928sg stage II ITB's and New Cams......
#46
Three Wheelin'
Somebody ping Mike and have him chime in here. I'm sure he can say exactly what's going on. Besides, not being a machinist, I would like to know how you do the actual drilling. That's a very long hole that's a significant portion of the diameter of the rod and it can't be easy to maintain stability during the drilling process. Not something an amateur could undertake, I suspect.
The gun drilling is indeed tricky and not possible with normal equipment. I have to send those out to a place with a machine as big as a house and pay them alot of money. A hollow tube is stronger than a solid round but the cams need no extra strength, they will never break like a cast one and are now one of the strongest parts on the car.
There are several reasons I did that but mainly it's because the cams are the result of me making something I love and design and high quality being all important, not cost or ease.
If I knew of a way to spend time and make the design or quality a tiny amount better, that would be done. That sounds crazy when there are suppliers selling easy to make but poorly engineered crap and the mass consumer expects instant gratification from buying something cheap with no problem with it being crap, it was only to fulfill thier need to have "it". The whole reason I'm into Porsches in the first place is an appreciation for quality and I would much rather make high quality stuff that few buy than mass sell what I wouldn't want to use myself.
Sterling and the others that have my cams are getting workmanship that is beyond what is expected and I really enjoy doing that for them because I appreciate their trust to make a critical part.
So in other words, I drilled them because it's better than not drilling them
BTW, the material is not 4150M.
It is a high strength alloy with a unique hardening procedure that is only done for me and my cams and I feel very good about it. That's one of the most expensive parts of making these and makes the material choice more expensive to use than even 8620 but it will give a very hard, wear resistant surface. Lifter compatability is always a concern. Greg Brown has an absolute solution for that though. If he builds you an engine with my cams you're getting the most reliable cam-lifter compatability in existance.
#47
Supercharged
Rennlist Member
Rennlist Member
Join Date: May 2002
Location: Back in Michigan - Full time!
Posts: 18,925
Likes: 0
Received 62 Likes
on
35 Posts
I was told but a guy way cmarter than me that by gun drilling a rod that is subjected to torque alng its primary axis, you essentially are removing the fulcrum, making it more rigid and liss like to break. It makes sense in my mind, but I don't know the math or engineering behind it AND I DON'T WANT TO KNOW.
Mike, you're making some kick *** stuff. Keep it up!
Mike, you're making some kick *** stuff. Keep it up!
#48
Drifting
Drilling the shaft makes it stronger in the durability sense. With a hollow center there is no point for stresses to concentrate and the fatigue life goes way up.
#49
Rennlist Member
He told me the open deck bores have the problem of vibrations at high RPM ,so the head gasket rings can went oval/smaller in the long term.
Mike prevent this with his new steel cylinder sleeves.
I think we should say on a long term prospect the engine can reach 100000 km with this configuration or the mod is crap.
If your goal is driving the engine for a limited time you can do silly things like very high rpm or to much boost.
But hopefully you have a clear failure mode or you can take the next engine for try and error.
Mike prevent this with his new steel cylinder sleeves.
I think we should say on a long term prospect the engine can reach 100000 km with this configuration or the mod is crap.
If your goal is driving the engine for a limited time you can do silly things like very high rpm or to much boost.
But hopefully you have a clear failure mode or you can take the next engine for try and error.
Last edited by Darklands; 09-10-2010 at 02:19 PM.
#50
Drifting
It has to work for 60,000 miles or it's crap? 1. I don't think that will be the case here. 2. I wouldn't mind throwing a new set of head gaskets on a really high performance engine every 3-5 years even if it were.
#51
I'd still like to know how that big house does it. Low or high speed, bits made from unobtanium, cutting fluid distilled from phoenix tears, rods held in place by the hand of God? Just seems like a nearly impossible thing to do and yet there it is.
#52
Drifting
It's probably very similar to how a gun barrel is drilled. There should be plenty of videos on youtube about that. I'd post one, but I shouldn't search that from work.
#53
Three Wheelin'
I do gun drilling here but smaller holes such as 3/16" going 8" deep. I run a carbide drill about 1000 rpms for that and if anything goes wrong I lose a drill and a part, I have some here with drills permanetly in them
To do a big camshaft hole takes a serious machine, more than will even fit in my building.
It's not something that everyone will want. You can add $400 for gundrilling 4 billet cams.
#54
Addict
Rennlist Member
Rennlist Member
I could use some more low down TQ as 2.20:1 US S4 diff in automatic GTS and high lift S3 cams do not work together. They start to wake up around 4.5-5k while revs drop closer to 3k on upshifts. There is over 1k dead spot on every gear. Next 5.7L GTS crank + 103mm piston bottom end build might fix the problem but if variocan bits are really cheap why not...
#55
Nordschleife Master
Keep in mind that the variocam bits will not really work with the stock engine management.
So plan to go to standalone EFI.
You are also able to advance the cams which will help bring the power curve back down.
So plan to go to standalone EFI.
You are also able to advance the cams which will help bring the power curve back down.
#56
Addict
Rennlist Member
Rennlist Member
I would build standalone box to run cam adjusters based on rpm feed and keep stock LH & EZK. I will probably change stock base lobe S3 cams in and see if it helps somewhat before 5.7L bottom end is ready. Though few degree advance is one option also.
#57
Man of many SIGs
Rennlist Member
Rennlist Member
Sterling, have you considered selling this technology? Why not re-coup your investment in time and money by re-producing this for others?
#59
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I'm guessing the flappy solenoid signal, programmable with the ST box, might make a suitable cam timing shift signal. No flappy with ITB's right?
#60
Nordschleife Master
Bingo,
there is no way to turn them on/off.
I have spoken with Sterling about these and I know that he had a great deal of fun trying to get them to work left/right as they were setup correctly for the passenger side, but the drivers side would be running the cam in the wrong position...
there is no way to turn them on/off.
I have spoken with Sterling about these and I know that he had a great deal of fun trying to get them to work left/right as they were setup correctly for the passenger side, but the drivers side would be running the cam in the wrong position...