JasonAndreas

After viewing the Lifter 101 Repair thread on the 993 forum I am REALLY curious if anyone here has switched their solid valve lifters for hydraulic? Does anyone have a list of the parts required for conversion? rocker arms? etc?

Arjan B.

Jason

The 964 valve train area is different. I removed all my rocker shafts in November, but there is no install spot for those and the rocker shaft of the 964 is completely as one shaft, and not with two bolts installed. Forget it. Second thing is, the pressure of oil for your lifter, where should is come from????

Forget it.

Michael Gibney

Jason,

Arjan is right - too difficult but to answer the question you would have to consider the following.

1. Are all the angles and distances on the rocker arms the same? If no forget it as new "conversion rocker arms" would need to be made - possibly cheaper to buy a 993 motor. If the rockers are the same go to 2

2. Is there a way to get oil pressure to the 993 rocker if it is mounted in your engine on your rocker shafts? Yes is the answer but again very tricky. You would need to modify the shaft by making a hole to get the oil from the inside to the outside so it can get into the rocker arm. Then you have to actually get the oil into the rocker arm shafts - all 12 of them. You would need to have some neat little trick fittings (possibly little banjo fittings under the hex head bolt and a grove beside the bolt shank and of course slightly longer hex head bolts) made to take oil from a gallery to the rocker arms. Very tricky and very expensive and possibly not reliable. It would be like the inside of a Rolex.

Anything is possible but somethings are not practical.

But - do 993 heads fit? That may be cost effective but there would be other matters to consider so the list goes on.

I agree with Arjan - nice thought though.

Regards, Michael

JasonAndreas

I remember two years or so ago reading about a kit/box of parts for the conversion retailing for around $1000USD. The wholesale cost would probably be close to $4-500USD. I think ImagineAuto was one of many that were selling this, I will have to check with them.

garrett376

Why would you convert it? The rockers are not hard to adjust, if the adjustment part is what you're trying to get away from.

Sounds more reasonable to sell your existing engine, and get a 993 engine to put in there - then you'd get VarioRam, too.

Arjan B.

Hydraulic lifter will fail also, more then you know......... There are a lot of 993 owners who replaced theirs already.

jmreiser

I realize this is an old thread... and the advice from Arjan makes good sense... but FWIW, if anyone is still curious...

What you would need is to put in 993 camboxes (aka cam towers), and 993 cams, or cut grooves into your 964 cams. Then a set of rockers & shafts and you should be good to go. If you did it with used parts, it would not be all that costly. I would probably put in new lifter cartridges though.

So you are looking at dropping the motor, and removing the intake & exhaust system, disassembling down to cams & chain gear out. It is almost a top end overhaul. Might as well do the valve guides while you're in there since the camboxes are off, the heads are sitting right there with nothing on them anymore.

Geoffrey

The conversion is quite simple, requiring 993 cam towers which provide the necessary oiling for the lifters, 993 rocker arms and shafts, 993 valve covers. For a street car I'd do it.

Chris M.

Just to avoid having to adjust them?

parsecnc4

And the benefit, other than not needing valve adjustments, would be....?

Just want this info for my education, when time for a top-end rebuild. I am also curiuos on why this would only be suggested for street car only?

JasonAndreas

Near perfectly adjusted valves for 50k miles...

If you already have the engine apart and can trade someone your stock 964 mechanicals for their 993 hydraulic lifters & associated parts then it's worth trying, otherwise forget about it. I'm not sure if its strictly age related or if there is a set number of miles but it seems like the 993 hydraulic lifters start to fail at 50-60k miles. So by switching you won't really save any money in avoiding the 15k mile valve adjustments. I was really curious about this a few years ago but now I just drop/lower the engine to adjust the valves.

parsecnc4

Wow I did not know that 993 hydraulic lifters will fail around 50-60K miles. I have been looking at a few 40-ish mile cars and now it makes me think twice or set aside $$ for the eventual repairs. At least adjusting the 964 valves can is a DIY job within my capabilities.

JasonAndreas

Like I said I don't know if it is just their age or some set mileage that causes them to fail but it seems to start happening at 50-60k.

If you DIY its not a big deal as the lifters can be purchased for between $40 and $88USD/each and their replacement is no more complicated then adjusting the valves but if you have to pay someone it can cost quite a bit.

With any 964 or 993 or 10+ year old sports car that might be a good idea.

NineMeister

As well as the cam carriers, shafts & rockers, you would also need 993 cams with their revised hydraulic lifter ramps & oil grooved front bearing along with the larger bore 993 oil transfer pipes from the chain housing to the cam carrier. Porsche also reduced the piston squirter size on the 993 to increase the oil flow capacity to the head assembly, hopefully the oil pump would supply enough for the larger squirters and the hydraulics.

Caveman

I've not heard of anyone this side of the pond having to change hydraulic lifters at 40 to 50k miles? Some guys have done it at 70/80/100 in the US where, presumably, you get a lot more heat/cold cycling???

Colin - have you seen much of this over here? (He asked nervously!).

Cheers,

David