SWFL Posted January 31, 2023 Report Share Posted January 31, 2023 I just got a 1978 620 with some aftermarket engine parts on a L20B with a U67 head. The intake manifold is not stock and doesn't have a PCV port as far as I know, but I haven't looked at it too close. It's got a Weber 38/38, with the Weber air cleaner. The PCV port/nipple on the valve cover is connected to the Weber air cleaner plate without any PCV that I can see. Normal or abnormal ( I haven't done a compression test yet ) blowby oil is making a mess in the air cleaner. Provided the engine is in good condition, what's the best way to deal with this? I plan to go with a stock air cleaner and modify it to fit the Weber. Do healthy L20B engines have much oil in the crankcase blowby? Water cooled VWs had an issue with oil splash from the camshaft, so they put a plastic baffle plate/separator/tray above the camshaft that helped a lot. Quote Link to comment
datzenmike Posted January 31, 2023 Report Share Posted January 31, 2023 Blow by is not a problem unless the rings are worn. Post a picture of the intake left side of the carburetor as after market should have provision for PCV. A PCV, while always a good idea to have functional, is not going to fix excess blow by. U67 is not the head for a '78 so it, or the engine, has been swapped from something earlier. A 38/38 is really too big for a 2 liter engine. It's more for a V6 or small V8. A 32/36 would be better. Quote Link to comment
Crashtd420 Posted January 31, 2023 Report Share Posted January 31, 2023 The port coming from the valve cover does not have a pcv it just pulls air from the air box.... There is the crank case vent under the intake, this should be connected to the pcv then the intake... Any chance that line is capped? What is the crankcase vent connected to? Quote Link to comment
SWFL Posted January 31, 2023 Author Report Share Posted January 31, 2023 (edited) 2 hours ago, datzenmike said: Blow by is not a problem unless the rings are worn. Post a picture of the intake left side of the carburetor as after market should have provision for PCV. A PCV, while always a good idea to have functional, is not going to fix excess blow by. U67 is not the head for a '78 so it, or the engine, has been swapped from something earlier. A 38/38 is really too big for a 2 liter engine. It's more for a V6 or small V8. A 32/36 would be better. What's the best image hosting website for this site? Imgur seems to be app only. I try not to use apps on my phone as much as possible. I don't see an option for adding pics without having a hosting account. The front ( closest to the oil cap ) intake runner has a threaded plug on top. The block is marked L20B with 76 or 78 as the first digits. The head is definitely marked U67. I do plan to go with a smaller Weber, although this one is supposedly tuned for the engine. It seemed to get around 22/23 MPGs on the trip. I'll try to do a compression test ASAP and hopefully camera the cylinder bores. 1 hour ago, Crashtd420 said: The port coming from the valve cover does not have a pcv it just pulls air from the air box.... There is the crank case vent under the intake, this should be connected to the pcv then the intake... Any chance that line is capped? What is the crankcase vent connected to? There's a big pipe that goes towards the firewall, with a hose with a breather at the end. I'll have to check that nothing is plugged up. Edited January 31, 2023 by SWFL Quote Link to comment
datzenmike Posted January 31, 2023 Report Share Posted January 31, 2023 4 hours ago, SWFL said: What's the best image hosting website for this site? Imgur seems to be app only. I try not to use apps on my phone as much as possible. I don't see an option for adding pics without having a hosting account. The front ( closest to the oil cap ) intake runner has a threaded plug on top. Usually it's on the rear runner and is a vacuum source for the brake booster. 4 hours ago, SWFL said: The block is marked L20B with 76 or 78 as the first digits. The head is definitely marked U67. The 76 or 78 is meaningless for identification. The block may be a '78 and the U67 swapped onto it or the entire engine was swapped. It matters little they run the same. 4 hours ago, SWFL said: I do plan to go with a smaller Weber, although this one is supposedly tuned for the engine. It seemed to get around 22/23 MPGs on the trip. I'll try to do a compression test ASAP and hopefully camera the cylinder bores. Oh the 38/38 will work but the 32/36 will be easier to drive. 4 hours ago, SWFL said: There's a big pipe that goes towards the firewall, with a hose with a breather at the end. I'll have to check that nothing is plugged up. That is the block vent. The PCV valve should screw into the intake and a small metered leak sucks fumes from the block and into the intake to be burned. The PCV removes water and gas fumes and combustion by-products and allow you to extend the oil changes to 5-6k. Single-handedly, the PCV extends the engine life by double. It would be simple enough to drill and tap the intake and connect the block vent. Quote Link to comment
SWFL Posted February 2, 2023 Author Report Share Posted February 2, 2023 Update: I did a compression test and have approximately 160 PSI across the board. I didn't have a chance to mess with the breather and vent hoses. Quote Link to comment
datzenmike Posted February 2, 2023 Report Share Posted February 2, 2023 160 all is pretty good. Quote Link to comment
SWFL Posted February 9, 2023 Author Report Share Posted February 9, 2023 (edited) I looked a bit more at my engine and intake manifold. The intake manifold is a Cannon. The back flange is blank and undrilled. There's a small threaded hole at the end of runner #4 next to the plenum, that's plugged. Runner #4 ( back of engine ) has a bigger threaded boss in the middle that's feeding the brake booster. Runner #1 ( front of engine ) has the same boss as runner #4, that's plugged. There's a split threaded flange on the side of runner # 1. There's a coolant nipple between runners #1 & #2 that is plumbed to the coolant system. According to my owner's manual, there's a "steel net" at the breather on the block that feeds the original PCV valve. I assume there's a fossilized o ring retaining the pipe and it's not easy to service with the exhaust in the way. How often does that "steel net" get sludged up? If that breather gets clogged to any significant amount, the crankcase will have to breathe through the valve cover vent, and possibly push oil out at the same time. I assume hooking up a PVC valve to one runner or too small of a port on the intake manifold will cause issues. I'm not opposed to running a PCV valve, but I done want to butcher up that intake manifold. I plan to run a stock air cleaner, modified to fit a Weber. Any issues with dry ( no oil drops ) crankcase fumes being sucked through the carburetor vs the intake manifold plenum? Edited February 9, 2023 by SWFL Quote Link to comment
datzenmike Posted February 9, 2023 Report Share Posted February 9, 2023 You really should but what year your 620 is in your profile. Saves asking. There were a lot of different changes to the 620 over the 7-8 year run. The fly screen covering the block vent pipe does not plug up because it is constantly 'rinsed' by splashing oil. You could direct the crankcase fumes to the front runner if large enough for the PCV valve to screw into. The reason it is mounted in the center below the carburetor is so the fumes are spread evenly between the 4 cylinders. I would just drill and tap a hole there. 1 Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.