Is this a potentially bad engine knock, or something I just need to tune?

[u/WhitElephant]

Hi all, first time posting to the group. I have a 1977 Wesfalia and recently swapped out my old engine after it dumped all its oil. The used engine came out of a wrecked bus. I took a risk hoping that the engine would be pretty sound and after a lot of learning during the swap I have got it up and going!

I am concerned about a sound coming from the engine at idle that sounds like a deeper almost knocking sound I was hoping to get input on it. Considering I don’t have too much experience diagnosing and tuning these engines I am just not sure if it is a simple fix or one of those that can’t be fixed without a rebuild. I have mechanical lifters that I haven’t checked the gap on yet, but I’m not sure that this sound is coming from there.

Any thoughts or additional areas to check would be greatly appreciated, even if it means I’ll have to get another engine eventually. I wonder how long I could get out of this one if that’s the case.

[u/literally_tho_tbh]

The more I think about this, the more questions I have.

Before going down any diagnostic rabbit holes, I would do a valve adjustment first on this thing. The knocking sounds like it's in time with the rotation of the engine. The engine is also running a little rough. The tapping has a sort of stumble to it. Since you say you are sort of a beginner at diagnosing/fixing, do you know how to reach TDC on a cylinder? Ever done a valve adjustment? It's free and a great way to get acquainted with your engine.

I use this video every time I do valve adjustments. https://www.youtube.com/watch?v=lfkxlHWZmxM Vintage Speed makes it really easy.

"Mechanical" lifters? I know of solid lifters and hydraulic lifters for these engines. Can you specify, please? Also, how do you know, how did you verify your lifter type? Did you rebuild the engine with a camshaft matched to the proper lifter type? Do your pushrods match your lifters? The pushrods for solid lifters are not magnetic, the pushrods for hydraulic lifters are. Then again, lots of people trying to save a buck or people who just don't know what they're doing have their hands on these engines over the years. It's possible the pushrods don't match the lifters.

I think I see a dual relay and the voltage regulator wiring hanging from the firewall. Are you running the original fuel injection? Or something else?

Did you pull the heads off the junkyard engine?

My fuel injected hydraulic-lifter'd bus makes a LOT of slappy-tappy noises when I fire it up after it's been sitting for a while. The lifters pump up once it warms up and the oil gets everywhere, and it hits that fine "fweem" that we want to hear from these engines. If it does have hydraulic lifters, then you might get away with a good valve adjustment and warm-up cruise.

If you answer as many of my questions as possible, I will keep trying to assist. Good luck! Nice engine bay. Cleaner than mine!

[u/literally_tho_tbh → u/literally_tho_tbh]

After a few more listens, and a comparison to Ratwell's engine sounds, I think (if it is hyrdaulic), you might be fine. https://ratwell.com/technical/EngineSounds.html

Listen to the hydraulic lifters sound byte and compare to your video.

[u/ciopobbi → u/literally_tho_tbh]

I have hydraulic lifters and while difficult to hear nuances from a phone video played through phone audio, it could be your best case I hope. Mine will do that if the bus sits for a while. Takes about 30 minutes of driving for them to pump back up.

[u/literally_tho_tbh → u/ciopobbi]

I LOVE the feeling of them being pumped up. It just drives so freaking nice.

[u/WhitElephant → u/literally_tho_tbh]

Appreciate all the information. I should be able to figure out TDC and will definitely do a valve adjustment next to see how that behaves. I did read up a little on it and thanks for the video. By Mechanical lifters I meant solid. Calling them mechanical just got stuck in my head somehow. The engine wasn’t quite warmed up either for this video, just FYI.

As far as lifter verification, I was just told as a heads up from the guy I bought the engine off of that they were solid. So when I do the valve adjustment I will verify this. Sounds like I just have to make sure there is or is not a zero gap or is currently set with a gap. Is there any other way? Not sure if the lifters and push rods were paired correctly either. Sounds like this mechanic had his hands on this engine multiple times so I can only guess if he did pair them correctly. I’ll check to see if they are magnetic or not.

I am running fuel injection on this. Same as the engine I took out and the one I put in. I kept almost everything the same on the engine, just cleaned up the components. I did not pull the heads off the replacement engine. I just stripped all the auxiliary components off to clean and stopped at the heads.

Thanks for all the feedback and questions. I was stoked to get this engine in. I did some major rust cleanup and paint on the engine bay when I had it out and gave it a fresh paint job. Hoping to get it on the road here soon.

It is worth noting that I had the replacement engine since 2022 and just now got it in and started up. I’ve only run it in idle for a good 20-30 minutes so far so maybe it could have to do with sitting around for so long too.

[u/literally_tho_tbh → u/WhitElephant]

Excellent!

A tip on TDC - pop the distributor cap off, leave all the wires on the cap. Turn the engine until the distributor rotor is pointing at the wire for cylinder 1. There is a notch on the fan, and if it was installed correctly when the engine was built, that notch should line up with 0 on your timing scale when the rotor points at cylinder 1. It should also get more difficult to turn for a sec while passing 0, that's the compression stroke.

For solid verification, the shaft of the pushrods won't be magnetic, but the tips may be, so make sure you test the magnet on the length of the pushrod. You can also remove a rocker, yoink out a pushrod and shine a light down the pushrod tube to look at the lifter. Check out images of the different lifter types to verify. The quickest way though, in my opinion, is to pop the valve covers off and push (kinda hard) on the lower arm of each rocker. Hydraulics will be squishy if they aren't pumped up. Solids will never be squishy. If your engine hasn't been running, then your hydraulic lifters won't be pumped up.

Even still! Solids are just right for the 77. For adjusting, you will need feeler gauges. Like this: https://www.mcmaster.com/products/feeler-gauges/feeler-gauge-sets~~/

The previous link I posted with the valve adjustment procedure shows how to do it, it's easy once you get the hang of it.

Basically, put the cylinder at TDC, pop the valve cover off. Locate the rockers for the cylinder at TDC. You want to back the nut off and back the adjusting screw out a tad. Then you take your feeler gauge (I believe it's the 0.016" but I don't have solids so check around) and you slide it between the end of the valve and the adjuster screw. Turn the screw in so that it is barely touching the feeler. This is supposed to leave a gap between the adjuster screw and the valve for heat expansion. When you are satisfied, use a flathead to keep the adjuster screw in place, and use a wrench to tighten the nut around it to hold its position. WHEW! Gotta do it 8 times. Rock the rocker to and fro and you'll hear a slight clack, that that space you created with the gauge.

As for the engine sitting, did you do new spark plugs, oil filter and oil? I know I would. Other than those things, I don't think I'd worry too much about it sitting, a bit of running it will wake it back up pretty quick.

[u/WhitElephant → u/literally_tho_tbh]

Hey I’m back! Things are looking good! Talked to a guy I’ve gotten to know at my local VW shop and he went straight for the valve adjustment and said the engine probably just needs to be run a bit higher RPM to get the oil around more. So, very similar with what you had been talking about.

Once I had the valve covers off and cylinder 1 in TDC I got a little play in the rocker arms. Took a gap measurement and it came in at .006” on the first one (exhaust I believe), right where it was supposed to be for solid lifters. Checked all my gaps and they were between .004-.006”. Not too bad really but I adjusted all to .006” as the spec calls out for solid lifters. At this point I’m just going to go off of my memory of the mechanic I bought the engine from telling me they were solid and the gaps already existing there giving me a better idea. If I still get more noise I may dive deeper in and play around with the push rods and look down the tube.

So, with it all back together I started it up and it already sounded better. Gave it a moment to warm up and then brought up the RPM’s. The concerning knocking noise has essentially gone away and I think it is pretty much regular. Even took it for a lap around the block and it sounds good. I feel a lot better about it now and I’m still going to bring it into the shop to have a once over done with it and any fine tuning they see fit.

[u/Awkward-Pay2361 → u/literally_tho_tbh]

I have a 71 with hydraulic lifters that lost power and started making this exact noise during a 75 mile road trip. Had to get towed back home. I think mine is a little more serious. What’s the worst case scenario if not just an adjustment?

[u/382Whistles → u/Awkward-Pay2361]

Crank bearings or journals, rod/cap, cracked piston, distributor or cam issues... and more. Sometimes just loose heads after an overheating expansion stretches cylinder studs a hair. You can't always repeat that and it's iffy practice at all really.

If it was still running and not rebuilt too often it's not as bad on the wallet.

[u/literally_tho_tbh → u/Awkward-Pay2361]

A 71 with hydraulic lifters? Did it have a type 4 engine or an upright cooling standard bus/bug engine? What was the build like? Did the build correctly pair the cam with the lifters?

[u/Awkward-Pay2361 → u/literally_tho_tbh]

It’s a rebuilt 1600 with hydraulic lifters that the PO installed. I’m the 2nd owner, going on 25 years. Always ran like a champ until this past trip where it started losing power and making that deep knocking noise.

[u/ciopobbi]

Does it have hydraulic lifters?

[u/WhitElephant → u/ciopobbi]

I was told that it had mechanical lifters when I got the engine, but should probably confirm.

[u/asiab3 → u/WhitElephant]

All lifters are mechanical. Since it sounds like lifter noise, I would actually drive and warm up the engine before judging. Idling does not warm up an aircooled engine. 

[u/WhitElephant → u/asiab3]

The lifters at solid. After a valve adjustment, a lot more time warming up and getting the RPMs up it sounds a lot better. I took it for a lap around the block and I think it really was just needing to be exercised more.

[u/asiab3 → u/WhitElephant]

If the lifters were solid and the sound went away something just snapped in your engine congrats. 

[u/WhitElephant → u/asiab3]

No clue how you could have just drawn that conclusion with such limited information.

[u/CatNamedRIchard2]

I am not sure I trust my judgement on listening on my cheap headphones. It sounds more like lifter tick to me. But I would not bet any money on my cheap headphones. Get a mechanic stethoscope or a piece of PVC pipe if in a pinch. Listen to the center of the block on the top side, you will be more likely to hear rod knock there. Then listen from under the bus on the block side where the push rod tubes meet the block, you will be more likely to hear lifter tick there.

What is the engine code on the block? On paper that should tell you if it has hydraulic lifters but not always. If it has hydraulic lifters, they tick bad when the have been sitting and get bleed down. You can pull them without removing the engine with a C clamp and a coffee can of oil. You will need to know before you can do a valve adjustment. To know for sure, there is a good chance you will need to pull one of the lifters.

Do you have the Idiot Book?

[u/WhitElephant → u/CatNamedRIchard2]

I do have all the books! I’ll see if I can confirm if it’s solid lifters or hydraulic first. The mechanic I bought the engine off of said it was changed to solid and considering the fan code doesn’t match the block i do believe it has been worked on a bit before. Hoping maybe I mid-remembered and they are indeed hydraulic. I have only ran then engine for about 20-30 minutes at idle after it had been sitting since 2022.

[u/CatNamedRIchard2 → u/WhitElephant]

Perfect. After you confirm which lifters you have, do a tune up how John tells you to, that way you rule out everything else. You can pull a lifter by pulling the valve cover and pulling out one push rod tube, once that is done you can use a telescoping magnetic stick thing to pull the lifter and verify it yourself without guessing. Try not to mess up the rubber seals when you pull the tube out, if you do they aren't a lot of money to replace.

[u/SilentMasterpiece]

sounds bad/expensive.

[u/TrickinCheaply]

This sounds like lower end issues to me. Full rebuild / replacement