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Re: 383 head question.
[Re: JoesMopar]
#788770
08/30/10 10:15 PM
08/30/10 10:15 PM
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Joined: Jan 2003
Posts: 8,941
Holly/MI
Dean_Kuzluzski
master
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master
Joined: Jan 2003
Posts: 8,941
Holly/MI
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Those heads are correct for all 383 and 440's in the 68 and 69 model years. Some of 1970, not sure if the whole year, the 346 head may have come in early.
The big block wedge motors did not have an HP specific heads in those years. 62-64 Max Wedge, yes.
R.I.P.- Gary "Coop" Davis 02/09/68-05/13/04
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Re: 383 head question.
[Re: JoesMopar]
#788773
08/31/10 01:53 AM
08/31/10 01:53 AM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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in stock form, they're probably good for 450-500 hp.
big drawback is the open chambers make for low compression ratios unless you get domed pistons.
I had a bone stock set on my 383 stroker and would guess it was putting 450 to the crank. stepped up to eddy closed chamber heads, extra flow, more compression, and actually took it to a dyno, just barely eeked out 500 hp on the dyno, which is why I GUESSTIMATE that it was making 450 before.
**Photobucket sucks**
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Re: 383 head question.
[Re: 70Cuda383]
#788774
08/31/10 02:09 AM
08/31/10 02:09 AM
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Joined: Jul 2006
Posts: 4,319
Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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Tough to get compression with a 383 and open chamber heads. The only off the shelf piston I know of that gets you even close to compression needed for a performance build is the KB400, but it's a hypereutectic piston, not forged. If no nitrous is in the plan, its a good option. I think a set of shaved 906's, with KB400's set up at zero deck (you'll have to deck the block), get you near 10:1. (If I remember correctly)
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: 383 head question.
[Re: JoesMopar]
#788776
08/31/10 05:22 AM
08/31/10 05:22 AM
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Joined: Jan 2003
Posts: 75,082
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,082
U.S.S.A.
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Quote:
Thanks. Are they worth using for a mild 383? I'm thinking KB flat tops, Voodoo 268 cam, Edelbrock Performer intake, stock everything else, except ARP Fasteners.
Don't use a KB flattop unless your goal is a low compression pig. they sit too far in the hole and have a canyon like valve trough. The best choice would be a diamond flat top, lighter and has valve reliefs , the down side is they are pricey.
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Re: 383 head question.
[Re: JohnRR]
#788777
08/31/10 06:49 PM
08/31/10 06:49 PM
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Joined: Aug 2007
Posts: 902
Seattle, WA
rss
super stock
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super stock
Joined: Aug 2007
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Seattle, WA
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Quote:
The best choice would be a diamond flat top, lighter and has valve reliefs , the down side is they are pricey.
Wouldn't the Sealed Power forged flat tops work for this application, or does the Voodoo 268 have too much lift for a flat top with no valve relief?
IIRC, compression height on the Sealed Power flat tops is 0.004" taller than the Diamond flat top, plus no loss of compression from valve reliefs 
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Re: 383 head question.
[Re: JoesMopar]
#788779
08/31/10 08:36 PM
08/31/10 08:36 PM
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Joined: Jan 2006
Posts: 3,535
Canuckville
68Cbarge
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master
Joined: Jan 2006
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Canuckville
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Piston choices for 383 are limited compared to a 440. Yes,I agree that the new pistons do sit down in the hole. I had to bore my block 40 over. I ended up using Sealed Power flat tops,decked the block ten thou,planed the 906 heads another seven thou,used a thinner head gasket,and lucky to get between 9.2 to 9.5 compression.   
'68 Newport Custom Barge on a Budget!! BOAB
1973 Satellite WAGON! 318- 3 on the tree!!
2008 Chrysler 300c HEMI!
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Re: 383 head question.
[Re: JoesMopar]
#788781
08/31/10 08:56 PM
08/31/10 08:56 PM
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Joined: Aug 2007
Posts: 902
Seattle, WA
rss
super stock
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super stock
Joined: Aug 2007
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Seattle, WA
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Quote:
Is the height, or compression height, of the new KB flat tops shorter than the originals? Maybe I should just re-use the originals if they're in shape to be re-used.
Not sure what the compression height of your original pistons would be. As far as I know, the compression height varied from year to year.
But for the sake of comparison, look at KB162 vs. Sealed Power forged flat tops.
Compression height for KB 162s is 1.908
Add to that valve relief volume = 5 CC
Compression height of SP Forged is 1.920
Flat tops with no valve reliefs
The shorter compression height and valve reliefs will probably end up dropping your compression ratio by at least half a point, maybe a bit more.
IIRC, the Diamond forged pistons have a compression height of 1.916 and valve relief volume of 4 CC, so they sort of split the difference between the KBs and SPs, but the Diamond pistons are about $600.
KB400s (domed) give you a compression height of 1.908 but have a 6 cc dome to bump up compression.
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Re: 383 head question.
[Re: JoesMopar]
#788782
08/31/10 08:58 PM
08/31/10 08:58 PM
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Joined: Jan 2006
Posts: 3,535
Canuckville
68Cbarge
master
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master
Joined: Jan 2006
Posts: 3,535
Canuckville
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I was hoping to re use my original pistons but the bores needed work.. Despite being a dished piston 383 2bbl motor,it still had a zero deck height. Note where a valve hit the piston. 
'68 Newport Custom Barge on a Budget!! BOAB
1973 Satellite WAGON! 318- 3 on the tree!!
2008 Chrysler 300c HEMI!
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Re: 383 head question.
[Re: JoesMopar]
#788784
08/31/10 11:07 PM
08/31/10 11:07 PM
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Joined: Jan 2005
Posts: 1,647
IL
71383beep
top fuel
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top fuel
Joined: Jan 2005
Posts: 1,647
IL
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I can tell you from personal experience that using kb162's and 906 heads with no real machining of the deck or heads will result in compression under 8:1. I ended up rebuilding with a set of 516 heads and it made a world of difference. By far the easiest way to get your compression up with the paltry piston selection is to go closed chambers. 516 and 915 heads are still available and can be built to do as well as the famed 906 heads (especially the 915s). just my  BTDT
'73 GK6 Challenger Rallye - 340 4-Speed
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Re: 383 head question.
[Re: rss]
#788786
08/31/10 11:29 PM
08/31/10 11:29 PM
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Joined: Jan 2003
Posts: 75,082
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,082
U.S.S.A.
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Quote:
Quote:
The best choice would be a diamond flat top, lighter and has valve reliefs , the down side is they are pricey.
Wouldn't the Sealed Power forged flat tops work for this application, or does the Voodoo 268 have too much lift for a flat top with no valve relief?
IIRC, compression height on the Sealed Power flat tops is 0.004" taller than the Diamond flat top, plus no loss of compression from valve reliefs
the 268 is probably small enough that valve reliefs would not be needed , but having them would give one room to grow.
As far as the sealed power being a better choice , they are cheaper and it ends there , they are a very heavy slug , 1000 grams with the pin. for a small upcharge Diamond will move the pin to get the piston closer to TDC (why they make it as short as they do is beyond me , but then again most all aftermarket mopar piston makers make the pistons too short) , but you still have a low compression engine , though the valve reliefs are not very big.
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Re: 383 head question.
[Re: 68Cbarge]
#788787
08/31/10 11:32 PM
08/31/10 11:32 PM
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Joined: Jan 2003
Posts: 75,082
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
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U.S.S.A.
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Quote:
I was hoping to re use my original pistons but the bores needed work..
Despite being a dished piston 383 2bbl motor,it still had a zero deck height.
Note where a valve hit the piston.
At blueprint deck spec those pistons are .0025 in the hole , the CH is 1.932, zero requires a 1.9355 .. assuming a 3.375 stroke .
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Re: 383 head question.
[Re: JoesMopar]
#788788
08/31/10 11:36 PM
08/31/10 11:36 PM
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Joined: Jan 2003
Posts: 75,082
U.S.S.A.
JohnRR
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I Win
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Quote:
Thanks for all the info.
How would the KB flat tops make less compression than the stock pistons?
I don't want to add nitrous, blowers etc. Just a decent stockish motor with enough grunt to blast onto the freeway easily. I'm not looking at throwing alot of money into building this motor, that's why I want to re-use alot of the stock components. If the car had 400hp I would be happy. I'm being a cheapskate with this car.
You will not make 400HP with the build you speced above , I'm building my 383 to NHRA spec using a cam similar to the 268 and it is not going to make that much HP and my build is going to be close to 11.0 compression.
The KB's make less compression because they are shorter in height than stock and that huge valve relief , they pretty much suck as far as piston choice goes .
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The only people who still consider the 906 heads to be anything spectacular are the #'s guys.
