Possible camshaft wear, tappets, CU engine, advice please

[937carrera]

I was told that the camper I have just bought suffers from a lack of power and will only do 40-45 mph. The garage that looked after the vehicle apparently told the previous owner that the camshaft lobes were worn - the engine has done around 120,000 miles. I can't take it out to test as there is no MOT in place, but though it starts and ticks over fine it does struggle to rev.

Before I start thinking about pulling the engine out I wanted to try and diagnose this for myself, and have done the following.

Removed plugs and checked gaps - one was 0.8mm so have reset to 0.7

Carried out compression test, shows 130,110,130,122 psi

Carried out leak test, shows leakage of 32%, 33%, 35%, 35% with some audible air bypass into the crankcase so perhaps the rings are worn

Pulled the cam covers off to inspect valve gear. As I have a 412 this looked very familiar. In fact I think it looked too familiar as it appeared to be exactly the same as the 412. I checked the tappets and gaps were as follows:

Cylinder ------- IN ------ EX
1 --------------- 0.15 ------- 0.20
2 --------------- 0.20 ------- 0.15
3 --------------- 0.15 ------- 0.20
4 --------------- 0.20 ------- 0.20

I know from the history file that the engine has had a replacement head fitted at some point and a top end rebuild. I am thinking that when the rebuild was done it has been converted to manual tappets as i expected that with hydraulic tappets there would not be any gap. However, this is my first T25 so am in the early learning stage.

I have taken a couple of photos of the cam area and will upload these when the battery in my phone has enough charge.

I would be grateful if somoone could confirm that the compression tests looks fine for a T25 , if my camper does have manual tappets and what else I can try and do to confirm that the cap is worn, other than splitting the crankcase

Many thanks for any help - I'm about to reassemble and check ignition timing

[Paul Weeding]

110psi is ok, but technically close to rebuild time!!

If you've got a 412, then the base engine is the same, just different tinware!!

So if you're struggling to get 45mph, then I'd be looking at the ht leads to make sure they're on right, timing, and possibly strip the carbs to check for junk in them

[BOXY]

My van would still get over 60 with only three cylinders coming to the party. Check the advance if 40 is the best it can do.

[937carrera]

Paul, many thanks for the reply. One of the reasons for going for an Aircooled CU engine was because it's just a development of the type 4 engine so lots of things would be familiar. I have no idea that there was a type 4 specialist just up the road either.

Here's the photos I took earlier

This is 1 & 2


Followed by 3 & 4


I have adjusted the timing - much more difficult on the T25 than a 412 as there's no hole in the top to point the timing light down. Anyway, it seemed to be set at just ATDC with idle plugs connected and vacuum hoses in place. It's now adjusted to 5 degrees ATDC which I believe is the specification. Idle has dropped and it does seem to be running smoother. Maximum advance is showing around 30 degrees, which seems a good value

CO at idle is around 3.5%, it does smell a bit rich.

One thing I have just found is that with the throttle wide open it will only rev to 4050 rpm. The rotor arm has a cut off at 5400 rpm and it did not feel that that was coming in early as there was no popping or banging. I though peak power was at around 4200 and they rev to just over 5000 rpm when in decent nick

I haven't got a dial gauge but used my vernier calipers to try and get a measure of the amount of movement at the rocker where it contacts with the pushrod. There only seemed to be 4.1mm of movement which given that the pin is about central in the rocker would only seem to translate to 4.1mm of movement on the valve which doesn't seem very much.

It's beginning to look as though it's carbs or something more fundamental. Further help and advice much appreciated

[kevtherev]

When the hydraulic tappets were replaced can we assume that the cam was changed too?

[937carrera]

I don't know if the cam was changed or not, I don't think so as I can't see any documentation that refers to the cases being split.

I assume Kev that you are confirming from the pictures that I do have manual tappets........ from reading the ratwell pages I understand the pushrods should have been changed at the same time as the tappets, but I just don't know yet. I'm just about to piuck the history file up and start reading it in more detail.

Maybe I'll have to pull a set of rockers off tomorrow ?

[kevtherev]

I don't know if the cam was changed or not, I don't think so as I can't see any documentation that refers to the cases being split.

I assume Kev that you are confirming from the pictures that I do have manual tappets........ from reading the ratwell pages I understand the pushrods should have been changed at the same time as the tappets, but I just don't know yet. I'm just about to piuck the history file up and start reading it in more detail.

Maybe I'll have to pull a set of rockers off tomorrow ?

I think so.
The pictures won't confirm that.
There's nothing wrong with using solid lifters...as long as it is converted correctly
Though personally I prefer hydraulic
It's no big deal to go back to hydraulic either.
I am unaware however that your power problem is attributable to the wrong cam profile being used.

[937carrera]

I've been through the history file again and had a look on Etka and in my Haynes manual to familiarise myself with the construction of the engine as its over 30 years since I built a type 4 up.

The history file goes back to 2005, so I'm blind to anything that was done before then

I can't see that the crankcase has ever been split in the past 10 years, so assume the camshaft is the original.

The engine was taken out, heads were removed with one replaced and a new inlet valve was fitted in 2012, about 10,000 miles ago. 8 months later 8 hydraulic tappets were fitted. In June last year, maybe 1500 miles ago 2 hydraulic tappets were replaced. Last month the tappets were "stripped out and modified to get engine running again". I don't know what that really means. All this work has been carried out by a VW Aircooled specialist.

Based on this I believe my engine still has hydraulic tappets (unknown quality), original camshaft, but appears to have valve lash set as though the engine has manual tappets which just seems wrong.

Looks like I should pull a set of rockers off tomorrow and check the pushrod type and see if I can remove a cam follower to see if it's hydraulic or not. Does that make sense ?

[kevtherev]

I think that's the best course.
When you know (and the lifters are very different) I hope this sorts out the problem.
It does read like there has been some confusion.

[Paul Weeding]

Just as an fyi, steel push rods indicate hydraulic lifters, and aluminum push rods indicate solid lifters

That's how they are from factory

My unit is at Heddon on the wall if you get to the point where you need a second set of eyes

07918992058

[937carrera]

Thanks guys.

OK, so I pulled the rockers off for number 1 cylinder earlier this afternoon.

It looks like I have hydraulic push rods with a diameter of 10mm and length 262mm



I also managed to get a photo of the cam follower. One of the tinware screws was rusted in so I couldn't remove a pushrod tube for closer inspection



I believe that the engine is "as factory" with the correct hydraulic tappets. I'm just trying to figure out why the tappets are adjusted as though they were solid (by someone who I believe is a VW Aircooled specialist)

Am I right in thinking that the poor adjustment will make the engine louder with rattly tappets and have less power due to restriction on flow through the valves deu to lower lift

[kevtherev]

I believe that the engine is "as factory" with the correct hydraulic tappets. I'm just trying to figure out why the tappets are adjusted as though they were solid (by someone who I believe is a VW Aircooled specialist)

Am I right in thinking that the poor adjustment will make the engine louder with rattly tappets and have less power due to restriction on flow through the valves deu to lower lift

Yes it will, the valves simply will not have time to draw in enough fuel/air and get rid of the gasses.
effectively strangling the engine.
As for the muppet who thinks he's a specialist, let's move on and call him special.
VW moved away from solid lifters in the seventies, and fitted hydraulic lifters and electronic ignition.. this guy clearly never knew that.

As for the sound your engine makes..yours must sound simply horrendous .
it should sound like 4 grandma's knitting in a kitchen

Warm engine (10 mins)
turn the screw in on the rocker on the firing stroke till just touching the valve
turn the screw in a further 1.5 turns to pre load the spring in the lifter.
repeat with the two valves on their firing stroke
1-4-3-2.

[937carrera]

Thanks Kev, no chance to do that today but I'm going to make the adjustments and see what happens

To be honest, the engine just sounds like a typical Aircooled T25, a bit loud but full of character.

Did you see the black lines / markings on the pushrod. They seem permanent as they didn't rub off with my finger. Is this normal for steel pushrods as I don't remember seeing anything like that on my 412 engines ?

[Paul Weeding]

I'm just trying to figure out why the tappets are adjusted as though they were solid (by someone who I believe is a VW Aircooled specialist)

Wouldn't be the first time... I've re-adjusted a few engines where they've been set up by a "vw specialist" as solid lifters when they're actually hydro!!

[937carrera]

Well, I've managed to adjust that tappets this evening, it didn't go as expected, or maybe hoped.

I went round each cylinder getting it onto TDC, checking that the play on the tappets was as measured at the weekend. Then released the lockscrew, screwed in until the tappet touched the top of the valve and then turned an additional 1 1/2 turns. I tried pushing the bottom of the rockers on one side to see it there was any movement. There didn't seem to be any movement so assume they are properly filled with oil and not air.

Put the covers back on, went to start the van and it turned over as though there were no spark plugs in. Just for fun I put the compression tester in one one cylinder and it said zero psi. I guess the valve(s) are not seating.

Have I adjusted the tappets correctly

Any ideas as to why the valves aren't seating. I somehow doubt that the valve seats have gone on every cylinder

On the bright side, at least the valves didn't hit the pistons