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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
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Allright, specs are
'70 318 1 bbl econo 100,000 miles |
#2
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Hey Fury Boy: At best you should only have 100 psi. Thats all that the specs call for...
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#3
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Hmm.... You think?
I don't think that will be it.
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#4
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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
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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. |
#6
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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
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Hey Smokedog: I use my Caprice as a tow car...
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#8
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What, ya mean in case you need something to tow?
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#9
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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
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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
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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
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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! |
#13
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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
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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
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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
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Pretty stout!
Hey a70duster, everyone said it would be below 160, just not above 140! ha ha ha! |
#17
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Quote:
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#18
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Quote:
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#19
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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
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Quote:
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#21
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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
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Quote:
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#23
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Quote:
Joking aside - it COULD be that high, if the cam was pretty small and closed the intake valve near BDC. |
#24
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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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