Good god cjv! I know you have been building this motor for years and years. Is it in a car yet ? I couldn't immagine spending that kind of coin for years and not being out there enjoying the car .. You are very patient my friend

 

As I write Jim McCrocklin is installing the Motec M880 and a Ramp type front LSD designed to handle 300 hp vs the stock one rated at about 50. Now, if we can only keep the front wheels down. The motor will be put back in during this work.

 

We not only installed head studs with a larger diameter, but more important we used a thread taper that provides greater grip. The stud holes were re bored to a depth where the stud in combination with taper cannot bottom out.

The heads were cc'ed, the combustion chamber, exhaust ports and upper section of GT3 Cup sized valves were ceramic coated. The heads were o-ringed and fire ringed. The valve seats were given a three degree angle.






We designed and manufactured our own head gasket. We needed to make it as thick as we would safely go so as to obtain all the extra deck height we could.

 

Eibach has springs that are about 10 lbs more seat pressure then stock. If I am not mistaken the turbo, gt3 and cup valve springs all have the same seat pressure. I did check all this but have forgotten the info as the eibach spring was the best choice for me. I bought them from Don@ EBS..

cjv,

To run cams like we do the owner of a turbo engine will need to spend large sums of money and would not be able to use the stock ecu unless they spend even more on a full custom intake cam. plus the fact that most turbo owners refuse to lose any low end grunt, lose of low lift cam. Something about cake and eating it too..

 

Tim,

Not sure we are looking at the same type of motor as related to design usage. The way many tuners set these high boost/hp motors require very fast closing valves. I have seen spring pressures cranked way up there to accomplish this. We accomplished the same results with less pressure. In our case the ability to use lighter spring pressures have to do with eliminating harmonic distortion from the cams. I can remember years ago TK shaking his head at the valve pressures we were able to use with this motor.

The above cams are more difficult to run in a 996tt. We built the above cam using GT3 Street cam markers (as opposed to 996tt, GT2 Cup or GT3RSR markers.) For those who are wondering what pointers are, they are marks etched into the cam and are read by the cam sensor. The information is relayed to the ecu which uses the info to start and control your motor. You are correct, stock 996tt ECU would not function with GT3 cam markers, I believe you could place a GT3 Street program on a 996tt ecu and then make changes to control boost with the GT3 Street cam marker..

Low end grunt is better with 4.3L's. Torque comes on earlier. Certain things like oval TB's, dual injectors (fuel can be kept ideal for low or high demand) and Motec help with the control and expand overall range utility.

I agree with your assessment that this (or almost any) motor cannot hold top 996tt speed records and beat most 996tt's on the track at the same time. They are different goals requiring different approaches. I enjoy the track and this is the reason we are downsizing our current turbo's in order to make the car more responsive over shorter distances. I admit I have made my share of mistakes.

 

For the front differential or center differential/VC?..I ask because the VC seems to be a common failure point/not very effective and I don't know of anyone who's finally built a good solution, if so very cool!

 

It is the front differential, with the RAMP LSD, the VC is removed. We had a manufacturer take the stock case, gut it and then install the RAMP LSD parts in the stock casing. It is due to the case that the power design is lower. The cost of a new designed case would have been beyond belief.

Cost as done under 5K.

 

Valves ...... remember, we started this build nine years ago. We decided to use Cup heads and the Cup size valve as opposed to turbo, GT3 Street or GT3 RSR valve sizes. A little free information to avoid mistakes. Depending on the components being used (turbo, GT3 Street, Cup, RSR ) and the lifter (tappet) ...... the length of that particular valve stem is different. They cannot be interchanged.I found this out the hard way.

At the time, given the GT3 Cup valve size and stem size, no one made that large of a valve in that stem size for both the intake and the exhaust valve in a super alloy. Solution was to use a Manley exhaust valve and a Forrera intake valve. The reason being neither one made both the exhaust and intake that large in the stem sizes required.



After valves were ceramic and friction coated.

 

I must say ,,, You do pay attention to every detail ,, Its all the little extra things that add up...

 

WOW, fire ringing. This is what the big boy diesel sled pullers are doing to there blocks to handle 70+ psi of boost with 2,500whp+ ... LOL

[QUOTE=cjv;3977304]We not only installed head studs with a larger diameter, but more important we used a thread taper that provides greater grip. The stud holes were re bored to a depth where the stud in combination with taper cannot bottom out.

The heads were cc'ed, the combustion chamber, exhaust ports and upper section of GT3 Cup sized valves were ceramic coated. The heads were o-ringed and fire ringed. The valve seats were given a three degree angle.







QUOTE]

 

Another item that was not mentioned is the heads were machined at the location of the head bolts so as to accept tapered washers. These washers prevent any lateral head movement.

 

xxxx

 

How many have seen a GT1 oil pump. They are three index pumps. We closed up the tolerances and had friction coating applied. Bottom line is were drew a vacuum in the case and were able to reverse the end main seals so as to run with a vacuum. Yes, hp recovered the the most unlikely of places.

This can also be done with a less expensive roots type oil pump.

GT1 Pump


Roots type pump

 

Breaking down a GT1 three index pump.

 

xxxx