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View Poll Results: my compression is?
below 100 PSI 9 32.14%
below 120 PSI 9 32.14%
below 160 PSI 5 17.86%
below 140 PSI 5 17.86%
Voters: 28. You may not vote on this poll

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  #1  
Old 04-26-2001, 11:05 PM
Fury Boy Fury Boy is offline
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Biggrin

Allright, specs are
'70 318 1 bbl econo
100,000 miles
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  #2  
Old 04-26-2001, 11:18 PM
carguy carguy is offline
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Lightbulb

Hey Fury Boy: At best you should only have 100 psi. Thats all that the specs call for...
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  #3  
Old 04-26-2001, 11:21 PM
Fury Boy Fury Boy is offline
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Red face Hmm.... You think?

I don't think that will be it.
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  #4  
Old 04-26-2001, 11:27 PM
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Cool

Unless you have a problem, it should be pretty close. I have a 73 chevy 400 small block with 165,000 miles and it is with 5 psi of specs on all cylinders. And its in a 5,000 pound caprice wagon. Its a old dog that won't die...
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  #5  
Old 04-27-2001, 01:10 AM
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MOPARMANJAMES MOPARMANJAMES is offline
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Cool

Hmmmm.....
I just did a compression check on my smog dog 83 ramcharger a few weeks ago and it has about 80k on
the remanufactured engine. It was 125 psi so I'll guess 125 also since yours is a 70 with higher mileage.
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  #6  
Old 04-27-2001, 02:32 PM
SmokeDog SmokeDog is offline
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I'm with the 125 psi. guess, there is a reason we are Mopar nuts. P.S. carguy. Just a reminder, this is moparchat.
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  #7  
Old 04-27-2001, 09:51 PM
carguy carguy is offline
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Unhappy

Hey Smokedog: I use my Caprice as a tow car...
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  #8  
Old 04-27-2001, 10:02 PM
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NitroMethane NitroMethane is offline
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Biggrin

What, ya mean in case you need something to tow?
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  #9  
Old 04-27-2001, 10:08 PM
carguy carguy is offline
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Biggrin

hey Nitro: that was a good one. I live in NC.I'm always finding parts cars and stuff to drag home. ain't gonna use no Mopar for that...
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  #10  
Old 04-27-2001, 10:17 PM
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NitroMethane NitroMethane is offline
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Why not? I use a 90 3/4 ton 4x4 named Ogre for the dirty work...Drags all my friends' Chevys home without blinkin' (and the occasional Ford!)
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  #11  
Old 04-29-2001, 09:14 PM
djswwg djswwg is offline
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Biggrin compression

Furyboy, I don't know what your compression is, but I'd sure like to see a picture of that 1 bbl. carb sitting on that 318! Would you post a picture of that for us please!?
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  #12  
Old 04-29-2001, 09:37 PM
Fury Boy Fury Boy is offline
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Biggrin OOOPS!

My mistake(actually, I was just going by my dads words) it is a 2bbl! I was comparing with a 383 2 bbl and it looked totally different, same year and everything. But I got my Cudas and Challengers resto book and it is a 2 bbl, sorry!
Compression is

150 PSI!!! HAHAHA! I guess that means a lot of people were way off!
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  #13  
Old 04-29-2001, 10:34 PM
carguy carguy is offline
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Lightbulb

Hey Fury Boy: You may be right.. I looked in the Chilton's and they call for a minimun of 100 psi on a 70 318 2bbl. The 69 list a 318 2bbl having 140 psi. Now the big diff. is that the 70 has 8.4 to 1 comp ratio and the 69 has 9.20 to 1. Hmmm
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  #14  
Old 04-29-2001, 11:25 PM
PLUM CRZY PLUM CRZY is offline
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Hey Fury Boy....before you go HAHAHAing other people, you might want to measure it. Worn engines or rebuilds, due to a thicker head gasket, might have pressure WAY below what a book says. Remember the old saying, "you cant always believe what you read!"
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  #15  
Old 04-29-2001, 11:53 PM
Fury Boy Fury Boy is offline
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Biggrin Actually...

I did measure it, it is 150 in all the cylinders but one were it is 145. I didn't realize they had a book that told what your cylinder pressure would be... And by the way, all my books(about 3) say it is 8.8 to 1 CR.
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  #16  
Old 04-30-2001, 10:32 AM
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MOPARMANJAMES MOPARMANJAMES is offline
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Thumbs up

Pretty stout!
Hey a70duster, everyone said it would be below 160, just not above 140! ha ha ha!
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  #17  
Old 03-31-2005, 12:22 PM
TK TK is offline
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Quote:
Originally Posted by Fury Boy
My mistake(actually, I was just going by my dads words) it is a 2bbl! I was comparing with a 383 2 bbl and it looked totally different, same year and everything. But I got my Cudas and Challengers resto book and it is a 2 bbl, sorry!
Compression is

150 PSI!!! HAHAHA! I guess that means a lot of people were way off!
it might as well be a 1bbl!
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  #18  
Old 03-31-2005, 03:22 PM
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toad490 toad490 is offline
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Quote:
Originally Posted by Fury Boy
I did measure it, it is 150 in all the cylinders but one were it is 145. I didn't realize they had a book that told what your cylinder pressure would be... And by the way, all my books(about 3) say it is 8.8 to 1 CR.
Check your gauge
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  #19  
Old 04-10-2005, 07:46 AM
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rallye72 rallye72 is offline
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My 318 is 160 psi across the board with the factory 318 heads and a .050 head gasket(uncrushed). It's just a standard 1974 318 mill with 100,000 plus miles. Runs great just not a race car engine.
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  #20  
Old 04-11-2005, 11:12 PM
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toad490 toad490 is offline
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Quote:
Originally Posted by rallye72
My 318 is 160 psi across the board with the factory 318 heads and a .050 head gasket(uncrushed). It's just a standard 1974 318 mill with 100,000 plus miles. Runs great just not a race car engine.
I didn't know a engine could carbon up that bad.
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  #21  
Old 04-12-2005, 03:24 AM
Tarrbabe Tarrbabe is offline
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Default Lot's of carbon build up............

Running it really hard for a few days could drop the compression to more like 125.
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  #22  
Old 04-12-2005, 05:45 PM
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rallye72 rallye72 is offline
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Quote:
Originally Posted by toad490
I didn't know a engine could carbon up that bad.
I pulled the engine from a challenger, plucked off the heads to check the bores and ridge at the top of the cylinder. Everything looked good so I lapped the valves, new felpro gaskets, checked the bearing clearances, installed a 340 cam. I checked the compression after I broke in the cam. heads and pistons were free of carbon build up when it went back together.
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  #23  
Old 04-13-2005, 10:54 PM
Mills Mills is offline
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Quote:
Originally Posted by toad490
I didn't know a engine could carbon up that bad.
Hey - be nice - perhaps it was tested 500 ft below sea level.

Joking aside - it COULD be that high, if the cam was pretty small and closed the intake valve near BDC.
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  #24  
Old 10-29-2006, 03:56 AM
451Mopar 451Mopar is offline
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I guess I missed out, My guess would have been 155psi for a stock 8.9:1 compression 318. This is mostly due to the very small 240 duration cam, where the intake closes at just 50 degrees after Botton Dead Center.

Here is a cut-and-paste of the data:
ENGINE 318
Number of Cylinders 8
Bore (in) 3.910
Stroke (in) 3.310
Rod Length (in) 6.123
Block Deck Height (in) 9.600

PISTONS
Replacement Part Number SL-1266
Piston Compression Height (in) 1.741
Piston Dish Volume (cc) 2

HEAD GASKET
Bore Diameter (in) 4.180
Gasket Thickness (in) 0.020
Gasket Volume (cc)(est.) 4.498

CYLINDER HEADS
Cylinder Head Volume (cc)(est.) 60

CAM SPECS
Intake Duration 240
Intake Lift (at valve with 1.5 rocker) 0.373
Exhaust Duration 248
Exhaust Lift (at valve with 1.5 rocker) 0.399
Lobe Seperation Angle 109
Installed Centerline 110
Intake Open Point (BTDC) 10
Intake Closing Point (ABDC) 50
Exhaust Open Point (BBDC) 52
Exhaust Closing Point (ATDC) 16
Overlap 26

OTHER INPUTS
Engine RPM 6,000
Atomsphere Air Pressure (PSI) 14.70

CALCULATED
Piston Deck Height (in) -0.081
Cylinder Swept Volume (cid) 39.74
Volume Above Piston (cc) 82.44
Volume Above Piston (cid) 5.031
Total Cylinder Volume (cid) 44.77
Compression Ratio 8.90
Engine Displacement (cid) 317.95
Total Engine Volume (cid) 358.20

Rod Ratio 1.85
Piston Speed (4,000-5,000 max) 3,310
Piston Acceleration (100,000 f/s^2 max) 69,149

Piston Position (stroke) @ Intake Closing 2.799
Effective Cylinder Volume 33.60
Effictive Compression Ratio 7.68

Absolute Cranking Pressure (PSI) 170
Gauge Pressure (PSI) 155
Volume Pressure Index (est ft/lbs Torque) 274
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