928ntslow

Garth, did you notice a difference in performance after you put the GT cams in?(other than the stall) Had you done anything else besides the cams?

Garth

I noticed a big jump in HP (see dyno sheet discussed earlier in thread). I also have a full Louie Ott exhaust (including cross over and high flow cats). I've replaced the stock GTS air tubes with the Mercedes Benz air tube combination. there are a couple of other smaller things that have been done.

One more thing, I've noticed that my gas mileage has taken a dive. It may have something to do with pressing on the loud pedal more with the performance and sound.

Garth

One other thing. While it was very strong, it seemed like the low end grunt was replaced with more high end power.

Doug Hillary

Hi,
Nick & Erkka - can you tell me the exact description and specification of the engine oil you have been using.
It would help if you state the oil change interval used too

Thanks
Doug

drnick

doug, i found my engine on-line at a wreckers yard so i dont know much about it except its claimed low mileage at around 30 k which appears to be correct.

garth, that dyno on louis site looks like no drop in low end grunt, just increases across the board?? when do you feel the engine coming on the cam now, is it around 4k like the GT, what about before? it sounds like the gain in top end was so significant you dont mind if there has been a loss down low. what about changing the intake vs exhaust timing to bring the torque back down?

rob, nice pics and dont those valves look good - im jealous! my budget is soooo stretched even now dont tempt me with more shiny metal..

martin D

Garth
John Speake JDS Porsche can supply 'GT' chips for your ECU's if you wanted to convert, he has most year chips to convert any '87-'95 ECU to any other year

Also Re. your Merc. intake tubes, 2 friends have just acquired GTS's & their tubes are crap, I've searched for the MB tubes info with no luck, do you have any P/N's or year/model ?

BC

Where did you get your 968 valves rob?

When you say "motorsports cam chain" what do you mean exactly?

Thanks

Garth

Odd isn't it? I suspect that it is just the "seat of the pants" comparison of the power band. The dyno didn't lie. Since I was more interested in the high end power, it was fine with me.

Garth

It takes 4 of these units:
Vehicle: 1987 Mercedes Benz 560SEL
Air Intake Hose: B2000-15637

I get them at this Link

rob rossitto

Where did you get your 968 valves rob?
When you say "motorsports cam chain" what do you mean exactly?

think tony is the real pic-meister, but thanks... not as much $$ as you think in the context of a complete valve job...

IIRC, devek and others sell the valves under $29ea, seats are even less... only need 16... a bit more machine work, and for an AT street car anyway, porting is minimal too...

here's what I paid for a worst case, from scratch (no heads to start with) complete valve job:
(2) 1990 Cylinder Heads $1200.00
(16) 968 Intake Valves $33.00ea $528.00
(16) 968 Exhaust Valves $32.00ea $512.00
(16) Intake Guides $4.40ea $70.40
(16) Exhaust Guides $5.52ea $88.32
(32) Valve Stem Seals $2.25ea $72.00
(32) Shims $1.00ea $32.00
(2) Oil pressure relief valve kits $45.00
Intake Valve Seats $12.20ea $195.20
Spring 928-104-129-00 1
Seat 928-104-121-00 8.38
Guide 928-104-119-01 11.85
Oring 999-701-654-40 .92

Machine Work:
Resurface Cylinder heads $65ea $130.00
Port and Polish Intake and Exhaust for Normally Aspirated Motorsport $560.00
Machine Work R&I seats, R&I guides, grind and weld water corrosion, and perform
3 angle valve jobDisassemble heads and Assemble heads for 0.020" reduced base circle camshafts $995.00
Shipping and insurance: $60.00

Labor: $1844.42
Parts: $2792.92

done by motorsport in UT: 801 699 6542/garrity... US dollars, but they might take gold or something to keep them warm too... very helpful guys who like 928 stuff.... they are not devek or kelly moss, but they did put up w/my endless questions and stupid ideas along the way.... (yes, I have lots of both)

I suspect most folks can deduct quite a bit from this, and by the time your finished, you'd be out the door for a whole lot less w/some monster heads...hp claims vary wildly, so many variables in each motor, but every little bit does help...

the porsche motorsport cam chains I bought from garrity are just 944 motorsport chains, but since P/motorsport doesn't think the 928's exist, you have to pick up scraps as you can from whereever... supposed to be a bit beefier, not a lot of $$ (under $40/ea) so I figured what the heck... looks cool on a spec sheet, but I don't think it'll make or break your top speed/dyno run/etc...

IIRC, the closer to a continious valve seat (ie more angles), carbon is more prone to get stuck in the seat and cause problems... supposed to help w/low lift angles a bit though...might want to talk to garrity/devek/etc about that... dr p's gang didn't leave a lot on the table for us to "clean up" and get huge gains, so we'll have to pay for them... (unlike the old detroit gangs)...

hope this helps... tempted yet drnick? (just tell her the devil made you do it)

Doug Hillary

Hi,
adding another perspective, this type of problem (pitting) - which is/was common on many engine families - is usually a metallurgy issue and occurs often in low use engines but the following situations can contribute;

a) infrequent/extended oil drain periods coupled to b) below,
b) use of an unsuitable engine lubricant (such as 10w-30 viscosity),
c) valve component issues(misalignment etc)

It is important in any 928 that the engine lubricant have these qualities;

d) be at least a Group 3 synthetic (or semi synthetic) and,
e) be to ACEA A3-96>/B3-96> quality rating and or,
f) be to API SJ>/CF> rating (the CF> is very important)
g) Be Porsche "Approved" or,
h) meet "mixed fleet" HDEO standards or,
i) have a HTHS viscosity of about 4cSt
j) have a "winter" viscosity rating below 20W and an upper rating of 40 or 50 (eg 15w-50) according to prevailing ambient (5w-40 is a good viscosity for all year round use in a 928)

Many of these ( d) to j) ) relate to the minimisation of valve train wear generally and especially to cam lobe wear, pitting and cleanliness. Usually the quicker the cam grind/wiping pressure the greater the problem

The Porsche recommended oil change period should be followed

It should be noted that cam lobe pitting can NOT be picked up by Used Oil Analysis until it is at an advanced state. In engine families prone to this problem it is preferable to cut open the oil filter at each change and inspect the nature of any metal residue. A magnetic drain plug will/may also tell the same story and should be analysed at each oil drain

I hope this adds another dimension

Regards
Doug (ex Dunedin, NZ Nick)

Vilhuer

My situation is similar to Nick's. Don't know much about first owner other than his name and address. Have no idea what oil was used other than one Shell oil change sticker in engine bay. There's 155k kilometers in the odo.

BC

Thanks Rob.

drnick

just an update for those interested in things camshaft related. ive just received an email from piper cams and they have measured the stock GTS profiles and suggested some modifications - which ive agreed to as follows:


Dear Nick

Your cams have been clocked, their spec is as follows:


*************************** in*** *** *** ex


Total Duration******* 252.8**** *240.7***********


Cam Lift*** *** *** *** .374"*******.335"


I propose to modify them to the following fast road spec:


*************************** in*** *** *** ex


Total Duration******* 254*********252***********


Cam Lift*** *** *** *** .400"*******.368"


*


*

BC

That should be nice.