I just purchased a 76 Duster with a 360 that was rebuilt less than 400 miles ago by a professional race shop with all the top parts. Niether the block or the heads were milled but they were surfaced and magnafluxed. It was punched .030, KB pistons, chrome molly rings, bronze guides, stainless valves, roller rockers, heavy duty springs etc. It's a 69 block and heads. I have major blow-by on the left bank.

Here's the kicker. A young kid and his dad bought the car from the builder and had it less than 50 miles. They have no idea what a screwdriver is much less any other mechanical know-how, they addmitted this. Regardless of all the receipts and the knowledge of the original builder they took it to a small 2 stall shop that soaked them hard for new parts and work that didn't need done. Before there was a blow-by issue they took it to this shop who told them the engine needed a ton of work, despite $7,600.00 in receipts from the machine shop that speciallizes in race engines did the build. They convinced them it needed a new intake gasket, new oil pan, new starter,(the receipt for the brand new high torque mini starter was under the seat), new master cylinder(the builder backed off the brakes to load it on the transporter after installing new everything from MC to wheel cylinders, disc brakes up front the whole 9 yards for which all of the receipts were in the folder) and did an oil change. After leaving the shop the engine immediately started having the blow-by issue so they took it back to this same shop and they told them it needed new rings and called every 2 days hounding them that they had the time and could get it right in if they brought it back to them.

I seriously question the integrity of this shop after talking to others and talking to the original builder. No expence was spared on this car and everything was tight and right when it was loaded on the transporter. The kid didn't even know what the recall selector or erase function on the tach were for and I checked it and it had never been over 3200 rpm nor has it ever been above 192 degrees. They put less than 50 miles on the car before putting it back up for sale because the kid was scarred of it.

I've only put about 130-150 miles on the car and have been easy on it. I have no oil in radiator, no water in the oil nor do either get bubbles or foam when the car is running. The left bank has a breather cap but the right bank only has two regular caps on it. When I pull one of the right bank caps it smokes as much as the left. All the plugs are excellent and there is no tell-tale pfssst noise from a head gasket. I do have some moisture out the back but I suspect it may just be condensation because our humidity is way up and the temps are way down. Everything feels equal at the exhuast. I checked the torque on all of the head bolts and they're right at 95 lbs. The shop insured me that the windage tray was put back in when they changed the pan. The PCV valve may be bad as there is no RPM change at all when I hold my thumb over it.

Here's my question. Could that shop have put a light grade oil in the engine that would magnify the blow-by issue from regular break in? I suspect that the rings aren't even seated yet and the original owner feels the same way. Could this be something as simple as the shop putting a light oil in it knowing that they had completely gullable customers with a big checkbook on the hook? I haven't had a chance to check compression accross all of the cylinders yet nor have I done a leak down test on it. My new shop just got finished Wed. and I don't have power yet so I'm trying to do simple things while I wait for it to be ready to move into. How long does it take for chrome molly rings to seat? I haven't been able to wrench on anything for over 20 years so I'm really rusty at diagnosing. I'd like to try as many simple things as I can while waiting for my shop. I plan to change oil and put in a 20-50 synthetic oil.

Any input or guidance on which way to head on this would be greatly appreciated.

Thanks
MOPARDUDE6876

360 Blow-by single choice
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Votes accepted starting: 06/05/09 06:52 PM
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I wouldn't consider synthetic oil at this point. I don't recall the 360 being made in 1969. If there is even a possible problem I'd think maybe gas in the oil causing a problem. I'd change the oil if it has any indication of fuel in it. How does it run? How do the plugs look?

Need something cleared up. You say major blow-by on left bank, then you say the breathers on either bank smoke the same. Do you get smoke out the tailpipes? If so, what color? How does the car run? Do you have vacuum to the PCV?.
I hate to say it, but it sounds like you have been ripped off.
Definitely do NOT go synthetic at this point.You need a good break in oil like Joe Gibbs BR, if this is so fresh.If they did a poor job on the intake, you could be pulling oil and misfiring. It could be that simple. Keep us updated and good luck.

You might do a leakdown test and read this. "break in secrets" at www.mototuneusa.com

A compression test is about as simple as it gets. Do that first IMO

You're right, it's a 70 I screwed up. It runs great, no miss or lope(other than from the cam), it idles perfect has great throttle responce and doesn't flutter or bog. The oil is thin, but no gas smell or discoloration. The plugs are carboned, but not fouled. There is some smoke out the back, blue not white, but it's minimal.

Thanks

When I pull the PCV out RPM picks up 700-900 and there's good vacuum. There is only one breather cap on the left bank, the right bank has regular sealed type caps and when I pull one off the smoke level seems balanced out both banks. No noise like leaking past a guide or anything. There is some blue not white smoke out the back but it's minimal. Thanks for the advice from everyone about the oil, I'll stay clear of synthetic and pick up a good break-in oil. As soon as I can get a leak down test done I'll let you all know. Like I said, there was no issue until that shop did the "work" on it. Even that buyer said it was fine until they went to leave the shop after all the alleged work.

Thanks

If i remember right..

A. Chrome molly ring's take longer to seat.
B. They require a certain cross hatch pattern in the cylinder to seat properly.

First thing, one valve cover should have a PCV valve leading to full intake manifold vacuum. The opposite valve cover should have a breather with a filter or a hose going to your air cleaner.

Next, do a compression test then a leakdown test. This will tell you for sure if there's a sealing problem.

This may be part of the problem. The PCV comes out of a port on the right bank to direct intake vacuum. But...My breather (front of left bank)doesn't have a hose to my air cleaner. It's got an aftermarket K&N type pleated filter with the pleated lid. Nowhere to connect any hose unless I try and drill into the base and rig some sort of nipple and change out the breather cap.

I've seen other posts talking about a vacuum cannister with a recovery tank. SOmething about using a coffee can and draining the oil periodically. Not for me, is there an aftermarket system that is decent looking? I'm not really into a lot of underhood chrome but something in a clear anodize finish might be okay. Even better would be something I could hide. I also saw someone post to "run a hose from the breather to the back of the car. Put a chrome tip on it and call it your dual exhaust."! LOL I'd have to split the difference between the duals and figure out something else to call it. Can't think of anything real tasteful right now though.LOL
Thanks

If you're unsure of the history of the pcv valve, I'd stuff a nice new mopar unit in there.

The 360 did not appear until 1971. It may have a 1970 casting date, but it was cast for the 1971 model year

It may take 500 miles to 1000 miles for moly rings to break in the cyl. walls. Longer if they hone with too course of a stone. Unless you have a breather on one side and a PCV going to your carb on the other you WILL have blowby. Probably will anyways on hard acceleration (low vacuum) until the rings seat properly. And like green blur says... Drive it like you stole it! Best for proper break in. Also sounds like it needs some serious freeway time (also good for breakin)

Seating the rings is the most important thing on a rebuild like this and its done in the first 1/2 hour. It sounds like it wasn't done right which would be a shame. First do a compression test and then a leak down test to get an idea of whats going on inside.

I'm really screwed up on this block. I've never owned a 360 before and don't know squat about them. Is there a good site to go to to help date cadoe the block and the heads so I know EXACTLY what I have? Are the casting #'s for the heads in the same location as the 318/340's? I've had 318's up the wazoo and a couple of 340's plus a freind had a 340 Duster that we put a zipper in the hood because the engine was in and out so much it made things easier. I know the 360 is essentially the same but I think more than anything I'm timid. It's been so long since I've had anything to do more than regular maintenance on. That was 25+ years ago though and I haven't wrenched much since(obviously). A buddy is going to help me do a leak down at his shop this week and I'll go from there. The only place I've got to do anything is in the driveway until I get the power run to the new shop and the inside wiring done.

Somewhere in all of my searching on this issue a guy posted a message saying that he had bought an engine that he suspected the break-in wasn't done correctly on. He claims he let the PCV vacuum line suck up some Bon-Ami while the engine was running. The locic being the fine grit in the Bon-Ami would somewhat rescuff the cylinder walls and allow the rings the opportunity to reseat. I have a real hard time putting ANY foriegn material into an engine. Wouldn't the "fine grit" also wreak havoc with the valve train if it's coming through the intake?

He claims that after doing this you have to do a propper engine flush, but he swore it worked. I wish I could find the site in my history so I could post the link.

Anyone ever heard of the wive's tale? Is it some old wrench from the 50's secret discovery?

Thanks again to everyone for all the ideas and help. I need to start at square one and code this engine though.

I wouldn't go putting abraisives down the intake to seat the rings, with what little I've done they either seal up in the first few minutes of run time or never seal.

On my lastest 318 with moly rings they sealed within 4-5 min, well before I finished breaking in the cam, it had a 320 finish on the walls if I remember right, if they honed with a stone for cast rings it may have trashed the moly coating as soon as it was fired.