys run for cranking compression [Re: rook440] #2451990
02/15/18 02:27 AM
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There is no one "right" cranking pressure number.

What type of fuel do you use?

Re: What do u guys run for cranking compression [Re: rook440] #2451993
02/15/18 02:31 AM
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Cranking compression doesn't mean jack nothing. Hit your starter with 24 volts and watch the cranking pressure go up. Means nothing.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: What do u guys run for cranking compression [Re: rook440] #2452004
02/15/18 03:37 AM
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Re: What do u guys run for cranking compression [Re: BradH] #2452048
02/15/18 10:26 AM
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Originally Posted By BradH


What type of fuel do you use?


This.

If you are using pump gas, you're pretty close now. You won't make 200 w/o using better fuel.

Re: What do u guys run for cranking compression [Re: rook440] #2452074
02/15/18 11:49 AM
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That's a ton of duration for a 11.5-1 452". That's why it's below expectations.
Doug

Re: What do u guys run for cranking compression [Re: rook440] #2452121
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Originally Posted By rook440
It's a 60 over440 11.5 compression 67 heads fully ported big valves m1 intake cam is .645 lift intake .650 exhaust 280 at .50 intake 285 at.50 exhaust 106.5 Sep install at 103.5. .020 intake lash.016 exhaust


You have 280@050 duration? I'm surprised it even runs with that much duration. My pump gas 470 makes 775 hp and has 264@050 duration so I think your cam is way too big.

Re: What do u guys run for cranking compression [Re: rook440] #2452150
02/15/18 03:02 PM
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Back in the day I ran a stock 440SP motor with the CC.650/290@.050 SFT cam at approx 9.8:1, CP was only around 150psi, not ideal yes but it ran real sweet, ticked over@900rpm but only made 490flyhp on the track, weight/mph, mainly cos of the poor intake/small 850DP carb, not good enough 906's (255cfm) and of course the horrible weight of the bottom end, (2000gms per hole), still managed 10.6's with it....was planning to go to 12.5:1 pistons but it never happened.

Last edited by rb446; 02/15/18 03:12 PM.

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Re: What do u guys run for cranking compression [Re: rook440] #2452156
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Originally Posted By rook440
Mines at 160 would like to see it up around 200...whats your opinions..thanks rook


170-175 w/an Isky solid roller 276-281 @ .050 470 cubes and fwiw, a buddy went low 8's a while back w/150........... work


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Re: What do u guys run for cranking compression [Re: rook440] #2452180
02/15/18 04:03 PM
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What Brad said....There is not a magic number. Look for consistency. You would be surprised what we are at for a cranking compression at over 16-1. TO many factors for their to be a perfect answer.


"I am not ashamed to confess I am ignorant of what I do not know."

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Re: What do u guys run for cranking compression [Re: rook440] #2452195
02/15/18 04:29 PM
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280@.050, 11.5cr, and you're getting 160psi?

Sounds about right........ Maybe even a bit more than I would have expected.

My 383 @ just under 11:1, 256@.050 solid cam in at 102 would pump about 200 in 8 pumps, all plugs out, wot, battery charger on, engine warm.

My old 448 @ 9.8cr, 259@.050 roller cam in at 106, would pump about 155-160 in 8 pumps, all plugs out, etc.

I know several of the FAST guys have combos that pump 240-260.
Lots of compression and short duration cams.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: What do u guys run for cranking compression [Re: rook440] #2452589
02/16/18 03:11 PM
02/16/18 03:11 PM
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Cranking compression has a lot a variables, cam grind the main one, but not the only one. Performance trends engine analyzer will calculate what your cranking compression will be, give you an advance curve, and estimate spark knock for various octane fuels. Like every computer program garbage in garbage out, take the time to input accurate numbers and it is accurate within 10% used it for years. http://performancetrends.com/Engine-Analyzer.htm

Re: What do u guys run for cranking compression [Re: rook440] #2452603
02/16/18 03:41 PM
02/16/18 03:41 PM
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I run about 220 on my pump gas 410 stroker in my dakota, 11 to 1 221@.050 cam, pulls like mad anywhere between idle and 6000 RPM, a shorter duration cam can bump up the cranking compression as can a bunch of other things like ring seal, engine temp, sterter RPM, valve seat seal...


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Re: What do u guys run for cranking compression [Re: HotRodDave] #2452746
02/16/18 07:56 PM
02/16/18 07:56 PM
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Originally Posted By HotRodDave
I run about 220 on my pump gas 410 stroker in my dakota, 11 to 1 221@.050 cam, pulls like mad anywhere between idle and 6000 RPM, a shorter duration cam can bump up the cranking compression as can a bunch of other things like ring seal, engine temp, sterter RPM, valve seat seal...
What sort of heads do you have, ignition timing, and do you run on pump-gas?

Re: What do u guys run for cranking compression [Re: rook440] #2452918
02/17/18 03:08 AM
02/17/18 03:08 AM
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My small block runs from 195-200 cranking compression with 10.9 comp. and a 255/266 duration cam. I have never ran anything but 93 octane pump gas. It has aluminum heads.


1.33 60 ft,6.21 at 110.59 in the 1/8, pump gas small block,2950lbs,drag radials,mufflers and driven to track ...
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