I’m going to put this in one post to try and get some help and get my 2.0 CU engine back running The backstory: We took it for a big trip last year and decided at the end of that to do some upgrades to get her up and running sweet for this year as she struggled at times beforehand. The engine was removed and the top end rebuilt, new mahle barrels and pistons and new amc heads, other than that everything stayed the same on the engine except replacing seals here and there. At the same time I also replaced the clutch, heat exchangers and fitted a 42mm csp python exhaust I bought a set of Dellorto DRLA 36’s and the csp linkage and manifolds, it previously had twin solex pdsit’s Where I’m at: The van runs but has not really had a good run in, maybe only done 50 miles and a lot of idling on the drive. The compressions I’m currently getting as of today are Cylinder 1: 105 Cylinder 2: 105 Cylinder 3:105 Cylinder 4:125 these seems very low to me for an engine that’s just been rebuilt. I can get the van to run with the dells installed but having a nightmare balancing them and getting it to run nicely, seem to be getting spitting through the carbs and also popping in the exhaust. When I try to balance them cylinder 3 is much higher than the rest and won’t come down The dells are jetted with 30 Venturi 33 pump 180 air 60 idle 122 mains 9164.2 emulsion 3.0 fuel pressure Fuel hoses go from pressure regulator to right hand carb and then from right hand carb over to left hand banjo I have a 123ignition distributor with vac set to number 2 on the adjustable gauge and timed to 10 degrees at idle The van has hydraulic tappers and the valves have been adjusted with the van stone cold to just touching and then another 1 and a half turns in. I’m very confident on this one because I’ve done it 3 or 4 times to make sure this isn’t what’s going on Hopefully this makes sense and someone can point me in the right direction
I’m almost at your stage, I’m sure I saw something about bedding rings in …. accelerating to 50 and then easing off several times…. I may have made that up …. as surely reving engine and then reducing revs would have same effect.
I’ve had it out for a half hour drive and done that because I was told that by someone on here, I think my issue is I’ve changed so many things at once that it’s hard to pin down the issue
105 does seem low, think my lowest ( other than the broken cylinder) was about 130 …. think that they should be 150+
135-140 psi is about right for a healthy engine. If you lubed up your cylinders with engine oil that's enough to prevent then bedding in. If you breather is chuffing away that could be it. With new B&Ps and heads, did you measure your deck height and calculate you CR? As for the hydraulic followers it's very easy to get it wrong and likely keep getting it wrong if you do. Do you have a picture of your rockers? If there's more than a couple of threads visible past the lock nuts it's likely you have them set wrong. All the above would make it pretty well impossible to set up your carbs which should be fine with the jetting you have.
Chris what mains are you using. Previously you said My current settings are 30 chokes 131 mains 180 air 60 idle 40 pump 9164.2 emulsion now you are saying The dells are jetted with 30 Venturi 33 pump 180 air 60 idle 122 mains 9164.2 emulsion your mains are too small now for 30 vents
I didn’t put any oil on the cylinders when fitting them, the breather is going through an empi oil breather and then out through the tinware. I didn’t measure deck height or compression ratio I just ordered like for like barrels and pistons and then a cylinder head for the engine I have, I assumed that fitting the same parts would save me any issues. I don’t have a picture of the rockers but to set them I am putting it to TDC on each cylinder loosening them completely off then screwing them in by hand until they just make contact and then giving them another 1 and a half turns in. I have read elsewhere that the compression can be low on a rebuilt engine until it all beds in is this correct?
I changed the mains from 131 to 122 and had the pump jet sizing wrong I had written somewhere they were 40’s but they’re 33’s I have seen on the samba forum people with the 36 carbs using 30 vents, 50 idle and 122 mains so that’s why I gave the 50’s and 122’s a try but my van idled horribly with the 50 idles I’ve read elsewhere that having the mains 4x the vent size plus a size up can work well, I think that’s possibly elsewhere on this forum that was said
I'm no expert on these engines yet but have rebuilt many others in the past and this method unless you have described it incorrectly is ringing alarm bells with me. I would suggest you should be putting the cylinder to TDC, tightening the centre adjuster down on to the correct sized feeler guage then tightening the lock nut without allowing the adjuster to move. I believe this should be done with these engines stone cold.
. Maybe its the oil is too heavy for the hydraulic tappet adjusters, so when they do pump up, the valves are staying open too long messing with compression and making setting the carburettors up impossible. That might have been the real original problem that caused the rebuild . Also, replacing Mahle cylinders and AMC heads means the parts you replaced were not original. Maybe some machining was done in the previous rebuild that you missed when you swapped parts, meaning that e.g. measurement of deck height might have shown up some difference.
It’s hydraulic tappers in the engine, the method I’ve done is what is in the Bentley manual (only they suggest 2 turns) and what others on the forum have said to do
Perhaps I wasn't clear, I meant lubing the inside of the barrels/pistons/rings. I did this once and regretted it, the rings never bedded in though it ran well enough. Sounds like you got the tappet setting correct. Pity really, that would have been an easy fix. Compression should be all there from the word go, it literally takes a few miles to bed the rings in and even before that you would not notice. As others have already said, much as it would be nice to fit those new components and go you can't really do that nowadays. You might get lucky, you might not. Having said that despite you doing no measuring you wouldn't be the first and it should run smoothly if not as well as it could. 60 idles should be fine 33 pumps fine 30 vents fine (28 might be better in the long run but not a problem) .2 emulsions correct 180 airs correct I've found 135 mains for 30 vents is about right so run your biggest or get bigger. 122 are way too small. There's nothing obviously wrong enough in what you describe to prevent a nice even idle so I'd be looking for an air leak. If you used fibre manifold/head gaskets they need a second tighten after it's been run up to temp. Otherwise maybe the manifolds are not seated on the heads correctly. The head shrouds can get trapped under aftermarket manifolds, it's par for the course to have to grind quite a lot of material from the manifolds to get them to fit. Sooo... look for leaks, get some 135 mains then if you're still struggling take it back to pieces, measure everything including ring gaps, calculate CR, lap in the valves and try again. Very low CR is no fun to drive though as said it should still run smoothly. Whereabouts are you? Somebody might pop round, two heads can be better than one. Good luck.
oil gets to the barrels , rings and piston as soon as the engine runs . The oil scraper ring will just wipe it away . I think the biggest mistake the op did was just a top end rebuild . Second was just bolting on parts expecting them to work . Thirdly your main is still way too small . Yes there are calcs to get you close but my 1.7 needs a 130+ main with 28 vents . Every engine is different and one size doesn’t fit all .. I just kept upping my main until my AFR reading were where I wanted them .
I must confess Chris like you I’ve made similar mistakes with the first type 4 engine i did a top end on. Just swapping parts like for like without measuring & expecting it to work. It did but wasn’t great. Also swapping several other parts at the same time then coming across problems & not knowing which part was the cause. I have learned a lot over the years about aircooled engines and gained a lot of great information on the latebay as well as manuals & not forgetting good old Jake Raby. Rather than pulling your hair out over it not running right bite the bullet, get the engine out, heads off & measure deck height. Easy enough then to work out CR. Head combustion chamber volume with AMC heads is usually pretty consistent if you check out previous type 4 engine rebuild threads on here there’s a myriad of information
What was the compression before you decided it needed a top end rebuild? Was it burning oil or had blow by? What did you find wrong with the parts you removed? Excessive ring gap? Broken rings? Scored bores? Cracked heads? Burnt valves? My guess is the CR is very low, did you fit head gaskets with the AMC heads? 30 vents are really too big for a standard 1971cc bus engine and tuning the carbs will be more difficult. 122 mains are far too small, especially with 30 vents. 10 degrees BTDC at idle might be too much, what is the timing at max advance? Assuming you had the piston on TDC compression 1½ turns should be okay for tappit preload. But hydraulic followers and cam wear relatively quickly and could be the cause of the poor performance.
Just to wrap this up, I couldn’t get the carbs to run well so ended up getting it to a garage that specialises in air cooled motors, they ended up suggesting that the engine gets a complete rebuild rather than just the top end due to quite a bit of wear on the camshaft. Got the full engine rebuilt with a scat C25 cam, solid lifters which they said will give some better performance with good carbs and the python exhaust I have. Once they reassembled the engine they were still having bother with the dells they couldn’t get it to rev properly through the range, they went over them set everything up, ultrasonically cleaned them and still no luck so they ended up swapping them out and fitting IDF 40’s and it’s running really nice now. It’s been a bit of a saga but at least she’s back on the road and got much better power than what it used to have. Appreciate all the help and advice but it ended up just being beyond my capabilities and was just going round and round in circles and not getting anywhere
I am glad they sorted it, but a bit surprising about the need to change carburettors. Its usually smaller carburettors succeed more on stockish engines.
