Re: What do u guys run for cranking compression
[Re: rook440]
#2452990
02/17/18 12:05 PM
02/17/18 12:05 PM
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You could use more static for sure with that cam I bet. J.Rob
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Re: What do u guys run for cranking compression
[Re: madscientist]
#2452991
02/17/18 12:08 PM
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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. Totally wrong IME. Plug your compression gauge in and start the engine. Tell me what it says. J.Rob
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Re: What do u guys run for cranking compression
[Re: AndyF]
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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 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. I agree ^^^^^^^^^^^^^^^^^^^. J.Rob
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Re: What do u guys run for cranking compression
[Re: BSB67]
#2452993
02/17/18 12:11 PM
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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. Do not understand how fuel quality effects a compression test. J.Rob
2009 PHR\EMC Competitor 2010 PHR\EMC Competitor 2011 PHR\EMC Competitor 2012 PHR\EMC Competitor 2013 PHR\EMC Competitor 2014 HotRod/EMC Competitor 2015 HotRod/EMC NoShow 2016 HotRod/EMC 3rd place SPEC Bigblock 2018 HotRod/EMC 7th place G3
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Re: What do u guys run for cranking compression
[Re: Thumperdart]
#2452995
02/17/18 12:12 PM
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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........... You could absolutely use more static. Your buddy too. J.Rob
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Re: What do u guys run for cranking compression
[Re: fast68plymouth]
#2452997
02/17/18 12:15 PM
02/17/18 12:15 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. Agree about 1000%. Any of my real good engines pump 240-260psi and 150-160 on the first crack of the needle. Most people don't really track or understand a proper compression test. J.Rob
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Re: What do u guys run for cranking compression
[Re: HotRodDave]
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02/17/18 12:19 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... This I wish more people would take note of.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Starter RPM is the only misnomer with this post. You must be on top of the tuneup but man I bet this engine is incredibly fun and crisp. I shoot for a minimum of 175 if the customer is VERY average and I shoot for 195-200 if a customer is VERY aware. J.Rob
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Re: What do u guys run for cranking compression
[Re: D-50]
#2453002
02/17/18 12:21 PM
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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. You're right in the sweet spot for pump gas and aluminum heads. You still have a decently wide tuning window. Good combo. J.Rob
2009 PHR\EMC Competitor 2010 PHR\EMC Competitor 2011 PHR\EMC Competitor 2012 PHR\EMC Competitor 2013 PHR\EMC Competitor 2014 HotRod/EMC Competitor 2015 HotRod/EMC NoShow 2016 HotRod/EMC 3rd place SPEC Bigblock 2018 HotRod/EMC 7th place G3
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Re: What do u guys run for cranking compression
[Re: RAMM]
#2453062
02/17/18 03:06 PM
02/17/18 03:06 PM
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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........... You could absolutely use more static. Your buddy too. J.Rob I'm fine thankxxx and running 6.15's at 112 in my street car tells the story kinda like leakdown #'s. Doug Sikora set a national record w/more that 20%.............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: What do u guys run for cranking compression
[Re: rook440]
#2453139
02/17/18 06:13 PM
02/17/18 06:13 PM
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The number can be misleading. I picked up 15 psi opening my valve lash only .004 in, and I picked up 20-25 changing my old, early style starter for a mini starter.
IMO I'm also surprised you have that much with that cam and CR.
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: What do u guys run for cranking compression
[Re: RAMM]
#2453193
02/17/18 08:46 PM
02/17/18 08:46 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... This I wish more people would take note of.^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Starter RPM is the only misnomer with this post. You must be on top of the tuneup but man I bet this engine is incredibly fun and crisp. I shoot for a minimum of 175 if the customer is VERY average and I shoot for 195-200 if a customer is VERY aware. J.Rob In theory starter RPM should not change it but in real life it does. If you had absolute zero leakdown it should not matter but turning an engine over on the stand would be impossible by hand if it held 200 PSI at hand turning RPM. Even with zero gap rings and such you can still turn the engine a little bit wait a little bit and turn it some more. At least I have never found one with complete perfect sealing.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: What do u guys run for cranking compression
[Re: rook440]
#2453334
02/18/18 02:40 AM
02/18/18 02:40 AM
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Strictly speaking, even converter/flywheel inertial mass affects CCP - the engine slows down as it approaches TDC.
Boffin Emeritus
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Re: What do u guys run for cranking compression
[Re: RAMM]
#2453335
02/18/18 02:41 AM
02/18/18 02:41 AM
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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. Do not understand how fuel quality effects a compression test. J.Rob It doesn't. But apparently you were too busy being an expert to read and understand my post. At some point, fuel and detonation can and will be a limiting factor. He has iron heads, and IF he is using pump fuel, he probably won't get to 200 psi without having a detonation problems.
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Re: What do u guys run for cranking compression
[Re: rook440]
#2453492
02/18/18 03:20 PM
02/18/18 03:20 PM
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I've seen engines with 160 cranking pressure rattle themselves to death. I've personally run 225 and ran what I consider a normal tune up and ran it on pump gas.
Cranking pressure means very little, especially comparing it to other engines. Maybe the same engine with the same starter and maybe you'd get some useful info.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: What do u guys run for cranking compression
[Re: rook440]
#2454844
02/20/18 11:34 PM
02/20/18 11:34 PM
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Mines at 160 would like to see it up around 200...whats your opinions..thanks rook What's the application/purpose of the motor?
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Re: What do u guys run for cranking compression
[Re: rook440]
#2454913
02/21/18 01:50 AM
02/21/18 01:50 AM
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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.. From your earlier post, change the cam for sure. But not sure your thread is for a real info gathering or just a hoax fun question.
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Re: What do u guys run for cranking compression
[Re: LSP]
#2455589
02/22/18 01:51 PM
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Mines at 160 would like to see it up around 200...whats your opinions..thanks rook What's the application/purpose of the motor? ??
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Re: What do u guys run for cranking compression
[Re: LSP]
#2455727
02/22/18 06:02 PM
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Mines at 160 would like to see it up around 200...whats your opinions..thanks rook What's the application/purpose of the motor? ?? this is in my drag car..a 2700 lb 68 charger..i use race gas...and this question is not a hoax...lol
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Re: What do u guys run for cranking compression
[Re: rook440]
#2455818
02/22/18 09:13 PM
02/22/18 09:13 PM
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Mines at 160 would like to see it up around 200...whats your opinions..thanks rook What's the application/purpose of the motor? ?? this is in my drag car..a 2700 lb 68 charger..i use race gas...and this question is not a hoax...lol Never thought it was a hoax . What is max rpm you'll turn it?
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