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Re: what to do with a low compressior 383
[Re: Jerry]
#1435281
05/12/13 08:44 PM
05/12/13 08:44 PM
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Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
1_WILD_RT
Management Trainee
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Management Trainee
Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
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11.5  never happened... The best they claimed was 10.5 & the best they built was 9.6........ Most were less than 9.0... Bolt on a set of closed chamber heads after you mill them .030... 915's are best but 516's are far better than were you are now...
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: what to do with a low compressior 383
[Re: Jerry]
#1435282
05/12/13 09:43 PM
05/12/13 09:43 PM
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Joined: Jan 2003
Posts: 5,186
Wherever I am.
Junky
master
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master
Joined: Jan 2003
Posts: 5,186
Wherever I am.
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You most likely have "346" heads. They're ok for a mild build for the street. How deep in the hold are the pistons? Those engines had 9 to 1 compression, advertised. In reality less than that. I have a 383 out of a '71 Newport. Pistons are 0.020 in the hole. I milled the heads 0.30, blended and ported the heads and had a 3 angle valve job done. Installed the heads with steel shim gaskets. Running the Hughes Whiplash cam with headers and a 750 Holley. Runs pretty good for what it is. The Whiplash cam is designed for engines such as yours with stock exhaust manifolds and intake. Hughes
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Re: what to do with a low compressior 383
[Re: Jerry]
#1435285
05/12/13 11:38 PM
05/12/13 11:38 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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new timing chain set/Hughes cam/alot of dist adv curve work/mill heads .060 or so. AVS or thermoquad? HP ex manifolds/mandrel X pipe 2&1/2" system would a good addition & exhaust is the most restricted part of the (air pump) system. converter/deeper gears. less ohm ballast
live every 24 hour block of time like it's your last day on earth
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Re: what to do with a low compressior 383
[Re: ahy]
#1435287
05/13/13 01:36 AM
05/13/13 01:36 AM
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Joined: Jun 2006
Posts: 5,162
CT
GTX MATT
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master
Joined: Jun 2006
Posts: 5,162
CT
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Have the heads milled to turn them into closed chambers, that would give you about 2 full points. It would require excessive milling though (.120 thou or so), but you can get iron heads for a dime a dozen nowadays. I would have been worried about doing this, but I'm finding out that people used to build their race 383s/440s like this often before any aftermarket heads were available. I've never tried it but I've got an okay set of 906s that can get by with a valve lapping that I'm saving for something like this when the time comes.
Or have them shaved the factory recommended max of .060 thousandths, that would give you about a full point.
Run steel shim gaskets too.
Last edited by GTX MATT; 05/13/13 01:39 AM.
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Re: what to do with a low compressior 383
[Re: Jerry]
#1435292
05/13/13 10:29 AM
05/13/13 10:29 AM
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Joined: Jan 2003
Posts: 75,015
U.S.S.A.
JohnRR
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I Win
Joined: Jan 2003
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Quote:
i'm not looking for this car to be a 10 sec drag strip beast, but i'd like it to get out ahead of the honda civic crowd. i know being a convertible its heavy and will need all the torque i can get, so i was thinking the 268 or 274 duration cam. also unfortunately the exhaust is original and i'd hate to mess with it, but i would like some 2.5" pipes going back. i still have the original resonators and tips on the car.
a stroker is in the works just not right now as i'm finishing up my 73 challenger hard top.
There is a thread on cam choice for a 383, it actually shows a cam a little smaller than the 268 as the best choice for a torquey 383 to get a heavy car moving, though the whiplash cam might be worth looking into ?
I'd find a set of 516 heads (those and open chamber heads are the only heads a dime a dozen ) and have a good valve job, 1.74 exh valves and a pocket port done to them, that would be wiser than cutting .120 off a set of 906's, and cheaper than cutting heads that much, plus the cost of cutting an intake because you cannot take .147 off the intake side of the head.
Plus when you cut .120 off the heads now your valley pan is not going to fit unless you cut the china walls on the block .147 also, or cobble up some sort of valley pan.
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Re: what to do with a low compressior 383
[Re: 62maxwgn]
#1435294
05/13/13 10:48 AM
05/13/13 10:48 AM
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Joined: Jan 2003
Posts: 75,015
U.S.S.A.
JohnRR
I Win
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I Win
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Quote:
Jerry,is your head spinning yet ? 
It should be , he's getting a lot of bad info in this thread...
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Re: what to do with a low compressior 383
[Re: LaRoy Engines]
#1435296
05/13/13 11:06 AM
05/13/13 11:06 AM
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Joined: Jan 2003
Posts: 75,015
U.S.S.A.
JohnRR
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I Win
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Quote:
What kind of increase would you get if you just swapped to a set of factory iron heads with 40 cfm more and kept everything else the same?
Is this a test ???
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Re: what to do with a low compressior 383
[Re: JohnRR]
#1435297
05/13/13 11:30 AM
05/13/13 11:30 AM
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Joined: Jan 2003
Posts: 6,988
Warren, MI
Jerry
OP
master
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OP
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Joined: Jan 2003
Posts: 6,988
Warren, MI
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well right now, i plan on taking the car to the dyno and see what she pulls. i've got new plugs wires and cap and rotor and a recent oil change already, new filters etc. so the tune up is good, but i'm not planning on doing any more tuning. then i will make the changes cam, possibly heads, and intake and see what some bolt ons will do. obviously i'll publish the results here on the site and on my website. the goal of this will be a budget build for an enjoyable cruiser.
i know cutting heads .120 is not a good idea so thats out. 516 heads are relatively cheap and available so i will look for those. i believe i've got a good set of stock valves here already if i don't the 516 will get 2.14/1.81 valves.
intake wise, i've got a dp4b and the stock cast iron unit and the car already has a 650 dp carb and i've got a 750 vs carb here as well to try.
cam choice is kind of up in the air right now, but my previous comments apply, need some torque to move a heavy convertible. i'm not opposed to go going with a mechanical cam, just don't know if i can find one small enough.
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Re: what to do with a low compressior 383
[Re: Jerry]
#1435298
05/13/13 11:36 AM
05/13/13 11:36 AM
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Joined: Jan 2003
Posts: 75,015
U.S.S.A.
JohnRR
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I Win
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Quote:
i believe i've got a good set of stock valves here already if i don't the 516 will get 2.14/1.81 valves.
Unless you do the required porting , changing to those valves , especially in the 516 isn't going to gain you really anything other than a lighter wallet.
The right cam change would be the best bang for your buck.
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Re: what to do with a low compressior 383
[Re: JohnRR]
#1435299
05/13/13 11:42 AM
05/13/13 11:42 AM
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Joined: Oct 2011
Posts: 559
Idaho
LaRoy Engines
mopar
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mopar
Joined: Oct 2011
Posts: 559
Idaho
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Quote:
Quote:
What kind of increase would you get if you just swapped to a set of factory iron heads with 40 cfm more and kept everything else the same?
Is this a test ???
Yes.
The 1971 cast crank 383 is bolted to the dyno. Someone has put on a 1969 4bbl cast intake. I believe this has 346 heads on it but we've never pulled the valve covers. Hopefully it still has the stock low compression cam, will know later today when we swap to the 915 heads.
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