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Re: Raising compression in a 400?
[Re: hemigod426]
#303091
04/30/09 02:02 AM
04/30/09 02:02 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Doesn't the low compression 440 pistons in a 400 bring it up to 10.1? You may have to cut valve reliefs but..... 
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Re: Raising compression in a 400?
[Re: hemigod426]
#303094
04/30/09 03:04 AM
04/30/09 03:04 AM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
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Posts: 21,318
Manitoba, Canada
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Quote:
Quote:
516 might spec at 74cc but unless it's already been milled they typically measure 84cc....
And that 8.5 C/R estimate is pretty optimistic as well...
i just milled my 906 heads 40 and there are now 74cc and those are open chambers, 516 are same chamber as 915 closed there 74-5 ccs now unmilled. you can have a 8.2 to 1 400 seen many with taller than factory deck like plus 20-25 thou. got my 906 head soo tight by also putting in 2.14/1.88 monster farera nontulup valves 
I don't remember the formula off hand, but I really don't think cutting .040 is going to bring a 90cc 906 head down to 74cc.
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Re: Raising compression in a 400?
#303096
04/30/09 07:31 AM
04/30/09 07:31 AM
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Joined: Jan 2004
Posts: 640
AZ
FM370RR
mopar addict
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mopar addict
Joined: Jan 2004
Posts: 640
AZ
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Re: Raising compression in a 400?
#303097
04/30/09 08:26 AM
04/30/09 08:26 AM
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Joined: Jan 2003
Posts: 75,326
A gulag near you.
JohnRR
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I Win
Joined: Jan 2003
Posts: 75,326
A gulag near you.
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Quote:
You use the "Lighten up Francis" ALMOST as much as you use the "Outside the box thing" Think up some new ones or crawl back under your rock PLEASE!!!!!!!
Do you actually have anything constructive to add , if not go back under your BRIDGE ... PLEASE ...
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Re: Raising compression in a 400?
[Re: hemigod426]
#303098
04/30/09 08:32 AM
04/30/09 08:32 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Quote:
Doesn't the low compression 440 pistons in a 400 bring it up to 10.1? You may have to cut valve reliefs but.....
you cant put 440 pistons in 400, 440 has 4.32 bore 400 has 4.34 bore and 440 has 6.76 long rod for raised block 400 is low deck with monster bore
you can get .020 over 440 pistons at 4.34" or .030 over at 4.35". 0 deck on a 400 block should be a compression height of ~ 1.932". federal mogul stock replacement pistons are 1.813" CH, so I'd imagine the stock pistons would be ~.120" in the hole. low comp 440 replacement pistons are 1.912" CH, so they'd be ~.020 in the hole if the deck is at blueprint spec.
assuming blueprint deck height on 9.98", .020" steel shim head gaskets, 90cc open chamber heads, and .020 in the hole low comp 440 pistons, you're looking at 9.12:1 compression by the math.
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2017 Grand Cherokee Overland
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Re: Raising compression in a 400?
[Re: hemigod426]
#303099
04/30/09 08:35 AM
04/30/09 08:35 AM
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Joined: Jan 2003
Posts: 75,326
A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,326
A gulag near you.
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Quote:
Quote:
516 might spec at 74cc but unless it's already been milled they typically measure 84cc....
And that 8.5 C/R estimate is pretty optimistic as well...
i just milled my 906 heads 40 and there are now 74cc and those are open chambers, 516 are same chamber as 915 closed there 74-5 ccs now unmilled.
Someone must have milled those 906's then because out of the factory it will usually measure 90 cc. typically every .005 is 1 cc so with .040 off you only pulled out 8cc . the specs you are quoting for the 915 is NHRA I'm guessing which is alot smaller than ACTUAL .
As far as everyone telling him to change to a taller CH piston with it the way it is another post brought up a valid point ... CYLINDER RIDGE , unless he removes the ridge he will BREAK the new rings and from the sounds of it , NO ENGINE HOIST and he says he has NO CAR the block isn't coming out of whatever it's in anytime soon .
Buy hemigod's 516's and thats the best you will do with the constraints you have to work around for the short term fix .
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Re: Raising compression in a 400?
[Re: 64Post]
#303102
04/30/09 10:10 AM
04/30/09 10:10 AM
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Joined: Jan 2003
Posts: 75,326
A gulag near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,326
A gulag near you.
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Quote:
I'm sure a head change will yield some increase in compression, but with worn bores and rings I gotta think blowby is going to be increased greatly. So, how much additional compression is he really going to get?
Judging by where and how this is bouncing all over the place you are just adding more facts that are confusing the issue and I don't think it really matters, if I'm reading this right getting any work done outside of just bolting on parts to the shortblock as is is the only course of action ?
There isn't a piston that will swap directly in that's not going to cause havoc with the rings and the current ridge, that's an issue being ignored.
One thing that is been glossed over is no 440 piston is going to fit a standard bore 400 because the standard bore of a 400 is 4.342 , thats .022 oversize .
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Re: Raising compression in a 400?
[Re: JohnRR]
#303103
04/30/09 10:32 AM
04/30/09 10:32 AM
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Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
64Post
master
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master
Joined: Aug 2003
Posts: 8,716
Baltimore/Denver
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Quote:
Quote:
I'm sure a head change will yield some increase in compression, but with worn bores and rings I gotta think blowby is going to be increased greatly. So, how much additional compression is he really going to get?
Judging by where and how this is bouncing all over the place you are just adding more facts that are confusing the issue and I don't think it really matters, if I'm reading this right getting any work done outside of just bolting on parts to the shortblock as is is the only course of action ?
Yeah, that's why I was trying to stay out of it. But it's like a train wreck... 
Quote:
One thing that is been glossed over is no 440 piston is going to fit a standard bore 400 because the standard bore of a 400 is 4.342 , thats .022 oversize .
Nothing that a piston stretcher or some aggressive knurling won't fix... 
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Re: Raising compression in a 400?
[Re: JohnRR]
#303104
04/30/09 10:37 AM
04/30/09 10:37 AM
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Joined: Dec 2006
Posts: 3,533
Indiana
Fury Fan
master
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master
Joined: Dec 2006
Posts: 3,533
Indiana
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Quote:
As far as everyone telling him to change to a taller CH piston with it the way it is another post brought up a valid point ... CYLINDER RIDGE , unless he removes the ridge he will BREAK the new rings and from the sounds of it , NO ENGINE HOIST and he says he has NO CAR the block isn't coming out of whatever it's in anytime soon .
Buy hemigod's 516's and thats the best you will do with the constraints you have to work around for the short term fix .
 Don't buy new pistons to put in an old, worn block. You're gonna spend $200-300 on pistons and rings but what kinda ring seal will you have???
If you want some ideas on low-compression fixes, read this one:
https://board.moparts.org/ubbthreads/show...rue#Post5195287
Aside from that, I have to be harsh here:
If you have no daily driver, no engine hoist, etc, you are lacking some of the basic resources to do this job properly. 
By 'properly', I'm not even referring to a high-HP engine, I'm just talking about an engine that will last for a few years.
If you're not planning for this engine to be used for a few years when you get it running, just skip this activity altogether and plan for the next step - either getting a good used engine or a well-planned rebuild. 
Parts I seek:
driver doorpanel, 65 Sport Fury, prefer black, needs to be 7-8 on 10 scale, might buy set
16" x 6" Dodge truck wheel(s), from early 70s?, takes 9" dogdish - need for a research job so cheaper is better.
69-73 C-body caliper brackets and/or splashields
Send a PM.
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Re: Raising compression in a 400?
[Re: Fury Fan]
#303105
04/30/09 11:03 AM
04/30/09 11:03 AM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Quote:
Don't buy new pistons to put in an old, worn block. You're gonna spend $200-300 on pistons and rings but what kinda ring seal will you have???
Exactly what I said way back when. But nobody seemed to agree and kept on with the new piston thing. 
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