Hi, have look at this web page and is it worth converting to hydrolic lifters???

http://www.mofoco.com/item/TYPE_1_HYDRAULIC_KIT/693/c75 

IMO - No.

Part of servicing an aircooled motor is re-tensioning the bottom row headstuds so you have the rockers off to do this anyway.

The only benefit would be a quite valvetrain.

No, it's not a required step according to the factory service manuals. Some tuners do it on modified engines that run increased compression ratios, but for stock engines you leave the studs alone once the engine is in and running. The studs - top and bottom - will have already been correctly torqued during the assembly process.

As for hydraulic tappets - they work very well. They are self-adjusting, so once set up you no longer need to adjust the tappets to 0.15mm every 5,000 km. They have an internal hydraulic clearance, so they always allow the valve to close, thus preventing burnt valves. They run much more quietly than solid lifters. Volkswagen fitted them on the air-cooled 2-litre engines in the T3 Transporter, as well as some very late T2 Kombis. late Mexician bugs had hydraulic tappets too.

For our Type 1 engines there are a few difficulties. Some after-market hydraulic lifters require machining of the lifter bores, as they are larger than stock lifters. Other units, such as the Scat (Eagle) lifters (no longer available I think) fit straight in. You will need shorter pushrods, usually by around 10-12 mm, or even shorter if you also have ratio rockers. You should fit swivel-feel rocker screws. And you MUST have a full oil filtration system. The stock mesh screen is not adequate - hydraulic tappets hate the smallest pieces of grit and will block up and rattle. Your oil must be squeaky clean. You also should have a larger oil pump, as they need a larger flow of oil than solid lifters. You need to prime the lifters with oil before you install them - usually done in a drill press, immersed in a steel cup of oil with an old pushrod. Then they are installed and lubed as normal. Hydraulic lifters work fine with stock and mild-mid cams, but if you expect to see 6000+ rpm regularly (race cars etc) stick with solid lifters.

Before starting, the valves are adjusted snug to zero lash, tighted up just to the point of no slop in the valve train. Then turn in one full turn. Now start the engine and keep the rpms in the lower range to let them settle in. Listen carefully for any clicking at idle. It usually takes them a minute or two to prime on the first go, so be patient. Try another quarter turn on a noisy tappet. Once settled, you will be amazed how much quieter they are.

In normal driving, you will find that they all click and rattle for 10 or 20 seconds when you start. The are mounted horizontally so the oil drains away overnight when you park. Next morning they need repriming, which takes the motor a few moments. It's disconcerting until you get used to it, but after that they should be fine. It doesn't happen as much on V8s and so on as the lifters are more upright in those engines. The longer you leave your hydraulic VW without starting, the longer it takes to reprime. Leave it a week and it might take a minute or more. Using a thinner oil can help - hydraulics don't like thick oil.

Fantastic post Phill. I do recommend checking them occasionally though.

As for tensioning the lower head studs.....BULLOCKS....( sorry Gracey), even high comp engines shouldn't require that, if assembled correctly!!!!

I can't say this often enough.

The engines that come loose at the lower head studs are being over stressed (normally temperature related) or were never assembled properly in the first place.

Agree'd why retension only the bottom ones? if they're loose then good chance the top ones will be too

That's exactly the responses I expected.

No need to apologize Matt, I've got thick skin, the fact is we won't all agree with each all of the time, that's what makes life interesting.

The theory behind re-tensioning the bottom row head studs is these studs only ever get hot "cooling" air, the air has already passed over the heads and cylinders. This makes life a lot harder for these head studs.

Re-tensioning a stud does not effect the tension of the other studs, as essentially you do one at a time, remember the other studs are either at tension or close to it.
Anyway each to his own.

Ps. Stan Pobjoy recommends re-tensioning the bottom row head studs and he's built an engine or two.

Fair enough theory Gracey, Earth is turning beautifully

The way I see it is the stress on the studs is from the expansion of the cylinder. The coefficient of thermal expansion for cast iron is 11 where as for chromoly it is 7 (as chromoly is used for performance head studs I figure it's an appropriate material to use for an example) so if the cylinder expands more than the stud, the actual max stress is due to the force applied by the expanding cylinder. If the stud is stressed to the point of loosing tension, it's because the cylinder has expanded beyond the stretch limit of the stud, and beyond the elasticity that the material can recover from. How different the temperature is between top and bottom is yet to be seen (I like to have ALL or even better than stock lower tin to maintain even barrel temperatures), but even so, would the difference amount to enough that the stud is hotter than the cylinder when it's the cylinder that is containing the combustion in the first place.

Ps, I've repaired reputable engine builders engines when they have failed prematurely due to excessive temperatures in a 1/2 decent Queensland summer.

Hi

I always checked lower head stud tension in a service, I found motors with 10 mm studs were most prone to loosening.

A well looked after motor never needed a retension. A retension would often get rid of dreaded head flap sound.

Steve

10mm stud twin port engines are shocking for it, but nearly everyone I've dealt with its been a block with no casesavers and the threads were letting go.
especially in the hands of people who cane the shit out of them when still cold