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'68 390 Mods

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Blue68SST View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blue68SST Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2017 at 9:54am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blue68SST Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2017 at 10:52am
As for the cylinder heads, I agree, the lower compression ratio works for the reasons you mention, as the car for me is a strong, reliable sunny day cruiser. I’m not looking for perfection or maximizing performance.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote White70JavelinSST Quote  Post ReplyReply Direct Link To This Post Posted: Dec/05/2017 at 12:06pm
Originally posted by Buzzman72 Buzzman72 wrote:

Dead umbrella valve seals in drainback holes? Had a '70 Javelin 360 with bad valve seals and plugged drainback holes. Used a quart to 50 miles. Used the twisted end of a coat hanger to corkscrew the drainback holes open, and instantly changed oil consumption to a quart every 500 miles. Later I did a valve job and replaced the seals with the kind that required machining the outside of the guide and installing with a driver. Problem solved. Umbrella seals are a waste of time.


I bought a 1970 390 several years ago. The oil pickup tube and screen that is threaded into the bottom of the block had rubber umbrella pieces packed inside it from sucking them out of the pan. Rubber umbrella seals are junk, unless you change them often enough that they don't deteriorate, get brittle, break up and end up in the pan.
70 Javelin SST, second owner, purchased 1972
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Dec/05/2017 at 9:50pm
Have a look at the front of the intake where it is bolted to the head. the paper gaskets are about .060", and the valley pan about .025". You can usually tell; you can see if it is sheet metal. The PCV is plumbed into the front carb, so it really is entirely possible that is the oil problem. Not a perfect guarantee, but definitely likely. I stock the gaskets, but it is best to have both the factory baffle and the factory gasket. Baffles I do not have (actually I might have one, but I'm keeping it!), and are getting harder to find. The non EGR one should fit that intake although there are a couple different rivet patterns. Usually afternmarket intakes have both, but not sure about that intake. I always thread the holes and use small bolts with locktite instead of rivets.
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348AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 348AMX Quote  Post ReplyReply Direct Link To This Post Posted: Dec/11/2017 at 2:01pm
Originally posted by Ken_Parkman Ken_Parkman wrote:

The stock valley pan gasket and stock intake PCV baffle are critical for PCV oil control. The system seems to be OK with at least one, but it is best to have both. It is a very well engineered system from the factory, and often intake changes screw it up as the guy does not understand the system; using paper gaskets and not bothering to rivet the intake baffle on. IIRC the Offy intake has a threaded port at the front, and if the PCV is plumbed to that it's entirely possible that is your oil problem. Nothing wrong with the actual engine.

360 heads on a 390 are a great improvement. Actually the 74 and up 360 heads were 60.1 ccs; some of the sites have this slightly wrong. The drop in compression make pump gas easy, and those flow better than the higher compression heads. There should be no significant difference in power, but a lot less grief to tune on pump gas.

Let me know if I can help; I'm just up the road from you. Think we met at the Milton cruise?


out of curiosity do the 60CC heads have less, the same, or more velocity than the high compression square ports?

Edited by 348AMX - Dec/11/2017 at 4:07pm
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67 Marlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Mar/08/2018 at 4:44pm
The Offy doesn't come with the PCV baffle. But, it does have the little mounting holes. While I was checking, took some comparative photos and measurements. The AMC intake is the factory manifold for your 390. I think the hole between the carb mounts on the Offy is for the power brakes.

The ports on both intakes are 1 1/16" wide, though the AMC unit narrows going toward the ceiling and floor. The AMC is 2 1/32 to 2 1/16" tall; the Offy ports are all 2 1/8" tall.




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67 Marlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Mar/08/2018 at 5:00pm
Here's another Offy photo. Have some questions, too, maybe answers can help the OP.

1. Is the hole, under where the rear carb mounts, where Offy intended the PCV valve hose to lead to? Or, did Offy intend for this to be a vacuum gauge connector fitting? It's threaded.

My 1967 AFB has rear PCV and the OP's has them on the front. Since the power brake vacuum connector is between the carb mounts, maybe connecting to the front-side of the rear carb PCV would be super tight and make accessing the idle air screws difficult.

2. Why is front-side PCV preferential to the back of the carb? There's got to be a reason, otherwise Carter wouldn't have made the switch.

3. How does connecting to the front carb PCV act any worse than to the rear carb?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blue68SST Quote  Post ReplyReply Direct Link To This Post Posted: Mar/08/2018 at 7:54pm
Thanks 67 Marlin.
That really makes me wonder if I have a baffle on my intake. I suppose it’s worth the price of a gasket to find out......now I just need a baffle. The hole behind the rear carb has a threaded plug in it on my intake.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Blue68SST Quote  Post ReplyReply Direct Link To This Post Posted: Mar/12/2018 at 6:11pm
I was checking out another thread for someone having similar oil consumption problems, and there was a suggestion to use a screwdriver down the pcv grommet hole to determine if there is a baffle on the intake.
If the screwdriver only goes down about 2 1/2 inches there is a baffle. More than that, there isn't. Makes sense. The 4 inch screwdriver went all the way in.
The hunt for a baffle begins.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Mar/12/2018 at 11:59pm
Why is the baffle so big? Why does it need to cover the entire center part of the intake? If it's just a PCV baffle, then isn't the only part that's really needed the quarter section in the upper left-hand of the photos, where the PCV valve is? Could someone just fab up a piece of sheet metal in that one place and meet the need?
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