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Cranking Compression versus Oil Control #2717901
11/20/19 06:43 PM
11/20/19 06:43 PM
Joined: Mar 2003
Posts: 4,923
Tri-Cities, Washington
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VITC_GTX Offline OP
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VITC_GTX  Offline OP
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V

Joined: Mar 2003
Posts: 4,923
Tri-Cities, Washington
Bought a '69 roadrunner with original 383, 93,000 original miles and the motor has never been apart. I checked the compression when I bought it (170 psi in 6 cylinders, 165 in 1 and 175 in 1) so I was pretty happy with that, especially with that many miles on the engine. Unfortunately the engine uses quite a bit of oil (1 quart in 500 miles) that I assume is cause by bad oil rings or possibly the valves/heads.

Question is; do you believe that I have oil control issues due to the rings with compression that high/consistent or do suspect the valves/heads?

Re: Cranking Compression versus Oil Control [Re: VITC_GTX] #2717996
11/21/19 06:19 AM
11/21/19 06:19 AM
Joined: Mar 2006
Posts: 9,815
MI, usa
dvw Offline
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dvw  Offline
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The valve seals are probably toast. Intake gasket leak is also worth looking at. Possible stuck oil rings, but I doubt it.
Doug

Re: Cranking Compression versus Oil Control [Re: dvw] #2718026
11/21/19 10:14 AM
11/21/19 10:14 AM
Joined: Jan 2003
Posts: 8,018
Tulsa OK
Bad340fish Offline
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Bad340fish  Offline
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Tulsa OK
I would imagine the valve seals are dry and crusty. I would buy a nice spring compressor and change the seals out before I looked further.

Then on my other shoulder there is the little guy saying ti could probably benefit from freshening the heads up and putting hardened seats in for the exhaust. Or Edelbrock sells nice mostly ready to go aluminum heads also lol.


68 Barracuda Formula S 340
Re: Cranking Compression versus Oil Control [Re: Bad340fish] #2718229
11/21/19 09:20 PM
11/21/19 09:20 PM
Joined: Mar 2003
Posts: 4,923
Tri-Cities, Washington
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VITC_GTX Offline OP
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VITC_GTX  Offline OP
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Tri-Cities, Washington
Thanks for the opinions guys.

All the plugs are fowled so I suspect it's not an intake leak. I'll take a look at the valve seals when I get a chance.

Re: Cranking Compression versus Oil Control [Re: VITC_GTX] #2718236
11/21/19 09:34 PM
11/21/19 09:34 PM
Joined: Mar 2011
Posts: 3,068
Michigan
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A727Tflite Offline
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A727Tflite  Offline
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Michigan
Maybe you should change the oil first - wouldn’t be surprised to see some of the valve seals in the pan after 50 years.

Re: Cranking Compression versus Oil Control [Re: VITC_GTX] #2718295
11/22/19 02:01 AM
11/22/19 02:01 AM
Joined: Mar 2007
Posts: 3,277
West Coast, USA
jbc426 Offline
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jbc426  Offline
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West Coast, USA
The old rubber umbrella seals harden, crack and fall apart. It's pretty quick and easy to change them out. If you are going to keep the car, throw a fresh set of gaskets on the intake, put in a fresh double roller timing set, a windage tray and clean the oil pan while you're at it. You may need a fresh accelerator pump plunger if it sat for a long time. Add a phenolic spacer under the carb and insulate the fuel lines near the motor.

Then recurve the distributor so you can run a bit more initial with out going over 34 -36 total. Make sure you hook the vacuum up to manifold vacuum, so it retards when the throttle is opened..


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
Re: Cranking Compression versus Oil Control [Re: jbc426] #2718310
11/22/19 08:58 AM
11/22/19 08:58 AM
Joined: May 2019
Posts: 6,220
nowhere
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Sniper Offline
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Originally Posted by jbc426


Make sure you hook the vacuum up to manifold vacuum, so it retards when the throttle is opened..


what do you think ported vacuum does when the throttle is opened?

Re: Cranking Compression versus Oil Control [Re: Sniper] #2718316
11/22/19 09:43 AM
11/22/19 09:43 AM
Joined: Jun 2008
Posts: 3,916
usa
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lewtot184 Offline
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usa
the engine is wore out. all the oil in the chambers is propping up cranking compression. the valve seals have fell apart long ago, guides probably shot. I believe those engines came with cast rings and rope seal. if you yank a head i'll bet there's a noticeable ridge at the top of the cylinders. those old HP engines were rode hard back in the day and the lead in the gas ate them up. freshen it up and go another 90,000 miles.







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