DodgeForum.com

Here are as many 5.2 V8 Magnum (post 1992)
engine technical specs as I have been able to acquire various places.
Please check these dimensions and post any mistakes you find or additional
stuff.

Some of this stuff came from PerformanceTalk and I repost it in the
hopes it may help someone else - particularly those playing around with Engine
analysing computer programs.

I will post 5.9 Magnum measurements later.

Bore 3.91
Stroke 3.31
Connecting Rod length 6.123 inches

Deck height of block 9.585 inches according to Hot Rod Magazine 'Magnum
Manifesto' Aug 1998 but I suspect this is incorrect ...may only apply to 1997
MP Crate Engines...old LA spec was 9.599 inches

Distance from piston quench pads to cyl head quench pads approxmately
0.050 with 9.585 deck height or 0.064 with 9.599 dk ht.

18 degree inclined valve angle

Combustion Chamber size...nominal 65 cc according to Hot Rod in 'Magnum
Manifesto' article in Aug 1998...62 cc according to Marlan Davis in 'High Perf
Mopar Engines' ISBN 1884089518 ....62cc as measured by Ray Barton Engines on
Dakota owner's 1995 5.2V8. Several moparts.com forum members report they have
measured Magnum chambers at 62-64cc.

Cylinder head intake port volume 153cc (RT MP cyl head 162cc)
Cylinder head exhaust port volume - unknown (70 cc ?)

Compression height of factory cast aluminum pistons 1.81 inches
Volume of piston valve clearance 'eyelass' cut-outs: 5 cc
Compression ratio 9.1 advertised (8.7 with clean metal chamber....carbon
deposits said to increase ratio by at least 0.5 in first 10,000 miles of
driving)

See this webpage for piston picture:

http://www.kb-silvolite.com/page39.htm#SECT2

Throttle body: dual 50mm bores. Chrysler patented 'Progressive Bore'
necks this down to 48 mm at throttle shaft )
Theoretical Throttle Body Flow capacity: 680 cfm alone,
or 440 cfm as part of the air intake system.....due to restrictive
air intake system or 'Progressive Bore choke point

Intake Manifold runner length along centerline: 15 inches. Top of runner
17.75 inches and bottom length 12.75 inches.

Intake Manifold runner 'equivalent' diameter 1.59 inches
Intake manifold design type: single plenum with 90% divider (almost a
dual
plane....

Cylinder head gasket thickness 0.047 inches
Intake port flow: 208 cfm at 0.450 lift
Exhaust port flow: 173 cfm at 0.450 lift

Intake valve diameter 1.925 inches
Cam design type: mild hydraulic roller
Intake valve timing:
......Lobe centerline 115.5
......Advertised duration 251 degrees
......Opens btdc 10 degrees
......Closes abdc 61
.....maximum lobe lift 0.27 inches
.....rocker arm ratio 1.6
.....gross intake valve lift 0.432
Exhaust Valve diameter 1.625 inches
.....Lobe centerline 109.5
.....Advertised duration 261
.....Opens bbdc 60 degrees
.....closes atdc 21
.....maximum ex lobe lift 0.27
.....rocker arm ratio 1.6
.....gross exhaust valve lift 0.432

{all of the above data can be used to show that the new cam at the
factory is
installed 3 degrees retarded, but timing chain wear might gradually
advance
this. The camshaft specs may have changed a few times since 1992 as the
factory tweaked them a bit, and eliminated EGR in 1997}

Streamlined type cast iron exhaust manifold
.... 2.500 inch outlet in 1992, 2.125 inch outlet afterwards

Approximate CFM capacity of factory exhaust system: 184 cfm at 20.4
inches
water. Note that most exhaust companies test at 28 inches water.

Coolant temperature 195 degrees F (180 makes little difference according
to Kenne Bell but helps reduce pinging)

Mgnum engine water pump allegedly pumps 100 gpm at 5000 rpm according to
Larry Shepard in 'Magnum Engines' Mopar Perf book.

Air and pressure at dyno:
....Society of Auto Engineers standard is 77 F, 40 F dew pt and 29.6
baro,
but...
.....130 F, 40 dew pt, and 29.92 seems to give better hp and torque
match and
is what I measure with actual Scantool on 5.9 engine in '95 truck.

Notes:
Factory Dakota RT exhaust seems to be about 550 cfm, resulting in +15 hp
increase.

According to Larry Shepard, 42 inch long primaries with 1.625 dia with 6
inch
collector specs make a good 4 into 1 header specification. To use this
primary length catalytic converter must be moved back behind factory installed
spot. Most aftermarket headers are very short so that they can mate to
existing Y pipe and cat.

Hope this data helps.
Please check and pass along any mistakes spotted.

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I have received tips by email that:

(1) In the April 2000 issue of Mopar Performance News Larry Shepard
writes about the new aluminum Magnum head. In the article he says that the 5.2
and 5.9 use the same cast iron Magnum head, and that head's combustion chamber
is 'nominal 60cc.'

Shepard also writes that the aluminum head loses more heat to the
coolant, so they upped the compression ratio of the aluminum head by 1 pt of
CR to compensate. I guess that makes the Aluminum Magnum head cc about 53 cc.
Each cast iron Magnum head is 48 lbs, and the new Aluminum Magnum head is 25
lbs. Aluminum Magnum head is said by Shepard to make 15 HP more 'out of the
box.'

(2) In the Nov/Dec 1999 issue of Mopar Performance News there is a tech
article about the short block assemblies. In this article they say that the
deck height of the old LA blocks was 9.60, the factory Magnum blocks are 9.58,
and the used shortblock assemblies from Mopar Performance they call 'seasoned'
blocks are milled down to 9.56 prior to re-assembly.