90GT Greg Brown Engine Build
01-28-2016, 09:30 PM
#36
Rennlist Member
Thread Starter
One of the cables was trashed, the other was a casualty. The third (cruise control) also needs replacing, in theory we have one on order from Germany.
Last edited by jcorenman; 01-28-2016 at 10:45 PM. Reason: speling
01-28-2016, 10:42 PM
#37
Rennlist Member
Thread Starter
OK, more pics... These are "before" shots, what we found disassembling a 240K GT motor.
As I mentioned, the coolant parts of the head gaskets were trashed (fire-rings and oil seals were fine):
Heads were OK, except for grunge from the gaskets and some corrosion from old coolant (likely many PO's ago):
Nothing interesting here, except maybe how Brad Penn oil just sort of clings to everything:
Rod bearings, nothing here to write home about. Worn to be sure, but no signs of distress and 2/6 look pretty much like all the rest.
Main bearings all looked OK except for #3 (thrust bearing) had more wear, and also copper showing on the rear (nearside in this pic) from clutch pressure:
The #1 main bearing was distinctly odd, however, with funny wear patterns. It was worn to copper in one spot, and most of the wear was towards the (car's) left side where the alternator and timing belt apply pressure.
The girdle (and block) also showed the same markings as the outside of the #1 main bearing:
The block and girdle also showed some "fretting" that Greg thought was unusual. It wasn't much and cleaned right up with a razor blade, but still odd:
Our only theory here was the harmonic dampener, the rubber was hard and cracked and it hadn't done anything other than being a dead weight for some time.
No idea whether that is right or wrong, but we have a nice new ATI dampener now.
Still to come: Bores and pistons, then some pictures of pretty new parts.
As I mentioned, the coolant parts of the head gaskets were trashed (fire-rings and oil seals were fine):
Heads were OK, except for grunge from the gaskets and some corrosion from old coolant (likely many PO's ago):
Nothing interesting here, except maybe how Brad Penn oil just sort of clings to everything:
Rod bearings, nothing here to write home about. Worn to be sure, but no signs of distress and 2/6 look pretty much like all the rest.
Main bearings all looked OK except for #3 (thrust bearing) had more wear, and also copper showing on the rear (nearside in this pic) from clutch pressure:
The #1 main bearing was distinctly odd, however, with funny wear patterns. It was worn to copper in one spot, and most of the wear was towards the (car's) left side where the alternator and timing belt apply pressure.
The girdle (and block) also showed the same markings as the outside of the #1 main bearing:
The block and girdle also showed some "fretting" that Greg thought was unusual. It wasn't much and cleaned right up with a razor blade, but still odd:
Our only theory here was the harmonic dampener, the rubber was hard and cracked and it hadn't done anything other than being a dead weight for some time.
No idea whether that is right or wrong, but we have a nice new ATI dampener now.
Still to come: Bores and pistons, then some pictures of pretty new parts.
01-28-2016, 11:07 PM
#39
Rennlist Member
Jim/anybody: what is the purpose or function of the rubber on the damper? I may have made it worse with pullers, but the previous shop which I believe was Beverly Hills Porsche, left it with small pieces missing, enough that I thought the balance was affected. I replaced it.
01-28-2016, 11:32 PM
#40
Rennlist Member
Thread Starter
To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating element (e.g. rubber) absorbs the vibrations. Unquote (wikipedia).
Actually I am not sure about that energy-absorbing bit, rubber seems more elastic than energy-absorbing. But in any case hard rubber is neither elastic nor energy-absorbing.
Crankshaft failure is not an issue here, those things are indestructible. But undamped vibration may show up elsewhere, e.g. the marking and fretting that we saw. Harmonic dampeners/balancers are universally ignored (even by Beverly Hills Porsche), I am wondering if that might be a mistake.
01-28-2016, 11:43 PM
#42
Rennlist Member
^^^ the "harmonic" waves cancel the bad vibes man.......its all a matter of reflection.
Interesting memories of my interest in the car when Louie was selling
Love all the description of how the engine was at 250k miles......awesome.
Interesting memories of my interest in the car when Louie was selling
Love all the description of how the engine was at 250k miles......awesome.
01-28-2016, 11:50 PM
#43
Three Wheelin'
Originally Posted by Rob Edwards
Just a great result- the striking thing to me is how much benefit there is to the porting work Greg did on the intake. We have similar pistons, heads, exhaust, cams, and tuning capabilities. And Jim's 5.9 makes the same peak hp as my 6.5 does, albeit 400-500 rpm later.
Jim's making 394 rwhp at 6000 rpm, my 6.5 with the stock S4 intake made 393 rwhp SAE at 5600 rpm:
Jim's making 394 rwhp at 6000 rpm, my 6.5 with the stock S4 intake made 393 rwhp SAE at 5600 rpm:
Now if Greg could get us a couple of his special intakes...
01-29-2016, 01:15 AM
#44
Former Vendor
.
I spent literally weeks on end (thanks for your patience Jim and Sue) working-up/flow bench testing these heads and intake system, just to see what the potential actually was. Jim/Sue's heads have stock valves and flow considerably more air than Rob's heads with big valves.
I'm not sure if we will ever bolt this intake onto Rob's 6.5, but it sure would be an interesting data point.
My custom intake is back on the front burner and is smoking....
