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Sat Feb 22, 2025 9:31 am

I have a 71bus lost Compression can I just rebuild the top end

Sat Feb 22, 2025 10:09 am

Lost compression? Go find it! :D

You could do a topend refresh but, you'll likely find other issues, depending on the mileage since it was last rebuilt.

Remove the engine, tear the topend down and inspect the pistons and heads carefully.
While the cylinders and pistons are off the engine, look through the case/cylinder registers and have a look at the camshaft and lifter surfaces for damage.

Check your crankshaft end play. If it's more than .007-.008" it is likely time to go through the whole engine and replace the bearings/camshaft/lifters and seals.

You won't know what you have going on until you tear it down and inspect the parts.

Sat Feb 22, 2025 10:30 am

Welcome to TheSamba, where we need details, and occasionally punctuation marks. Help us help you!

Perhaps you could just adjust the valves… but it’s kinda hard to help answer your question without having far more information. Did it happen suddenly? All cylinders or just one? What’s your mechanical skill set like?

Robbie

Sat Feb 22, 2025 2:38 pm

Welcome to thesamba.

You need to come back and tell us more for anyone here to really help you.

Sun Feb 23, 2025 9:30 am

talked to someone that use to work on them he said that the engine was probably over heated and burnt a valve the engine has about 10 to 12 thousand miles on it

Sun Feb 23, 2025 10:09 am

[email protected] wrote: talked to someone that use to work on them he said that the engine was probably over heated and burnt a valve the engine has about 10 to 12 thousand miles on it

The people who responded actually work on them currently. You have over 100 combined years of VW knowledge that replied.

How did this “Someone” you talk to determine it overheated? Perhaps you gave that “Someone” more information, pictures, or they had their hands on your engine?

Sun Feb 23, 2025 11:11 am

Or someone f’d up a valve adjustment. Or didn’t adjust the valves. Or didn’t measure correctly. Or your engine is actually fine and it’s just slow like they all are.

Trust me, rebuilding an engine costs a little more than making sure your basics are covered. Like, four thousand times more.

Robbie

Sun Feb 23, 2025 1:31 pm

you haven’t given any specific information about your situation despite being asked several times.

start with year of bus and engine type.

go back, and read each post, and answer each question.

if you don’t know how to answer, ask for knowledgeable vw mechanics or samba folk in your area.

then ask for a list of questions your could ask them.

the guy saying it might be a burnt valve might not be the best to help you troubleshoot your problem.

Sun Feb 23, 2025 8:48 pm

I have 1971 bus with a 1600 dual port was driving down the high way at 60 mph when all if the sudden it started losing power was able to get i home and that is where it is now. if anyone knows of someone that works on them in my area I would appreciate the help

Mon Feb 24, 2025 2:31 am

[email protected] wrote: I have 1971 bus with a 1600 dual port was driving down the high way at 60 mph when all if the sudden it started losing power was able to get i home and that is where it is now. if anyone knows of someone that works on them in my area I would appreciate the help

tell us about your mechanical skills. By chance did the generator light come on while this was happening? Were there any noises, smoke, oil pouring out? Could be as simple as a wire or hose came loose. Sometimes it isn't the engine that lost power - meaning that the clutch slipped, or a CV joint started slipping etc..

Mon Feb 24, 2025 8:30 am

it could be as simple as a clogged fuel filter,dirty fuel,burnt points,
over heat in Mi at this time of year,is that even possible

Mon Feb 24, 2025 8:39 am

no lights on dash but the plug wires on #3 and #4 were melted and they had the lowest compression#3 was 35 and #4 was 0

Mon Feb 24, 2025 8:56 am

The engine comes out to be evaluated in that case. I would expect bothe head and piston and cylinder damage.

$1500 for a good used engine installed, 3x that for a rework of current engine, if possible

Mon Feb 24, 2025 9:30 am

Could I just rebuild the top end or would the bottom end need rebuilding too

Mon Feb 24, 2025 11:50 am

[email protected] wrote: Could I just rebuild the top end or would the bottom end need rebuilding too

It could be possible but you won't know until you pull the heads and cylinders off to see what you're up against.

Mon Feb 24, 2025 2:22 pm

Turn the key on and see if the alternator/generator warning light comes on. Then check to see if the fan belt came off. If it did, the engine needs to be completely rebuilt. Bearing material can sluff off when an engine gets hot enough to melt wires. If the fan belt is there, with the engine OFF, turn the generator/alternator and see if the belt slips. That will tell you why it melted, unless critters moved into it over the winter and built a nest.

Mon Feb 24, 2025 3:09 pm

[email protected] wrote: Could I just rebuild the top end or would the bottom end need rebuilding too

There's the thrust clearance, measured by how far the crankshaft shifts forward & backward in the main bearing saddles, that determines how 'tired' or spent the bottom of the engine is. The other ways of checking include the rod side clearance (got to pull heads/pistons for that)
And pulling a rod cap. If the rod bearing cap surface is not worn to the point of showing copper/brass through the soft overlay, you have an idea of how many miles the engine has run. This all takes time. The thrust clearance is the quickest seeing as it can be done with the engine pulled but not disassembled.
The more you want to know, the more you have to unbolt : l

Mon Feb 24, 2025 3:21 pm

[email protected] wrote: Could I just rebuild the top end or would the bottom end need rebuilding too

I think your best next step is to get an actual air-cooled VW expert to look at the engine.
Speculation is fun and all, but cold hard data, a thorough diagnosis, and a repair plan, is your best path forward to getting it running again.

Along the way, you will learn what warning signs to catch before serious engine damage occurs.
Colin

Mon Feb 24, 2025 4:49 pm

The problem I have is that I can't find anyone in my area that knows Volkswagen air cooled engines. If anyone knows of someone in west Michigan I would appreciate the help

Tue Feb 25, 2025 10:24 am

If you are dedicated enough, you will find plenty of basic videos on Youtube showing engine building.

If you were happily hammering a 1600 at 60mph without having given it a basic set of adjustments, it is easy to melt parts of the engine.

Trouble is that if you melt a hole in a piston through the classic "set the timing by ear, it goes like a train" , it sprays melted aluminium dust down into the engine. It then gets circulated round as a powder and gets everywhere. So the engine has to come totally apart for cleaning, to remove all that metal.

But there is nothing stopping anybody from performing a rebuild on a VW engine if you have the space.. or even in the back of the bus.. . That was a rebuild I did a few years back .