First post- 993 Engine Assembly and Hydro-lifters

[agrabau]

Good morning everyone.

I'm in the process of rebuilding a M64/60 (993tt) engine. To keep things as short as possible this rebuild involves a few aftermarket performance parts supplied by Todd at Protomotive who has been super helpful the whole way through and I'm very appreciative of that.

The engine is now a 3.8 liter with Web "GT2 Evo" cams and forged rods/pistons etc. The problem I'm having as a new guy to Porsche motor building is setting the cam timing. The factory/Baum tools to lock things in place don't fit the Web cams (no grooves on the back of the cams) and after much studying and measuring with a wheel we've got things sorted out (we think)

We followed cam instructions on PCar Workshop, followed Todd's instructions and also measured lift via the supplied cam card that accompanied the Web cams. We used a shaved 964 rocker on the intake cam of cylinders 1 and 4 when we did our setup and measurements.

We have verified that the right cam is on the right and the left cam on the left.

After turning the engine over by hand with the mechanical rocker in the first position of both the right and left side (cyls 1 and 4) we installed the hydro lifter/rocker assy. and the engine turns about 20 degrees and there's interference.

This was confusing. I then removed the hydro-lifter/rocker assy and rechecked. Seemed fine with the mechanical.

We are using hydro-lifters on the recommendation of the engine parts supplier (and expert, which I am not) The cams are built for mechanical rocker assy's and it seems that most guys are using the 964 cam gear setup as well.

What I'm thinking is that the hydro lifters are not bled down, or are dimensionally different in such a way that they are compressing the valves all the time and over lifting them at full compression of the valve spring.

Another possibility is that the web cams have a larger base circle diameter which I am looking into now. This has been semi-proven by a rough measurement I took with the Web cams installed last night. I can't confirm this yet but I don't want to remove the Web cams and disrupt my timing unless it's a last resort.

In this photo i have passed the rocker pivot rod through both the mechanical rocker and the hydro rocker to have them aligned on their axis. The rocker pads are also lined up. This shows a big height difference between the hydro lifter as it sits and the mechanical one which was previously set for a basic lash. Does it need to be bled down?



Thanks for any help

Alex

[pete911]

Are these new lifters? The turbo ones are different from the normal 993's Maybe you have the wrong lifters. Also I thought that with hydraulic lifters you need a cam that is designed to work with them. ie you can use mechanical (solid) lifters with any cam, but you need a "hydraulic" cam to work with the hydraulic lifters.

Pete

[syncroid]

You should be posting this in the Engine rebuilding section. Not here.
http://forums.pelicanparts.com/911-engine-rebuilding-forum/