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#2426939 - 01/01/18 12:38 AM Re: Higher compression ratio options when starting with 7.5:1? [Re: Cab_Burge]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
Originally Posted By Cab_Burge
If I'm remembering your shop location correctly it is right at sea level, correct?
I have seen the density altitude at Thermal airport(150 Ft. below sea level) be right at 8700 Ft in the mornings in June, I have also raced at the old street races in Indio in March when the D.A. was probably around 1200 Ft. shruggy
The motor knows how thick or thin the air is regardless of the Pro Charger, correct shruggy


If you dyno an engine at sea level, or 5000ft. up, it does not matter...it's called a correction factor.
His uncorrected HP on that pull was 895.
His car has already run 9.90's in full street trim at 780HP...much faster than some Dusters out there with 750HP BB's....
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#2426941 - 01/01/18 12:46 AM Re: Higher compression ratio options when starting with 7.5:1? [Re: Cab_Burge]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
Originally Posted By Cab_Burge
If I'm remembering your shop location correctly it is right at sea level, correct?
I have seen the density altitude at Thermal airport(150 Ft. below sea level) be right at 8700 Ft in the mornings in June, I have also raced at the old street races in Indio in March when the D.A. was probably around 1200 Ft. shruggy
The motor knows how thick or thin the air is regardless of the Pro Charger, correct shruggy


I am going to ask you nicely to leave my posts alone...I do not need you trying to correct me. This is not your Post, and nothing has been directed at you except for me being stupid enough to actually try and explain something to you.
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#2427058 - 01/01/18 11:05 AM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
Uberpube Offline
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Registered: 11/30/13
Posts: 209
Loc: Southern Alberta
Back to the OP, I would keep the 7.5:1 if you are turbo'ing this thing...

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#2427192 - 01/01/18 01:10 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: ou812]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
9 to 1 compression works great with E85 turbo supercharged or whatever. I would not be afraid to do that up to 18 PSI of boost. Use an NGK number 7 spark plug that is non projected as a starting point.
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#2427543 - 01/01/18 10:34 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: ou812]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
What # indicates the 7?


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#2427545 - 01/01/18 10:37 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: Uberpube]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Will it even run/start on e85 with 7.6:1 comp.?
Have you ran it that low before on E?
This is suppose to be a street car with only a few 1/8 or 1/4 blasts a year.
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#2427546 - 01/01/18 10:40 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: ou812]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Or these?


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#2427730 - 01/02/18 11:25 AM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Holy Smokes,
Custom pistons from Diamond?
$1160!!!!!

And they still can’t make them 522g so I would need another rebalance.
Said new materials and machining techology would put them in the upper 400 gram range.

I really don’t want a low comp. laggy/peaky motor in my 3400# car.

hmmmmm
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#2427767 - 01/02/18 12:25 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
FastmOp Offline
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Registered: 01/20/03
Posts: 5075
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Fail to plan, plan to fail.

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#2427769 - 01/02/18 12:31 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: FastmOp]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
Less than 9:1 is harder to make power with using E85...it won't like it.
Plug is NGK -7 non projected. Similar to the -8 and -9 but hotter.
Never get a light piston using BOOST!
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#2427862 - 01/02/18 02:44 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
WO23Coronet Offline
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Registered: 01/08/08
Posts: 4006
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I’m sure you’ll be fine since you’re going with boost. Not optimal but you should really be able to crank the boost to it. Once boost hits it won’t be laggy at all

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#2427925 - 01/02/18 04:32 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Local machine shop said both heads done is $162 to deck heads to specified cc of 58.
$75 to mill intake sides.

final compression will be 8.3:1
This may be the way i go.


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#2427926 - 01/02/18 04:33 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: FastmOp]
prochargedmopar Offline
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Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Originally Posted By FastmOp
Fail to plan, plan to fail.


Yup,
I bought the rotating assembly parts 14yrs ago.
Just now deciding to use them (this past year collecting more parts)
Would have been fine with the magnum heads, 93, and the blower.
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#2428027 - 01/02/18 07:52 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
Can you afford the loss of P/V clearance? Also, correcting intake face, pushrods?
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#2428059 - 01/02/18 09:02 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
WO23Coronet Offline
master

Registered: 01/08/08
Posts: 4006
Loc: Canada
Originally Posted By prochargedmopar
Local machine shop said both heads done is $162 to deck heads to specified cc of 58.
$75 to mill intake sides.

final compression will be 8.3:1
This may be the way i go.



I really think you should just live with it. With boost, 7.5:1 is not that big of a deal. Good lord, every Mopar engine built after ‘72 was around that ratio N/A. You need the deck thickness in the heads to deal with the boost. I really don’t understand why you’re so twisted up about this

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#2428077 - 01/02/18 09:33 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: WO23Coronet]
prochargedmopar Offline
enthusiast

Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Originally Posted By WO23Coronet
I’m sure you’ll be fine since you’re going with boost. Not optimal but you should really be able to crank the boost to it. Once boost hits it won’t be laggy at all


Because from what i understand after google searching e85 requires a high compression ratio.
And can also run with a much higher compression increasing efficiency.

If this was race only I’d get the next size up turbo and have at it.
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#2428079 - 01/02/18 09:35 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: ou812]
prochargedmopar Offline
enthusiast

Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Originally Posted By ou812
Can you afford the loss of P/V clearance? Also, correcting intake face, pushrods?


Yes, I’ve only got a .505 lift cam 230/240.
One of the last items to purchase for assembly is pushrods.
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#2428087 - 01/02/18 09:47 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
I can sell you some CP bullet series pistons and rings for less than that. Changing pistons is THE only way to go, because you really need to leave the heads unmilled.
9:1 is really where you should start....
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#2428088 - 01/02/18 09:49 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: prochargedmopar]
ou812 Offline


Registered: 01/31/03
Posts: 5345
Loc: SoCal
Also, what are your engine specs...like crank, rods, cam, etc....?
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#2428350 - 01/03/18 12:57 PM Re: Higher compression ratio options when starting with 7.5:1? [Re: ou812]
prochargedmopar Offline
enthusiast

Registered: 01/21/17
Posts: 238
Loc: Granbury TX
Originally Posted By ou812
I can sell you some CP bullet series pistons and rings for less than that. Changing pistons is THE only way to go, because you really need to leave the heads unmilled.
9:1 is really where you should start....


How much?
Need comp. height of 1.545
Chevy .927 pin dia.
Valve reliefs
And a weight of 522 grams

Diamond tech said his pistons because of new technology and machining processes would be lighter.
I’d prefer not to rebalance.

6cc reliefs with flat top would be perfect.


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8353DB11-50FD-4C32-A9CC-4A6C2AF0FB7E.png




Edited by prochargedmopar (01/03/18 12:58 PM)
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