Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: PorkyPig]
#1822093
05/08/15 08:20 PM
05/08/15 08:20 PM
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Joined: Feb 2006
Posts: 1,051 The Great White North
RAMM
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Did it go from having no quench to a real quench area with the milling? If so, I'd think that would have something to do with it needing less ignition lead.
Did the BSFC numbers improve, too? This is what I was getting at. .040 compressed head gasket? Just looked and saw RAMM got a 6% increase, much higher than the Vizard chart I posted predicted. I suspect he found some "bonus points" by building quench into it, too. Well, RAMM? Yes as I have stated many times over I am a BIG believer in quench. Because Mopars suffer so badly from basement level piston to deck heights from the factory this serves as a prime example of getting it "right" and can and does reap excellent results. Also in play is the extreme reduction of "crevice volume" I believe quench and crevice volume share an extremely close relationship. Yes the gasket is a true .039" compressed thickness--I reused them BTW. The BSFC's did improve by a remarkable amount. They are low to mid .4's as of now. I also believe that the intial "suck" on the intake port is a touch better with the closer relationship with respect to the intake valve/valve pocket--This is why minimum valve to piston clearance can be a power maker. 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: 1 full comp point increase is worth what? Dyno results insyd
[Re: 67Satty]
#1822098
05/08/15 08:25 PM
05/08/15 08:25 PM
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Would a switch to aluminum heads allowed you to keep running the 38 degrees of timing and resulted in even more of a power jump? This is interesting. I would like to have expanded on this even further. What if I had preserved the comp ratio @ 9.4 with a -.055" deck vs. a 9.4 comp ratio @ zero deck? I believe the difference would have been more on the order of 1.5-2%--maybe less! To answer your question--first I don't have an answer I have never done this. Second--I doubt it. Aluminum heads are not some magical engine parts. I'm not going to explain it here but --think of excessive advance as "negative torque" or not getting the job done as "fast burn" stuff. J.Rob
Last edited by RAMM; 05/08/15 08:28 PM.
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: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822104
05/08/15 08:32 PM
05/08/15 08:32 PM
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Joined: Oct 2003
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Crizila
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Like the title implies I had the chance to test a 440 RB @ 9.4 static compression ratio and then again (due to an oil leak) @ 10.4 static compression.
This is a 446 I recently built for a customer using '915 heads and flat top Wiseco forged pistons. It ran all right during the initial dyno session but the rear main was leaking a little and that was not acceptable so I took it off the dyno and couldn't leave it alone.
When I was assembling the engine the pistons measured .055" in the hole. Also understand the customer really wanted to save these pistons so I cleaned them up and CNC machined them with a slight conical dish netting a little more volume. Basically I knew there was plenty of room to play with here so I decked the block exactly .045" per side which put it @ 10.4 comp. I had the chance to re-dyno with NO other changes. The power increase is somewhat expected but the timing requirements changed dramatically. Previous timing for max power was 35-36 total--Now 30-31 total is all that it likes. Interesting to say the least. So +30 HP +38 ft/lbs at the peaks was observed--the graph tells a much better story. J.Rob Although positive, just too many changes to equate the gain to CR change alone - which renders the info - info.
Fastest 300
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: Crizila]
#1822115
05/08/15 08:50 PM
05/08/15 08:50 PM
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Joined: Feb 2006
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob
Last edited by RAMM; 05/08/15 08:51 PM.
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: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822117
05/08/15 08:53 PM
05/08/15 08:53 PM
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pittsburghracer
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob I for one thank-you for sharing info. keep up the good work.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822166
05/08/15 09:42 PM
05/08/15 09:42 PM
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R/T1968R/T
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The quench helped more than the compression.Try a steel shim gasket and get a perfect quench. Cometic .027 would make an ideal .037
Last edited by R/T1968R/T; 05/08/15 09:47 PM.
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822349
05/09/15 12:31 AM
05/09/15 12:31 AM
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Joined: Aug 2003
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Cab_Burge
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What fuel where you using on both test? Any idea of how much the weather changes where? One of the local Mopar races did some testing on one of his pump gas street motors and had a issue with ignition timing on that motor, he says he verified the TDC on the motor and tried 34 or 36, CRS and it pinged noticably enough to stop the pull. We talked about the plug heat range, carb. jetting, timing light accuracy and jetting, the AFR where fat and the symtoms he was having. He ended up retarding the timing to 25 BTDC for the best results, which where substanstial I'm having troubles with my computer and ISP opening PDF files so I can't open and read the dyno sheets to help illustrate thhis results Test, test and test some more
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: pittsburghracer]
#1822425
05/09/15 02:32 AM
05/09/15 02:32 AM
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob I for one thank-you for sharing info. keep up the good work. X 2
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822548
05/09/15 11:42 AM
05/09/15 11:42 AM
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Joined: Oct 2003
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Crizila
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob Sorry if my reply came off a little harsh, but your thread title leads one to believe that the HP gain could be attributed to a CR change alone, and my point was that that was not the case ( although stated poorly by me ). As stated in this thread, I think a quench change had partly to do with the improvement, and maybe piston top reshaping, etc. I to, appreciate all your hard work and sharing the results. Just wanna clarify to all that adding a point to your CR my not automatically have the same positive results as you did. Making multiple changes is my personnel nemesis, as I don't have easy access to a dyno - and 2 - 3 trips down the track once a month can give pretty limited info.
Fastest 300
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822550
05/09/15 11:43 AM
05/09/15 11:43 AM
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polyspheric
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What does that prove? That there was much more taking place than the CR increase.
Boffin Emeritus
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: Crizila]
#1822583
05/09/15 12:19 PM
05/09/15 12:19 PM
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Joined: Feb 2006
Posts: 1,051 The Great White North
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob Sorry if my reply came off a little harsh, but your thread title leads one to believe that the HP gain could be attributed to a CR change alone, and my point was that that was not the case ( although stated poorly by me ). As stated in this thread, I think a quench change had partly to do with the improvement, and maybe piston top reshaping, etc. I to, appreciate all your hard work and sharing the results. Just wanna clarify to all that adding a point to your CR my not automatically have the same positive results as you did. Making multiple changes is my personnel nemesis, as I don't have easy access to a dyno - and 2 - 3 trips down the track once a month can give pretty limited info. The piston tops were reshaped for the initial build. I did not do anything different other than decking the block .045" This was the ONLY change. Pistons were in the same configuration both times. 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: 1 full comp point increase is worth what? Dyno results insyd
[Re: skrews]
#1822607
05/09/15 01:00 PM
05/09/15 01:00 PM
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Joined: Oct 2008
Posts: 458 Michigan
BPE
mopar
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mopar
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob I for one thank-you for sharing info. keep up the good work. X 2 x 3 Rod
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: RAMM]
#1822643
05/09/15 01:52 PM
05/09/15 01:52 PM
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Joined: Oct 2003
Posts: 7,506 Az
Crizila
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob Sorry if my reply came off a little harsh, but your thread title leads one to believe that the HP gain could be attributed to a CR change alone, and my point was that that was not the case ( although stated poorly by me ). As stated in this thread, I think a quench change had partly to do with the improvement, and maybe piston top reshaping, etc. I to, appreciate all your hard work and sharing the results. Just wanna clarify to all that adding a point to your CR my not automatically have the same positive results as you did. Making multiple changes is my personnel nemesis, as I don't have easy access to a dyno - and 2 - 3 trips down the track once a month can give pretty limited info. The piston tops were reshaped for the initial build. I did not do anything different other than decking the block .045" This was the ONLY change. Pistons were in the same configuration both times. J.Rob Not how I read your OP - "CNC machined them with a slight conical dish". No matter, interesting post anyway. Regarding timing, had a similar experience when going from cast iron heads to aluminum heads. Timing requirements changed considerably. Wanted lots more. Besides changing the CR and in turn chamber design, could be material also ( cast iron to aluminum ). Think you were pretty much in the "sweet spot" as far as getting as much as you did with the CR change. I remember when the 426 max wedge motor first came out in 63. two versions - 11:1 and 13.5:1. In 64 they were only offering 12.5:1 on the high side. Diminishing returns?
Fastest 300
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: MR_P_BODY]
#1822656
05/09/15 02:02 PM
05/09/15 02:02 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
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Good info... from the testing I did.. the lower the starting compression the bigger the gain... as in going from 9.1 to 10.1.. its a deminising return thing EXACTAMUNDO..........found similar results.
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Re: 1 full comp point increase is worth what? Dyno results insyd
[Re: BPE]
#1822662
05/09/15 02:10 PM
05/09/15 02:10 PM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
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That's all that I am saying. I increased through machine work-the compression ratio exactly 1 full point--these are the results. Make of them what you may. I offered my thoughts on why and how--I do not know for sure--I only know what I know and have observed. J.Rob I for one thank-you for sharing info. keep up the good work. X 2 x 3 Rod X4
Last edited by Cab_Burge; 05/09/15 02:10 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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