Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2295863
04/29/17 12:07 AM
04/29/17 12:07 AM
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Joined: Mar 2010
Posts: 1,308 Spencer NY
killermopar
pro stock
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pro stock
Joined: Mar 2010
Posts: 1,308
Spencer NY
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I can't tell you exact compression ratios, but dished pistons are gonna put you way lower than a flat top will.
Last edited by killermopar; 04/29/17 12:08 AM.
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Re: Edelbrock heads and piston questions
[Re: killermopar]
#2295913
04/29/17 02:21 AM
04/29/17 02:21 AM
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Joined: Aug 2003
Posts: 43,307 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,307
Bend,OR USA
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I can't tell you exact compression ratios, but dished pistons are gonna put you way lower than a flat top will. Me thanks some thing has gotten lost in the translation between your engine builder, piston maker and you and us Is he wanting to use a quench dome piston instead of a flat top with valve releifs Your not saying what C.I. your motor will be but my first pump gas 505 C.I. 400 block stroker motor had to have 22.0 CC dish piston at .025 down in the cylinders to have 9.25 to 1 compression ratio with 84.0 CC heads I had a set of large valve ported and polished 906 iron heads on that motor originally and later swap them to a set of Eddy RPM with 84.0 CC heads, the compression ratio stayed the same so I ended up swapping out the 4.25 stroke crankshaft to a 4.300 stroke crankshaft the next winter to raised those dished pistons up to zero deck to get 10.3 to 1 compression ratio. Most of the pump gas stroker motors I build now have a reverse dome (half a dish) pistons in them with around 10 to 14.0 CC to get 10.4 to 11.0 to 1 compression ratio to run with aluminum heads on the street on pump swill
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Edelbrock heads and piston questions
[Re: Cab_Burge]
#2295946
04/29/17 08:56 AM
04/29/17 08:56 AM
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Joined: Feb 2005
Posts: 4,320 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,320
Prospect, PA
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I can't tell you exact compression ratios, but dished pistons are gonna put you way lower than a flat top will. Me thanks some thing has gotten lost in the translation between your engine builder, piston maker and you and us This. Any 500 stroker with 84 cc heads and zero deck flat tops will put you over 11:1. If it is a 451 motor, you should be close to what you are looking for.
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Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2296009
04/29/17 11:57 AM
04/29/17 11:57 AM
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Joined: Dec 2013
Posts: 403 Romulus, MI
GTS340
mopar
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mopar
Joined: Dec 2013
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Romulus, MI
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The initial plan my engine builder and I had discussed was to build a 400/512 using a 440 Source kit with flat top pistons. We intended to use Edelbrock RPM 84 cc heads (which I already have) that will be ported. The plan was to have a compression of somewhere between 10.5 and 10.8 in order to be able to run on pump gas. He told me after talking to someone at 440 Source that we wouldn't be able to use flat tops without milling the heads in order to achieve the targeted compression. I recommend you find a new engine builder, as BSB67 said, a 4.25 stroke engine with flat tops and 84cc chambers will be over 11:1 and a decent builder would not rely on 440 source to figure out such a basic concept like compression calculation
Last edited by GTS340; 04/29/17 11:59 AM.
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Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2296021
04/29/17 12:16 PM
04/29/17 12:16 PM
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Joined: Jan 2003
Posts: 17,914 S.E. Michigan
ZIPPY
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I Live Here
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Posts: 17,914
S.E. Michigan
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Agreed, either something is lost in translation, or engine builder is not really a builder. But even if they were relying 100% on 440 source for that information, the charts on 440 source's website are actually pretty accurate. OP, take a look at the spreadsheet/chart for "400-512" on their website to give you an idea of what is required and what ballpark CR you will arrive at http://store.440source.com/Stroker-Kits/products/3/A 512 with rpm heads and flat tops, even .015 or so in the hole, is going to be close to 11.5:1. Attempting to "read between the lines", maybe this is what they're talking about: 440 source offers only one dish volume-24cc. If that doesn't work for you, then you'll be milling heads or buying new heads to arrive at the target CR. Maybe the real question is, should it be left alone at 9.7:1 or will it be worth it to mill the heads to 75cc and arrive at 10.6:1? Was that really the question?
Rich H.
Esse Quam Videri
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Re: Edelbrock heads and piston questions
[Re: viperblue72]
#2296026
04/29/17 12:23 PM
04/29/17 12:23 PM
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Joined: Feb 2005
Posts: 4,320 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,320
Prospect, PA
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With a 4.25 stroke, I would just use a flat top piston and aim for 11 to 1. Use a bigger cam with some overlap to bleed off some cylinder pressure and you'll have a great running pump gas engine. Everything else being equal, more overlap increases cylinder pressure.
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Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2296053
04/29/17 01:04 PM
04/29/17 01:04 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
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I Live Here
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State of confusion
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Don't need a dish and mine are milled to 72cc'a and at .002 below the deck I'm at 12.1.1 comp w/a JE flattop..........
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: Edelbrock heads and piston questions
[Re: ZIPPY]
#2296137
04/29/17 03:42 PM
04/29/17 03:42 PM
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Joined: Aug 2007
Posts: 732 USA
440mopar
OP
super stock
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OP
super stock
Joined: Aug 2007
Posts: 732
USA
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Attempting to "read between the lines", maybe this is what they're talking about:
440 source offers only one dish volume-24cc. If that doesn't work for you, then you'll be milling heads or buying new heads to arrive at the target CR. Maybe the real question is, should it be left alone at 9.7:1 or will it be worth it to mill the heads to 75cc and arrive at 10.6:1? Was that really the question? Yes, that is what I would like to know. After looking at the 440 Source chart, I think I misstated what I was told. I believe what he said was using the 84 cc heads with flat tops was going to result in a comp ratio too high to run well on pump gas and using dish pistons with the heads milled down to 72-75 cc's would give the desired comp ratio. I believe he said the cc's would have to be in the low 90's in order to use flat tops to get the desired comp ratio. This is all Greek to me but given this information, is there any reason that flat top pistons would be preferred over dish? Thanks.
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Re: Edelbrock heads and piston questions
[Re: ZIPPY]
#2296233
04/29/17 09:24 PM
04/29/17 09:24 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
I Live Here
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I Live Here
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Mt. Vernon, Ohio
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I think lowering compression is his goal.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2296452
04/30/17 12:15 PM
04/30/17 12:15 PM
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Joined: Jan 2003
Posts: 75,095 A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,095
A Banana Republic near you.
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The initial plan my engine builder and I had discussed was to build a 400/512 using a 440 Source kit with flat top pistons. We intended to use Edelbrock RPM 84 cc heads (which I already have) that will be ported. The plan was to have a compression of somewhere between 10.5 and 10.8 in order to be able to run on pump gas. He told me after talking to someone at 440 Source that we wouldn't be able to use flat tops without milling the heads in order to achieve the targeted compression. Then you need to get different parts or talk to someone that has a clue as to what they are talking about . What stroke crank are you using and what is the CH of the piston in the kit? The most common piston is 1.320 and it works with multiple stroke cranks, and it's close to zero deck in most builds. you might actuially need a D shape dish piston to keep the compression ratio in check ... 12cc's out the heads
running up my post count some more .
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Re: Edelbrock heads and piston questions
[Re: BSB67]
#2296456
04/30/17 12:21 PM
04/30/17 12:21 PM
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Joined: Jan 2003
Posts: 75,095 A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,095
A Banana Republic near you.
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Sell the Edelbrocks, buy the TF 240. You'll probably be out $500 in the end, but way ahead in the log run. You'll have a better head, and better CR without milling stuff or compromising stuff. This is probably the best solution because he said he was going to have the head ported, adding all the porting and head machining in it would probably be a wash , no porting required on the TF and they don't need to be milled either ... That is assuming he uses the Dish piston and it's a D dish to retain the quench effect that will be needs to run pump gas ...
running up my post count some more .
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Re: Edelbrock heads and piston questions
[Re: 440mopar]
#2298300
05/03/17 02:54 PM
05/03/17 02:54 PM
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Joined: May 2003
Posts: 6,570 Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,570
Downtown Roebuck Ont
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"Give Ron Beaubien at Diamond Pistons a call."
Tried calling him a couple of days ago and apparently he doesn't return voice mails as I never heard back from him.
Another suggestion that had come up is to increase the heads cc's to 92 in order to increase the compression. I'm not sure I would want to do this (or milling for that matter) in the event I ever wanted to use the heads on another motor. I'm thinking of going back to my original plan of building a 470 and using the RPM heads as-is with flat tops to avoid having to alter the heads in any way (other than porting). Increasing chamber cc's reduces the compression ratio. If this "builder" is telling you otherwise, run do not walk away. The simple solution is to pick a compression ratio and then find a piston with a reverse dome/dish volume that will deliver that number at zero deck with your chamber CC and .039" head gasket. Like MR_P_BODY said, if you can't find a shelf piston, a $35 upcharge gets you exactly what you need. I don't know if 440Source is still a Ross dealer but Ross did up a 34cc reverse dome for my 4.15 493 Source kit that became a shelf stock item until Brandon changed suppliers. I was looking for no more than 9:1 for 87 regular gas and a 34cc dish put me at 8.97:1 with zero deck with RPM heads. Kevin
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